The influence of fibre cross-sectional shape and production speed on the performance potential of polyester-viscose and polyester-cotton ring- and MJS yarns has been studied. The data indicate significant differences in the performance of the yarns produced with different spinning speeds and the yarns spun with high spinning speed display better structural intrigrity, high compress ional resilience, low compress ional energy, high abrasion resistance and more hairiness than the yarns spun under identical condition but with lower speed. Incorporating non-circular fibre in the mix greatly reduces structural integrity, abrasion resistance and hairiness for both yarn structures. The reduction in their characteristics is highly dependent on the fibre mix and production speed. For all experimental combinations, the MJS yarns possess better structural integrity, better compress ional resilience, less hairiness and lower abrasion resistance than the ring - spun yarns.

Invariably, MJS yarn fabrics exhibit lower tearing strength, lesser pilling, higher crease recovery and have lower abrasion resistance than the ring-spun yarn fabrics. Fabrics made from a non-circular polyester show lower tearing strength, lesser pills, higher crease recovery and higher abrasion resistance. Finished fabrics have higher tearing strength, abrasion resistance and higher crease recovery but show fewer pills than the grey fabrics

The effect of scouring with enzyme and caustic soda on mechanical and surface characteristics of cotton ring- and rotor-spun yarns has been studied. For both yarn structures, the flexural rigidity, hairiness, yarn-to-metal friction and dye uptake increase markedly on scouring with enzymes and sodium hydroxide. Conventional scouring with NaOH renders the yarns strikingly strong and less extensible. However , the tenacity of both types of yarns is considerably reduced on enzyme scouring .Scouring causes a marked increase in dye uptake of ring- and rotor-spun yarns; the increase is , however , more in NaOH scoured yarns than in the yarns spun yarns with identical processing conditions but scoured with enzymes . The dye uptake decreases marginally with increasing rotor speed . The effect of opening roller speed on dye uptake is also minimal.

The influence of process parameters and annealing treatment on structural parameters, tensile properties, flexural rigidity and abrasion resistance of polyester dref-3 yarns has been studied. Annealing leads to a marked increase in helix angle and helix diameter, and a decrease in mean fibre extent. The results show significant improvement in breaking extension, work of rupture and abrasion resistance, and appreciable decrease in tenacity, hairiness and flexural rigidity on annealing. The degree of change in these characteristics is more marked in the yarns made from a circular polyester fibre and the coarse fibre denier, thicker core and higher production speed facilitate it. Compared to the yarns made from a trilobal fibre, the yarns spun from a circular fibre exhibit higher thermal shrinkage which further increases with the increase in spinning speed.

The effect of processing conditions in air-jet spinning on the characteristics of polyester-viscose core-spun yarns has been studied. It is observed that the increase in main draft leads to a significant increase almost in all mechanical characteristics. Reduced yarn linear density also has a potential for an appreciable increase in these characteristics .Increased spinning speed also provides a noticeable increase in yarn tenacity , breaking extension , initial modulus , energy-to-break and flexural rigidity .

The relationships between handle characteristics of polyester-viscose and polyester-cotton ring and MJS yarn fabrics and yarn bulk and rigidity have been studied using FAST evaluation system. Generally, MJS yarn fabrics are relatively thicker, more rigid and provide a lower shear rigidity and enhanced formability. There are significant changes in the compression, shear rigidity and formability with variation in fibre profile and a marked improvement in these characteristics is obtained with trilobal polyester fibre .Increased polyester component leads to a noticeable increase in bending and shear rigidities. A polyester- cotton fabric has been found preferable to a polyester-viscose fabric in respect of fabric handle.

The annealing treatment of polyester dref-3 yarns reduces their initial modulus, structural integrity and compress ional resiliency, but increases compress ional energy. There is high tendency for the yarns made from circular fibre to have a larger reduction in initial modulus and compress ional resiliency , less increase in compress ional energy and a greater decay than do the trilobal fibre yarns . The magnitude of change in these characteristics depends on the fibre linearity, core-wrapper ratio and the production speed.

Polyester-viscose MJS yarns exhibit more wrappers and wraps/cm, larger helix angle and larger helix diameter than the polyester-cotton MJS yarns. Each of these structural parameters show an ascending relationship when both polyester content and spinning speed increase. Yarns spun from a non-circular fibre, on the other hand, show fewer wrappers, fewer wraps/cm and larger helix diameter. Furthermore, MJS yarns display considerably lower tenacity, lower extension, poor abrasion resistance, higher rigidity and lower elastic recovery than their ring-spun counterparts.

Yarn structure plays an important role in influencing clothing comfort as witnessed by the fact that the fabrics made from MJS yarns perform better than those of the ring-spun yarn fabrics in respect of air and water-vapor permeability and absorbency. Furthermore, wicking is poor with MJS yarns. Non-circular polyester fibre produces fabrics with higher air-permeability, higher water-vapor transmission, higher absorbency, higher thermal insulation and higher workability. Nevertheless, polyester-viscose fabrics are superior to polyester-cotton fabrics in respect of all these characteristics except thermal insulation.

The influence of ply twist and plying technique on the properties of rotor yarns spun from acrylic and viscose fibres has been studied. It is observed that the tenacity, abrasion resistance, unevenness and hairiness of OE rotor-spun yarns substantially improve after plying. The two-for-one plied yarns produced using the same processing conditions are weaker by3-13%, more extensible by 6-22%, more even by 2-7%, less twist lively by 12-22%, more hairy by 9-26% and have 2-5% lower abrasion resistance than the ring plied yarns in both twisting techniques .Increasing the ply twist factor increases the tenacity, abrasion resistance and twist liveliness but decreases the hairiness of plied yarns. The properties of the fibre material and draw-off nozzle also affect the quality of OE rotor-spun yarns.

The effect of fibre profile, fibre linear density, core content and yarn draw-off speed on structure and mechanical properties of polyester DREF-3 yarns has been studied. It is observed that the tribobal fibres offer no significance benefit in friction spinning with regard to yarn quality. The yarns produced with a thicker core, in general, are significantly stronger, less extensible and yield higher work of rupture and abrasion resistance than the equivalent yarns produced with a thinner core. Higher production speed and fibre denier lead to a marked decline in these characteristics but increase the mean fibre extent and helix diameter. In general, the trilobal fibre yarns exhibit lower values of mean fibre extent, helix angle and helix diameter than those of the circular fibre yarns.

The thermal comfort characteristics, viz. air permeability, water vapour diffusion, wickability, absorbency and thermal insulation, of scoured and finished fabrics made from polyester-cotton MVS yarns have been evaluated. The experimental results reveal that the air permeability and the water vapour diffusion of the scoured fabrics initially increase with increasing twisting jet pressure of Murata vortex spinner and then decrease. Wickability and thermal insulation of these fabrics, on the other hand, register a decrease initially with the increase in twisting jet pressure and then increase with further rise in twisting jet pressure. Wider nozzle distance enhances air permeability and water vapour diffusion of MVS yarn scoured fabrics but has a deleterious effect on wickability and thermal insulation. Higher cotton content is also effective in improving wickability, absorbency and thermal insulation properties but lowers the air permeability and water vapour diffusion. The chemical finishing significantly reduces the air permeability, water vapour diffusion, wickability, absorbency and thermal insulation of these fabrics.

The effect of yarn linear density, yarn structure, twist factor and rotor speed on low-stress properties of mercerized cotton ring- and rotor-spun yarns has been studied. For both ring- and rotor-spun yarns, the initial modulus at 1% and 3% extensions, packing density and hairiness change markedly as a result of mercerization treatment. Flexural rigidity increases significantly, however it is considerably lower for ring-spun yarns. The abrasion resistance of both type of yarns decreases but yarn twist increases it.

The effect of some jet spinning parameters on the low-stress characteristics of scoured and finished fabrics woven with polyester-cotton jet-spun yarns have been studied. It is observed that the compressional energy, shear energy and coefficient of friction of MVS yarn fabrics decrease initially when the twisting jet pressure is increased from 4 kg/cm 2 to 5 kg/cm 2 and increase thereafter with the further increase in twisting jet pressure. An increase in nozzle distance on the MVS spinner, on the other hand, causes a significant decrease in these properties. Furthermore, the use of fine yarns decreases compressional energy and coefficient of friction, and the fabrics made from yarn spun with higher jet pressure and wider nozzle distance have higher bending rigidity. The chemical finishing significantly decreases the compressional energy, shear energy, coefficient of friction and bending rigidity.

The effect of various parameters such as draw-off nozzle profile, twist factor, yarn linear density and material type on the recovery properties of OE rotor-spun yarns has been studied. Analysis of variance suggests that the profile of the draw-off nozzle has a profound influence on the recovery characteristics of acrylic-cotton OE rotor-spun yarns. Notched nozzle generally results in higher immediate elastic recovery and delayed recovery for acrylic-cotton yarns. However, both these characteristics decrease considerably with the increase in cotton content and twist factor. Reasonably lower cotton content, low twist factor and a notched nozzle are needed to reduce permanent set. Increased yarn linear density leads to a decrease in permanent set but conversely increases immediate elastic recovery and delayed recovery.

The influence of mercerization on processing performance and other characteristics of knitting, weaving and sewing yarns has been studied. It is observed that mercerization markedly improves the seam efficiency of fabrics stitched with cotton sewing yarns but reduces yarn capacity to sustain failure during weaving.

The influence of twisting jet pressure, delivery speed, nozzle distance, yarn linear density and yarn composition on the characteristics of polyester-cotton MVS yarns have been studied. Contrary to MJS yarns, the coarser yarns are stronger than the finer ones due to the higher proportion of load-bearing core fibres. The twisting jet pressure has a direct effect on the tensile characteristics of polyester-cotton MVS yarns and the optimum pressure is dependent on yarn linear density. Moreover, the use of excessive high jet pressure adversely affects yarn tensile characteristics. The use of higher nozzle distance improves the yarn tenacity; the latter, however, deteriorates at very high nozzle distance. A higher delivery speed produces weak, less rigid, less uniform and more hairy yarns.

The influence of twisting jet pressure, delivery speed, nozzle distance, yarn linear density and yarn composition on the structural parameters of polyester-cotton yarns spun on Murata Vortex Spinner (MVS 810) has been studied. It is observed that the MVS yarns have about 50-60% core fibres and remaining as wrapper or wild fibres. The structure of MVS yarn has been classified into four main categories, viz. tight wrappings, long wrappings, irregular wrappings and unwrapped. The tight wrappings are found to increase with the increase in jet pressure but at very high jet pressure, they get converted into irregular wrappings. The long wrappings increase with the nozzle distance while unwrapped structure decreases with both jet pressure and nozzle distance up to a certain level. The finer yarns have low proportion of core fibres. The wrapper and wild fibres increase with the jet pressure but at very high jet pressure of 6.0 kg/cm 2, the wild fibres increase significantly. An increase in delivery speed leads to a further increase in wild fibres.

The response of cotton ring- and rotor-spun yarns to mercerization treatment has been investigated. It is observed that the caustic mercerization causes major changes in the mechanical and frictional behaviour of yarns, though the magnitudes of changes are different for different ring- and rotor-yarns, depending on the process parameters used. Both mercerized ring and rotor yarns display higher knot and loop strength and lower extensibility, elastic recovery and surface friction than the corresponding unmercerized yarns. Mercerization is an effective means of reducing hairiness and twist liveliness of both types of yarn.

The effect of twisting jet pressure, nozzle distance, delivery speed, yarn linear density and fibre composition on the performance and low-stress characteristics of polyester-cotton Murata vortex spun yarns has been studied. The coarser yarns produced using the same conditions exhibit higher abrasion resistance, tensile energy and compressional energy but lower per cent decay. Higher jet pressure and wider nozzle distance offer considerable advantages in respect of structural integrity, abrasion resistance and resilience but there is deterioration in these characteristics at a very high jet pressure. Tensile energy initially increases with the increase in jet pressure and nozzle distance and then drops when jet pressure is further increased. Compressional energy, on the other hand, exhibits a decrease followed by an increase with the increasing jet pressure. Structural integrity and abrasion resistance deteriorate with the increasing delivery speed.

The thermal comfort properties of woven polyester-viscose fabrics and their relation to the process variables – fibre linear density, fibre profile and weave pattern has been studied. It is observed that the twill woven fabrics are more air permeable and yield higher water vapour diffusion, wickability, absorbency and thermal insulation than equivalent plain woven fabrics. The use of non-circular polyester fibre markedly improves absorbency and thermal insulation but impairs air permeability.

First nozzle pressure and main draft are the most important parameters affecting the mechanical properties of polyester MJS yarns. Both short and long hairs register higher values with increasing main draft and first nozzle pressure.

The influence of twist factor and rotor speed on the properties of polyester ring and rotor yarns spun from polyester fibres of circular and trilobal cross-sections has been studied. The results show that the fibre profile plays a key role in determining the mechanical and surface properties of all-polyester, polyester-viscose and polyester-cotton yarns, as evidenced by the fact that both ring and rotor yarns spun with trilobal polyester fibres have lower tenacity, higher breaking extension, more twist liveliness, lower work of rupture and higher flexural rigidity. Furthermore, lesser yarn-to-metal friction, higher dye pick-up and low hairiness can be obtained for blended yarns having polyester fibres of non-circular cross-section. Both twist factor and rotor speed strongly affect all yarn properties and the behaviour is similar for all the yarns.

The relationship between the hairiness measured by Uster-3 tester and Zweigles hairiness meter (G565) and some process parameters has been studied. In rotor spinning, higher values of twist factor and rotor speed offer considerable advantage in respect of yarn hairiness. Test speed produces large changes in the hairiness, the magnitude being dependent mainly on the processing factors. Hairiness is linearly related with yarn linear density. No direct distinct statistical relationship could be evidenced on comparing the instrumental readings recorded by Uster-3 tester and Zweigles hairiness meter.

The influence of add-on finish and process variables on the recovery properties of jet-spun polyester yarns has been studied using the Box-Behnken design. It is observed that the add-on finish plays a key role in determining the immediate elastic recovery of jet-spun polyester yarns which tends to increase with the increase in level of add-on finish. Immediate elastic recovery hardly alters with spinning speed but it increases significantly with the increase in both first nozzle pressure and main draft. Both delayed elastic recovery and permanent set, on the other hand, invariably decrease with increasing main draft, and are considerably lower for the yarns spun with higher add-on finish than for the yarns spun without finish. An increase in spinning speed increases the permanent set but adversely affects the delayed recovery.

The influence of fibre profile, spin finish and opening roller speed on quality of polyester OE rotor-spun yarns has been studied. The spin finish and opening roller interact with each other to determine yarn properties. This is because the inter-fibre friction, which depends to a large extent on the combined influence of fibre structural variants and spin finish, plays an important role in influencing fibre separation by opening roller. It is observed that the yarns made from a trilobal fibre are inferior to the yarns made from a circular fibre spun under the same condition in terms of tenacity, breaking extension, work of rupture, hairiness and regularity. The yarn tensile properties generally show a desceding trend with increasing opening roller speed. The drop in tensile properties, however, depends on the level of add-on finish. The yarn regularity is also highly dependent on the add-on finish and opening roller speed. The yarns produced with higher opening roller speed show lower unevenness and fewer imperfections, particularly at higher level of add-on finish.

The impact of some process variables on sheath-slippage resistance and other properties of viscose-covered polyester filament MJS core-spun yarns has been studied. It is observed that the air-jet spinning can be used for producing core yarns after optimizing process parameters. A relatively higher first nozzle pressure is advantageous for improving sheath-slippage resistance. The use of higher spinning speed and wider condenser markedly improves the tenacity, breaking extension, initial modulus and sheath-slippage resistance but adversely affects the yarn hairiness, mass irregularity and flexural rigidity. Such decline in the properties at higher spinning speed is, however, more marked in the fine yarns than in coarse yarns. On the whole, MJS core yarns have hairiness and irregularity characteristics similar to those of 100% viscose yarns, but the mechanical properties of these yarns are better than those of pure viscose yarns, obviously due to the presence of a strong core material.

The knitting potential of acrylic-cotton OE rotor-spun yarns has been assessed. The knot strength ratio and loop strength ratio have been used as important factors in evaluating the knittability. Both the ratios increase with the increase in acrylic content and exceed the performance requirement limit for knitting. The knittability of acrylic-majority yarns is superior to that of cotton-majority yarns, although the acrylic-majority yarns are more stiffer. Additional advantages of acrylic-majority yarns are their lower twist liveliness, higher elongation, higher bulk and lower hairiness.

The effects of add-on finish and some other process variables on mechanical and irregularity characteristics of air-jet spun polyester yarns have been studied using the Box-Behnken design. It is observed that the add-on finish plays a dominant role in influencing the yarn properties. The correlations between spinning parameters and mechanical properties are found to be highly significant. On the other hand, the yarn irregularity exhibits poor correlation with the process variables. Imperfection indices show a general ascending relationship with add-on finish and other process variables studied.

The relationship between magnitudes of the instrumental measurement of the elastic recovery properties and some yarn parameters has been studied. In general, the coarse yarns have low immediate elastic recovery, high delayed elastic recovery, and a large permanent set than the fine yarns prepared under the identical processing conditions. The use of higher first nozzle pressure and main draft produces high immediate elastic recovery but low delayed elastic recovery and permanent set. Both amplitude and rate of extension produce a large variation in the elastic recovery properties, the magnitude being dependent mainly on processing factors.

The influence of ply twist and twist direction on the structure and properties of polyester MJS yarns has been studied. It is observed that the effect of plying on fibre and yarn structural parameters is significant. If the direction of Z-wrapped surface fibres is coincident with the direction of ply twist, the helix angle and helix diameter are high, but the mean fibre extent is very low. The increase in ply twist factor results in larger helix angle, larger helix diameter, smaller yarn diameter and lower fibre extent. Yarn properties also remarkably improve after plying. The improvement in yarn properties depends upon the amount and direction of ply twist. A plied yarn produced by twisting in a direction opposite to that of wrapping of surface fibre is stronger, less extensible, less rigid, more ever, and has higher abrasion resistance. Yarns plied in the Z-direction are more rigid than those plied in the S-direction. While the flexural rigidity of yarns plied in the S-direction with higher ply twist factor in considerably lower than that of the corresponding single yarns, the flexural rigidity of those yarns ply twisted in the Z-direction invariably decreases as the ply twist factor is increased.

The influence of processing parameters on the hairiness of polyester MJS yarns has been studied. It is observed that the spinning speed has considerable influence on the hairiness followed by the first nozzle pressure. For a constant first nozzle pressure (2.0 or 2.5 or 3.0), an increase in spinning speed from 180 m/min to 200 m/min increases the yarn hairiness. The hairiness decreases with the decrease in fibre denier, main draft and yarn linear density, and on annealing. Plying also significantly reduces the yarn hairiness; the reduction is more in Z-ply yarns and it increases with the increase in ply twist.

Fibre cross-section is an important factor in determining flexural rigidity and elastic recovery of OE rotor-spun yarns. The level of spin finish, tex twist factor, draw-off nozzle profile, rotor speed and opening roller speed have profound influence on flexural rigidity. The variation either in twist factor or in rotor speed hardly affects elastic recovery; the elastic recovery, however, increases with the increase in level of spin finish. The increase is highly dependent on the draw-off nozzle profile and opening roller speed.

Fibre profile plays an important role in OE rotor spinning. The yarns made from a trilobal fibre perform no better than the yarns made from a circular fibre in respect of twist deviation, tensile parameters and mass irregularity. The yarn hairiness is a more serious problem with circular fibres. The spinning of rotor yarns with a low twist factor and rotor speed produces yarns within the acceptable hairiness limit. Yarns with trilobal fibres pick up more dye than the yarns with circular fibres. The dye uptake decreases with the increase in tex twist factor but the decrease in the uptake of dye reduces with the decrease in polyester fibre denier.

The comparison of the properties of OE rotor and Dref-3 yarns spun from polyester staple fibre reveals that the Dref-3 spinning system produces a substantially stronger, less extensible, less even, more rigid and more elastic yarn followed by the rotor spinning system. Both core content and friction ratio significantly influence tenacity, initial modulus and abrasion resistance of Dref-3 yarns. These properties register higher values as core content and friction ratios are increased.

The influence of level of fibre finish in relation to total draft and spinning speed on characteristics of polyester MJS yarns has been studied. It is observed that different levels of fibre finish exhibit different trends at different drafts. A higher level of fibre finish significantly increases the tensile properties but adversely affects the flexural rigidity. Both yarn hairiness and abrasion resistance show an initial improvement followed by deterioration with the increase in fibre finish. Within the spinning speed at 150-210 m/min, the yarn evenness characteristics generally deteriorate with the increase in spinning speed, whereas the yarn tensile properties improve. The flexural rigidity shows a minimum at a spinning speed of 150 m/min. The influence of total draft on tenacity, breaking extension, abrasion resistance, flexural rigidity and hairiness is similar to that of spinning speed.

The influence of fibre denier, ribbon width, main draft and yarn linear density on the properties of polyester-jet spun yarns has been studied by using factorial design. It is observed that the ribbon width has a direct effect on the tensile properties of MJS yarns, depending on the fibre and yarn linear densities. The use of higher main draft substantially improves the tensile properties but adversely affects the evenness, rigidity and hairiness.

The effect of spin finish level, opening roller speed and types of draw-off nozzle on the mechanical properties of the polyester OE rotor yarns has been studied. It is observed that the higher level of spin finish and notched nozzle offer considerable advantage in rotor spinning in respect of yarn tensile properties. The opening roller speed has the greatest influence on yarn breaking strength, breaking extension, work of rupture and abrasion resistance. All these properties deteriorate to different degree, depending upon the level of spin finish. Twist efficiency is higher with a higher level of spin finish, higher opening roller speed and a notched nozzle.

The effect of pressure and position of first nozzle and spinning speed on the properties of acrylic MJS yarns has been studied. It is observed that the first nozzle pressure has the highest influence on the yarn properties followed by the spinning speed. Higher first nozzle pressure significantly improves the yarn tenacity and breaking extension but adversely affects the yarn regularity, residual shrinkage and flexural rigidity. The less rigid yarns are produced with a low spinning speed and a small gap between the first nozzle and the nip of front roller.

The influence of opening roller speed and sliver preparation on the properties of viscose OE rotor yarns spun from the fibres of different linear densities at high rotor speeds has been studied. It is observed that the fine fibres offer significant advantage in regard to yarn tenacity, breaking extension, work of rupture, abrasion resistance and mass irregularity. Each of these quality parameters improves initially but deteriorates thereafter as the opening roller speed is further increased beyond the optimum level. The rate of decline in the properties is greater when the yarns are produced at higher rotor speeds. Such decline in the properties at higher rotor and opening roller speeds is, however, more marked in yarns spun with single passage drawframe sliver.

The influence of composition and level of spin finish and of opening roller speed on the characteristics of OE friction-spun yarns spun from acrylic fibres has been studied. It is observed that a change in composition or level of spin finish significantly affects the yarn twist, tenacity, mass irregularity, abrasion resistance and flexural rigidity. An increase in opening roller speed significantly increases the breaking extension but does not cause any systematic variation in other yarn characteristics except the mass irregularity and flexural rigidity, which show an initial decrease followed by an increase with the increase in opening roller speed.

The relationship between the magnitudes of the instrumental measurement of the inverse relaxation and some yarn factors has been investigated. It is observed that the inverse relaxation index and load induced are influenced by the blend composition, yarn linear density and first jet pressure. In MJS yarns, a systematic decrease in yarn linear density greatly increases the inverse relaxation index. The use of higher first jet pressure produces higher inverse relaxation but reduces load induced. Also, the inverse relaxation index increases with the increasing retraction level but shows descending relationship with the increasing polyester content.

Flax-viscose blends can be easily spun on the rotor spinning system, though the mechanical properties of the blended yarn deteriorate with an increase in flax content. It has been observed that flax content should not exceed 30% for spinning stability. Alkali treatment remarkably increases the bulk and breaking extension but decreases the tenacity, initial modulus and flexural rigidity. The decrease in tenacity, initial modulus and flexural rigidity of the treated yarns shows descending relationship with flax content but it increases with the decrease in twist factor.

Acrylic-rich MJS yarns are considerably stronger, more extensible, more rigid and yield higher abrasion resistance than the yarns with higher cotton content. These characteristics register higher values with the increase in injector-jet pressure, main draft and spinning speed. A decrease in yarn linear density increases tenacity and breaking extension but decreases flexural rigidity and abrasion resistance.

The effect of yarn linear density, core content and friction ratio on radial packing density and mechanical properties of polyester DREF-3 yarns has been studied. It is observed that the packing density is maximum at the core and it decreases towards the surface. The packing density of a fine yarn is less than that of a coarse yarn, irrespective of the process parameters. The higher the core content and the friction ratio, the higher is the packing density. An increase in the core content and friction ratio results in large increase in tenacity, initial modulus, breaking extension, flexural rigidity and abrasion resistance of yarns.

Flax-viscose yarns process well on OE rotor spinning system, but the flax content in the fibre-mix should not exceed 30% for improved spinning stability. Yarns produced with lower twist factors are more regular and have fewer imperfections. The flexural rigidity increases with increase in flax-content. Higher twists and rotor speeds produce more rigid yarns.

Acrylic-cotton yarns at all levels of twist are weaker, less extensible, less rigid and yield lower abrasion resistance than acrylic-viscose yarns. Both toughness index and abrasion resistance are very much related to tensile properties and reflect their effect for different blend ratios. Twist efficiency is markedly low in acrylic-cotton OE rotor yarns than in acrylic-viscose yarns.

Spinning speed appears to have the highest influence on yarn characteristics followed by feed ratio in air-jet spinning. Position of first jet has an insignificant impact on yarn tensile properties. However, yarns produced with a wide gap between first jet and the nip of first roller are slightly more regular.

The response of polyester-viscose MJS yarns to annealing under relaxed condition has been studied. It is observed that the annealing significantly increases the breaking extension but adversely affects the tenacity and initial modulus of yarn. The flexural rigidity of yarn considerably decreases whereas the elastic recovery increases on annealing. The variation in properties on annealing is more conspicuous in the yarns produced with higher proportion of polyester fibre and lower first jet pressure.

The influence of core content and friction ratio on the properties of polyester DREF-3 yarns has been studied. It is observed that the properties of DREF-3 yarn are greatly influenced by both core content and friction ratio. Thicker yarn core offers significant advantage in terms of improved tensile properties. Yarn tenacity and breaking extension increase but evenness, hairiness and bulk decrease with the increase in friction ratio.

The relation between the properties of acrylic MJS yarns and machine parameters is reported. The spinning speed appears to have the highest influence on the yarn characteristics followed by feed ratio. High feed ratio produces stronger, more extensible and more regular yarns respective of spinning speed. Increase in spinning speed has a positive influence on both tenacity and breaking extension, but adversely affects yarn regularity. Increasing gap between first jet and the nip of front roller increases flexural rigidity.

The response of polyester-viscose jet-spun yarns to the repeated extension has been studied by varying fibre composition, yarn linear density and first jet pressure. The observations reveal that repeated extension causes deterioration in yarn mechanical properties to various degrees, depending mainly on processing factors and test parameters.

The influence of sliver preparation and opening roller speed on the properties of OE rotor-spun viscose yarns spun from fibres of different lengths has been studied. It is observed that the longer fibres offer no advantage to yarn tenacity, breaking extension, mass irregularity and abrasion resistance. Each of these parameters shows an improvement initially with the increase in opening roller speed but they decline with further increase in opening roller speed. Such decline in quality at high opening roller speeds, however, is less marked in the yarns spun from slivers produced with two draw frame passages.

The steam-relaxation treatment of acrylic-rich yarns reduces their tenacity and abrasion resistance, but increase extensibility and bulk. The adverse effects associated with steaming are more pronounced on OE rotor yarns than ring yarns and become larger with increase in both acrylic content and yarn tex. Yarns produced from the cotton-majority mix, on the other hand, show slightly higher tenacity and lower breaking extension, residual shrinkage and abrasion resistance after steaming.

The impact of heat treatment under relaxed condition on the mechanical characteristics of polyester-viscose ring and MJS yarns has been studied. Heat treatment markedly decreases the rigidity of both ring and MJS yarns, but the loss in tensile strength is also considerably higher. The decrease in rigidity is highly dependent on the blend ratio, yarn tex and type of spinning system. Some other changes in yarn properties include remarkably enhanced breaking extension accompanied by deterioration in evenness.

Jet spun yarns produced with higher acrylic fibre content showed substantially higher bulk, abrasion resistance, flexural rigidity, tenacity and breaking extension than the yarns spun with higher cotton fibre content. Reasonably higher acrylic content is needed to enhance yarn bulk. Use of a narrow condenser and lower main draft reduces rigidity and yarn bulk.

Plain woven fabrics have higher breaking strength, higher abrasion resistance and lower crease recovery as compared to twill and satin. Fabric crease recovery decreases with increase in picks per cm. As the float length in fabric made from polyester-viscose MJS yarn increases, the crease recovery, abrasion resistance and pilling propensity of the fabric increase.

The effect of yarn blend composition, pick density and weave construction on grey and finished air-jet woven fabrics made from polyester-viscose MJS yarns has been studied. It is observed that finished fabrics have lower value of flexural rigidity than the equivalent grey fabrics. Crease recovery improves very much in finished fabrics. Plain woven fabrics have lower crease recovery than twill and satin fabrics. The crease recovery decreases with increase in pick density but increases with increase in polyester content.

Yarns spun with higher polyester content are considerably stronger, more extensible more even and have fewer imperfections then acrylic-majority yarns. However, yarns spun at higher spindle speed show deterioration in yarn evenness. Yarns spun with acrylic-majority mix exhibit higher flexural rigidity, which increase with increase in spindle speed.

In comparison with cotton-majority yarns, acrylic-cotton (70 : 30) yarns have higher strength, breaking extension, flexural rigidity and abrasion resistance. More than 50% acrylic is required for improvement in tenacity. The use of spiral nozzle has little effect on flexural rigidity but considerably lowers the tenacity, breaking extension and abrasion resistance.

The influence of process parameters on quality of polyester-viscose MJS yarns has been studied. It is observed that coarse yarns produced using the same conditions are substantially weaker, less extensible, less irregular and more rigid than finer ones. The yarn breaking strength and breaking extension show an increase with the increase in polyester content, first nozzle pressure and feed ratio. The flexural rigidity decreases with a small gap between the first nozzle and the nip of front roller, a lower fist nozzle pressure, lower yarn tex and a lower feed ratio.

The effect on acrylic ring and Murata jet-spun yarns of changes in nozzle pressure, spinning speed and distance between first nozzle and front roller nip before and after treatment has been studied. Steam-relaxation treatment of acrylic MJS yarns results in significant increase in breaking extension but reduces yarn tenacity and flexural rigidity. The influence of treatment on these properties decreases with increasing second nozzle pressure and spinning speed. Yarn residual shrinkage is insensitive to second nozzle pressure. The elastic recovery is low in yarn spun with higher second nozzle pressure, but increases after steaming.

Acrylic-cotton rotor-spun yarns are substantially weaker, more even and extensible, and have lower abrasion resistance than the equivalent ring-spun yarns. The difference in tenacity of ring- and rotor-spun yarns is much less for coarse yarns. An increase in twist factor significantly increases the abrasion resistance of rotor yarns. However, with 70 : 30 acrylic-cotton ring yarns, the abrasion resistance does not show any change with increasing twist factor. Acrylic content in the fibre mix should be more than 50% for improvement in yarn characteristics.

The P/V yarns produced by varying feed ratio, ribbon width and distance between first nozzle and the nip of the front roller show variance in their properties. An increase either in ribbon width or the gap between first nozzle and the nip of front roller raises the flexural rigidity and elastic recovery. The use of higher feed ratio also has the simillar effect. Increasing distance between first jet and the nip of front roller and feed ratio reduces yarn unevenness.

Higher proportion of acrylic fibres in acrylic-cotton MJS yarns can give more strength, extensibility and regularity. The elastic recovery is also high in these yarns.

Acrylic-polyester yarns spun from various fibre content and twist factors exhibit different characteristics. Acrylic-majority yarns are more regular; however, increase in twist factor makes them uneven. Both abrasion resistance and flexural rigidity are higher for coarser yarns and increase with polyester content. Hairiness is low in fine yarns and increases with increasing acrylic content.

Fibre linear density plays a key role in determining the flexural rigidity and elastic recovery of MJS yarns. The feed ratio, main draft, nozzle pressure and production speed have significant influence on flexural rigidity. The variation in either second nozzle pressure or production speed has little effect on elastic recovery. The elastic recovery, however, increases with the increase in feed ratio, main draft and first nozzle pressure.

The core-wrapper ratio has a considerable influence on the characteristics of acrylic friction-spun yarns, followed by spinning speed. Supplying more than 40% wrapper fibres reduces the yarn strength, breaking extension and evenness due to the disorientation of wrapper fibres. Any increase in spinning speed with core-wrapper ratio exceeding 60 : 40 results in a general deterioration in yarn tenacity, evenness and elongation.

The apparent twist loss is higher in coarse yarns and it increases with the increase in tex twist factor and decrease in draw frame passages. Two draw-frame passages are more beneficial for the fine rotor yarns than for the coarse yarns. It substantially improves tenacity, extension, unevenness and imperfections. The draw-frame passages have therefore to be chosen according to the yarn linear density and the fibre to be used.

The influence of fibre linear density, feed ratio, main draft and second nozzle pressure on viscose MJS yarn characteristics has been assessed. It has been observed that tenacity increases with increase in feed ratio, main draft and second nozzle pressure. Yarn evenness tends to improve when feed ratio and main draft increase, and to deteriorates when the second nozzle pressure increases. An increase in second nozzle pressure raises the flexural rigidity but produces no effect on elastic recovery.

The effects of yarn twist, yarn composition and draw-off nozzles, (notched and spiral) on the properties of polyester-viscose rotor spun yarns have been studied. It is observed that the surface characteristics of the draw-off nozzle have greater influence on the polyester fibre yarns than on viscose fibre yarns. Yarns spun from 100% polyester fibre or its blend with viscose rayon exhibit considerably higher tenacity, breaking extension, unevenness and imperfections than the viscose fibre yarns. Notched draw-off nozzle produces stronger, more extensible and more even yarns. The improvement, however, depends upon the yarn composition and text twist factor.

The influence of the type of draw off nozzle on tensile properties is more prominent for polyester-majority yarns. For polyester-viscose rotor-spun yarns, the tenacity and breaking extension do not alter with increasing twist factor, but an increase in polyester content improves these characteristics. The tenacity and breaking extension are lower for spiral draw-off nozzle at all levels of extension rates.

MJS yarns spun from fine fibres are stronger, more extensible, more even and have fewer imperfections. The tenacity of these yarns increases with increase in first nozzle pressure and the distance between first jet and the nip of front roller. An increase in first nozzle pressure increases the flexural rigidity but reduces the elastic recovery.

The effects of polyester fibre denier, tex twist factor and yarn composition on the properties of polyester-viscose rotor yarns spun at higher rotor speeds and ring yarns have been studied. It is observed that twist loss is minimum for polyester-minority rotor yarns spun from 1.0 denier fibre and it increases with the increase in tex twist factor and rotor speed. The tenacity and breaking extension are considerably lower for polyester-viscose rotor yarns than for ring yarns. The tenacity of all the yarns hardly changes with the variation in tex twist factor and rotor speed but it increases with the increase in fibre fineness and polyester fibre proportion. Polyester-majority rotor yarns possess larger diameter than the ring yarns. The diameter decreases with the increase in rotor speed and tex twist factor. An increase in tex twist factor, rotor speed and polyester fibre content offsets the evenness.

Yarn extractive nozzle exerts a marked influence on twist loss. The minimum twist loss corresponds to notched nozzle and increases with both yarn linear density and twist factor. Further, an increase in fibre linear density raises the twist loss, the increase being less in yarns spun with lower rotor speeds.

In 67 polyester – 33 viscose rotor yarns, the twist efficiency is higher in yarns spun from polyester fibres of fine denier and decreases significantly as the twist factor is increased. An increase in rotor speed causes a decrease in twist translation efficiency. Rotor yarns are significantly weaker, more regular, have lower breaking extension, and have fewer imperfections than ring spun yarns. However, yarns spun from coarse polyester fibres, on the other hand, show a significant deterioration in strength and evenness. Twist factor and rotor speed hardly affect the yarn strength breaking extension and evenness. However, yarns spun at 50,000 rpm have slightly lower strength, lower breaking extension and lesser evenness.

MJS yarns are about 10 to 20% weaker and more extensible as compared to their ring counterparts depending upon the fibre composition, yarn linear density and nozzle pressure. However, the difference in tenacity between the ring and MJS yarns decreases as the yarn becomes finer. Second nozzle pressure significantly affects the yarn tenacity, which tends to increase with the second nozzle pressure. MJS yarns more regular and have fewer imperfections than ring-spun yarns. For these yarns, evenness deteriorates markedly with the increasing second nozzle pressure. However, an increase in the polyester fibre content minimises the deterioration in quality of MJS yarns. Thermal treatment of polyester-viscose ring and MJS yarns results in significant increase in breaking extension and yarn linear density but adversely affect the yarn tenacity, evenness and imperfections. The decrease in tenacity is higher for MJS yarns than those of ring yarns and it decreases with the decrease polyester fibre content. On the other hand, the increase in braking extension of MJS yarns is more for coarse yarns and it increases with the increase in proportion of polyester fibre.

Unlike ring yarns, air-jet yarns owe their surface cohesion to wrappers and their formation could be related not only to the turbulence in the two nozzles but also to the combined influence of the fibre properties and other process parameters. This paper reports the contribution of polyester fibre denier, spinning speed and second nozzle pressure to the characteristics of polyester-viscose yarns spun on Murata-jet spinner. It is observed that MJS yarns are slightly weaker, more even, have fewer imperfections and higher extension, flexural rigidity and elastic recovery. An increase in second nozzle pressure and spinning speed causes an increase in the yarn tenacity and flexural rigidity but has an adverse effect on yarn evenness. Breaking extension, on the other hand, decreases with increase in second nozzle pressure and decrease in spinning speed.

Yarns spun with spiral nozzle exhibit higher twist loss, higher bulk and have more imperfections than the equivalent yarns spun with plain nozzle. The false twist, which increases the torsional moment at the end of the yarn and facilitates yarn formation, depends mainly on the fibre-to-metal friction, the doffing tube design, the yarn twist and linear density.

Acrylic-majority yarns are slightly weaker, more extensible, less hairy, less rigid, more bulky and have higher yarn-to-metal friction than viscose-majority yarns. For all the yarns, bulk hairiness and yarn-to-metal friction reduce with increasing twist factor in respective of fibre content.

The influence of fibre linear density and twist factor on the flexural rigidity and elastic recovery of polyester-viscose and ring- and rotor-spun yarns has been studied at different rotor speeds. It has been observed that the polyester-viscose rotor yarns possess slightly higher flexural rigidity and elastic recovery than the corresponding ring-spun yarns. For rotor yarns, flexural rigidity increases with increase in polyester fibre linear density and twist factor, and elastic recovery hardly changes with twist factor and rotor speed but decreases with increase in polyester fibre linear density.

Polyester-cotton rotor yarns show substantial improvement in tenacity, breaking extension and unevenness on doubling. The improvement depends upon polyester content and singles’ and doubles’ twist factors. S/Z rotor yarns have bigger diameter than S/Z ring yarns. The diameter of S/Z rotor yarns decreases as the doubles’ twist factor increases, the decrease being less in polyester-majority yarns.

Stitch density does not change with fibre composition or yarn twist but increases appreciably with increasing tightness factor irrespective of the relaxation treatment. Dry-relaxed knits from acrylic-majority yarn are more prone to pilling, the latter, reduces considerably with increasing twist. Loose knits exhibit lower area shrinkage.

The plying of polyester-viscose rotor-spun yarns markedly improves tenacity, breaking extension and evenness. Fibre linear density and singles twist multiplier exert a significant influence on overall yarn quality index. The use of polyester fibre of fine denier and low singles twist reduces the difference in tenacity of polyester viscose ring- and rotor-spun ply yarns.

Yarns spun from higher proportion of polyester fibres are stronger, more regular, have higher breaking extension, have fewer imperfections and register higher abrasion resistance. An increase in twist leads to an increase in abrasion resistance but have an adverse effect on yarn evenness.

80% acrylic-20% viscose yarns are slightly weaker and more extensible than 20% acrylic-80% viscose yarns. An increase in twist factor leads to a substantial increase in yarn tenacity and tensile factor but has no effect on breaking extension.

The plying of polyester-viscose ring- and rotor-spun yarns leads to a substantial improvement in yarn tenacity, extension at break, unevenness and imperfections. The improvement, however, depends upon yarn composition, singles and doubles twist factor.

Rotor-spun yarns are slightly weaker, more extensible, more regular and have fewer imperfections and higher yarn quality index than their ring-spun counterparts. However, polyester-majority yarns require higher twist factors than polyester-minority ones in spinning on a rotor frame. Further, the effect of twist factor on yarn characteristics, in general, depends upon the fibrous components and polyester content.

Core-spun yarn finds its application mainly in industrial sectors for the production of tarpaulins, belts, tentage, hose, filter fabrics etc. But it can also be used for the production of light weight apparel fabrics by using soluble core. In this work polypropylene/cotton core-spun yarn with polypropylene as core has been produced on a conventional ring frame, fitted with spring loaded tensioning device, with an objective to investigate the effect of twist multiplier, ring frame draft and position of core on the ultimate yarn properties.

Although the requirements of an ideal filter fabric are well established in qualitative sense, it has not been possible to provide a definite specification of filter fabric for a given application. In the present work a nonwoven punched filter fabric of 100% polyester fibre with varying constructional parameters i.e., needling density, depth of needle penetration and presence of scrim as a reinforcing material was manufactured. In this paper, the effect of the above variables on the fabric thickness, density, air permeability and pressure drop are discussed. The effect of increasing needling density and depth of penetration causes reduction in fabric thickness and air permeability. The use of scrim reduces fabric thickness and air permeability.

In the present study the different testing procedures are being discussed in regards to the measurement of filtration properties for polyester needle punched felts. The procedures of particle size measurement are also discussed.

In this paper the fabrication of an instrument for measuring filtration parameters i.e. air permeability, pressure drop and filtration efficiency, is being discussed. The instrument is very simple in construction and easy to handle.

The filtration characteristics of a bag filter depends on fibre, fabric, machine and process variables and the filtration parameters are varied and from process to process. Therefore, it is necessary to analyze the filtration parameters of a filter fabric to judge its suitability and performance in different end usages.

The influences of machine and process variables on the performance of needle punched filter fabrics are reviewed. It is observed that the filtration properties are dependent on the needle dimensions and needle density. The treatment and chemical finishes also influence the performance of a filter fabric.

The filtration characteristics of a non-filter fabric for dust and gas filtration are influenced by the type of fibre, fibre denier, and fibre crimp. For general filtration, both cotton and polyesters are the most common fibres. Polypropylene fibre is also being used for low temperature filtration.

In the present study, the different types of bag filters and their cleaning methods are discussed. Generally, shaker cleaning and reverse flow cleaning techniques are used to clean the dust cakes from the woven bag filters. The pulse jet cleaning method is used for non woven bag filters to clean the dust cake.

The siro yarn can gain those areas which are presently reserved for conventional two fold yarn. The properties of siro-yarns are comparable to those of conventional two-fold yarns along with cost saving. Siro-yarn is now being used to produce mens wear, ladies wear, skirting, blousing etc. It can also be used for upholstey fabrics and knit goods.

Hollow fibre fabric shows maximum thickness followed by trilobal and normal round fibre fabrics. With the increase in needling density, the pressure drop increases gradually at any rate of air-flow. For the same rate of air flow or air permeability, hollow fibre fabric shows maximum pressure drop followed by normal round and trilobal fibre fabric. Highest tenacity at break and lowest strain were observed for 300 punches/cm 2 needle density.

Non woven needle punched dust filter from 100% polyester fibre of 2 different denier (1.2 and 3.0) were prepared with varying constructional parameters, i.e., wt./unit area, needling density, depth of needle penetration, presence of scrim. The fabrics produced were studied for thickness, density, air permeability, pressure drop, filtration efficiency and cleaning efficiency. It has been observed that filter fabric made of finer fibres gives lower thickness, higher density, lower air permeability, higher pressure drop and higher filtration efficiency. The effect of increasing needling density and depth of needle penetration is reduction of fabric thickness, reduction of air permeability, increase in filtration efficiency (up to certain limit) and an increased pressure drop. The use of scrim reduces fabric thickness, air permeability and increases filtration efficiency and pressure drop.

Air pollution is considered to be an industrial by-product or waste emitted from various sources. The problems of air pollution and its influence on human health and nature are, therefore, of major concern today. The chemical and physical characteristics of the dust and gases are important parameters for a mass of polluted air. In order to reduce or minimise the concentrations of noxious dust or gases in the environment, different filter medias are used. The separation of dust from the emitting gas or air is mainly achieved by the various separating devices or dust collectors, i.e., cyclones, fabric filters, electrostatic precipitators and scrubbers. Both woven and nonwoven filter fabrics are used for filtration purposes. Hollow polyester fibres are being used extensively for various applications, including dust filtration and gas separation. The use of hollow fibres has found good applicability in separating gases from their mixtures.

The selection of the air filter medium is critical to the overall performance of air intake systems of engines and industrial dust collection systems. The medium in these systems is primarily a surface loading medium typified by the establishment of a dust cake on the surface of the medium. The contaminant collects on the surface of the medium bridges the pores between the fibres to form a porous dust cake that becomes the filtering medium. The objective of the filter medium is to maximise the possibility of collision and the subsequent retention of the suspended particles in the air stream with the medium’s fibrous structure while minimising the energy loss to the stream of air. There are basically three mechanisms i.e. Intertial Impaction, Interception and Diffusion, by which these collisions take place and these mechanisms have varying influence cover the range of particle sizes of the contaminant in the air stream. In this paper the particle capture mechanisms and the theories involved in those mechanisms are reviewed.

Filtration is the process whereby a solid is separated from a liquid or gas by means of a porous medium which retains the solid but allows the fluid to pass. In general, the pores of the medium will be of a tortuous shape and larger than the particles which are to be removed. The filter will work efficienctly only after an initial deposit has been trapped in the medium. The conditions under which filtration is carried out are very varied and the choice of the most suitable type of equipment will depend on a large number of factors including the properties of the fluid, the nature of the solid, the concentration of solid etc. Whatever type of equipment is used, filter cake gradually builds up on the medium and the resistance to flow increases progressively throughout the operations. The most important factors on which the rate of filtration depends are pressure drop, the area of filtering surface, the viscosity of the filtrate, the resistance of the filter cake, etc. In this paper the filtration mechanisms and the theories involved in those mechanisms are discussed.

Bag filters are extensively used as a separating device to separate the dust particles from the gas/air streams. Filter fabrics are having unique characteristics of capturing particulates, mainly because of smaller openings with fibrous surface and therefore are able to capture bigger particles by means of sieving mechanism. Fibres are also responsible in capturing large particles with the help of Interception/Impingement mechanisms. Arresting of bigger particles further reduces the openings of a filter fabric and hence aids in the capturing of smaller particles – resulting in cake formation. This cake formation increases the filtration efficiency but at the cost of air drag. Moreover, after sometime the blinding occurs. At this juncture, the cleaning of the dust deposits must be taken into account. In this study, the different cleaning methods are discussed. The most common cleaning method is mechanical shaking. However, the pulse jet cleaning is becoming increasingly popular because of it’s quick action of cleaning the bags.

The early stages of filtration occurs with the capture of individual particles by single fibres as a result of any one combination of the classical particulate capture mechanisms. The particles which deposit on fibres projecting into the gas flow then act as additional sites for capture of further particles and eventually chain-like aggregates result. Once such a matrix is built up, subsequent particle capture is by true surface filtration or sieving and the function of the cloth – apart from acting as a support – becomes nominal. Following a cleaning action, more particles in the gas stream collide with particles which have remained on the fibres and cake building process recommences. In the present study, different dust filtration and particles capture mechanisms are discussed.

Power generation, waste incineration and industrial processes are inevitably associated with the production of pollutants with a potentially adverse affect on the environment. Woven and nonwoven filter fabrics are increasingly used among the other dust collectors to remove the foreign particles from gases or liquids. Performance of filter fabrics are greatly influenced by the yarn and process variables. In this study, the effects of yarn, fabric and process variables on filtration characteristics are reviewed.

Rotor yarns are considerably weaker, less extensible, more regular and have fewer imperfections as compared to their ring counterparts. The tenacity of all the yarns hardly changes with change in tex twist factor and rotor speed but increases with increase in fibre fineness and proportion of polyester fibres.

The flexural rigidity is highest for 2.5 denier trilobal fibres followed by 3 denier trilobal fibres and 3 denier circular fibres. An increase in twist factor results in a significant increase in yarn flexural rigidity. The yarns spun from fine denier fibres show higher elastic recovery. However, for both trilobal and circular fibres, twist factor has no effect on yarn elastic recovery.

The effect of sheath-fibre denier, twist and core parameters on the characteristics of nylon-viscose core-spun yarns was studied. Core-spun yarns, with the same core component but a finer denier viscose sheath fibre, give a higher strength, the latter, however, decreases with increase in the number of filaments constituting the core. Yarn-breaking extension increases with a decrease either in sheath or component denier. Core-spun yarns with finer denier sheath fibres are more regular but an increase in twist makes it uneven.

Yarns spun from circular fibres are slightly stronger, more regular and more hairy than their trilobal counterparts. Yarns with trilobal or fine denier fibres pick up more dye then the yarns with circular or coarse fibres. Dye absorbency decreases with the increasing twist, irrespective of the fibre linear density and cross-sectional shape.

Yarns spun from delustered fibres are slightly weaker, less extensible, bulkier and less hairy than their bright counterparts. An increase in twist leads to a reduction in yarn diameter and hairiness, the reduction in hairiness being less in yarns spun from fine denier fibres.

The coefficient of friction is higher in circular fibre yarns, the former, however, decreases with an increase in fibre linear density and twist. For all yarns, the maximum coefficient of friction corresponds to the lightest traveller and decreases with increase in traveller weight and yarn number. Viscose rotor yarn experiences a lower coefficient-of-friction than acrylic rotor yarn. For cotton yarns, the coefficient of friction is lower for rotor yarn than corresponding ring yarn and decreases with increasing twist for both yarns.

The plying of core-spun yarns leads to a significant improvement in tenacity and breaking extension. The increase in the tenacity of Z/Z ply yarns is more sensitive to the change in doubling ratio than the increase in the tenacity of corresponding Z/S ply yarns; the former, however, decreases with increase in doubling ratio. Diameter of Z/Z ply yarns is much less and it decreases with an increase in doubling ratio.

The breaking strength and extension of acrylic siro yarns are higher than those of normal single yarns. Both increase initially and decrease thereafter with increasing strand spacing. Steam relaxation treatment results in significant increase in breaking extension accompanied by a decrease in tenacity and abrasion resistance. The decrease in breaking strength is less in yarns spun either with wider strand spacing or higher proportions of high shrinkage fibre.

Stream-relaxation treatment of siro-spun acrylic yarns results in a significant increase in breaking extension accompanied by a decrease in tenacity. The decrease in tenacity is more in yarns spun with shorter strand spacing and higher content of high-shrinkage fibres. Residual shrinkage is more in yarns spun with higher proportions of high-shrinkage fibres and it decreases with the increasing strand spacing.

Tension mercerisation is more beneficial for rotor than ring spun yarns. It improves the tenacity but has an adverse affect on yarn-breaking extension. Multiple stretching of both type of yarns results in a decrease in the tenacity and breaking extension, the decrease being less in unmercerised yarns. In rotor yarns, the decrease in tenacity appears to be less marked at low twists and increases with an increase either in the amplitude of extension or the number of cycles.

The breaking strength and extension of acrylic Siro yarns are higher than those of normal single yarns. Both increase initially and decrease thereafter with increasing strand spacing. Steam relaxation treatment results in significant increase in breaking extension accompanied by decrease in tenacity and abrasion resistance. The decrease in tenacity is less in yarn spun either with wider strand spacings or higher proportion of high shrinkage fibre.

Mercerization of ring- and rotor-spun yarns results in significant increase in tenacity but adversely affects the breaking extension and evenness of these yarns. The increase in tenacity is higher for rotor yarns and appears to be substantial at low twist levels.

The physical characteristics of plain knits made from acrylic-viscose rotor-spun yarns of varying twist and tightness factors have been investigated. Courses/cm, wales/cm and stitch density do not change with fibre composition or yarn twist but increase appreciably with the increasing tightness factor irrespective of the relaxation treatment. Dry-relaxed knits from acrylic-majority yarn are more porne to pilling but the incidence of pilling reduces considerably with increasing twist. Fabrics knitted with lows-tightness factor exhibit lower area shrinkage.

Rapid straining of ring yarn is known to result in a higher breaking load. This may or may not hold good for rotor yarns, owing to their different structure. In this work, we have studied the influence extension rate and test length on the tenacity and breaking extension of acrylic and viscose rotor yarns and their blends. We report some interesting results that are contrary to what one generally expects.

The optimum rotor and combing roller speeds for realising the maximum yarn tenacity seems to be 45,000 rpm and 7,000 rpm. respectively. The optimum values are dependent upon the rotor diameter used. An increase in the combing roller speed above 7,000 rpm results in a weaker and more irregular yarn. A smaller rotor gives higher YQI. An increase in rotor speed decreases YQI. Increasing combing roller speed, on the other hand, adversely affects YQI. Very high combining roller speeds are detrimental to all the yarn characteristics; and large rotor and high rotor speeds result in less hairy yarn.

The contribution of fibre parameters and strandspacing to the characteristics of acrylic-viscose siro-spun yarns was investigated. Siro-spinning leads to a substantial improvement in characteristics of acrylic-viscose yarns as compared with their ring counter parts.

The steam-relaxation treatment of acrylic-viscose rotor-spun yarns decreased their tenacity significantly but increased breaking extension. Acrylic-majority yarns exhibited higher bulk and residual shrinkage. Residual shrinkage increased slightly with increase in twist but bulk decreased.

Rotor-spun yarns showed a decrease in breaking strength and extension with an increase either in the amplitude of extension or the number of extension cycles, the decrease being less in acrylic-majority and low-twist yarns.

The effect of sheath fibre denier, twist and dyeing treatment on the characteristics of core-spun yarns having a mono- and multi-filament nylon core was studied. Yarn strength and breaking extension decreased with increase in core filament denier, but were higher for yarns spun with finer denier sheath fibres. Yarns dyed with a direct dye showed a greater loss in strength and extension than the yarns dyed with a reactive dye. Core-spun yarns with multifilament core exhibited a smaller diameter, which increased after dyeing.

All-viscose fibre yarns showed higher flexural rigidity and lower elastic recovery. An increase in twist led to a significant increase in yarn flexural rigidity. The rigidity of the fibres being blended and their position in the yarn also affected the flexural rigidity of the blended yarn.

All-viscose fibre yarns showed higher flexural rigidity and lower elastic recovery. An increase in twist led to a significant increase in yarn flexural rigidity. The rigidity of the fibres being blended and their position in the yarn also affected the flexural rigidity of the blended yarn.

Rotor-spun yarns possess a lower mean breaking strength than the corresponding ring-spun yarns owing to the incidence of wrapper fibres and twist loss. Doubling twisting improved the tenacity of acrylic-viscose rayon yarns markedly by increasing the inter-fibre cohesion in the yarn.

Yarn twist has a great influence on the characteristics of ring-spun yarns. The impact of yarn twist could be very different in the case of rotor-spun yarns owing to rotor yarn’s structural difference with ring-spun yarns. The effect becomes even more complex because of non-homogeneous characteristics of the blend fibres. This study reports the contribution of twist to the breaking strength, extension at break, and any association between twist loss and yarn unevenness in acrylic-viscose rotor-spun yarns.

The effect of sheath-fibre denier, twist and core parameters on the characteristics of nylon-viscose core-spun yarns was studied. Core-spun yarns with same core component but a finer denier viscose sheath fibre give a higher strength, the latter, however, decreases with increase in number of filaments constituting the core. Yarn breaking extension increases with decreases either in sheath fibre or core component denier. Core spun yarns with finer denier sheath fibres are more regular but an increase in twist makes it uneven.

Different siro-yarns, normal single-yarns and ply yarns were spun under identical processing conditions. The combined effect of staple length, fibre linear density and strand spacing on the characteristics of siro-yarns was studied. Siro-yarns, spun from optimum fibre parameters and strand spacing, could be better than ply yarns of equivalent count.

Yarns spun from a majority of polypropylene fibres showed high strength and low extension. The yarn breaking strength tended to increase after boiling-water treatment. Thermal treatments had no significant effect on either unevenness or imperfections. Boiling-water treatment caused a higher yarn residual shrinkage than heating at various temperatures.

The characteristics of yarns spun from J-34 saw gin cotton in response to rotor diameter, rotor speed and combing roller speed were studied. Apart from studying the influence of combined rotor parameters on yarn characteristics an integrated effort has also been made to optimise the aforesaid parameters for best possible quality yarns.

Viscose rayon yarns after being dyed exhibited a decrease in hairiness, breaking strength, breaking extension and yarn quality index. Yarn unevenness and imperfections did not show any significant change after dyeing. Yarns spun with fibres of finer denier or low twist showed a higher optical density after dyeing.

The effect of sheath-fibre denier and twist on the characteristics of core-spun yarns, with a constant polyester core, was studied. Core-spun yarns with the same core component but with finer-denier viscose sheath fibre gave a higher strength and an overall higher yarn quality index. Alteration of twist did not affect the number of neps, which however decreased with increase in fibre denier. Thick places increased with increase in fibre denier. Flex abrasion resistance decreased with decrease in twist, but was higher for yarns spun with finer-denier sheath fibre.

Each of single-strand strength, breaking extension, abrasion-resistance, yarn-quality index and yarn diameter increases with increase in proportion of polypropylene fibre in the blend; Uster values, on the other hand, show a consistent reduction. With increase in polypropylene content in the blend, fabric tightness, fabric thickness, brusting strength and abrasion-resistance increase. As the wet relaxation process progresses; the tightness factor, areal shrinkage, stitch-density, brusting strength, and abrasion-resistance increase with increase in proportion of polypropylene in the mix.

The effect of thermal treatment on acrylic-polypropylene yarns has been studied. It is observed that yarn diameter, linear density and breaking elongation increase with increase in setting temperature ands duration of exposure. Residual shrinkage decreases with rise in heating-temperature. Yarn hairiness reduces due to the shrinkage of the fibres. Heat setting causes an alteration in the geometry of the yarns when the material is in relaxed-state. The fact is, however, reduced in the fabric form an account of the cross-over of yarns.

An integrated effort has been made through present investigation to determine the potential of acrylic-polypropylene blends for bulked yarns. Apart from studying the influence of acrylic-polypropylene blend proportion on the characteristics of bulked yarns such as yarn denier, bulking factor, relaxation shrinkage and mechanical characteristics, an attempt has also been made to correlate the various blend parameters with the experimentally determined physical and mechanical characteristics of acrylic-polypropylene bulked yarns.

Cotton contains natural waxes and oil which, undoubtedly, have desirable lubricating properties for spinning but may interfere with the fullest development of strength in yarns and fabrics because of their contribution to fibre slippage. Treatment with solvents like benzene or sodium hypochlorite or subjection to any other process for removing wax and oil, results in increased yarn strength by 25 per cent.

The study of the physical and mechanical properties of various industrial filter fabrics made up of polypropylene fibre shows that polypropylene filter fabrics fulfil all the requirements as fabric weight, thickness, air permeability, abrasion resistance, breaking strength, and breaking elongation. For a given filter fabric, the properties affecting the filtration characteristics of the filter fabric are air permeability, weave and sett. Air permeability and resistance to flow affect the amount of filtrate collected in unit time, where as weave is responsible for blinding tendency of the filter fabric. For all the filter fabrics woven out of 100% polypropylene yarn, there exists an optimum driving pressure at which the amount of filtrate collected is maximum and afterwards decreases.

Good mechanical properties, excellent chemical resistance and dimensional stability of new born polypropylene fibre have increased its commercial utility for manufacture of industrial filter fabrics for wet filtration.

Polypropylene, the recent synthetic fibre, is in direct competition with other natural and synthetic fibres. Because of its good mechanical properties and excellent chemical resistance the future of polypropylene in the field of industrial filtration is quite encouraging. In this paper the effect of constructional parameters on physical and mechanical properties of polypropylene filter fabrics has been investigated.