| More than80percent of spun yams are produced by ring frame in the world; there are almost100million ring spindles in Chinese textile industry. Hairiness is one of the most important problems for yarn manufature because excessive hairiness will cause sever weaving abrasion and shed clinging for yarn weaving, pilling and uneven dyeing problems for resultant fabric. Therefore many novel ring spinnig methods are applied to reduce yarn hairiness such as pneumatic condensed spinning, mechnical condensed spinning, sirospinning, solospinning. These novel spinning methods can enhance fiber-strand control via various conventional external mechnical actions; however there still exists inadequacy for some of them. For example, sirospinning and solospinning have a limited application and are not suitable for high count staple yarn production; pneumatic condensed spinning (PCP) has been widely recognized as the most expensive method due to its high intallation and operation costs. Furthermore, PCP contributes very little to the improvement of spun yarn hairiness during the ring spinning of high rigidity or hi-crimp staple fibers. Different from aforementioned methods, this paper established soft and smooth ring yarn production theory on a basis of mechanism of moisture and temperature influence on cellulose textile fibers’ tensile properties. Soft and Smooth Ring Spinning (denoted as SSRS) devices were also well developed to conduct a successful production of Cotton, Ramie and Rayon smooth yarns.Thermal properties of cellulose fibers were characterized by using TD-FTIR and TG-DSC-QMS. TD-FTIR analysis results indicated that strong-bond-water of fiber evaporated gradually without obvious thermal degradation for cotton and ramie when they were heated under a rising temperature from25℃to210℃; Rayon cellulose fiber suffered a strong-bond-water loss without chemical structure change when it was exposed at a temperature lower than150℃. TG analysis results indicated that cotton mass loss at30-200℃corresponded to strong-bond-water evaporation, loss at250-600℃corresponding to thermal degradation; ramie mass loss at30-250℃corresponded to strong-bond-water evaporation, loss at280-600℃corresponding to thermal degradation; Rayon mass loss at30-220℃corresponded to strong-bond-water evaporation, loss at240-600℃corresponding to thermal degradation. According to cotton DSC curve, the fastest water losss occurred at65℃while the fastest mass loss due to thermal degradation ocured at371.2℃. Four endothermic peaks in ramie DSC curve could be explained as follows:peak1corresponded to strong-bond-water evaporation; peak2was ascribed to non-cellulose material degradation and cellulose softening; peak3corresponded to cellulose degradation; peak4was ascribed to secondary degradation. Rayon DSC curve showed that the fastest strong-bond-water evaporation occurred at63℃. QMS results showed that cotton fiber released NO, CO2, CH4, and C3H4during high-temperature decomposition, ramie fiber releasing O2, NO, C4H7, CH4, C4H3, C3H6and C3H3.Self-built heating devices were applied to study effect of temperature on cellulose fiber static tensile properties. Results showed that cotton fiber initial modulus decreased first, then increased slightly at90℃, afterwards decreased obviously as the heating temperature rised. However cotton fiber break force and elongation decreased gradually as the temperature increased. Ramie fiber initial modulus, break force and elongation decreased abviously as the heating temperature increased. Wetting treatment could reduce ramie fiber initial modulus, which was because water could weaken hydrogen bonding between cellulose macromolecules. Ramie fiber tenacity increased after wetting treatment; this could be ascribed to the increasing of inner macromolecules’parallelisms and improving of fiber inner structure to decrease weak regions during the wetting drawing process. Moreover, ramie fiber showed a large decrease of initial modulus and break-force and an increase of break-elongation for drawing in hot vapor condition.DMA-242type dynamic mechanical thermal analysis instrument was used to test cellulose fibers’dynamical tensile properties. Results indicated that severe vibrations exsisted for single cotton fiber E’-T and tanδ-T curves; while single ramie fiber E’T and tanδ-T curves were much smoother. This resulted from that cotton fiber had natural convolution while ramie fiber was relatively straight. At low temperature, wet ramie storage modulus was lower than that of dry one, which indicated that wetting could reduce the rigidity of ramie fiber as hydrogen bonding weakened between cellulose macromolecules. DMA results of cotton and ramie fiber bundles were consistent in that the bundle of4fibers had a lower storage modulus than that of2fibers. This could be explained as follows:higher twist factor in the bundle of4fibers would inhibit more elastic recovery by increasing the friction between fibers; furthermore, more fibers in the bundle meant larger contact surface to result in higher loss modulus and lower storage modulus.On the basis of the mechanism of moisture and temperature influence on cellulose textile fibers’ tensile properties, Soft and Smooth Ring Spinning (denoted as SSRS) method was firstly established as follows:a hot surface was applied to contact and soften fibers in the spinning trangle during the ring spinning process; softened yarn hairs could be easily re-spun into yarn stem under a synergitic action of contact gripping force and twisting tortional force; then a smooth yam was produced as its surface hairs were largely reduced. Theoretical analysis of SSRS indicated that the longer the hair was, the easier the hair could re-spun into yam stem; a more sever softening of fibers meant a larger yam hairiness reduction; a longer yam contacting hot surface resulted in a larger hairiness reduction; a lower spinning speed resulted in a larger hairiness reduction; a nearer of the contact surface to the front nip line caused a larger hairiness decrease. Fiber accumulation in a short distance of yarn stem during hairiness reduction should be suppressed to avoid deteriorated yarn evenness.Efficient apparatus was successfully developed for soft and smooth ring spinning of cotton, ramie and rayon fibers respectively. Results showed that SSRS apparatus could eliminate60%3mm hairs of conventional cotton yarns, and cotton smooth yarn (denoted as "cotton Sm") produced by SSRS had less hairiness, higher strength and non-deteriorated unevenness compared with the corresponding conventional ring cotton yarn. Ramie Sm with a less hairiness was also successfully manufactured by SSRS apparatus; in specialty,70.45%3mm hairs were reduced during ramie SSRS.60%3mm hairs were eliminated by SSRS apparatus during the rayon spinning; thus, rayon Sm was much smoother than the conventional rayon yarn.The influence of key SSRS parameters on spun yarn properties was also investigated. Results showed that the nearer of SSRS apparatus to the spinning triangle resulted in higher hairiness reduction ratio and higher strength improvement of yarn; however the yarn unevenness showed a very slight deterioration as the fixed SSRS apparatus was apt to cause unexpected drawing due to dynamical spinning tension when it contacting a more loosened yarn section. Fiber mass concertration in a short distance to deteriorate unevenness could be avoid by delivering yarn to SSRS apparatus surface in a right angle of (45-60)°with the entrance edage of SSRS apparatus; Under situation, much better hairiness and tensile properties of Sm yarn were still secured. Among such three types of contact surfaces as plane, concave and micro-convex, the micro-convex hot contact surface produced Sm yarn with the least hairiness. The hot contact surface with a higher friction would reduce more hairs, yet lead to a worse unevenness of yarn during the SSRS process. A tighter contacting of spinning strand with the hot surface meant a higher friction and more twist block; therefore the corresponding spun Sm yarn had less hairiness and worse unevenness. Under the same spinning paramenters, the thiner roving used to produce Sm yarn, the longer the Sm yarn information zone would be; thus SSRS apparatus could reduce more hairs by nesting the fiber ends in yarn stem more tightly during the spinning of a thinner Sm yarn. Soft and Smooth Ring Plying (denoted as SSRP) method was firstly introduced as follows:a hot and wetting surface was applied to contact and soften single yarns in the spinning trangle during the ring plying process; softened hairs of single yarns could be easily re-spun into yarn stem under a synergitic action of contact gripping force and un-twisting tortional force; then the singles were combined to twist with each other to further trap reduced hairs into plied yarn structure. Theoretical analysis of wet SSRP indicated that wet SSRP could reduce hairiness and improve unevenness of plied-yarn as wet SSRP would avoid fiber mass concertration to deteriorate yarn unevenness when reducing yarn hairs during the hot-wetting plying. Furthermore, self-built SSRP apparatus was employed to the plying of two Ne80s single cotton yarns for validation of the SSRP theoretical analysis. Results indicated that smooth plied cotton yarn produced by self-built SSRP apparatus processed much fewer hairs, higher tenacity and better unevenness than the convetional ring plied cotton yarn. |
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