The Structure And Properties Of Differential Shrinkage Multi-filament Air-jet Texturized Yarn

The rapid developing of textured yarns in the last semicentury, especially the appearing of air-jet texturing technique made the woollike yarn become a success to be achieved by textured yarns. In the latest decade or so, the single texturing method kept growing up to the compound texturing method which was considered the symbol of a well-rounded period of woollike yarn technique. When an air-jet textured yarn made from differential-shrinkage multifilament was heated , the differential-shrinkage filaments air-jet multi-texturized yarn (VAT for short later in this paper ) was manufactured. It had been found that, the VAT would sever good woollike effect, and be worthy of a further researching.There are four items on the forming of textured yarn, first, multi-differential properties ingredients & laminated structure was the basic structural feature of short fiber yarn, at the same time the primary purpose of woollike yarn processing as well, while the filament served the suitability for texturing; second, the classic spun was designed according to a entropy reducing process, but the texturing run a completely inverse direction; third, a new notion named multi-texturing from Wang Shangyuan was mentioned; at last, an optimization model and the terms for the making of a primary texturing method was served.There are two methods on the preparation of differential-shrinkage multifilament, one, the same spinneret method, and the other, blending method. The same spinneret method was discussed in detail by analyzing the forming process. The blending method was used here, where the differential-shrinkage multifilament was manufactured by direct heat treatment to the high-shrinkage polyester filament used as raw material. This simple, easy to be controlled blending method could serve excellent samples. Three primary structural features of the textured yarn were discussed: skin-core structure, disordering structure and snarling structure.Both air-jet texturing and differential shrinking texturing could transfer different filaments and their different segments in and out, this made the skin-core structure come into being. At the same time, its parameters and structure model, as well as its effect on the textured yarn properties were discussed.On disordering structure, the forming of textured yarn is such a reverse process to that of classic yarn, where the filaments and their segments aggregation were turned from ordered to disordered, from regular to irregular, namely, a entropy increasing process. A density function standing the situation of filaments' dispersing in space was served. Then the disordering structure was characterized, meanwhile, its testing methods were designed.On snarling structure, it was found that the snarling degree of air-jet texturized yarn go directly with its bending rigidity. In further researches, a particle-spring model was used to describe mechanical theory of snarling structure, as well as its notion, characterization and testing was done.On the VAT structure, first, the VAT forming process was described, and then structured model was discussed and the features of multi-ingredient VAT structure were analyzed. Three groups of structure testing had been done: 1^st, skin-core structure parameters testing including appearance average diameter, general diameter and height of loop; 2^nd, disordering degree test where the AT( air-jet textured yarn) and VAT was chose as samples; 3^rd, snarling degree testing, also to AT and VAT. Generally speaking, VAT was made from differential shrinking textured AT, so its structure was also built up on the basis of air-jet texturized yarn's, where the both skin-core structure and disordering structure were enhanced. This improved its appearance and handle in turn, then a better woollike effect could be expected. But on snarling structure, the differential shrinking texturing worked in two ways: one, the interspace of a snarling structure unit would become narrow while the filaments were growing fat. And then the snarling structure was enhanced, and a higher snarling degree was got; on the other hand, the bounding spot might loose or even completely disappear when filament slipped against another one. Both of these two possibilities severed the VAT an asymmetry snarling structure distribution, as well as a bigger CV of bending rigidity.On the morphological structure of VAT, an uniform notion of bulk was built up, and many kinds of yarn's bulk threshold were tested; Uster4,EIB and YG172 hairiness tester was used in VAT hairiness test on the basis of projection counting method. For the YG172 results were too far from that of Uster4 and EIB, the YG172 hairiness tester was not a good choice in textured yarn hairiness testing; for textured yarn, the appearance evenness(EIB) and mass evenness(Uster) was all different.On the VAT thermo shrinking dynamics, to yarn especially to the VAT, it is the first time that a thermo shrinking dynamic analysis was done. The VAT boiling water shrinking mechanism was analyzed firstly, and then the basic thermo shrinking dynamics basic theory was served, as well as a differential shrinkage filaments boiling water shrinking dynamic testing was done. According to viscoelasticity theory, a exponential equation was built, which match the dynamic curves well. The testing results were used in discussion on the VAT boiling water shrinking dynamic properties, and then a further structure analysis was followed. At last, to all the different filament ingredients used in VAT, DMA and DSC testing were done.On the woollike effect testing, based on a great number of experiments, linear density, bulk, hairiness index, appearance evenness CV, luster, breaking strength and elongation, bending rigidity, remnant boiling water shrinkage, and structure stabilization, totally nine parameters as well as their testing method were assigned.