Study On The Mechanism, Structure And Properties Of Rotor-Spun Composite Yarns With Filaments And Staple Fibers

In comparison with normal staple fiber yarns, the composite yarns consisting ofstaple fibers and filaments have shorter working procedure and higher output rates.They have special morphology and properties, and may be applicable to differentkinds of fabrics. In this research, filament yarns and staple fibers were combined on amodified rotor spinning frame, and the composite yarns possessed the characteristicsof both filament yarns and staple fiber yarns. This new spinning technique not onlykeeps the advantages of rotor spinning, such as high speed, high output rates, shortflow, reduced production costs, improved yarn evenness, but improves the yarnbreaking strength radically, and different kinds of rotor-spun composite yarns can beproduced by varying the spinning technique.This paper includes four parts: Firstly, the modified rotor was developed and theeffects of filament over-feed ratio, yarn twist factor and filament component ratio onthe yarn qualities were investigated; Secondly, the structure and properties ofrotor-spun composite yarns were analyzed by theory and testing methods; Thirdly, thespinning mechanism of rotor-spun composite yarns was discussed, in which the yarntension during the rotor spinning process and the effects of yarn tension on thestructure of rotor-spun composite yarns were analyzed; Finally, the spinningtechnology of rotor spun spandex composite yarns was investigated and the spinningparameters were optimized by the method of orthogonal experiment.The modified rotor that can feed filaments directly was developed at first. The filament yarn passed straight through the filament guide tube and was drawn into therotor freely by suction, in which the filament yarn was combined with the staple fiberstrand to form the composite yarn. The cotton fibers and polyester filaments wereused to produce different kinds of rotor-spun composite yarns, and the effects offilament over-feed ratio, twist factor and filament component ratio on the spinningprocedure and yarn qualities were investigated respectively. The adjustment of thefilament over-feed ratio can lead to the changes in filament tension and has greatinfluence on the appearance, structure and properties of composite yarns. As thefilament tension increases with decreasing filament over-feed ratio, the filamentmoves from the surface into the center of the composite yarn, and the tensileproperties, irregularity and hairiness of composite yarns change accordingly. The yarntwist factors have significant effects on the morphology, measured twist, twistingefficiency and the properties of rotor-spun composite yarns at two filament over-feedratios. With the increasing yarn linear density, the filament component ratio incomposite yarns decreases gradually, and the appearance and properties of compositeyarns change accordingly. In comparison with the normal rotor-spun yarns under thesame linear density, the breaking tenacity of composite yarns increases over 12ï¼….On the basis of spinning technique analysis, the structure and properties ofrotor-spun composite yarns were investigated by theory and testing methods. Thecomposite yarn structure depends on the difference between the filament tension andthe tension of staple fiber strand, and this difference has remarkable effects on thepath way of filament in the composite yarns. By the EIB and Questar Hi-scope videomicroscope system, the surface structure of normal rotor-spun yarns and compositeyarns were observed. In comparison with the normal rotor-spun yarn, the morphologyof wrapper fibers near the composite yarn surface is tighter and clearer. When thefilament over-feed ratio changes, the appearance and structure of rotor-spuncomposite yarns are different. When the filament over-feed ratio is high relatively, thefilament tension is less than the tension of staple fiber strand, so the filament yarnwraps over the staple fiber strand and follows a helical path; As the filament tensionincreases with decreasing filament over-feed ratio, the filament moves from the surface into the center of the composite yarn, and the filament relative radial positionr, filament twist, composite yarn twist, twist deviation, yarn diameter will changeaccordingly. The tensile properties of rotor-spun composite yarns not only depend onthe load-extension curves of each component, but also have great relations with thestructure of composite yarns, and the filament over-feed ratio has great influence onthe tensile process and morphology of yarn breakage ends. The tensile properties,irregularity and hairiness of rotor-spun composite yarns are improved compared withthe normal rotor-spun yarns under the same technique parameters.The yarn tension during the rotor spinning process and the effects of yarn tensionon the structure of rotor-spun composite yarns were investigated. In spinningrotor-spun composite yarns, there are two yarn formation points, the staple fiberstrand and the composite yarn. As the filament tension changes with varying filamentover-feed ratios, the formation point of the composite yarn is moved between thecollecting surface and the doffing tube, and the tension of staple fiber strand at theformation point of the composite yarn is different. This difference between thefilament tension and the tension of staple fiber strand has remarkable influence on thestructure and properties of rotor-spun composite yarns. The main factors influencingon the tension of staple fiber strand at the formation point are listed as following: thelocation of formation point, the linear density and twist level of staple fiber strand, therotor speed and diameter, the navel material and specification, et al. When thespinning parameters of staple fiber strand are invariable, different kinds of rotor-spuncomposite yarns can be produced by control the filament tensions, and the filamenttension can be controlled by adjust the filament over-feed ratio in spinning process.The rotor-spun spandex composite yarn was developed to meet the market needsof elastic yarns. The spinning technology of rotor-spun spandex composite yarns wasinvestigated; and the spinning parameters were optimized by the method oforthogonal experiment. The effects of rotor speed, spandex draft ratio, twist factor onthe properties of rotor-spun spandex composite yarns were analyzed, and the effectsof spandex draft ratio is the most significant. The optimum spinning technology wasobtained by 49300 r/min rotor speed, 4.5 spandex draft ratio and 500 twist factor. Under the optimum technology, the rotor-spun spandex composite yarn and thenormal rotor-spun yarn were produced and compared. The integrated properties ofrotor-spun spandex composite yarn are improved and can be applicable to the weave.