physical characteristics of cotton/polyester core spun yarn made

AUTEX Research Journal, Vol. 9, No1, March 2009 © AUTEX2500200015001000core yarn energy to breakPoly/RFpoly/AJwere no significant differences in U% values among thedifferent core spun yarns made on the ring frame. It is clearfrom Table 6 that air-jet yarns have lower U% values than ringcore yarns because they have more parallel fibres at the corethan ring core yarns. It was also observed that crimped ordrawn yarns at the core do not contribute to yarn uniformity.3.7. Total imperfection500030/DR44/DR70/DR3.5. Core yarn initial modulus30/CR44/CR70/CR100% cFigure 6. Core yarn energy to break.The initial modulus of different core yarns was tested on anInstron machine. From the results it was observed that thecore yarn initial modulus was mostly influenced by the initialmodulus of the filament yarns at the core, the yarncharacteristics, and characteristics of the spinning systems.It was seen that a high initial modulus filament at the coreprovided a higher initial modulus of the core yarn. For example,44 den. yarn had a high modulus, which directly shows thehigher modulus of the core yarn. The low modulus of yarn like70 den. polyester yarn was also influenced by the low modulusof the final core yarn. Because there were more straight fibresat the core of air-jet yarns (70 den.), the initial loads wereimmediately shared by the filaments and therefore the initialmoduli of those yarns showed higher values.The total imperfection of different core yarns was tested on aUT4 evenness testing machine. From the results it wasobserved that there were no clear trends in total imperfectionvalues within the ring frame and air-jet yarns. But air-jet coreyarns showed minimal imperfection values compared to ringspuncore yarns. When the percentage of filaments wasincreased at the core it was observed that imperfection valueswere reduced in ring-spun core yarns, which was not observedin air-jet core yarns.25020015010050030/DR44/DR70/DR30/CR44/CR70/CR100%CPoly/RFpoly/AJCore yarn initial modulasFigure 9. Total imperfection of different core yarns.5045403530252015105030/DR 44/DR 70/DR 30/CR 44/CR 70/CR 100%CFigure 7. Core yarn initial modulas.U%Poly/RFpoly/AJ3.8. Evaluation of percentage coverage of core yarn byscanning electron microscope (SEM)Cross-sectional views of the final double yarns were observedby scanning microscope to estimate the extent of cover ofcore filament yarns by the sheath cotton fibres. In this study,drawn core yarns and crimped core yarns showed similartypes of properties. Moreover the chance of filaments comingout at the surface is greater in crimped core yarns than indrawn core yarns. However, because of resource constraints,only cross-sectional views of crimped core yarns wereobserved.1098765432103.6. U%30/DR44/DR70/DR30/CR44/CR70/CRFigure 8. U% values.100%CPoly/RFpoly/AJThe U% of different core yarns were tested on a UT4 evennesstesting machine. From the results it was observed that thereThe results are shown in Table 2 and the respectivephotographs are shown in Figs. 10–16.Table 2. Evaluation of percentage coverage of core yarn.Description 30/CR/A 44/CR/A 70/CR/A 30/CR/R 44/CR/R 70/CR/R 100%CActualcover bycotton100% 100% 98% 100% 100% 98% 100%It was observed that polyester core filaments were placedexactly at the centre with 30 den. and 44 den. yarns in ring andair-jet systems. It was observed that in the case of 70 den.polyester yarns at the core of air-jet and ring core yarns, therewas 98% cover of the filament by the cotton. It can beconcluded that when finer denier yarn was inserted at thecore and represented only a 15–25% proportion, it was wellcovered by the cotton sheath fibres. When the core percentagewas 40%, the sheath cotton could not give 100% coverage ofthe core, but the cover was reasonably good.http://www.autexrj.org/No1-2009/ 0305.pdf17