Structure And Properties Changes Of Polyester Industrial Yarns Under Application Conditions

Polyester(PET)fiber has been widely used in industrial fields such as tire cord and airbag due to its high performance,such as high tenacity,high modulus,dimension stability and heat-resistance.In this paper,structure and properties of PET fibers from different processes were studied.To illustrate the difference of performance caused by polyester industrial yarns' structural factors,wide-angle X-ray diffraction(WAXD),small-angle X-ray Scattering(SAXS),sonic velocity,FTIR and static/dynamic mechanical properties testing was employed to characterize the structure and properties.Furthermore,the structure and properties of PET industrial fibers under the condition of stress,temperature and stimulated seawater were studied to evaluate the application properties.Firstly,the relationship between structure and properties of PET industrial fibers from different processes were discussed.The results show that the High Tenacity(HT)fiber has high crystallinity(37%),large grain size and perfect crystal,which is the dominant factor in producing high-strength(7.5 cN/dtex).But the creep resistance is worst and creep rupture will occur when the strength is greater than 50%of the breaking strength(3.7 cN/dtex)for a long time test.The High Modulus and Low Shrinkage(HMLS)fiber obtained by high-speed spinning,mild cooling conditions is good for fiber orientation and crystallization.In addition,the drawing temperature and drawing ratio is high,making the final crystallization degree highest(37%)and;a low degree of amorphous orientation(84%),low shrinkage(3.7%),and good dimensional stability.The creep rupture occurs when the stress is greater than 80%of breaking strength.The High Tenacity and Low Elongation(HTLE)fiber with small elongation(14%)and high orientation in amorphous regions(9I%)due to the high drawing ratio and intense heat setting,so its elongation is small(14%)and creep rupture occurs when the stress is greater than 80%of breaking strength.Secondly,the structure and properties of PET fibers after heat treatment under constant length status were studied.The research results show that for High Tenacity yarns,the tenacity,modulus,Lase-5 and Tg increased after heat treatment,especially when the treatment temperature is higher than Tg.And excellent mechanical properties and dimension stability are also obtained.Thirdly,the fatigue property was studied with the effect of the stimulated stress and temperature.The analytical results indicate that mechanical properties and dimension stability will decrease when it is used under high temperature,especially for High Tenacity and Low Elongation yarns(HTLE).Finally,the structure and properties of PET fibers after immersed in stimulated seawater were studied.The results indicate that High Tenacity yarns(HT)show long life in seawater due to the increase of mechanical properties and dimension stability after immersed in seawater.