Preparation And Properties Of LMTPEE/PET Eccentric Sheath-core Composite Fibres

Low melting point composite fibers are known as"green adhesives"due to their high bonding speed,strong adhesion,non-toxic and harm Less,widely used in sofa,cushion,vamp,silk-like cotton,and other fields.Among them,the low melting point polyethylene terephthalate(LMPET)/polyethylene terephthalate(PET)sheath-core composite fiber is low cost and can be maturely prepared,but have great physical rigidity and high modulus,leading to a poor flexibility and handle of its nonwoven fabric products.Low melting point thermoplastic polyether ester elastomer(LMTPEE)is modified from TPEE.Hard polyester segment microcrystals in LMTPEE contributes to the mechanical strenghth and recoverability via forming physical cross-linking structure.The soft polyether segments,meanwhile,contributes to the flexibility of LMTPEE.Comparing with sheath-core composite fibers,eccentric sheath-core composite fibers could achieve a three-dimensional spiral self crimping structure after heat treatment,leading to a good breathability and resiliency for their nonwoven fabrics.In order to prepare low melting point composite fibers with excellent flexibility and resilience,an eccentric sheath-core composite fiber was prepared via melt spinning with LMTPEE as the sheath component and PET as the core component.The basic properties of LMTPEE raw materials,such as chemical structure,thermal properties,rheological properties,and compressive properties,as well as the effects of composite ratio,draft ratio,and heat setting temperature on the properties of eccentric composite filaments were studied.Simultaneously,eccentric composite staple fibers were prepared,which were compared with common LMPET/PET cored composite staple fibers with a melting point of 110°C and a composite ratio of 50∶50.The tensile properties of original fibers,shrinkage and compression properties of fibers after heat treatment were compared.The specific work included three parts as following:In order to prepare the LMTPEE/PET eccentric sheath-core composite fiber,chemical structure,thermal properties,recovery properties and melt rheological properties of two commertial LMTPEE products were investigated and compared.According to the results of ~1H-NMR testing,the chemical structures of the two LMTPEE raw materials are different.LMTPEE chip A is synthesized with PTA,1,4-BDO,IPA and PTMG,while LMTPEE chip B is synthesized with PTA,1,4-BDO,AA,EG and PTMG.The intrinsic viscosity of chip A is higher than that of chip B.Melting point of chip A is tested as 158°C,and that of chip B is 152°C.The thermal decomposition temperature of both chip A and chip B are higher than 350°C,and that of chip A is slightly higher than chip B.The melt index of chip A is lower than that of chip B,and its melt has weaker sensitivity to time and temperature than chip B.Compression testing results show that the compression recovery rate and flexibility of chip A are better than that of chip B.Therefore,LMTPEE chip A was selected as the cortical material for the shealth component in LMTPEE/PET eccentric composite fibers.The eccentric composite filament with LMTPEE as the sheath component and PET as the core component was prepared through a POY-DY two-step method.The effects of composite ratio(sheath to core),draft ratio,and heat setting temperature on the properties of composite filaments were investigated.The results show that with the variation of the composite ratio from 40∶60,50∶50 to 60∶40,the cross sections of composite fibers have stable eccentric morphology.The breaking elongation and dry heat shrinkage of composite fibers increase,while tensile strength,sonic velocity,melting enthalpy and crystallinity decrease gradually.At a composite ratio of 60∶40,with the increase of drafting ratio and heat setting temperature,the breaking elongation of the composite filament decreases,and tensile strength,melting enthalpy,crystallinity,sonic velocity,and dry heat shrinkage force gradually increase.However,the changes of heat shrinkage are different.The dry heat shrinkage and boiling water shrinkage of composite filaments increase with the increasing drafting ratio,but decrease with the increase in heat setting temperature.The LMTPEE/PET eccentric composite filament with a composite ratio of 60∶40,a draft ratio of 1.4,and a heat setting temperature of120°C shows the superior crimping performance after treated at 140°C for 10 minutes.Based on the optimized spinning process of the eccentric composite filament with a composite ratio of 60∶40,the LMTPEE/PET eccentric composite staple fiber was prepared.LMTPEE/PET eccentric composite staple fiber was compared with LMPET/PET sheath-core composite staple fiber in tensile properties,thermal shrinkage properties,and compressive properties.Meanwhile,the adhesive and crimping properties of LMTPEE/PET eccentric composite staple fibers under different heat treatment conditions were discussed.The results show that breaking elongation of eccentric composite staple fiber is 56.4%,and the tensile strength is 2.1 c N/dtex,while the breaking elongation of normal sheath-core composite staple fiber is 45.4%,and the tensile strength is 3.4 c N/dtex.The dry heat shrinkage of both low melting point composite staple fibers increases with increasing test temperature,and the dry heat shrinkage of the eccentric composite staple fiber is significantly lower than that of the normal sheath-core composite staple fiber at each test temperature.The compression test of a cotton board with 25%low melting point composite staple fiber and 75%conventional polyester staple fiber shows that,the initial hardness of the cotton board made of eccentric composite staple fiber is lower than that of the cotton board made of normal sheath-core composite staple fiber,and the compression recovery rate is higher.The optimize treating temperature of cotton board made of LMTPEE/PET eccentric composite staple fibers to obtain superior compression performance is 200°C,and that of LMPET/PET sheath-core composite staple fiber cotton board is 180°C.According to the adhesion test of the LMTPEE/PET eccentric composite staple fiber,the LMTPEE component turns as a viscous state,and adheres with each other when treated for 10minutes at 170°C or higher.While PET component still maintains its original state,playing a role of skeleton.According to the test results of the crimping performance of eccentric composite staple fibers,eccentric composite fibers have superior crimping performance after treated at 140°C for 15 minutes.In this paper,an eccentric composite fiber with good flexibility and compression resilience and low dry heat skrinkage was prepared using LMTPEE as the sheath component and PET as the core component.It is expected that the experimental results can provide a reference for the preparation and application of such low melting point self crimping fibers.