Cooperative Modification Of Low Melting Point Polyester And Its Fiber Hot Melt Bonding Properties By Organic And Inorganic Components

Low melting point polyester is a kind of modified polyester,the melting point range is generally about 90～240℃.The fiber with hot melt bonding can be prepared by melt spinning of polyester with low melting point,which is an excellent basic material for non-woven fabric.At present,the modification of low melting point polyester is mainly through chemical methods to introduce the third and fourth components in the synthesis stage for copolymerization,destroy the regularity of polyester molecular chain,reduce the intermolecular force,so that the random increase,melting enthalpy decrease to achieve melting point reduction.However,the regularity of macromolecular chains of polyester is destroyed,and the crystallization capacity of low-melting polyesters is often poor,and some even do not crystallize.The glass transition temperature is also low,and the strength of spun fibers is low,which limits the use of low-melting polyesters to a certain extent.Therefore,on the basis of the existing multi-component copolymerization,this paper designs the preparation of low melting point polyester by introducing the cooperative modification of organic and inorganic components,and comprehensively regulates the melting point,crystallization and bonding of the prepared low melting point polyester.In this paper,a series of low melting point polyester was prepared by adopting quaternary copolymerization,selecting the modified system of aromatic dibasic acid and aliphatic diols.Firstly,the addition ratio of m-phthalic acid was selected as the variable,and the types of diols and inorganic materials were screened.On this basis,the structure and thermal properties of series modified low melting point polyesters were analyzed by ¹H NMR and differential scanning calorimeter（DSC）.The results show that when the molar ratio of 1,4-butanediol to ethylene glycol copolymerization is 2:8,the molar ratio of m-phthalic acid increases from 5%to 20%,and the melting point of modified polyester decreases from 205℃to 195℃and then becomes amorphous polymer.The melting point of long carbon chain diol modified polyester also decreased significantly.According to Tm=ΔH/ΔS,the melting enthalpy of modified polyester increased obviously after adding 0.5%Si O₂ inorganic component.At the same cooling rate,the sample with Si O₂inorganic component showed a crystallization peak,indicating that the inorganic component of Si O₂significantly improved the crystallization rate and crystallinity of polyester,which was consistent with the data characterized by XRD.The adhesive properties of modified polyester were characterized by universal testing machine.It was found that the adhesion properties of modified polyester were decreased by adding 2.18MPa of M-phthalic acid and aliphatic carbon chain diols.The bonding strength of modified polyester with the introduction of Si O₂ inorganic components increased from 1.97Mpa to 2.18Mpa,mainly because aromatic dibasic acid and long carbon chain diols destroyed the regularity of polyester molecular chain,resulting in the decrease of intermolecular force and thus the bonding strength.The inorganic component of Si O₂ improves the crystallization property of low melting point polyester,thus improving the bonding strength of polyester.Scanning electron microscopy was used to observe the tensile fracture of the modified low melting point polyester and polyester cloth after bonding.The results showed that the tensile fracture was caused by the failure of cohesion,and the bonding property was significantly affected by the intermolecular force of the modified polyester itself.By analyzing the rheological properties of a series of polyester samples,it is found that the shear viscosity of modified polyester decreases with the increase of shear rate,which is a typical pseudoplastic fluid.When the content of M-phthalic acid increased and the introduction of long carbon chain diols or Si O₂ inorganic components,the apparent viscosity at different temperatures showed a decrease trend,and the non-Newtonian index increased.The inorganic components of Si O₂ and m-phthalic acid played a synergistic effect in improving the fluidity of polyester melt.According to the structural viscosity index,the melt spinning temperature of low melting point polyester is about 255℃.The non-isothermal crystallization kinetics data showed that t_1/2decreased significantly after the addition of Si O₂ inorganic components,indicating that the inorganic components of Si O₂ played the role of crystallization nucleating agent and accelerated the crystallization rate of low melting point polyester.The mechanical properties and bonding properties of the spun fibers were characterized.It was found that the changing trend of bonding properties of the fibers was consistent with that of the polyester with low melting point.Both m-phthalic acid and long carbon chain diols reduced the mechanical properties and bonding properties of the fibers.The addition of Si O₂ with a mass fraction of 0.5%has a positive effect on the mechanical properties and bonding strength of the fibers.