Preparation And Properties Study Of The Thermoplastic Poly(ether Ester)Elastomer

Thermoplastic poly(ether ester)elastomers(TPEE)can freely adjust the Shore hardness by changing the mass ratio of hard and soft segments during its synthesis process.Due to the special micro-phase separation structure between its soft and hard segments the thermoplastic poly(ether ester)elastomers(TPEE)exhibit excellent mechanical properties,impact resistance,bending fatigue resistance.In addition,the synthesized poly(ether ester)s can also exhibit good biocompatibility,chemical solvents resistance,creep resistance,high and low temperature resistance and other characteristics by selecting the appropriate monomers.It combines the softness and elasticity of rubber,the rigidity and processability of thermoplastics.All of these outstanding performance make TPEE widely used in automotive products,electrics,construction,medical equipmentand other fields.But different products require different hardness,this problem can be well overcomed by varying the ratio of hard segments and soft segments during the synthesis process or introducing a second hard segment.In this paper,a series of thermoplastic poly(butylene terephthalate)(PBT)/poly(tetramethylene oxide)(PTMG)elastomers(TPEE)with different proportions of hard and soft segments were prepared by two-step transesterification and melt polycondensation.The dimethyl terephthalate(DMT),dimethyl phthalate(DMP),PTMG(M,=1000 g/mol)and 1,4-butanediol(BDO)were selected as monomers,tetrabutyl titanate and magnesium acetate as catalysts,Irganox1098 and Sunox168 as antioxidants.The fourier transform infrared(FT-IR)and nuclear magnetic resonance(NMR)were used to characterize the structure of synthesized poly(ether ester)s,and the results showed that the hard and soft segments were freely arranged and intertwined.To explore the number average molecular weight(Mn)and polymer distribution index(PDI),we tested the poly(ether ester)s on a gel permeation chromatography(GPC),and the results showed that the number average molecular weight varied widely from 2.5 to 3.6 million,while the polymer distribution index is concentrated between 2.2 to 2.5.In order to observe the crystallization ability and dynamic mechanical behavior,we used differential scanning calorimetry(DSC)and dynamic mechanical thermal analyzer(DMTA)to analyze the synthesized poly(ether ester)s,the results showed that with the increase of hard segments content,the glass transition temperature(Tg),melting point(Tm)and crystallinity(Wc)gradually increased,while the crystallinity of hard segment itself(WcPBT)changed little.Combining with scanning electron microscopy(SEM)we observed that the following four phases were presented in the structure of poly(ether ester)s:an amorphous hard segment phase,an amorphous soft segment phase,a crystalline phase of hard segment,and a mixed amorphous phase of hard and soft segments.Its micro-crystalline domains and amorphous domains are co-continuous and interpenetrating.Furthermore,the micro-crystalline domains is non-oriented and formed physical crosslinking points.When the poly(ether ester)materials are subject to stress,the stress scattered off by the crystal structure.Tensile testing indicated that poly(ether ester)s had excellent tensile strength and elongation at break.With the improvement of its hard segment content,the tensile strength increased,and the elongation at break and permanent deformation rate at 100%elongation decreased first and then increased.Besides,the synthesized copoly(ether ester)s had good thermal stability,thermal gravimetric analyzer(TGA)showed its thermal decomposition temperature above 390 ?.In order to reduce the rate of permanent deformation and Shore hardness of synthesized copoly(ether ester)s,as well as explore its crystallization behavior,we fixed the hard and soft segments mass ratio of 50/50,introduced another hard segment poly(butylene phthalate)(PBP)in the synthesis process,and synthesized PBT-co-PBP/PTMG multiblock copolymers.The results showed that with the addition of a second hard segments PBP,the permanent deformation rate and hardness decreased obviously,with a slight decline in the degree of crystallinity.When the mass ratio of the two hard segments PBP/PBT changed from 5:45 to 10:40,the melt index and hardness gradually decreased,elongation at break and tensile strength decreased first and then increased.When the mass ratio of the two hard segments PBP/PBT was 8/42,the permanent deformation rate at 100%reached the minimum value of 30%,and had a lower Shore hardness of 37D.