Synthesis And Study On Properties Of The Novel Thermoplastic Polyester Elastomer

Thermoplastic polyester elastomer, also named after TPEE, is an environment-friendlyand reusable thermoplastic molding elastomer material, which has been developed in recentyears. To some extent it may solve the non-reusable problem of rubber products. The novelthermoplastic polyester elastomer, featuring poly(trimethylene terephthalate)(PTT) with agood elastic recovery itself as hard segment, attracts much more attention than the commercialpoly(butylene terephthalate)(PBT)-type TPEE.In this paper, the novel TPEE was synthesized using terephthalic acid(PTA),1,3-Propanediol(1,3-PDO) as raw materials, polytetrahydrofuran(PTMG) as the thirdmonomer by means of direct esterification-prepolycondensation-final polycondensationthrough a5L stainless steel reactor. The chemical structures of products were characterized byinfrared spectra; the intrinsic viscosity was determined with an Ubbelohde viscometer; the endcarboxyl content and chromaticity indexes of samples were detected by photometric titratorand chromatography; the spherulite morphology was observed by Polarized opticalmicroscopy(POM); the crystallization properties were analyzed by Differential scanningcalorimetry(DSC); the thermal degradation was studied by TGA and the tensile propertieswere tested with a testing machine.The FTIR spectra of TEEEs showed that the samples were expected target products;while the intrinsic viscosity and molecular weight indicated that all the products to the level ofpolymer were in line with requirements. By the analysis and discussion of the basic physicalparameters and factors affecting the synthesis process, we could sum up the optimum reactionconditions: PDO:PTA=1.7:1(mol ratio); the esterification temperature is235-237℃(Tmax=242℃) under the pressure of0.25-0.30MPa for about3h; theprepolycondensation temperature is245-250℃under the pressure of0.1MPa-100Pa forabout45min; the final polycondensation temperature is257-262℃(Tmax=265℃) under thepressure of20Pa for about2h. By the observation of POM, we detected that the spherulitemorphology changed with different PTMG contents and crystallization temperatures.DSC results indicated that the characteristic temperatures including the glass transition,melting and thermal crystallization temperature, were affected greatly by the content of the third monomer PTMG. The nonisothermal crystallization kinetics of samples were describedwith modified equation of Jeziorny, Ozawa and Mo. The value of exponent n with the rangefrom0.9to2.8through Jeziorny method showed a more complex crystallization process. Theresults by Mo method that F(T) increased with Xtimproving informed that the crystallizationrate was decreased with an increased Xt. Whereas it is the curves which were not all straightthat make it not suitable for describing the nonisothermal crystallization kinetics ofPTT-PTMG copolymers.The results of TGA showed that TPEEs with more PTMG content had lower thermaldegradation temperature than pure PTT, suggesting that the thermal stability of copolymerswere worse. The tensile testing indicated that PTT-PTMG copolymers had smaller tensilestrength than pure PTT, while its increasing elongation was good for the outstanding elasticityof rubber.