Synthesis, Structure And Properties Studies Of Poly(Ethylene Succinate), Poly(Ethylene Adipate) And Their Copolymers

In the present work, we prepared biodegradable poly(ethylene succinate)(PES), poly(ethylene adipate)(PEA) and their novel copolyesterspoly(ethylene succinate-co-ethylene adipate)(P(ES-co-EA)). Crystal structure,thermal stability, crystallization kinetics, and morphology of P(ES-co-EA)copolyesters with the ethylene adipate (EA) comonomer composition rangingfrom5.1to15.3mol%were studied in detail with WAXD，TGA，DSC andPOM and compared with those of PES. It is found that P(ES-co-EA)copolyesters have the same crystal structures as neat PES; however, thecrystallinity is slightly smaller in the copolyesters than in neat PES. Both neatPES and P(ES-co-EA) copolyesters have high thermal stability; moreover, thepresence of EA composition has improved significantly the thermal stability ofP(ES-co-EA) compared with neat PES. Increasing the EA compositionreduces apparently glass transition temperature, melting point temperature, and equilibrium melting point temperature of P(ES-co-EA). The overallcrystallization rates of P(ES-co-EA) decrease with increasing the EAcomposition and crystallization temperature; however, the crystallizationmechanism remains unchanged for both neat PES and P(ES-co-EA). Theeffects of the EA composition and crystallization temperature on thespherulitic morphology and growth rate of P(ES-co-EA) were alsoinvestigated. Both neat PES and its copolyesters show a bell shape for thegrowth rates in a wide crystallization temperature range despite the EAcomposition. All the samples exhibit a crystallization regime II to III transition;furthermore, increasing the EA composition shifts the crystallization regimetransition temperature to low temperature range.Meanwhile, the crystal structure, thermal behavior, melting behavior,thermal degradation analysis, overall isothermal melt crystallization kinetics,and spherulitic morphology of biodegradable poly(ethylene adipate)(PEA)and its copolymer poly(ethylene adipate-co-5mol%ethylene succinate)P(EA-co-5mol%ES) were investigated in detail. The incorporation of EScomonomer unit does not change the crystal structure of P(EA-co-5mol%ES)compared with that of neat PEA. Double melting behavior has been found forboth neat PEA and P(EA-co-5mol%ES) after isothermal crystallization, whichcan be explained by the melting, recrystallization, and remelting mechanism.The equilibrium melting point of P(EA-co-5mol%ES) is reduced obviouslybecause of the incorporation of the ES composition. Both neat PEA and P(EA-co-5mol%ES) copolymer show good thermal stability. Isothermal meltcrystallization kinetics of neat PEA and P(EA-co-5mol%ES) copolymer wasstudied in a wide crystallization temperatures range and analyzed by theAvrami equation. Crystallization mechanism of P(EA-co-5mol%ES) does notchange, but the overall crystallization rate of P(EA-co-5mol%ES) is reducedwith increasing crystallization temperature and the ES content. Bandedspherulites in neat PEA and P(EA-co-5mol%ES) have been observed only in anarrow temperature range,(32＜Toc＜38C) and (28＜Tc＜34oC), respectively.