Crystallization Behavior Of Plla/Pea Blends And P(Es-co-Esub)Copolymers

In this work, a low-molecular-weight polyester poly(ethylene adipate)(PEA) was synthesized then blended with poly(L-lactide)(PLLA). Fully biodegradable polymer blends were prepared by solvent cast. Basic thermal behavior, crystallization behavior and mechanical properties of PLLA/PEAblends were investigated by different methonds, which including differential scanning calorimetry (DSC) and tensile test. The presence of PEA reduced glass transition temperature (7g), nonisothermal crystallization peak temperature (Tc), equilibrium melting point temperature (Tmo) while induced crystallization enthalpy (△Hc). Spherulitic morphologies of PLLA/PEA blends were similar with that of neat PLLA whereas spherulitic radius of PLLA/PEA blends were slightly lager than that of neat PLLA. These results indicated that the presence of PEA accelerated crystallization of the blends, however, not changed crystallization mechanism. The elongation at break of PLLA was improved significantly by adding PEA, although tensile strength and Young’s modulds decreased.The other part of this work was synthesized a series of copolymers with ethylene succinate and ethylene suberate monomers poly(ethylene succinate-co-ethylene suberate)(P(ES-co-ESub)) by two-step melt polycondensation method and investigated basic thermal behavior, crystallization kinetics and spherulitic morphology of P(ES-co-ESub).Tg,Tm,△Hm,△Hc, Tmo and degree of crystallinity were decreased with ESub monomer increased. The spherulite growth rate versus temperature shown a bell shape for neat PES and P(ES-co-ESub), however, spherulite growth rate decreased with ESub content increased when at a same crystallization temperature. As for homopolymer poly(ethylene suberate)(PESub), thermal stability, mechanical properties and degradable behavior were investigated in detail. The results revealed that PESub has good thermal stability and has one-step thermal degradation mechanism. Activation energy of thermal degradation calculated by Kissinger plot was207.0kJ/mol while by OFW plot was213.5kJ/mol. PESub has good mechanical properties with elongation at break was about281.6±16.3%. The hydrolytic degradation mechanism was proved to be surface erosion and amorphous region of PESub was degraded prior to crystalline region.