苹果酸基脂肪共聚酯反应性共混制备超韧聚乳酸共混物

Preparation of Super-tough Poly(lactic acid)Using Malic Acid-based Copolyester via Reactive Blending

通过反应性共混使聚乳酸(PLA)与增韧剂原位生成接枝共聚物,可增强界面相互作用,有效提高不相容共混物的韧性.本研究将聚(癸二酸/苹果酸-co-丁二醇/丙二醇)酯(PBSePM)在六亚甲基二异氰酸酯(HDI)作用下与PLA反应性共混制备了PLA/PBSePM共混物.重点研究了HDI对PLA/PBSePM共混物的力学性能、流变行为、相形态和熔融结晶行为的影响.结果表明,HDI的加入可以显著提高共混物界面相容性和韧性.随着HDI用量的增加,反应程度加剧,共混物的凝胶分数和复数黏度增加,共混物的相界面变模糊,相容性明显变好.在低HDI含量时,基质中存在空穴,可以耗散大量的能量.随着HDI含量进一步增加,共混物的相界面几乎完全消失,界面黏附力过强,韧性有所下降.添加2.9 wt%和4.3 wt%的HDI,共混物的缺口冲击强度大于80 kJ/m^(2).随着HDI加入,共混物的结晶能力下降,玻璃化转变温度和冷结晶温度升高,熔融焓减小.

Reactive compatibilization is an efficient way to enhance the interfacial adhesion and improve the toughness of the blends.In this study,a fully bio-based aliphatic polyester(PBSePM)containing malic acid moiety was synthesized.Then,super-tough poly(lactic acid)(PLA)/malic acid-based aliphatic polyester blends(PLA/PBSePM)were prepared by reactive blending in the presence of hexamethylene diisocyanate(HDI).The reactive blending behavior was investigated by torque,proton nuclear magnetic resonance(1H-NMR),Fourier transform infrared spectroscopy(FTIR),and wide-angle X-ray diffraction(WAXD).The effects of HDI addition on the tensile properties,rheological behavior,phase morphology,and melting and crystallization behavior of PLA/PBSePM blends were studied by dynamic rheometer,scanning electron microscopy(SEM),and differential scanning calorimetry(DSC).The results showed that the gel fraction and complex viscosity of the blends increased with the increase of the amount of HDI.In the reactive blending processing,HDI reacted with PBSePM and PLA.The in situ PLA-PBSePM copolymer was formed,which acted as a compatibilizer to enhance the interfacial adhesion between PLA and PBSePM.With the increase of HDI,the phase interface of the blends became blurred,and the compatibility was significantly improved.The cavities emerged in the tensile fracture surfaces and impact fracture surfaces of the reactive blends,which would dissipate energy during the stretching and impacting evolution.With the increase of HDI content,the interfacial adhesion was too strong,which delays the occurrence of matrix yielding;hence,the toughness decreased.All the blends presented a great tensile toughness with an elongation at break higher than 300%.The impact toughness of the blends significantly increased first and then slightly decreased with the increasing amount of HDI.The notched impact strengths of all the reactive blends are higher than 53 kJ/m^(2),indicating a super-tough behavior.The highest notched impact strength of 81.5 kJ/m^(2) was achieved while adding 2.9 wt%HDI.With the increase of HDI,the crystallization capacity of PLA decreased,the glass transition temperature and cold crystallization temperature increased first and then almost remained unchanged;meanwhile,the melting enthalpy decreased.This study suggested that incorporated malic acid into aliphatic polyester and then reactive blending would be an efficient way to obtain bio-based super-tough PLA materials.