聚L-乳酸/聚(天冬氨酸-co-乳酸)共混物的制备及其相容性研究

采用氯仿/乙醇共沸溶液浇铸法制备了混合均匀的聚L-乳酸/聚(天冬氨酸-co-乳酸)共混物(PLLA/PAL)体系.研究了PLLA/PAL共混体系的热性能、结晶行为、形态结构和力学性能,评价了PLLA和PAL之间的相容性.结果表明,PAL对PLLA的结晶行为和热性能产生了较大的影响,共混物的结晶度较低,共混体系中部分PAL会进入PLLA球晶的片晶而导致PLLA球晶结构不完善,熔点降低.PAL的含量小于20%的PLLA/PAL共混物的拉伸强度和断裂延伸率均高于纯PLLA.PLLA和PAL分子链相互缠结,产生的氢键使分子链间存在较强的相互作用,具有较好的相容性.

PREPARATION AND MISCRIBILITY STUDIES OF POLY(L-LACTIC ACID)/POLY(ASPARTIC ACID-co-LACTIC ACID)BLENDS

Blends of PLLA and PAL were prepared by solution-cast method using co-boiling reagents including chloroform and ethanol(93/7,V/V),and the co-boiling temperature was about 60℃,which could avoid the phase splitting of PLLA and PAL caused by different evaporate speed of the two solvents or polymer asynchronous precipitation.Thus,PLLA/PAL blends were obtained with uniform dispersion.The thermal properties and morphologies of the blends were studied,and the miscibility of PLLA and PAL was evaluated by DSC and POM.Each PLLA/PAL blend has a single T_g,and each tested T_g is closed to the calculated one according to Fox theory.Thus,the blends have homogeneous amorphous phase,and PAL and amorphous region of PLLA are miscible.In the blends,PLLA's T_m was reduced by adding into PAL,and the melting blends were thermodynamically stable systems.Amorphous PAL showed obvious effect on the thermal properties and crystallization behaviours of PLLA in the blends,which indicated PLLA and PAL were compatible.PLLA in the blends exhibited faulty spherulites,lower melting points and lower crystallinity.The growth of PLLA spherulites was varied from homogeneous coring to heterogeneous coring in the presence of PAL.POM micrographs showed that PAL was among the lamellar crystals of PLLA spherulites,and changed the PLLA crystal shape to faulty spherulites.PAL had the retardarce action on the crystallization speed of PLLA melt,and caused PLLA spherulites to become imperfect.Because of the chain entwisting and hydrogen bond forming,the interactions between PLLA and PAL chains are strong.Thus,PLLA and PAL are miscible and form the blends with miscible structures.When PAL content was less than 20%,the tensile strength and break elongation were higher than those of pure PLLA,and the blend of 10% PAL content showed the best tensile properties.