中文摘要：

为了探究四臂聚乳酸对线性聚乳酸结晶行为的影响,将四臂聚乳酸与线性聚乳酸的共混物在示差扫描量热仪（DSC）和偏振光显微镜（PLM）热台中加热到熔点附近的不同温度下恒温后分别进行了降温—升温程序,考察了四臂聚乳酸对线性聚乳酸的结晶行为的影响.结果表明,随着四臂聚乳酸含量增加,四臂聚乳酸在共混物形成的晶体中的比例增大且四臂聚乳酸有促进共混物晶体完善的作用,导致了熔融过程中熔点的上升.进一步研究证明,在共混物中完全熔融的四臂聚乳酸的支化结构能够促进结晶成核点的形成,从而促进四臂聚乳酸/线性聚乳酸共混物的结晶;而部分熔融的四臂聚乳酸能大幅促进共混物的结晶能力,这是未完全熔融的晶体的成核作用所导致的.

英文摘要：

To investigate the influence of the branch structure of four-arm poly（ L-lactide）（ 4A-PLLA） on the crystallization behavior of linear poly（ L-lactide）（ linear PLLA）,a series of non-isothermal programs were carried out on a differential scanning calorimeter（ DSC） and a polarized light microscope（ PLM） equipped with a hot stage. The samples were heated to 200 ℃ /180 ℃ /170 ℃ /160 ℃ to obtain totally-melting and partially-melting status. According to PLM images after cooling to room temperature,it was proved that the branch structure of 4A-PLLA could promote the crystallization at a cooling rate of 10 K / min when the content of 4A-PLLA exceeded 3 wt% after totally-melting at 180 ℃ and higher. On the other hand,partially-melting4A-PLLA and linear PLLA could both act as the nucleating agents in the aforementioned cooling program after melting at 170 ℃ and lower to promote the crystallization of the blends. Partially-melting samples displayed stronger crystallization and weaker cold crystallization in the cooling and the 2ndheating programs,while the PLM images illustrated more crystalline regions with smaller size for blends with higher 4A-PLLA contents after cooling to the room temperature. The second heating curves of samples showed higher high-melting temperatures as 4A-PLLA contents increased,which was attributed to the crystallization perfection effect of 4APLLA and its proportion rising in the crystals of the 4A-PLLA / linear PLLA blends.