作　　者： ; ; ;

机构地区： 中山大学化学与化学工程学院高分子研究所

出　　处： 《高分子学报》 2004年第5期726-730,共5页

摘　　要： 为考察不同链结构的聚乳酸在物理老化过程中聚集态结构的变化 ,分别在 0℃、2 5℃、37℃对聚 (D ,L 乳酸 ) (PDLLA)、非晶态的低左旋度聚 (L 丙交酯 ) (l PLLA)和左旋聚 (L 丙交酯 ) (PLLA)进行长达 6个月的物理老化 ,用温度调制式差示扫描量热法 (MDSC)研究了它们在物理老化过程中的玻璃化转变行为的变化 .结果表明 ,PDLLA和l PLLA对物理老化十分敏感 ,在一定老化温度下 ,它们的玻璃化转变温度 (Tg)随老化时间延长向高温移动 ,老化过程中产生的非可逆热焓 (ΔHnon)逐渐增加 ,这种趋势在老化 1w内变化明显 ,随后趋缓 ;而老化温度越高 ,Tg 升高和ΔHnon增加的速率都越快 .不同温度下老化 ,PDLLA和l PLLA的ΔHnon 与老化时间的对数都有较好的线性关系 ,ΔHnon的变化速率对温度的倒数作图 ,l PLLA的斜率绝对值比PDLLA的略大 ,说明有较高立构规整性的分子链形成物理缠结需要较高的活化能 .PLLA由于结晶度高而非晶相含量较低 ,未观察到明显的玻璃化转变及其在物理老化过程中的变化 . To investigate the changes in structure of cohesional state of poly( lactic acid) s with different chain tacticities, poly(D, L- lactic acid) (PDLLA), a low optical activity poly(L-lactic acid) (1-PLLA) without crystallinity, and poly( L-lactic acid) (PLLA) were physically aged at 0degreesC 25degreesC and 37degreesC for up to 6 months. Their glass transition behavior after physical aging was monitored by means of modulated temperature DSC (MDSC) The results showed that the glass transition behavior of PDLLA and 1-PLLA is sensitive to physical aging as indicated by the non-reversing thermal enthalpy (DeltaH(non)) generated in the physically aged samples. The rates of physical aging were higher in the early stage of aging and slowed down after aging for one week. At a given temperature, the T-g's of PDLLA and 1-PLLA shifted to higher temperatures and the DeltaH(non) increased with increasing aging time. The increasing rates of T-g and DeltaH(non) were speeded up as aging temperature raised. It was found that good linear relationships between DeltaH(non) and logarithm of aging time for PDLLA and 1-PLLA existed at different. aging temperatures. Linear dependences of the changing rates of DeltaH(non) as functions of reciprocals of aging temperatures were obtained for both PDLLA and 1-PLLA, and the absolute value of the slope for l-PLLA was slightly larger than that of the PDLLA, indicating that macromolecular chains with higher tacticity need higher activation energy to form physical entanglements. No obvious glass transition was observed for PLLA whether it was aged or not due to its high degree of crystallinity.

关 键 词： 聚乳酸 丙交酯 物理老化 玻璃化转变 物理缠结 调制式差示扫描量热法

领　　域： [化学工程]