聚对苯二甲酸1,3-丙二醇酯溶液浇铸薄膜形态结构

聚对苯二甲酸 1 ,3-丙二醇酯 ( PTT)是典型的半结晶聚合物 ,从熔体结晶形成球晶 ,在某一结晶温度范围内 ,在球晶中可观察到环带结构[1～ 4 ] .一般认为 ,环带球晶的形成归因于片晶沿球晶径向的周期性扭曲[1,2 ] .本文研究了 PTT溶液浇铸薄膜在溶剂挥发过程中等温结晶的形态结构 .1　实验部分　　 PTT样品为美国壳牌化学公司产品 ,熔点为 2 2 8℃ .将 PTT粒料于 1 1 0℃溶解在苯酚和1 ,1 ,2 ,2 -四氯乙烷 (质量比为 60∶ 40 )的混合溶剂中 ,配成质量分数为 0 .2 %～ 2 %的溶液 ,滴少许溶液在加热的云母片上 ,在预先设定的结晶温度 ( 90～ 2 0 0℃ )下等温结晶 ,然后将 PTT薄膜快速冷却至室温 .用 Leica DMLP偏光显微镜 ( PL M)和 SPA- HV30 0原子力显微镜 ( AFM)进行形态表征 .2　结果与讨论　　图 1为 PTT溶液浇铸薄膜在不同温度下等温结晶后的 PLM图 ,可以清楚地看到 Maltese十字消光现象 .PTT溶液浇铸薄膜在 90～ 1 30℃的结晶温度范围内 ,形成环带球晶 ;当结晶温度为 1 40℃...

Nonisothermal crystallization behavior of poly (L-lactide)-poly(ethylene glycol) dibloick copolymer

The nonisothermal crystallization behavior of poly (L-lactide)-poly(ethylene glycol) ( PLLA-PEG) diblock copolymer was studied by means of real-time WAXD, DSC and POM, and Ozawa equation was used to analyze the kinetics of PLLA-PEG under nonisothermal crystallization conditions. During the crystallization of the high-T-m block (PLLA), the low-T-m block (PEG) acts as a noncrystalline diluent, and the crystallization behavior of PLLA obeys the Ozawa theory. When the PEG block begins to crystallize, the PLLA phase is always partially solidified and the presence of the spherulitic microstructure of PLLA profoundly restricts its crystallization behavior, which results in that the overall crystallization process does not obey the Ozawa equation. Furthermore, the study of the crystalline morphology of PLLA-PEG at different cooling rates indicates that when the cooling rate is from low to high, the crystalline morphology undergoes a transformation from the ring-banded spherulites to the typical Maltese cross spherulites, which experiences the mixed crystalline morphologies of ring-banded and typical Maltese cross spherulites, and the spherulitic size becomes smaller.

The formation of ring-banded spherulites of poly(epsilon-caprolactone) in its miscible mixtures with poly(styrene-co-acrylonitrile)

Ring-banded spherulites in polymer blends of poly(epsilon-caprolactone) (PCL) and poly(styrene-co-acrylonitrile) (SAN) were investigated by optical microscopy equipped with a digital image analysis system. PCL/SAN blends exhibit not only spherulites with a Maltese cross, but also distinct extinction rings. The periodic distance of rings changes with blend ratio and crystallization temperature and was plotted as a function of the undercooling and overall mobility of the mixtures, respectively. It was found that the overall mobility of chain segments in the mixtures could be mainly attributed to the origin of the formation of ring-banded spherulites. It was believed that for the first time a quantitative experimental result was obtained about the relationship of periodic distance of rings and the overall mobility of the mixtures. This relationship may be useful to explain the formation mechanism of ring-banded spherulites in polymer blends or even in homopolymers in the future. (C) 1977 Elsevier Science Ltd.

THE RING-BANDED SPHERULITE STRUCTURE OF POLY(EPSILON-CAPROLACTONE) IN ITS MISCIBLE MIXTURES WITH POLY(STYRENE-CO-ACRYLONITRILE)

The structure of the PCL spherulite in poly(epsilon-caprolactone)/poly(styrene-co-acrylonitrile) (PCL/SAN) blends was investigated by optical microscopy and small angle light scattering. The spherulite structure with a Maltese cross has been observed in pure PCL. Similar PCL/SAN blends exhibited not only spherulites with a Maltese cross, but also distinct extinction rings. The H(v) light scattering pattern especially caused diffraction rings in PCL/SAN blends but not in pure PCL. The spherical symmetry of spherulite PCL becomes more incomplete and the twist of the lamella becomes more irregular with increasing SAN content. It is found that the spherulite structure of PCL/SAN blends is dependent on the crystallization temperature and the concentration of SAN in PCL/SAN blends.