sPS摻合之結晶探討─IR光譜量化研究

Abstract

本研究以純sPS及摻合物中sPS的結晶行為為主題，並兼及增容劑在摻合時增容效果之探討。摻合體系為sPS/PBT(聚對苯二甲酸二丁酯)及sPS/PET(聚對苯二甲酸二乙酯)，所用增容劑為styrene/glycidyl methacrylate共聚合物。 對純sPS的結晶行為，分別研究了melt crystallization及cold crystallization兩種情況；對摻合物中sPS的結晶行為，則是針對melt crystallization分別研究了不含增容劑，及含有增容劑兩種情況。最後並由扭力塑譜儀、毛細管流變儀偵測增容劑之作用情況，以及由SEM直接觀察增容劑所造成的相形態變化。 歸納本研究之結果為： 就純sPS的melt crystallization而言，當溫度≧240℃時，在結晶記憶完全消除的情況下，生成的均是apha結晶，即使降溫速率高達100℃/min，仍無□結晶生成；當溫度<240℃時，則同時會有apha及beta結晶生成，因此降溫速率不是形成或的影響因素，結晶溫度才是。 純sPS的cold crystallization則會同時生成apha及beta結晶，但若以“結晶溫度”的觀點檢視，則cold crystallization其實和melt crystallization是同一道理所支配，蓋cold crystallization是由常溫加熱產生結晶，升溫過程中，在遠低於240℃的溫度下，結晶已經開始，根據“結晶溫度”原則，生成的當然是□結晶，只有在≧240℃後，若還有結晶空間(若結晶度尚未達最大結晶度)，生成的才是beta晶，同時，原已生成的apha結晶，也會有部分轉成beta結晶，這就是cold crystalliztation會同時生apha及beta結晶的原因，但就支配因素言，和melt crystallization是相同的。 對sPS/PBT摻合的情況言，若未加增容劑，摻合物中sPS之melt crystallization和純sPS相同，溫度≧240℃時，生成的均是□結晶，而溫度<240℃時，會有少量apha結晶同時存在。但就結晶速率言，則會較純sPS緩慢，原因應是sPS的球晶成長受到PBT domain阻礙所致。 當加入含有環氧基之增容劑，則不但使sPS的結晶速率更形緩慢，且melt crystallization生成的均是apha結晶，不論在何種溫度。 若加入的只是atatic polystyrene的單聚物，則情況和純sPS相同，只是結晶速率會較慢而已。 在sPS/PET的摻合中，情形和sPS/PBT的摻合完全相同。 和上述分子鏈段尺度對照的，則是SEM所觀測到的相形態及扭力塑譜儀、毛細管流變儀所測得的扭力值、黏度值變化，對於未加環氧基增容劑之sPS/PBT摻合物，其扭力值較低，熔融黏度亦較低，SEM所觀測到的PBT分散相顆粒也較大，當加入環氧基增容劑時，則扭力值、熔融黏度值均升高，且PBT分散相顆粒大幅變小。 因此，對於sPS和飽和聚酯－PBT、PET的摻合，在未加含官能基之增容劑時，除了結晶速率會稍受影響外，其他性質和純sPS幾乎相同，因為sPS和PBT或PET之間，除了鏈段排列之瞬間外，形同各自獨立，但加入含官能基之增容劑時，則不論微觀尺寸或亞微觀尺度，都顯現出互為對應之變化，總而言之，對於黏度值、相形態的改變，其實可以追溯至鏈段尺度下的變化。

The goal of this study is to explore the crystallization behavior of pure sPS and the sPS component in polymer blends. The blend systems investigated include sPS/PBT and sPS/PET with/without the styrene/glycidyl methacrylate copolymer (SG) as the compatibilizer. For the purpose of comparing properties in terms of microscopic and the macroscopic viewpoints, the melt viscosity and morphology of the sPS/PBT blends were also studied. To understand the crystallization behavior of the pure sPS, both melt crystallization and cold crystallization were studied. To understand the sPS component in polymer blends with and without compatibilizer, the melt crystallization was investigated. Finally, the macroscopic properies of the sPS/PBT blend were studied by torque rheometer, capillary rheometer and SEM.

1.For the melt crystallization of pure sPS at 240℃and higher, the beta crystals are exclusively formed, no apha□crystal are formed even under cooling rate at as high as 100℃/min. If the melt crystallization temperature is performed below 240℃, crystals of both apha and beta forms are produced simultaneously. Therefore, the main controlling factor for apha or beta crystal formation is the temperature of crystallizatio, not the cooling rate. 2.In cold crystallization process, the pure sPS tends form both apha and beta crystals simultaneously. Therefore, same mechanism of apha、beta formation regardless of melt crystallization or cold crystallization. The process of carrying out cold crystallization is started from room temperature, so the onset of crystallization is far below 240℃. According to the rule of “temperature of crystallization”, the apha crystals are formed rather than beta crystals until the temperature is reached 240℃. The beta crystals start to form from the remaining amorphous region when the temperature is rasised above 240℃ because the crystallinity has not reached its maximum value. Since the apha crystal is kinetically more favorable while the beta crystal is thermodynamically favored, fraction of the apha crystals tends to transform into beta crystals. This is the reason why both apha and beta crystals are formed simultaneously in cold crystallization. 3.For the melt crystallization of the sPS component in the sPS/PBT blend without containing the compatibilizer, the crystals formed are essentially the same as the pure sPS. When the crystallization temperatures are above 240℃, essentially all beta form crystals are formed. When the crystallization temperatures are below 240℃, small fraction of apha form crystals are also formed except that the rate of crystallization is slower than that of the pure sPS because of interference of the PBT chains. 4.The compatibilized sPS/PBT blend results in even slower of the crystallization rate of the sPS component and apha form crystals are formed at temperatures. 5.In the sPS/aPS blend, the crystallization behavior of the sPS component is identical to the pure sPS except that the crystallization rate is slower. 6.The crystallization behaviors of the sPS component in the uncompatibilized sPS/PET blend are the same as the uncompatibilized sPS/PBT blend. 7.Results from SEM morphologies, torque values from torque rheomete, and shear viscositis capillary rheometer are all related to the microscopic and macroscopic phenomena. For the uncompatibilized sPS/PBT blend, both torque and melt viscosity are lower than those of the compatibilized counterpart. The PBT domain size is substantially larger in the uncompatibilized sPS/PBT blend than the compatibilized one based on SEM.