Syndiotactic polystyrene and its blend with atatic polystyrene：melt crystallization and crystal growth

• Main Authors: Chun-Feng Lo, 羅俊峰
• Other Authors: Chi Wang
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/02824695794828838439

碩士 === 元智大學 === 化學工程研究所 === 88 === Firstly, This dissertation is directed against on the inter-effect of these different crystal-structures, and taking the 260oC-500atm a-form, which were pre-produced at laboratory, then using the differential scanning calorimeter (DSC) to analyze any different crystallizing and melting performance cause of the pure syndiotactic polystyrene and itself. Knowing that a-form is a speedy in nucleartion forming and slowly in crystallinity raising. From the DSC, the Raising-Temperature-Melting curve of the isothermal-crystallization, knowing that if blend the aPS must suppress thus a-form crystal-structure, especially obvious if blend the mini-molecular-weight aPS; Meanwhile if the more aPS is blended, the more suppression of development a-form will encounter. Knowing that Avrami constant (n) of the s-PS’s blend (with aPS) is between 2.37~3.5. Also mean its in nuclear forming structure is the 2-dimensions or 3-dimensions diffusion-controlled hetergeneous nucleation. Avrami rate constant (k) will fallen accordingly with the raising of the isothermal-temperature. If blend aPS more, the k values be more minor. The comparison cause of these four different aPS as：sPS/aPS(S)=70/30＞sPS/aPS(B)=70/30＞sPS/aPS(B)=30/70＞sPS/aPS(S)=30/70. If observing the growth rate of the crystal by using the polarized optical microscope (POM), the growth rate of negative birefringent spherulites is much lower then the positive birefringent spherulites .Under the same ration of the blend, the G value will be came more fast if you blend the material in the large-molecular-weight aPS not in the mini-molecular-weight aPS. Meanwhile, From the Hoffman-Weeks equation analysis, knowing that; the equilibrium temperature of the a-form of the pure-s-PS is 2773 oC. and the equilibrium temperature of the a-form is 291.21 oC, and the equilibrium temperature of b-form of the blend is 295oC(approx.) It’s very close to the pure-s-PS. Also can find out the real equilibrium temperature is 280 oC, from the pure a-form sample. During the experiment procedure, knowing the “g “ value is not a fixed value, and related with the temperature and the time. So, the above mentioned equilibrium temperature is needing further amendment. (Keyword : a-form、syndiotactic polystyrene、atactic polystyrene、blend、negative birefringent spherulites、growth rate、equilibrium temperature)