臺灣博碩士論文加值系統

　　對位聚苯乙烯(Syndiotactic polystyrene，s-PS)為一性質優越之工程塑膠。但由於結晶速度太快，且具有多重晶態，導致加工困難及產品易脆化、龜裂的缺點。本研究以加入不定型的聚苯乙烯(a-PS)，PPO(poly-2,6-dimethyl-p-phenylene oxide)及熱處理條件的改變，對s-PS的結晶行為、微觀形態、結晶動力、熔融現象等加以討論，以期對s-PS的改質做一基礎的研究。由X-ray及DSC的結果，決定s-PS的結晶形態。利用偏光顯徽鏡(polarized-light microscopy)觀察球晶形狀及球晶成長速率。DSC的恆溫結晶及昇溫掃瞄則用以計算結晶動力和熔融現象改變的觀察。由實驗的結果，單純s-PS的熔融結晶形態由X-ray圖譜中，知道含有α、β、β'晶體的多重晶型，且α、β晶體的結晶比例會隨結晶溫度的升高而互有增減，在結晶溫度愈高的情形下，愈容易形成較穩定的β晶體。於s-PS系統中摻合a-PS或PPO，則會因為系統亂度增加，而使S-PS在研究的結晶溫度範圍內，均生成局晶體結晶。同時可由DSC昇溫掃瞄觀察熔融行為得到相同的印証，包括α晶體的一組熔融峰及β晶體的兩組熔融峰，由偏光顯微鏡的觀察，不定型高分子的加入，會使球晶成長速率降低。摻合a-PS對球晶大小影響不大，而摻合PPO則由於成核困難、成核數目減少，使球晶顆粒大小較原本的s-PS為大。在結晶動力分析方面，對於各系統在本研究的實驗條件下，Avrami參數n值均在2∼3之間，且隨著結晶高分子(s-PS)組成的減少，n值愈趨近於2，結晶溫度愈高，k值愈低；表示溫度愈高，結晶速率愈慢。

　　The crystalline, morphology, crystallization kinetics and induced changes of two syndiotactic polystyrene-based blends (s-PS/a-PS and s-PS/PPO) were studied and determined. s-PS presents a very complex polymorphic morphologies, with four different crystalline forms identified so far. The structure and morphology of s-PS and its blends were investigated using wide angle X-ray scattering diffractometer (WAXD) and differential scanning calorimetry (DSC); The literature shows that a mixture of the α、β and β' form is present in pure s-PS annealed sample. The relative intensities of these forms changed with the crystallization temperature(Tc), with Tc above 250℃ that favoring the attainment of the β form . Blending s-PS with PPO or a-PS was to found to favor the P form in these blends. The DSC melting curve also indicated same results, whuch shows one endotherm peak of a form and two endotherm peaks of f3 form. Isothermal spherulitic growth rates of s-PS and its blends with a-PS or PPO were determined over a range of crystallization temperature using polarized-light microscopy and a hot stage. The spherulite growth rate of s-PS decreased as the PPO(or a-PS) volume fraction was increased. The Avrami equation was used to analyse the data of the bulk kinetics of crystallization. The values of the Avrami index (n) range between 2∼3. indicating mixed crystallization and nucleation mechanisms. The Avrami rate constants (k) decreased with increasing crystallization temperature.