剪切作用對聚丙烯冷卻過程中的高階結構形成之影響

Abstract

由於高分子加工成形技術與高分子材料的發展，具有高功能性的塑膠元件的應用逐漸廣泛，為了提昇品質，減少並控制塑膠成形品的不良收縮與物理特性是極為重要之工作。 本研究針對高剪切應變率作用下的聚丙烯的高階結構的形成，自行設計施加高剪切應變率之實驗裝置，進行了各種不同結晶溫度、持溫時間與剪切應變率條件下的實驗。並利用偏光顯微鏡、DSC、SEM與其他光學顯微鏡等設備對結果進行分析與討論。結果發現順排聚丙烯本身為容易結晶之高分子材料，若提高結晶溫度、增長持溫時間與施加不同剪切應變率，均會使球晶核數目增多，但球晶之大小並未明顯改變。但在120℃施加140s-1的剪切應變率時，有β型球晶出現，使得在DSC曲線圖上另有一波峰凸起。而藉由不同方式的顯微照相對實驗所得試片作高階結構分析，均可觀察到試片截面具有直徑大小在30μm至60μm之球晶。

Today functional plastic products are widely used due to the progress of polymer processing technology and raw materials of polymer. To enhance the quality of plastic products, reducing the non-uniform shrinkage of the molding material and controlling the physical properties of the polymer are vital. This study focused on the effects of shear rate on the morphology of polypropylene. An experiment apparatus was designed for high-shear-rate test. Experiments were performed at different temperature, shear rate, and holding time. Polarized optical microscopy (POM), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and other optical microscopes were employed to analyze the samples. Experimental results showed that iPP was a polymer of easy crystallizing. The number of spherulite nuclei increased with temperature, holding time and shear rate; however, the size of spherulites did not change obviously. The β type spherulite appeared when the shear rate was 140s-1 and the temperature was 120℃, which caused another peak in the DSC diagram. Different ways were employed to analyze the morphology of the sample. Spherulites with the diameter of 30μm to 60μm were observed on the sample cross-section.