聚丙烯及聚甲基丙烯酸甲酯射出成形品的高次構造之初步觀察與分析

Abstract

微結構元件常藉由特定的結構幾何形狀、尺寸及位置關係的設計，來得到所期望的功能。為了擴展微結構元件更廣泛的創新功能特性，改變並控制微結構元件材料高次構造的所謂材料高次構造設計之概念與技術乃非常重要。 本研究在工業用範圍的模具溫度下，透過PP與PMMA兩種成形塑料與改變射出成形的模具溫度、射出壓力與保壓壓力等參數條件冀以影響微結構的充填性與其高次構造的組成，並透過光學顯微鏡、偏光顯微鏡與低溫高分辨穿透式電子顯微鏡等設備對結果作一探討與分析。實驗結果顯示高分子微結構成形良好與否以模具溫度70℃∼80℃為一分界線，低於此溫度線以下者，需施以較高的射出壓力才有較佳的成形品質。PP微射出成形品的基部組織由側邊到內部依次為表皮層、中間層與核心層等三種不同層相的高次構造，其截面厚度比約呈1：2：4的比率分佈。模具溫度是影響微結構內部結晶與否極為重要的因子之一，升高模具溫度能提升微結構之結晶度，在低模具溫度的成形條件下，微結構內部的組織大都呈現amorphous的高次構造；提高射出壓力雖能改善微結構充填，但卻有抑制球晶生長的現象產生；提高保壓壓力除了能促進核心層的球晶式高次結構成長外，對微結構的機械性質也有所幫助。

We usually acquire the functions that we want from the specimen of the microstructure by the size, geometric structure, and the relationship of the structural position which we design. For widely broadening the creative functions of microstructures’ specimens, it is very important to possess the concept and the technology of how to change and control the composition of superstructure of the microstructures’ specimens. Within the commonly used range of the industrial temperature, this thesis will investigate the relationship of parameter’s changes of the mold’s temperature, injection pressure and holding pressure between the filling and the composition of microstructures’ superstructure with an Optical Microscope, a Polarized Optical Microscope and a Cryo High Resolution Transmission Electron Microscope. Experimental results indicate that there is a dividing line between 70℃~80℃ of the mold’s temperature which is used to decide whether the filling of plastic microstructures is excellent or not. When the temperature is lower than the line, a higher injection pressure should be settled in order to get better quality of microstructures. The base-plate of the injection molded by PP part with microstructures is composed of three types of superstructure which are formed from the lateral surface to the interior: the surface layer, the middle layer, and the core layer. The proportion of each thickness of these three types of layers in a cross section is about 1:2:4. The mold’s temperature is one of the most important factors to decide whether the crystal in the microstructures can be formed or not. We could enhance the crystallization of the microstructures by increasing the mold’s temperature. Furthermore, there would be an amorphous superstructure of the microstructure’s composition in the condition of the lower mold’s temperature. Although higher injection pressure can improve the filling of microstructure, it also weakens the growth of the spherulites. Besides, increasing holding pressure not only improves the growth of the crystal superstructure in the core layer of the microstructure’s base-plat, but also advances the mechanical characteristic of the microstructures.