充填反壓機制對殘留應力和光學成型品品質之影響

Influence of Gas Counter Pressure for Residual Stress and Quality of Optical Molding Product

陳珮蓉(Pei-Rong Chen)

指導教授 ： 陳夏宗

中原大學/工學院/機械工程研究所/碩士(2014年)

https://doi.org/10.6840/cycu201400593

摘要

近年來光學塑膠產品在品質的要求大多著重於尺寸與形狀精密度、收縮率、轉寫性的控制，殘餘應力以及分子定向性與雙折射率降低等。在熱塑性高分子中高度排向會形成流動殘留應力及不等向性收縮，為翹曲變形重要的成因，使產品的精度難以控制，導致在光學性質上造成雙折射率差並影響光學品質。因此，本研究利用氣體反壓技術於傳統射出成型，控制熔膠波前的流動行為，進而改善流動產生的殘留應力，並觀察光學性質，以開發氣體反壓技術應用範圍。
　　本研究以不同熔融指數材料，控制模具溫度、熔膠溫度及射出率，搭配不同反壓壓力，以拉伸試片作為基礎實驗，利用收縮率、機械性質與光學性質的比較，進行反壓壓力對熔膠波前與殘留應力的探討；並實際應用氣體反壓在光學產品做為成型案例，說明氣體反壓可以改善光學性質。
　　研究結果顯示，氣體反壓技術對於傳統射出成型有兩大影響，其一為降低分子排向，其二是反向持壓。從收縮率結果看出，實驗與分析的結果在使用氣體反壓時收縮率皆降低，且反壓壓力越大其收縮率越小，可改善44.34% (PC 175)與33.98% (PC 122)。在彈性係數方面，當氣體反壓壓力越大其彈性係數會越大，但是要反壓壓力達到一定的程度其彈性係數才會高於傳統成型。而在拉伸強度部分，使用氣體反壓時，拉伸強度皆會略高於傳統，但會隨反壓壓力增加而有遞減的情形，且因黏度因素，高流動性材料提升程度會較低流動性材料明顯。從殘留應力可發現，當氣體反壓壓力越大，其殘留應力會越低，同時從分析可看出雙折射率將會有改善，進而發現到高分子定向會影響雙折射程度。光學性質的量測結果，在氣體反壓中，輝度值有增加的趨勢，其均齊度也隨之提升；輝度值約可提高3.8~7.8%，均齊度約可改善4.2~12.3%。並透過光學透鏡的案例驗證了氣體反壓可有效地降低收縮率、殘留應力，而提升輝度值以及改善光均勻度。

關鍵字

氣體反壓 ； 收縮率 ； 機械性質 ； 殘留應力 ； 雙折射 ； 輝度值

並列摘要

In recent years, most of the requirements of optical plastic injection molding product quality focus on precision of size and shape, shrinkage, controlling of transcription, residual stress, molecules orientation, decreasing of birefringence difference and so on. Thermoplastic polymer with highly orientation causes flow-induced residual stress and anisotropic shrinkage which is main reason for warpage. It makes precision of product hart to control and causes birefringence difference. It also impacts optical quality seriously. So far, this investigation uses convectional injection molding with gas counter pressure (GCP) technology to control melt front pattern. It improves flow-induced residual stress and observes optical property to develop application of GCP technology.
　　This investigation uses different melt index (MI) material with different mold temperature, melt temperature and injection speed. In the meantime, the study with a different GCP compares with basic experiment by tensile specimen. It uses compares of shrinkage, mechanical property and optical property to discuss influence of melt front pattern and residual stress by GCP. The practical application of GCP molding as in the case, indicating that the GCP can improve optical properties.
　　Investigation shows GCP technology for impacts of convectional injection molding has two points. One is decrease of molecules orientation; the other one is counter holding pressure. In the shrinkage result, both experiment and simulation show that using GCP causes decrease of shrinkage. When the GCP is higher, the shrinkage decreases. It can improve 44.34% (PC 175) and 33.98% (PC 122). In Young’s modulus result, higher GCP has higher Young’s modulus. However, GCP should reach a certain level, and then Young’s modulus is higher than convectional molding one. In tensile strength, using GCP has a little bit higher strength than convectional one. Then, because of viscosity, high MI of the material increasing strength level is more significant than low MI one. In residual stress result, when increases GCP, it reduces the residual stress. In the meanwhile, simulation shows improvement of birefringence. Therefore, polymer orientation can impact level of birefringence. In measurement result of optical property, the luminance increases in GCP process and the uniformity also increases, too. The luminance enhances about 3.8~7.8%; the uniformity enhances about 4.2~12.3%. Optical lens case verifies that GCP can decrease shrinkage, residual stress efficiently and increases luminance and improves light uniformity.

並列關鍵字

Residual Stress ； Birefringence ； Luminance ； Mechanical Property ； Gas counter pressure ； Shrinkage

參考文獻

16. 鍾明修，“ABS薄殼射出成型件縫合線之探討”，中原大學機械工程學系碩士論文 (2001)。

18. 朱淳衛，“探討射出成型製程參數與PC+ABS材料性質於縫合線強度影響之研究”，中大學機械工程學系碩士學位論文 (2008)。

31. 林鈺婉，“超臨界微細發泡射出成型反壓機制建立並應用於流變特性研究”，私立中原大學機械工程學系博士學位論文（2009）。

33. 許評順，“模內氣體反壓與動態模溫機制應用於超臨界微細發泡射出成型發泡控制與表面品質影響之研究”，私立中原大學機械工程學系博士學位論文（2011）。

34. 施銘奕，“氣體反壓對於含碳纖維高分子複材射出成型過程纖維配向度及導電度之影響研究”，私立中原大學機械工程學系博士學位論文 （2012）。