發泡核心材料匹配非發泡皮層材料共射出成型成型特性與機械性質之探討

Study on the Molding Characteristics and Mechanical Properties of Injection-Molding Foaming Polypropylene Parts

黃德坤(De-Kun Huang) ； 黃文昌(Wen-Chang Huang) ； 黃志強(Chih-Chiang Huang)

《明新學報》 33期 (2007/07) Pp. 275-282

https://doi.org/10.29688/MHJ.200707.0017

摘要

本研究利用PP材料對發泡射出成型與發泡核心材料匹配非發泡皮層材料之共射出成型之成型特性與機械性質作一深入探討。文中利用兩種不同厚度之零件模具設計針對製程參數對零件重量與機械性質之影響，以及零件厚度與發泡劑含量對發泡度之影響作一有系統之研究，實驗結果發現厚度0.5mm之薄殼發泡拉伸試片重量較以傳統射出成型時重量減少約4%~9%，而厚度15mm之厚件抗彎試片則減少約43%~50%，所以平板厚度對發泡度扮演一決定性的影響。而在製程參數對發泡射出成型零件之影響方面，零件重量、拉伸強度、撓曲強度與剛性皆隨料溫、模溫和射速增加而降低，同時隨背壓增加而增加。發泡導致重量降低，卻也造成機械強度減弱。當發泡劑含量從0.8%增加至1.6%，機械強度明顯變差。另外，非發泡匹配發泡材料之薄殼共射出成型可在不增加重量情況下，較純發泡射出成型有較好之表面品質以及拉伸強度。同時對PP材料而言，共射出成型零件之發泡核心與非發泡皮層有不錯之結合度。本研究結果可提供發泡射出成型與共射成型一成型準則藉以獲取較佳之成型品質。

關鍵字

共射 ； 發泡 ； 機械性質

並列摘要

This study concerns about the molding characteristics and mechanical properties of injection molded foaming PP parts and coinjection molding PP parts for foaming core material embedded in non-foaming skin material. Effects of processing parameters including injection velocity, melting temperature, mold temperature and back pressure on part weight and part mechanical properties including tensile strength, flexural strength and stiffness are investigated. Influence of part thickness and foaming agent content on the degree of foaming is also studied. Based on the measured results, it was found that for thin-wall tensile foam specimens with 0.5mm thickness, weight reduction is about 4%~9% whereas in the thick-wall bending foam specimens with 15mm thickness, the reduction is approximately 43%~50%. Part thickness plays a dominant factor for determine the degree of foaming. For injection molded foaming parts, part weight, tensile strength, flexural strength and stiffness decrease with increasing melt temperature, mold temperature and injection velocity whereas they increase with increasing back pressure. Foaming results in weight reduction but it also reduce part mechanical properties. The foaming agent content increases from 0.8% to 1.6%, the mechanical properties reduce significantly. Moreover, the coinjection molding thin-wall parts process for foaming core material embeded in non-foaming skin material results in a foam part with very good esthetics and higher tensile strength than injection molded foaming parts. Meanwhile, the foam core is well bonding to the non-foam skin in the coinjection molding parts. The present investigation provides a molding guideline for injection molded foaming parts and coinjection molding parts to achieve a specific objective of part quality.

並列關鍵字

coinjection ； foaming ； mechanical property

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