本研究探討聚乳酸 (Polylacit acid, PLA) 添加蠶砂 (Silkworm excrement, SE) 複合材料之射出成形對機械強度增進以及生物可分解性之試驗。首先將蠶砂原料毫米等級透過球磨細化成微米等級，再與聚乳酸塑膠粒利用重量百分濃度混合後，分別為PLA/SE 2.5%, 5%, 10% 及20%，經由雙螺桿押出機均勻攪拌並造粒成複合材料塑膠顆粒。複合材料接續將進行檢測及試驗，包含熱性質、模流分析、機械強度及生物分解性。熱性質分析結果，原材料PLA之氣化裂解溫度約364℃，蠶砂有多個裂解點則在288℃下有一劇烈裂解溫度，因此複合材料隨著蠶砂比例上升裂解溫度下降。而蠶砂顆粒可能成為PLA中的成核劑，促使PLA/SE產生冷結晶溫度(Tcc)，結晶度達41%。射出成形與模流分析結果，射出參數因子主要為射速、料溫及模溫，探討原始PLA收縮及翹曲影響，模溫高是收縮的主要影響因子，試片於高模溫有足夠時間收縮所致，翹曲則是不規則收縮，主要影響因子為料溫，高料溫於試片核心中及表面溫度差距大，造成收縮不均勻成翹曲。射出成形拉伸試片之強度結果表示，拉伸強度與核心層剪切應力隨著射速而增加及提升，主要是高分子於高射速具有較高的延伸所致，因此高射速拉伸強度優於低射速拉伸強度；在複合材料之拉伸強度相較於純聚乳酸無增益且隨著比例上升，拉伸強度隨之下降，主要蠶砂顆粒在拉伸過程中成為缺陷所致，反之，衝擊試驗結果顯示，PLA/SE 5% 相較於PLA提升強度最高約28.8%，另因PLA/SE 10% 和 PLA/SE 20%濃度過高，使得複合材料之衝擊強度皆無明顯增益比較於原PLA。生物分解實驗中，將額外壓製試片放置於有機堆土中並恆溫58℃，並維持7週期間，使得聚乳酸與複合材料加速分解；外觀表現上，當蠶砂濃度越高其分解情況越劇烈，而到最後仍然幾乎全部都在有機土堆中分解完畢並成為有機推肥。最後，複合材料將透過射出成形應用於枕頭填充物做實例，其他也可應用於、靠枕填充物和小盆栽堆土等用途。

This study is devoted to investigate the parameters of influence in injection molding (IM) process and analysis on mechanical properties and biodegradability of Polylacit Acid (PLA) and PLA/SE composites with silkworm excrement (SE) particles. To prepare the PLA/SE composites, the first step is to refine the SE to micron-scaled (�慆) particles by ball milling, then using a twin-screw extrusion to compound Neat-PLA pellets and refined SE particles with weight percentage, as PLA/SE 2.5%, PLA/SE 5.0%, PLA/SE 10% and PLA/SE 20%. Both TGA and DSC conduct to analyze the thermal properties of Neat-PLA and PLA/SE composites. For thermal properties, the Neat-PLA has higher decomposition temperature (Td) at 364℃ and SE has multiple peaks and a dramatic change at 288℃. In the DSC results, the SE particle may be a nucleation in the PLA and it raises the crytstallinity to approximately 41% in PLA/SE composites. It is found that the PLA/SE composites have lower Td with higher concentration of SE. Injection molding parameters are considering melt temperature and mold temperature. For Neat-PLA, simulation performance includes volumetric shrinkage and warpage. It is found that the temperature is a major factor for volumetric shrinkage and warpage. That means the melt temperature increasing in the filling stage, the maximum volumetric shrinkage and waprage obtain as respectively 4.4 % and 54 �慆. For the mechanical properties, the tensile strength and impact strength specimens have been experimentally tested by IM. For tensile strength, the PLA increased with higher injection velocity and that is due to the shear stress in the core layer of flow front in the melt polymer. The tensile strength of PLA/SE composites are not enhanced as compared with that of Neat-PLA because the SE particles become drawbacks while stretching in the tensile testing. For results of impact strength, the PLA/SE 5.0% is improved approximately 28.8% as comparing with that of Neat-PLA. However, for PLA/SE 10% and PLA/SE 20%, their impact strength are not enhanced because of the poor dispersion caused by the agglomeration of SE particles. In the biodegradability experiment at 58℃ and compost environment, both Neat-PLA and PLA/SE composites made by compression molding have been buried for testing. The appearance results of PLA/SE composites are faster and obviously disintegrated in 7 weeks. The Neat-PLA and PLA/SE composites can be almost biodegraded in this period of environment. Finally, the PLA/SE composites are fabricated into pillow filler pellets by injection molding for potential application of life medical consuming products or fertilizer.

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