1980年代，台灣環保意識抬頭，從1950年代以來普遍被使用的塑膠，也因為其原料來自於有限的石油，製造時不僅會造成環境汙染，使用後又不易分解，塑膠製品已經廣泛使用多年，但在一次性使用後所拋棄的塑膠廢棄物引發的環境議題受各國廣泛關注，進而熱議討論及尋找取代方案，而聚乳酸塑膠(Polylactic Acid, 以下簡稱為PLA)成為許多塑膠產品的替代方案，因為當聚乳酸塑膠在適當溫度及濕度的堆肥環境時，會被微生物快速地分解，若是試算全球的塑膠預計使用量，仍然需要大面積的土地作為堆肥使用。而本研究主要是探討非耐熱型聚乳酸(PLA)以及耐熱型聚乳酸(Crystalline Polylactic Acid, 以下簡稱為CPLA)之比較，可生物分解之塑膠製品回收再利用的可行性，回收過程中分子量降解的過程比較，在不同的氫氧化鈉清洗濃度和不同清洗溫度的條件下，進行聚乳酸生物可分解塑膠之物化性質以及熱性質的分析比較。 本研究為了解PLA和CPLA塑膠回收再利用之可行性探討，採用美國材料暨試驗協會(American Society for Testing and Materials, ASTM) G154 Cycle A的標準方法作為老化條件，此方法是最廣為使用的加速老化試驗之一，模擬陽光、溫度對塑膠材料的破壞作用，其塑膠材料老化包含強度降低、褪色、龜裂、脫落、粉化和氧化等等，樣品在模擬的環境中從幾個小時甚至數天的時間，可體現在戶外幾個月或是數年發生的損害。本研究將分成無照光老化條件的聚乳酸塑膠分解情形比較，以及使用UVA-340燈管照射8小時後，接著進入4小時黑暗期，總共循環20次，(總)實驗時長為240小時，其老化的加速倍數約為12倍，將探討有無經過照光老化240小時之PLA和CPLA進行熱性質與物化性質分析。;Environmental issues caused by single-use plastic products have received extensive attention from various countries, and have been banned and replaced. Polylactic acid plastic has become an alternative for many products to be used. PLA plastics are rapidly decomposed by microorganisms in a compost field with appropriate temperature and humidity, but compared with the global usage, a large area of land is still required for composting. The purpose of this study is to investigate the aging of PLA plastics in 10 days, the comparison of molecular degradation during the recovery process, the analysis and comparison of the physical and chemical properties of the recovered PLA w carried out at higher NaOH concentration and higher cleaning temperature. To understand the aging of polylactic acid wastes exposed to environmental, the accelerated aging standard method of American Society for Testing and Materials (ASTM) G154 was used, and polylactic acid fragments were exposed to air. Then, put it into the weather resistance testing machine (UVA lamp), the accelerated aging rate of this condition is about 12 times, and in order to understand the effect of light on the aging reaction, no light is used as the control group, both groups were aged for 10 days for physical property analysis.
