本研究主要是分作三部份實驗,第一部份實驗是利用設計之熱塑性澱粉配方(含澱粉、甘油、水、卵磷脂與酵素),探討四種不同澱粉/澱粉+聚酯比(S/S+E ratio)於30%、40%、50%與60%的擠壓原料之機械性質、成本與熱性質分析,以選擇可以進行塑膠袋吹膜之配方。實驗結果顯示,S/(S+E)比在40%左右的抗張強度(Tensile strength)可達7.6MPa。而伸長率部份(Elongation),當S/S+E比為30%,其伸長率>667%,當S/S+E比為40%,其伸長率為588%,當S/S+E比為50%,其伸長率為418%,當S/S+E比為60%,其伸長率為134%,四組配方之伸長率皆有不錯的表現。所以,本實驗選擇以S/S+E比在40%的配方(成本相當低,約USD 2.34/kg)所生產的樣品進行吹膜。在吹膜前測其玻璃轉移溫度(Tg)約為47℃,熔點(Tm)約為127℃。吹膜成品經封口與裁剪之後,已具備生物可分解背心袋之雛形。 第二部份的實驗是利用2^(4-1)部份複因子實驗設計法,以尋求S/S+E比在50%或60%等較低成本的配方,其機械強度改善之可能性。實驗結果顯示,S/S+E比在50%與60%的配方中,伸長率還是相當的優異,最好的結果為517%,不過在抗張強度部份,最好的結果是6.05MPa,尚有待加強。 第三部份的實驗是利用三變數五層級的反應曲面法,尋求S/S+E比在40%抗張強度之最佳配方。實驗結果顯示,此次反應曲面法各成份的添加比例設計範圍不夠寬廣,所以多數配方沒有明顯效應。不過在反應曲面法20組的實驗配方中,可達到不錯的抗張強度(9.14MPa)與伸長率(898%),且其每公斤成本只有約2.39美元。
In the first part of this study, base on the thermoplastic starch formula (including starch, glycerol, water, lecithin and enzyme), we investigate the effect of four different starch/starch+ polyester ratio (S/S+E) of 30%, 40%, 50% and 60% on the mechanical and thermal property of biodegradable plastics. The results show that sample of 40% S/S+E ratio can reach a good strength of 7.6MPa. Sample of S/S+E ratio at 30% can reaches elongation over 677%; sample of S/S+E ratio at 40% reaches 588% elongation; sample of S/S+E ratio at 50% reaches 418% elongation, but sample of 60% S/S+E ratio can only have 134% elongation. Consequence, we choose formula of S/S+E ratio at 40% to produce blow-film products. The blow-film product can be sealed to form a biodegradable bag. In the second section of this study, we use 2^(4-1) fractional factorial design to improve the formula of 50% and 60% S/S+E samples for better mechanical properties. We got a best sample of 517% elongation, but the best tensile strength can only reach 6.05MPa. The third part of this study, we use response surface methods to find the optimal mechanical properties for the samples of 40% S/S+E ratio. The best sample (from 20 runs of response surface design) shows a good tensile strength of 9.14MPa and good elongation of 898%, beside, the cost of this sample is only about 2.39 USD/kg.