Garalde Ray Anne, Thipmanee Ranumas, Jariyasakoolroj Piyawanee, Sane Amporn
Department of Packaging and Materials Technology, Faculty of Agro-Industry, Kasetsart University, Bangkok 10900, Thailand.
Center for Advanced Studies for Agriculture and Food, KU Institute for Advanced Studies (CASAF, NRU-KU, Thailand), Kasetsart University, Bangkok 10900, Thailand.
Heliyon. 2019 Mar 7;5(3):e01251. doi: 10.1016/j.heliyon.2019.e01251. eCollection 2019 Mar.
The objective of this work was to investigate blend ratio and storage time effects on the morphological, mechanical, and thermal properties of thermoplastic starch/poly(butylene adipate--terephthalate) (TPS/PBAT) films. TPS was prepared from plasticized cassava starch using a twin-screw extruder. TPS was subsequently melt-blended with PBAT with varied weight ratios (i.e., 20/80, 40/60 and 60/40) and blown to form TPS/PBAT films. It was found that increasing the TPS/PBAT ratio to 40/60 led to improved distributions of polymeric components and increased PBAT crystallization temperatures while reducing TPS melting transitions and tensile properties of TPS/PBAT films. After three months of storage at 30 °C, the tensile strength and secant modulus at 2% strain of TPS/PBAT films increased due to recrystallization of both TPS and PBAT. Blend ratios were the primary determinant for changes in TPS/PBAT film elongation at break with this storage time. Elongation at break decreased at low TPS:PBAT ratios (i.e., 20/80) and increased at high blend ratios (i.e., 60/40). The recrystallization of both TPS and PBAT components were observed from XRD and DSC analyses. Results obtained from both techniques confirmed the formation of additional crystalline structures of individual components during storage. The recrystallization phenomena also affected thermal transition temperatures of blend components. The crystallization temperature of PBAT-rich phase increased as starch could act as nucleating sites for PBAT. Using DMA, the curve of TPS/PBAT film exhibited two sharp individual peaks corresponding to the glass transitions of PBAT-rich and starch-rich phases. The of TPS-rich phase shifted to higher temperature due to recrystallization of TPS-rich phase.
本研究的目的是研究共混比例和储存时间对热塑性淀粉/聚己二酸丁二醇酯-对苯二甲酸丁二醇酯（TPS/PBAT）薄膜的形态、力学和热性能的影响。TPS由增塑木薯淀粉通过双螺杆挤出机制备而成。随后，将TPS与不同重量比（即20/80、40/60和60/40）的PBAT进行熔融共混，并吹塑成TPS/PBAT薄膜。研究发现，将TPS/PBAT比例提高到40/60会导致聚合物组分分布改善，PBAT结晶温度升高，同时降低TPS/PBAT薄膜的TPS熔融转变温度和拉伸性能。在30°C下储存三个月后，TPS/PBAT薄膜在2%应变下的拉伸强度和割线模量由于TPS和PBAT的再结晶而增加。共混比例是此储存时间下TPS/PBAT薄膜断裂伸长率变化的主要决定因素。在低TPS:PBAT比例（即20/80）下，断裂伸长率降低，而在高共混比例（即60/40）下，断裂伸长率增加。通过XRD和DSC分析观察到TPS和PBAT组分的再结晶。两种技术获得的结果证实了储存期间各组分额外晶体结构的形成。再结晶现象也影响了共混组分的热转变温度。富含PBAT相的结晶温度升高，因为淀粉可作为PBAT的成核位点。使用DMA，TPS/PBAT薄膜的曲线呈现出两个尖锐的独立峰，分别对应富含PBAT相和富含淀粉相的玻璃化转变。由于富含TPS相的再结晶，富含TPS相的玻璃化转变温度向更高温度移动。
