Department of Packaging and Materials Technology, Faculty of Agro-Industry, Kasetsart University, Bangkok 10900, Thailand; Center for Advanced Studies for Agriculture and Food (CASAF), Kasetsart University Institute for Advanced Studies (KUIAS), Kasetsart University, Bangkok 10900, Thailand; Kasetsart Agricultural and Agro-Industrial Product Improvement Institute, Kasetsart University, Bangkok 10900, Thailand.
Department of Packaging and Materials Technology, Faculty of Agro-Industry, Kasetsart University, Bangkok 10900, Thailand.
Int J Biol Macromol. 2024 Nov;280(Pt 2):136335. doi: 10.1016/j.ijbiomac.2024.136335. Epub 2024 Oct 31.
Increasing interest in biodegradable and cost-effective materials derived from renewable resources has led to the development of injection-moldable thermoplastic starch (TPS). Plasticizers constitute an indispensable additive for manufacturing TPS, influencing both its thermomechanical processability and performance. The aim of the current work is thus to study the effect of single and mixed polyol plasticizers on the performance of injection-molded TPS. This study was carried out by using three types of polyols - glycerol, xylitol, and sorbitol- as single and equal-weight binary mixed plasticizers to modify cassava starch via extrusion. The resulting TPS extrudates were converted to test specimens via injection molding. Melt flow index, moisture content, water contact angle, and tensile and dynamic mechanical thermal properties of the materials were examined. In addition, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis were also conducted. The results show that the higher-molecular-weight polyols (xylitol and sorbitol) exhibited lower plasticizing efficiency but formed denser hydrogen-bonding interactions with starch molecules than the smaller-molecular-weight one (glycerol). In both single and mixed plasticizer systems, increasing the molecular weight of the polyol plasticizer led to enhancements of the tensile strength (up to 27 MPa (200 % increment) and 26 MPa (115 % increment) for single and mixed plasticizer systems, respectively), Young's modulus (up to 386 MPa (240 % increment) and 458 MPa (185 % increment) for single and mixed plasticizer systems, respectively), decomposition temperature (2-3 °C), and glass transition temperature (30-50 °C) of TPS and a reduction in its moisture content (60-80 %) and surface stickiness, though disadvantages included poorer thermomechanical processability and higher melt viscosity and brittleness. In conclusion, using a co-plasticizer of glycerol and xylitol is appropriate for injection-molded TPS articles considering both processability and performance. The obtained TPS has potential applications in edible or single-use biodegradable rigid products, such as pet chew toys, chopsticks, cutlery, plant pots, etc.
对源自可再生资源的可生物降解和具有成本效益的材料的兴趣日益浓厚，促使人们开发出可注塑的热塑性淀粉（TPS）。增塑剂是制造 TPS 不可或缺的添加剂，它会影响 TPS 的热机械加工性能和性能。因此，本研究旨在研究单一和混合多元醇增塑剂对注塑 TPS 性能的影响。通过使用甘油、木糖醇和山梨糖醇这三种多元醇作为单一和等重的二元混合增塑剂，通过挤出对木薯淀粉进行改性。然后将得到的 TPS 挤出物通过注塑成型转化为测试样品。测试了材料的熔体流动指数、水分含量、水接触角以及拉伸和动态机械热性能。此外，还进行了傅里叶变换红外光谱、X 射线衍射、扫描电子显微镜和热重分析。结果表明，高分子量多元醇（木糖醇和山梨糖醇）的塑化效率较低，但与淀粉分子形成的氢键相互作用比低分子量多元醇（甘油）更紧密。在单一和混合增塑剂体系中，增塑剂多元醇的分子量增加导致 TPS 的拉伸强度（分别提高 27 MPa（200%增加）和 26 MPa（115%增加））、杨氏模量（分别提高 386 MPa（240%增加）和 458 MPa（185%增加））、分解温度（2-3°C）和玻璃化转变温度（30-50°C）提高，而水分含量（60-80%）和表面粘性降低，但缺点包括较差的热机械加工性能和较高的熔体粘度和脆性。综上所述，考虑到加工性能和性能，使用甘油和木糖醇的共增塑剂适合用于注塑 TPS 制品。所得 TPS 具有在可食用或一次性生物降解刚性产品中的应用潜力，例如宠物咀嚼玩具、筷子、餐具、花盆等。
