Watcharakitti Jidapa, Nimnuan Jaturavit, Krusong Kuakarun, Nanan Suwat, Smith Siwaporn Meejoo
Center of Sustainable Energy and Green Materials, Faculty of Science, Mahidol University, 999, Phuttamonthon Sai 4 Road, Salaya, Nakhon Pathom 73170, Thailand.
Department of Chemistry, Faculty of Science, Mahidol University, 999, Phuttamonthon Sai 4 Road, Salaya, Nakhon Pathom 73170, Thailand.
Polymers (Basel). 2023 Mar 31;15(7):1754. doi: 10.3390/polym15071754.
Instead of using finite petroleum-based resources and harmful additives, starch can be used as a biodegradable, low-cost, and non-toxic ingredient for green adhesives. This work employs KPO catalyzed transesterifications of cassava starch and methyl laurate at varying reaction times (1-10 h), resulting in the enhanced hydrophobicity of starch laurates. At longer reaction times, starch laurates having higher degrees of substitution (DS) were obtained. While starch laurates are the major products of transesterification, relatively low-molecular-weight byproducts (1%) were detected and could be hydrolyzed starches based on gel permeation chromatography results. Contact angle measurements confirmed the relatively high hydrophobicity of the modified starches compared with that of native starch. The modified starches were then employed to prepare water-based adhesives on paper (without any additional additives). Notably, the shear strength of the esterified starch adhesives appears to be independent of the DS of esterified samples, hence the transesterification reaction times. Additionally, the shear strength of water-based adhesives (0.67-0.73 MPa) for bonding to paper substrates is superior to that of two other commercially available glues by a factor of 10 to 80 percent.
淀粉可作为绿色胶粘剂的一种可生物降解、低成本且无毒的成分，而无需使用有限的石油基资源和有害添加剂。这项工作采用KPO催化木薯淀粉与月桂酸甲酯在不同反应时间（1 - 10小时）进行酯交换反应，从而提高了月桂酸淀粉酯的疏水性。在较长反应时间下，可得到取代度（DS）更高的月桂酸淀粉酯。虽然月桂酸淀粉酯是酯交换反应的主要产物，但根据凝胶渗透色谱结果检测到相对低分子量的副产物（1%），可能是水解淀粉。接触角测量证实，与天然淀粉相比，改性淀粉具有相对较高的疏水性。然后将改性淀粉用于在纸张上制备水性胶粘剂（无需任何额外添加剂）。值得注意的是，酯化淀粉胶粘剂的剪切强度似乎与酯化样品的取代度无关，因此也与酯交换反应时间无关。此外，用于粘结纸张基材的水性胶粘剂的剪切强度（0.67 - 0.73 MPa）比另外两种市售胶水高出10%至80%。
