Effects of Modified Microcrystalline Cellulose on Mechanical Properties in Thermoplastic Polyurethane Composites

초록

Cellulose is a well-known for eco-friendly, biodegradable and abundant polymer in nature. Many researchers investigated microcrystalline cellulose (MCC) for applications in lightweight polymer composites owing to the high crystallinity and mechanical properties originating from strong intermolecular hydrogen bonding. However, the strong interactions between MCCs often lead to their aggregation, leading to reduction in interfacial areas and reinforcement effects in polymer composites. To investigate optimum chemical structures of MCC for polymer composites, three different types of modified-microcrystalline cellulose (m-MCC) are employed to manufacture thermoplastic polyurethane (TPU)/m-MCC composites through an extrusion process. The hydroxyl groups in MCC are substituted by methyl (-CH3) or hydroxypropyl (-CH2CH(OH)CH3) groups to mitigate the aggregation since the substitution of hydroxyl group to methyl group reduces hydrogen bonding sites. Meanwhile, the substitution to hydroxypropyl group increases intermolecular distance due to its large molecular size. Three types of the m-MCC are (1) low substitution degree with methyl group (HP-0), (2) medium substitution degree with methyl and hydroxypropyl groups (HP-low), and (3) high substitution degree with methyl and hydroxypropyl groups (HP-high). Although the m-MCC has higher compatibility than that of MCC due to the reduced aggregation, the m-MCC has lower crystallinity and mechanical properties than those of MCC due to the decreased hydrogen bonding sites and longer intermolecular distance. In this presentation, we will discuss details of chemical modification effects of MCC on TPU/m-MCC composites with a focus on structure-property relationships.