Modified Physical Properties of Thermoplastic Polyurethane Composites with Chemically Modified Microcrystalline Cellulose

With the growing interest of eco-friendly polymer composites, many researchers employed cellulose as a filler for polymer composites. Especially, microcrystalline cellulose (MCC) has various advantages such as high crystallinity and mechanical properties originating from strong intermolecular hydrogen bonding. However, too strong interaction among MCCs can lead to aggregation of fillers in polymer composites, which can reduce the interfacial areas and reinforcement effects between the polymer matrix and filler. Herein, we employed three different chemically modified microcrystalline cellulose (m-MCC) where hydroxyl groups of MCC were substituted by either methyl (-CH₃) or hydroxypropyl (-CH₂CH(OH)CH₃) groups: (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). The different types of m-MCCs were compounded with ester type thermoplastic polyurethane (TPU) by an extrusion process. As the chemical substitution of hydroxyl groups can affect the number of hydrogen bonding sites or m-MCC intermolecular distances, both crystallinity of m-MCCs and polymer-filler interaction can also be manipulated. In this presentation, we will discuss structure-property relationships of TPU-MCC composites with focuses on correlation of crystallinity and dispersion of m-MCC with mechanical properties of the TPU-MCC composites.