Highly Unsaturated Microcrystalline Cellulose and Its Cross-Linked Soybean-Oil-Based Thermoset Composites

Microcrystalline cellulose (MCC) was highly decorated with unsaturation functionality through esterification with methacrylic anhydride (MAA) with the assistance of treatment. The degree of unsaturation on the MCC surface was tailored by adjusting the mass ratio of MAA to MCC during the modification process. The unsaturated-MCC was characterized by FTIR, XRD, XPS, NMR, and contact angle measurements. The degrees of substitution and unsaturation of the unsaturated-MCC were quantitatively determined by NMR and XPS analyses to reveal the grafting efficiency of MAA on the MCC surface. The unsaturated-MCC was further used as a reactive reinforcing agent for cross-linking with acrylated epoxidized soybean oil (AESO) to manufacture fully biobased MCC/AESO composites. The cross-linking mechanism between the unsaturated-MCC and AESO was discussed through the curing kinetic behavior of the MCC/AESO systems based on Kissinger's theory. The unsaturation functionalization of MCC resulted in significantly improved flexural strength and modulus, water resistance, storage modulus, glass transition temperature, thermal stability, and interfacial adhesion of the resulting unsaturated-MCC/AESO composites.