Functionalization of various coffee husk biofibers on the rheological and thermomechanical properties of poly(butylene succinate)-urethane blended composites

Abstract

Many studies have reported that surface-functionalized biofibers originating from plant waste can be used to improve the compatibility and processability of polymer blend systems. This study investigated the effects of size distribution and surface treatment of coffee husk (CH) biofibers on the rheological and thermomechanical properties of poly(butylene succinate)/thermoplastic polyurethane polymer blend composite. CH is a coffee waste with interlinked complex macromolecular structure of lignocellulose materials like cellulose, hemicellulose, and lignin. It was found that the handling and processability of the composites improved after the CH was surface-functionalized with diisocyanate/methacrylate prior to composite fabrication. Smaller-sized surface-treated CHs showed superior processability owing to the entanglement of fibers through the matrices associated with the improvement of interfacial adhesion. Therefore, the frequency-dependent rheological test revealed an increase in complex viscosity and storage modulus with the surface treatment and size reduction of CHs. Regardless of the size distribution, the degree of crystallinity of poly(butylene succinate) in the composites filled with surface-treated CHs reduced by about 20%. The composites with treated CHs also demonstrated superior thermal stability than their corresponding composites with raw CHs.