Polyglycerol citrate bioadhesive for sawdust green composites

Abstract

Wood waste, including trimmings, offcuts, shavings, and sawdust, holds significant repurposing potential. Beyond its common use in energy pellets via combustion, wood waste can be transformed into particleboard panels—an eco-friendly alternative to incineration. For sustainability and carbon neutrality, replacing fossil-based binders with bio-based ones is crucial. Sawdust/polyglycerol citrate composites were developed using glycerin, a byproduct of biodiesel production. Composites containing 25% sawdust by weight and a glycerin/citric acid molar ratio of approximately 1 were cured at 170 °C for 8 h. Water was added (water/glycerin ratio: 0–2.5) to improve sawdust-prepolymer mixability and promote densification after curing. In the absence of sawdust, curing slowed, suggesting that –OH groups in sawdust cellulose participate in esterification, supported by citric acid's known role as a wood binder. The composites were extensively analyzed via ATR-FTIR and TG–DTA in oxidative atmospheres. Tensile testing showed the composites possess mechanical properties comparable to hardwood (tensile strength < 2.5 MPa). Thermal conductivity ranged from 0.07 to 0.10 W/(K m), indicating potential for use as lightweight thermal and acoustic insulation in construction. These findings confirm that polyglycerol citrate is an effective bioadhesive for particleboard production, enabling the valorization of wood sawdust and glycerin from biodiesel processing.