Environmentally-friendly solvent pulping and grafting strategies for better foamability of poly(lactic acid)/agricultural waste biocomposites

In this study, the foamability of poly (lactic acid) (PLA) through a continuous extrusion process was enhanced by using an agricultural waste, environmentally friendly pulping methods, and reactive compatibilization of the lignocellulosic filler with matrix in the extrusion flow field. Both applied solvent-pulping methods by using chemicals with low safety and toxicity risks were considerably successful in purifying the micron-sized cellulosic fibers of rice straw (RS). The interface of PLA matrix with RS pulp fibers was modified by applying reactive compatibilizers containing maleic anhydride (MA) and epoxy functional groups. Both compatibilizers had the ability to simultaneously react with the hydroxyl groups of RS pulp fibers and end groups of PLA chains during the melt-compounding process. As a result of RS pulping and PLA/RS pulp compatibilizing reactions, the processability of PLA in an extrusion foaming process was substantially enhanced, in a way that the void fraction and cell density of PLA foam increased more than seven and two times, respectively. The extruded lightweight all-green biocomposite foams can be applied in construction and packaging applications.