Influence of wood thermal modification on the supermolecular structure of polypropylene composites

Abstract The thermal modification of wood can be an interesting way of improving adhesion in polymer composites, although the mechanical properties of composites with heat treated wood presented so far in many works arouse much controversy. In this work, effects of thermal modification of wood on the supermolecular structure and morphology of wood/polypropylene composites (WPC) were investigated using X‐ray diffraction, hot stage optical microscopy, and differential scanning calorimetry. A significant impact of the conditions of thermal wood modification on the formation of polymorphic varieties of the polymer matrix has been demonstrated. Furthermore, thermal treatment also affected the nucleation activity of wood, which was confirmed by determined parameters such as, crystal conversion, half crystallization time, and crystallization temperature. In addition, differences in the formation of transcrystalline structures responsible for the level of interfacial adhesion were depicted based on hot stage optical microscopy. Mechanical tests have shown that obtaining the appropriate strength properties of composite materials depends on the selection of appropriate conditions for thermal modification, which determine the supermolecular structure and nucleation activity. The obtained results, not reported so far, are extremely important when designing WPC composite materials with strictly defined physicochemical parameters.