End-grained wood-polyurethane composites, 2: Dimensional stability and mechanical properties

This paper is the second of a two-part series devoted to the preparation and the characterization of end-grained WPCs. WPCs were obtained by polycondensation and reactive grafting of PEG or PPG with diisocyanate derivatives within the wood structure. In this part of the study, the improvement of both the dimensional stability and mechanical properties were investigated. It came out that dimensional stability was influenced by the polyol nature, functionality, and content in wood. Both PEG and PPG appeared to be efficient to improve dimensional stabilization, especially at higher weight fraction in wood. A tuning of the impregnation conditions allowed to reach a dimensional stabilization as high as 70%. Performing compression and bending tests evidenced that the mechanical properties of the WPCs were not negatively affected by the reactive impregnation process. Moreover, it could be shown that the WPCs prepared starting from PPG displayed higher stiffness than PEG-based WPCs.