Investigation of bulk and in situ mechanical properties of coupling agents treated wood plastic composites

This paper presents the interfacial optimisation and characterisation of WPC by the use of maleated and silane coupling agents (MAPE, Si69 and VTMS), and its effect on the bulk and in situ mechanical properties. The results showed the treated WPC possessed better interface by showing improved compatibility between the constituents, wettability of wood flour, and resin penetration in the SEM images. The enhanced interface led to the increase in the tensile strength and stiffness of the treated WPC, which was confirmed by their superior load bearing capacity, namely the higher storage moduli measured by DMA. The observed shift of the relaxation peak of the treated WPC indicated the constraints on the segmental mobility of the polymeric molecules resulted from the treatments. Nanoindentation investigation revealed that the in situ mechanical properties were subject to a number of phenomena including fibre weakening or softening impact, crystalline structure transformation and cell wall deformation, concluding that the bulk mechanical properties of WPC might not be governed by the local property of materials within the interface.