Water Absorption and Hygrothermal Aging Behavior of Wood-Polypropylene Composites

Abstract

Environmentally sound composites reinforced with natural fibers or particles interest many researchers and engineers due to their great potential to substitute the traditional composites reinforced with glass fibers. However, the sensitivity of natural fiber-reinforced composites to water has limited their applications. In this paper, wood powder-reinforced polypropylene composites (WPCs) with various wood content were prepared and subjected to water absorption tests to study the water absorption procedure and the effect of water absorbed in the specimens on the mechanical properties. Water soaking tests were carried out by immersion of composite specimens in a container of distilled water maintained at three different temperatures, 23, 60 and 80 °C. The results showed that the moisture absorption content was related to wood powder percentage and they had a positive relationship. The transfer process of water molecules in the sample was found to follow the Fickian model and the diffusion constant increased with elevated water temperature. In addition, tensile and bending tests of both dry and wet composite samples were conducted and the results indicated that water absorbed in composite specimens degraded their mechanical properties. The tensile strength and modulus of the composites reinforced with 15, 30, 45 wt % wood powder decreased by 5.79%, 17.2%, 32.06% and 25.31%, 33.6%, 47.3% respectively, compared with their corresponding dry specimens. The flexural strength and modulus of the composite samples exhibited a similar result. Furthermore, dynamic mechanical analysis (DMA) also confirmed that the detrimental effect of water molecules on the composite specimens.

Preparation and Characterisation of Wood Polymer Composites Using Sustainable Raw Materials

“…The composites showed similar water absorption curves for the entire immersion period. Therefore, the water absorption percentages were considered to be consistent with Fickian diffusion [ 94 , 95 , 96 ]. Moreover, it shows that SD played a profound role on the water absorption behaviour of samples, that is, the water absorption increased with the increase of SD content, which is also consistent with the studies reported by other researchers [ 6 , 97 , 98 , 99 , 100 , 101 , 102 ].…”

Development of Wood Polymer Composites from Recycled Wood and Plastic Waste: Thermal and Mechanical Properties

“…Figure 8b shows the images of WPCs immersed in water. It can be observed that the water absorption rate increased rapidly in the first few days and it slowed down after 8 days [52][53][54]. The water absorption process continued with the prolonged immersion until the specimen reached saturation after 20 days.…”

Investigation of the effect of water absorption on thermomechanical and viscoelastic properties of flax‐hemp‐reinforced hybrid composite

“…Berges et al 27 reported that water aging has a diverse effect on storage modulus and significant decrement in the storage modulus is observed up to the saturated points. Wang et al 28,29 reported the mechanical and viscoelastic properties under hygrothermal aging and the transfer process of water molecules with the Fickiam diffusion model was discussed. The results showed that the diffusion coefficient increased with water uptake and elevated water temperature.…”