Abstract
The moisture sensitivity of wood–polymer composites (WPCs) is mainly related to their hydrophilic wood components. Coatings are among the alternatives that improve the dimensional stability of these composites. However, the adhesion of most coatings to the WPC surface is generally poor. Thus, chemical and/or mechanical treatments should be applied to the WPC surface to improve the coating adhesion. Therefore, the main objective of this study was to improve the adhesion coating of polypropylene (PP) WPCs through a chromic treatment. PP was reinforced by three different pulp fibers (kraft, thermomechanical (TMP), and chemothermomechanical (CTMP)) at three fiber contents (50, 60, and 70% w/w). A chromic treatment was applied to the PP-based WPCs to activate the surface of the composites and alter their roughness parameters, creating a higher interfacial zone that improved the bonding of the epoxy coating to the surface of the PP composites. The chromic treatment increased the roughness of the surface. An increase in profile and surface parameters was observed after treatment. This treatment modified the chemical composition of the surface by creating polar carbon–oxygen groups and increasing the carbonyl and hydroxyl indexes.
Highlights
IntroductionWood–polymer composites ( called wood–plastic composites, wood–polymer composites (WPCs)) are materials that combine two or more distinct components: the polymer as a matrix and the lignocellulosic fiber as reinforcement
Wood–polymer composites are materials that combine two or more distinct components: the polymer as a matrix and the lignocellulosic fiber as reinforcement
Adhesive bonding is necessary for the assembly of wood–polymer composites (WPCs) and the application of coatings
Summary
Wood–polymer composites ( called wood–plastic composites, WPCs) are materials that combine two or more distinct components: the polymer as a matrix and the lignocellulosic fiber as reinforcement. The use of WPCs in humid environments requires good resistance to water absorption and swelling. Their sensitivity to moisture is mainly due to the presence of hydroxyl groups from the lignocellulosic components [1]. To improve WPC behavior for exterior use, it is relevant to consider protective coatings. WPCs have low surface energy and poor adhesion properties. In this respect, the adhesion of the coating to a WPC can be improved by surface pretreatments, especially for composites that contain polyolefins as their contact surface is not active. The improvement of the adhesion of WPCs depends on wood content, the nature of the polymer, and surface roughness [2]
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