Comparative study on artificial and natural weathering of wood-polymer compounds: A comprehensive literature review

• Ageing phenomena in climate chambers adequately mirror degradation by natural weathering. • Mechanical properties of wood-polymer composites significantly degrade under weathering. • Ageing primary manifests itself by a loss of interfacial fiber bonding in the plastics matrix. • The lower the fiber content the more uniform is the strength-loss over exposure time. • The addition of agents to the formulation postpones and reduces ageing significantly. Wood-polymer composites (WPC) increasingly gain in popularity in the building industry. To date there is less long-term experience from façade applications which reliably confirm that relevant material properties are sufficient throughout their expected lifetime. Therefore it is common practice to simulate WPC material ageing in climate chambers. Artificial conditions, however, not necessarily mirror practical applications. To get a clearer picture about WPC ageing this literature review draws a comparison between artificial and natural weathering of divers WPC compound formulations usually applied in cladding products. It was found that both conditioning types provoke comparable effects in the material. UV-light in combination with moisture leads to polymer crystallinity with chain scissions and delignification. As a result, interfacial bonding gets weaker and fibers become detached from the matrix. In the further course lightening penetrates deeper reducing the stress bearing cross-section of the WPC profile. In this view, material ageing of WPC manifests itself as highly dependent on promoting agents. These aim at improving interfacial bonding between fibers and matrix and stabilizing polymer chains against radiation.