engleski

Photochemical stabilization of wood plastic composites

This work reports a study of the chemical stabilization of HDPE wood plastic composites (WPC) exposed to UV light in conditions of artificially accelerated ageing. Protection against photooxidation was tested with different concentration of UV stabilizers. The photochemical behaviour of WPC is of prime importance because the durability is the key factor for outdoor applications. Wood plastic composites are typically comprised of wood or other natural lignocellulosic fibers in a thermoplastic matrix. They have found their way into consumer, automotive and construction applications and are experiencing tremendous growth in these applications. WPCs are often seen as green composites because the wood is a renewable component sourced from a waste stream and the entire composite can be recyclable [1]. Furthermore, WPC lumber is promoted as a lower-maintenance alternative compared with solid wood. Most WPCs use wood flour as the wood component. Pine, maple, and oak with mesh sizes between 20 and 100 mesh are commonly available for WPCs. Wood flour is typically incorporated into WPCs at 50-60 % by weight. The growth in exterior applications results in a need to understand the durability of WPCs. Durability issues such as weatherability, moisture resistance, thermal and fire performance are needed to be set up. It is especially important to characterize and understand the changes that occur when WPCs are exposed to different weather conditions. Analysis by infrared spectroscopy of the WPCs after photoageing shows the presence of the products caused by degradation i.e. oxidation, which results in lower durability of the WPCs [2]. The aim of this study is to determine the optimum concentration of the photostabilizer in WPCs in order to ensure the most efficient durability of WPCs and delay the oxidation of the polymer matrix. In this study pine wood flour filled high-density polyethylene (HDPE) composites were manufactured through extrusion. The HDPE/wood fluor ratio in composites was 70/30 while the content of UV stabilizer was 0.5 and 1.5 phr. In order to simulate outdoor weathering conditions composites were exposed to UV light (vawelength 290 nm) in UV chamber (xenon-arc weathering apparatus). Attenuated total reflectance Fourier transform infrared spectroscopy ATR-FTIR) was useful in showing the changes in composite surface after weathering due to partial degradation.

wood plastic composites (WPC); polyethylene; degradation; UV stabilization

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