Wood Plastics Composites – A new opportunity
The concept of wood plastics composites (WPC) is starting to excite interest in Europe as methods of combining the two materials are developed and as the market continues to expand in the USA and other parts of the world. This new group of materials covers a wide range of polymer matrix types (including PP, PE and PVC) as well as a wide range of fillers and stiffeners (including wood flour, flax, jute and other cellulose based fibre fillers). The materials offer added strength, lower costs and a wide range of finishes but the high cellulose filler content of some products (up to 70%) may lead to some confusion in the market – is it wood or is it plastic? The plastics processing industry may change yet again as wood product companies transform themselves into composites companies.
The majority of the current applications are in the USA where significant advances are being made and finished products such as decking, cladding and window frames are already on the market. For the past 5 years the WPC market has grown at a rate of 100% per year and shows no signs of slowing down as new applications are developed for the materials. The majority of current applications are for the outdoor replacement of wood products but structural engineering applications are now being developed to use the improved physical properties of WPC.
The production of WPC typically uses a fine wood waste (sawdust in the 40 to 60 mesh range) mixed with various plastics. The powder is extruded to a dough-like consistency and the profile is then extruded through a single-step die (typically costing between?00 and?00) with no additional calibration and only a simple water bath for cooling.
Processing temperatures are less than 150 deg C, a temperature that allows high processing rates and low energy consumption. During production, the flow characteristics of cross-linked composite, through the extrusion system, permit the use of simple dies for even the most complex profiles. The simplicity of the die design means that lead times of six to eight weeks from design concept to production are usual.
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