Wood-Plastic Composites - Tangram

1 Wood- Wood-Plastic Composites A technical review of materials, processes and applications Tangram . TECHNOLOGY. What are wood- Wood-Plastic Composites ? The concept of wood- Wood- plastics Composites rapidly developing generation of currently cost money for (WPC) are a new group of WPC wood Composites ' have disposal are now a valuable plastics Composites materials that are generating good mechanical properties, resource - recycling can be both interest in both the UK and high dimensional stability and profitable and ethical. The (WPC) generating overseas. The term WPC' can be used to produce plastic can be from recycled interest as new covers an extremely wide range complex shapes. They are plastic bags and recycled of composite materials using tough, stable and can be battery case materials although methods of plastics ranging from extruded to high dimensional in demanding applications new combining the polypropylene to PVC and tolerances.

2 The new WPC plastics materials are used. The binders/fillers ranging from materials are high technology recycling ethos is to use materials are wood flour to flax. These new products for the most materials recovered from short developed. materials extend the current demanding applications. life cycle applications in long life concept of wood Composites ' cycle applications. The most common types of the The WPC market is from the traditional compressed new WPCs are produced by materials such as particle-board expanding in the and medium density fibreboard mixing wood flour and plastics to produce a material that can USA and other parts (MDF) into new areas and, more be processed just like a plastic importantly, a new generation of but has the best features of of the world. high performance products. wood and plastics . The first generation of wood The wood can be from sawdust Composites ' were a combination and scrap wood products.

3 This of recycled wood flour or chips means that no additional wood and binders. These were ideal resources are depleted in for relatively undemanding WPCs, waste products that applications. The new and The benefits of WPCs WPCs combine the WPCs can produce the final applications. They can cost- plentiful raw materials. Wood shape through extrusion effectively replace wood waste and recycled plastics best features of wood processing. This maximises products in applications such as become assets instead of resource efficiency and gives furniture, doorframes, liabilities. and plastics . design flexibility for improved decorative profiles, in fact fastening, stiffening, anywhere wood shapes are They are competitively priced reinforcement, finishing and used. They can cost-effectively and are competitive with joining. replace plastic products in traditional materials such as applications such as window timber, MDF and PVC-U.

4 WPCs are wood products that frames, cable trunking, roofline They are easily produced and need no further processing. products and cladding, in fact easily fabricated using WPCs are weather, water and anywhere that plastics shapes traditional wood processing mould resistant for outdoor are used. techniques. applications where untreated WPCs have many benefits: They are available in a broad timber products are unsuitable. They are true hybrid materials range of finishes and WPCs are plastic products with appearances. and combine the best exceptional environmental properties of both wood and They are easily recycled after credential and performance. plastics . use. WPCs have a wide range of They use low cost and WPC properties The wood particles WPCs are true composite a direct result of the structure. than the PVC based products materials and have properties Moisture can only be absorbed but the PVC products are easier are completely coated of both materials.

5 They have into the exposed sections of to paint and post treat. stiffness and strength between wood and is not transmitted with plastic. those for plastic or wood, but across the plastic boundaries. Pigments, UV stabilisers and fire retardants can all be added to the density is generally higher The result is that WPCs are the WPC raw material before than either. The properties of extremely moisture resistant, extrusion to improve specific WPCs come directly from their have little thickness swell in properties. WPCs have: structure: they are intimate water and do not suffer from mixes of wood particles and fungal or insect attack. Good stiffness and impact plastic. The plastic effectively resistance. The properties of WPCs can be coats the wood particle as a tailored to meet the product Dimensional stability. thin layer. The structure is requirements by varying the shown at left.

6 Resistance to rot. type of wood or the type of The high moisture resistance of plastic - the PE based products Excellent thermal properties. WPCs (water absorption of are cheaper and have a higher compared to for pine) is heat distortion temperature Low moisture absorption. WPCs and fire WPC properties are General experience shows that these cannot be directly ignitability tests and these are WPCs have a fire behaviour very translated into the relevant similar to the results for wood ideal for many similar to, or better, than that British and European standards. with similar density. of comparable timber products. This information is therefore applications. provided for guidance only. WPCs show good results in Ideal Fire tests relate to either spread of flame testing and the WPC. Material flammability or ignitability' As a general rule, the presence results can actually be better which considers the ease with of the plastic matrix appears to that those of wood with a which a material will catch fire improve the fire performance of similar density.

7 High Cost Low and sustain burning and the wood component in WPCs. The fire performance of WPCs spread of flame' which Many plastics , PVC-U, have can be modified and improved Low Flexural Modulus High considers the propagation of good ignitability and spread of by the addition of flame and fire by the material being flame performance and this smoke retardants to the raw High Thermal Conductivity Low tested. appears to be transferred to the material before processing. WPC when they are used as the Most of the fire testing of WPCs plastic component. Low Corrosion/Mould Resistance High has been carried out in the USA. using ASTM standards and WPCs show good results in Difficult Colour Easy Difficult Ease of Working Easy Low Fire Resistance High WPCs and the environment One of the main reasons for with their rising and cyclical raw formaldehyde or volatile High Environmental Impact Low using WPCs is environmental.

8 Materials costs. organic compounds. The environmental pressures on For users of wood products WPCs are recyclable and can industry in terms of recycling there is a need to improve the be reground and reused after and sustainability are growing resource efficiency and to their service life. daily. There is a clear need to recycle the raw materials waste extend the life cycle of WPCs are considered non- that inevitably occurs. WPCs traditional building materials hazardous waste and can be increase the efficiency of wood such as wood. This resource disposed of by standard usage by up to 40% compared efficient use of materials that methods. The basic material to traditional wood processing. are currently seen as waste structure of WPCs means that supports the developing WPCs provide other leaching from WPCs is concept of sustainable environmental benefits such as: minimal to non-existent.

9 Development. There is negligible waste and WPCs are environmentally For users of plastics products any that is produced reused. friendly materials. there is a need to reduce the dependence on petrochemicals WPCs contain no Processing WPCs WPCs are made using a variety and plastic mix to improve theand construction and the lack of Processing WPCs is an of raw materials. The basic processing and mechanical calibration tooling means that wood and plastic mix must be strength of the final manufacture lead times expert task but the modified with process and are short (6 to 8 weeks from results can meet the The basic wood product is a fine property additives to improve design to production). sawdust in the 40 to 60-mesh most demanding processing or the final range and this is dry blended A standard simple water bath is properties of the WPC. customer with the various plastics and used for cooling and the haul-off One of the major concerns with modifiers.

10 The mix is extruded also uses standard parts. After requirements. WPCs in the past has been the to a dough-like consistency haul-off, the engineered net difficulty in combining plastics through a simple die with none shape is complete and ready for intimately with the wood flour. of the calibration problems of use. The general technique is to use conventional extrusion. The flow Low processing temperatures a compatibiliser' or coupling properties and thermal (less than 150 deg C) give high agent' to improve the blending characteristics of the WPC. processing rates, low energy of the two materials. A typical blend means that simple dies consumption and improved compatibiliser is MAAP, which is can be used, even for the most safety around the extruders. used to treat the basic wood complex profile. The die design Working and finishing WPCs WPCs can be processed using the net shape extrusion means The effectiveness of welding WPCs can be cut conventional woodworking tools that many normal processes are with WPCs varies with the exact and have similar to wood or not needed.