Two years ago, in collaboration with the Wood Competence Center in Linz, Austria, WACKER started developing new processing aids for wood-polymer materials. These wood plastic composites consist of about 50 to 75 percent refined wood fibers and up to 25 to 50 percent of a polymer such as polyethylene, polypropylene or polyvinyl chloride. These plastics look similar to wood materials and have a similar feel. Thanks also to their durability and processing flexibility, they present an attractive alternative to normal plastics or wood for the construction, furniture and automotive industries.
To enable the wood-polymer components to bond optimally to each other in extrusion molding and to keep the resistance in the extrusion process as low as possible, additives are incorporated as lubricants. By developing new GENIOPLAST® additives for wood plastic composites, WACKER can now offer highly effective processing aids, whose many positive properties give them a competitive edge over comparable products.
The new additives contain a thermoplastic silicone elastomer. In comparison with conventional silicones, which cure irreversibly following vulcanization, thermoplastic silicones behave thermoplastic also within a certain range of temperatures. This makes them ideally suited as processing aids for thermoplastics with organic fillers.
GENIOPLAST® additives for wood plastic composites primarily act as lubricants. They reduce the coefficient of friction of the plastic and thereby the internal and external friction during extrusion. This enables the processes to run more stably and efficiently and save more energy. Tests show that one percent of the additive gives a significantly higher throughput – depending on the plastic blend and extruder used by between 15 and 25 percent. This leads in turn to lower unit costs in production.
The additives are also highly effective: even one percent is sufficient to achieve good lubricating properties. In comparison, conventional lubricants require WPC manufacturers to use between two and six percent of additive to achieve the same effect during extrusion.
GENIOPLAST® WPC additives can be blended easily as the thermoplastic silicone elastomer is already premixed with the corresponding plastic. This preformulated ready-to-use mixture enables the lubricant to be optimally integrated in the production process. At present, formulations with polypropylene (GENIOPLAST® PP 20A08) and polyethylene (GENIOPLAST® HDPE 20A03) are available.
GENIOPLAST® additives for wood plastic composites not only improve the production process, but also the properties of the end product. Wood-based plastics manufactured with the new processing aid have higher impact strength and flexural toughness than parts mixed with standard additives. GENIOPLAST® PP 20A08 and GENIOPLAST® HDPE 20A03 also reduce water absorption. The end products are consequently significantly more resistant to weathering.
Wood plastic composites are currently right on trend. They combine the positive properties of the natural product wood with the benefits of plastics. Whether they are used for decking boards, siding, fencing, windows, doors, furniture, parts for vehicle interiors or technical components – there is now a huge range to choose from. Thanks to their resistance and processing flexibility, wood-plastic materials offer an attractive alternative to unreinforced plastics for the construction, furniture and automotive industry. Wood-based plastics can be machined using all common woodworking machinery and can be worked with a great deal of freedom of design.