Wood-plastic composites may be one of the most dynamic sectors of today's plastic industry. Although the technology is not new, there is growing interest in the new design possibilities this marriage of materials offers.
The production of Wood-Plastic Composites typically uses a fine wood waste (cellulose based fiber fillers such as hardwood, softwood, plywood, peanut hulls, bamboo, straw, etc.) mixed with various plastics (PP, PE, PVC). The powder is extruded to a dough like consistency and then extruded to the desired shape.
Additives such as colorants, coupling agents, stabilizers, blowing agents, reinforcing agents, foaming agents, and lubricants help tailor the plastic end product to the target area of application.
With up to 70 percent cellulose content, wood-plastic composites behave like wood using conventional woodworking tools. At the same time, they are extremely moisture-resistant. There is little or no water present, thus increasing resistance to rot.
Wood-plastic composites are already widespread in outdoor use for decking, cladding, park benches, etc. There is also a growing market for potential indoor uses such as door frames, trim and furniture.
|  |
Products include: Lumber, decking and railing, window profiles, wall studs, door frames, furniture, pallets, fencing, docks, siding, architectural profiles, louvers, automotive components.
|
Characteristics
- Fastest growing sector of plastics industry
- Volume processors must produce faster, better, cheaper
- Weather ability and life cycle costs are major factors
- Formulation variations that increase wood content offer expansion into other uses
- Environmentally safe and efficient
Key Blending Considerations in Wood-Plastic Composites
Compared to many other processes, on-line compounding and extrusion exhibit short performance timescales, consistent with the mixing time of the extruder. For high formulation quality the feeding system must achieve and maintain its required blending accuracy within this brief time. |
Key to a feeder's ability to attain high accuracy over short intervals is the resolution of its weighing device and response of its process controller.
As the illustration at right shows, lengthy performance timescales permit a given blending accuracy to be attained with a low performance weighing system.
However, to achieve the same accuracy in the short interval characteristic of compounding and extrusion operations, a much higher weighing performance is required.
Additional important blending system considerations in wood/plastic composite processing include control and weigh system insensitivity to environmental disturbances, and the ability to reliably handle/control difficult organic components. |  |
-www.ktron.com
No comments:
Post a Comment