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static testing of structural polypropylene wood-plastic composites

   Date:2015-11-12  Author:Admin  Views:327
Wood-plastic composites (WPCs), defined as a thermoplastics reinforced with wood or other natural fibers, are principally produced from commodity thermoplastics such as polyethylene (PE), polyvinyl chloride (PVC), or polypropylene (PP). Current use of WPC materials includes automotive trim, window frames, roof shingles, and residential decking. Compared to timber, WPCs exhibit greater durability, require less maintenance, absorb less moisture, and provide superior fungal resistances . In addition, the wood filler improves thermal stability in contrast to other polymer composites.

Industrial structural applications of WPC materials have been limited, but a PVC wood-plastic composite formulation was successful utilized for a marine structure that required significant structural performance. Benefits exist for using an environmentally-benign material for marine applications, principally in reducing the permitting time and costs currently imposed on treated timber. The bridge industry also recognizes preservative treatment as the greatest hindrance for utilization of timber for bridge construction, reinforcing the motivation for developing structural WPCs. To reach this goal, these materials must resist a variety of structural loads while also maintaining resistance to moisture exposure and fungal decay .

Gaining acceptance for the use of WPCs within the structural design community requires a significant quantity of testing, analysis, and demonstrated use. Mechanical testing of WPCs developed for commercial use has been performed on other polymer types, including PE and PVC . The work presented 9 here builds on this previous research with the specific objective of establishing a PPbased WPC formulation that exhibits adequate extrusion characteristics, material properties, and water absorption. Such formulations would improve utilization of this emerging material class for structural applications.

Comparing the differences between maple and pine for a given formulation demonstrates that pine exhibits superior performance based on extrusion quality, swell, and absorption. On the other hand, maple demonstrates superior mechanical properties. Establishing the affects of material composition within a species is a more difficult process; however, the behavior is consistent between wood flour species. In general, extrusion quality, mechanical properties, and physical properties tend to be the best for formulations with median amounts of each material. The exclusion of MAPP within a formulation caused the largest reduction in mechanical properties, compared to any other material present. In conclusion, the pine formulation containing 58.8% wood flour, 33.8% PP, 4.0% talc, 2.3% MAPP, and 1.0% lubricant (P5 and P6) was deemed the optimum formulation by maximizing the mechanical and physical properties in addition to providing quality extrusion characteristics.
 
 
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