Wood and wood substitute materials can serve as exterior cladding, decking, trim pieces, fencing and the like and can be found on exposed areas around the exterior of building structures. Many consumers find wood cladding, decking trim and fencing to be highly desirable from an aesthetic standpoint, but often select alternative products (e.g., wood plastic composite decking, steel siding, vinyl siding and fencing, or molded plastic or press-formed cementitious sheathing products) due to their lower initial cost, ease of maintenance, and perceived longevity when compared to wood. In addition to their relative high cost, wood products are prone to splitting, mildewing and rotting over time as a result of being exposed to prolonged moisture (rain, snow, high humidity) and excessive or insufficient sun conditions.
Known commercial synthetic products, including fiber cement products and extruded plastic products, particularly polyvinyl chloride siding (commonly referred to as vinyl siding) which are made to mimic wood in a variety of applications and designs, have achieved reasonable market success. However, they still lack the authenticity of real wood siding, decking, fencing and similar products, particularly, for decking and cedar clapboard siding. The synthetic wood substitute materials are exposed to moisture and sunlight and can be altered by them. For example, vinyl siding, as a result of its expansion and contraction during daily thermal cycles is not typically fastened directly to the building structure, but rather must be hung and the ends of adjacent pieces overlapped, in order to avoid distortion of the siding or unsightly gaps between adjacent pieces. However, even with these precautions, permanent damage to vinyl siding can occur as the result of temperature increases from solar irradiation, which depend on siding color, reflection from windows and the like and can achieve temperature increases above ambient of as much as 25° C. or more or even 40° C. or more.
Filled oriented plastic composites have been taught as wood substitute materials. These materials are made by extruding a filled thermoplastic to produce an extruded polymer composition, temperature conditioning and then drawing the polymer composition through a solid state drawing die at a drawing temperature to produce an oriented polymer composition (OPC). During the drawing process cavities are produced proximate the filler particles to produce an article of reduced density compared to the polymer composition prior to the drawing process. OPC articles are particularly suitable for cladding as they can have a coefficient of linear thermal expansion (CLTE) low enough for the OPC cladding to be directly fastened to a substrate and without overlapping the ends of adjacent pieces.
However, many highly oriented filled plastic composition articles can shrink in the board length direction, the direction in which the polymer composition is oriented during the drawing process, even at moderate temperatures. The reduction in length (shrinkage) can be a problem in storage before product sale or in end-use applications. Depending on the duration and temperature of exposure, shrinkage in the length direction of the article of as much as one percent, 2 percent, or even 3 percent or more is possible. Over days, weeks, or months, under some extreme conditions, shrinkage of 5 percent or more can be possible. Shrinkage during storage can lead to product being of length less than the nominal professed length; shrinkage of boards used for decking or cladding, as a result of solar heating can cause even greater board shrinkage which can lead to unsightly gaps between abutting boards.