The coefficient of linear thermal expansion, α, between temperatures T1 and T2 for a specimen whose length is L0 at the reference temperature, is given by the following equation:
1.1 This test method covers the determination of the coefficient of linear thermal expansion for plastic lumber and plastic lumber shapes to two significant figures. The determination is made by taking measurements with a caliper at three discrete temperatures. At the test temperatures and under the stresses imposed, the plastic lumber shall have a negligible creep or elastic strain rate, or both, insofar as these properties would significantly affect the accuracy of the measurements.
1.1.1 This test method details the determination of the linear coefficient of thermal expansion of plastic lumber and plastic lumber shapes in their "as manufactured" form. As such, this is a test method for evaluating the properties of plastic lumber or shapes as a product and not a material property test method.
1.2 The thermal expansion of plastic lumber and shapes is composed of a reversible component on which may be superimposed changes in length due to changes in moisture content, curing, loss of plasticizer or solvents, release of stresses, phase changes, voids, inclusions, and other factors. This test method is intended to determine the coefficient of linear thermal expansion under the exclusion of non-linear factors as far as possible. In general, it will not be possible to exclude the effect of these factors completely. For this reason, the test method can be expected to give a reasonable approximation but not necessarily precise determination of the linear coefficient of thermal expansion.
1.3 Plastic lumber and plastic lumber shapes are currently made predominately with recycled plastics where the product is non-homogeneous in the cross-section. However, this test method may also be applicable to similar manufactured plastic products made from virgin resins or other plastic composite materials.
1.4 The values stated in inch-pound units are to be regarded as the standard. The SI units given in brackets are for information only.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
Note 1There is no similar or equivalent ISO standard.
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