Scope:

This test technique ASTM D1042-12 is intended to give way for assessing dimensional changes in plastic specimens, such as shrinkage or expansion, that occur as a result of specific heat and water conditionings. This technique is only designed to be used quickly to detect linear dimensional changes in polymers under controlled settings.

Procedure:

In ASTM 1042-12, first, a 100-mm radius arc is scribed on the test specimen’s surface. The needle is pressed firmly into the material immediately after the preconditioning. The other needle scribes the arc that will be utilized for all subsequent measurements. One needle is re-inserted in the original center and draws a brief arc with the other after conditioning. Using a caliper or a microscope, the distance (DB) between the old and the new arc is measured. The distance between arcs at similar places, such as center to center is measured. During exposure to accelerated service conditions, the specimen must not be clamped or otherwise restricted.

Data:

The amount of linear expansion is determined by the following equation:

Lᴄ = Dᴃ ⁄ Di × 100

Lᴄ= % of linear change

Dᴃ= distance between the scribed arcs

Di= Initial scribed distance