The thermoformability of polypropylene is directly related to the quality of the extruded sheet.
Sheet gauge uniformity (5% maximum variation) is important to minimize part-to-part variation.
The degree of orientation in the sheet also affects thermoforming. Orientation is measured as a
percentage of shrinkage in the machine and cross-direction of the sheet when heated to a
temperature between 340 to 365°F (170 to 185°C). For sheet less than 0.100 in. (2.5 mm) thick,
shrinkage should be 5 to 10% maximum.