Coefficients of Thermal Expansions of Plexiglas



10/14/2021 3:20 pm

Coefficients of Thermal Expansions of Plexiglas


Plexiglas® acrylic sheet will expand and contract with changes in temperature and humidity. Different temperature and/or humidity conditions on the inner and outer surfaces of Plexiglas® sheet may cause it to bow slightly in the direction of the higher temperature and/or humidity. However, this type of bowing is reversible. The sheet will return to its original flat state when the temperature and humidity differentials become zero.

Bowing does not affect visibility through flat Plexiglas® sheet, but may distort reflections. For translucent or opaque panels in which it is unnecessary to see objects through the sheet, surface textures or formed designs will help disguise specular reflection distortions.

In construction, Plexiglas® sheet is often used with other materials that undergo less expansion and contraction. The listing in the below compares the coefficients of thermal expansion of Plexiglas® sheet with other common construction materials.

Coefficients of Thermal Expansions
Inches/Foot/100 °F
Plexiglas® sheet
Plate glass

To ensure good performance in environments where temperature varies widely, Plexiglas® sheet should be installed in a channel frame that permits the sheet to expand and contract freely. The channel frame should be deep enough for the sheet to contract fully and still stay within the frame.

Avoid inflexible fasteners such as bolts that do not permit expansion and contraction. Tapes and sealants that adhere to both the acrylic sheet and the frame should be sufficiently extensible to accommodate thermal expansion of both.

Plexiglas® sheet may develop permanent deformation under long-term continuous loading. This cold flow characteristic may be minimized by using thicker sheet, reducing the size of unsupported areas, or using thermoformed configurations.

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