Thermal And Moisture Movement

The thermal expansion of most plastics is high. The expansion of GRP is similar to that of aluminium, but most other plastics have larger coefficients of linear expansion. For this reason, attention must be paid to careful detailing to allow for adequate thermal movement, particularly where weather exclusion is involved. Most plastics are resistant to water absorption, and therefore do not exhibit moisture movement. (Typical coefficients of linear expansion are polythene (HD) 110-130, polypropylene 110, ABS 83-95, PVC 40-80, GRP 20-35 X 10"6 deg C"1.)

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