Volume 10, Issue 4 (July 1982)
Effect of Weathering at Different Exposure Angles on the Tensile Impact Resistance of Thermoplastics
The ability of a thermoplastic to serve as an exterior building component depends to a large extent on its impact strength and the retention of this property during service. A study was undertaken of the effect of the Canadian climate on the tensile impact strength (TIS) of eight clear and opaque commercial thermoplastic sheets exposed at different angles, and on the mechanism responsible for their loss of impact strength. The TIS of unexposed thermoplastics ranged from 98 kJ/m2 for poly(methyl methacrylate) (PMMA) to 1225 kJ/m2 for ultraviolet-stabilized polycarbonate, surface unprotected (PC). Following south/vertical (S/V) and horizontal (H) exposure the TIS of these thermoplastics was reduced from 20% S/V and 30% H for PMMA after five years to 65% S/V and 85% H for PC with a protective film after one year. For most of the thermoplastics tested, loss of TIS may be attributed to deterioration of ability to undergo plastic deformation, rendering the material more brittle.