Why are car windows & windshields glass and not a kind of plastic?
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Primary issues with plastic: in the windshield/window application:
– Effects of UV exposure: which tend to “fog up” plastics that originally start out as transparent. This is frequently seen in older plastic car headlights or solar cells on cheap garden lights. Becoming non-transparent is a bit of a safety issue in this application
– Lack of scratch resistance: plastics scratch/scuff easily compared to glass which is an issue for windshields especially which are frequently subjected to small rocks and other debris
– Softening/deforming when heated: as others have noted, plastics tend to melt or deform at certain temperatures, which would could create issues.
Ultimately, a windshield/window needs to be able to handle arguably rough conditions while still being durable and transparent. Part of the reason we have so many types of plastics is because they all tend to have different properties that make them good for different applications, but in this situation it’s tough for plastic meet all these requirements and beat out good old fashioned tempered glass.
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