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Weight (plastics are lighter), and impact resistance.
Isn't the acrylic less likely to shatter?
Plastics are almost always going to be cheaper to produce, and their light weight makes them cheaper to transport.Plastics generally take less energy to make, but glass is easier to recycle (if one ignore transportation costs).In general we have seen a continual decline in the use of glass as a packaging material, because of cost of production, but at least as much because of the cost of transportation (due to weight). Glass is also impossible to incinerate.Glass has its advantages, because of its hardness (scratch resistance - although some plastics are improving in that regard), optical qualities, and relative inertness.
Quote from: another_someone on 22/08/2007 21:59:28Weight (plastics are lighter), and impact resistance.... and transparency (same thickness "real" glass will absorb more light than acrylic) and more easily moldable in different shapes (lower working temperature for moulding). But acrylic is less scratch resistant and scratches reduce clearness of a pane or lens.
Quote from: Karen W. on 23/08/2007 13:49:22Isn't the acrylic less likely to shatter?Yes, this is another advantage: more safety.
Depending on what optical property you want acrylic or ordinary (silicate) glass can be better.If you want to make lenses then silicate glass gives a large range of dispersion and refractive index to work with, but if you want a window the acrylic can do a better job. It has a lower refractive index than most silicate glasses so it reflects less light. Less reflection means more light gets through. Also acrylic can be made with better UV transparent than cheap silicate glass. (If you really want good UV transparency in a glass, you use fused silica).
If you were making car windows out of a plastic you would probably use polycarbonate, which is really tough, acrylic (perspex) will snap, but you have to work really hard to break polycarbonate. They are also coming up with coatings for it which mean it is more scratch resistant.One of the first uses for perspex was for bubble canopies on aeroplanes like spitfires.
Quote from: daveshorts on 24/08/2007 13:54:37If you were making car windows out of a plastic you would probably use polycarbonate, which is really tough, acrylic (perspex) will snap, but you have to work really hard to break polycarbonate. They are also coming up with coatings for it which mean it is more scratch resistant.One of the first uses for perspex was for bubble canopies on aeroplanes like spitfires.Polycarbonate is the stuff they use for the outer shell of crash helmets. It is surely tough