Manufacturing
There are two methods to manufacture faceshields, extrusion and injection molding. Faceshields cut from extrusion sheets provide better impact resistance than injection molding faceshields because extrusion sheets are made of high molecular weight plastic pellets while injection molding must use lower molecular weight plastic pellets, which provide better melt flowing property needed by injection molding. For example, even 0.8 mm thickness faceshields made of extrusion polycarbonate sheets can withstand the impact of a 6 mm nominal diameter steel ball traveling at the speed 120 m/s (Europen standard, protection against high-speed particles – medium energy impact), while injection molding faceshields must have at least 1.5 mm thickness to withstand the same impact. However, injection molding can provide more complicated shape than extrusion.
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