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The addition of glass fiber to nylons leads to very significant increases in strength, stiffness, heat distortion temperatures, abrasion resistance and dimensional stability, though properties can be anisotropic - including mould shrinkage, leading to potential distortion. In the case of nylon 6,6, unlike many polymers, this is achieved without loss of impact strength, though elongation to break is, as usual, reduced very substantially. Glass reinforced nylon is commonly colored black.
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Flame Resistance PA6 Nylon 6 With Glass Fiber