A: Quartz sand is often used as a filler material in plastic composites. It enhances the mechanical properties of plastics, such as strength, stiffness, and wear resistance. Additionally, it can improve the thermal conductivity and dimensional stability of plastic products.

A: Quartz sand enhances the durability of refractory materials by providing excellent resistance to high temperatures and thermal shock. Its high melting point ensures it can withstand extreme heat, while its ability to resist sudden temperature changes prevents cracking and damage to the refractory lining.