PEX (cross-linked polyethylene) and PVC (polyvinyl chloride) are not the same; they are distinct materials used for different applications in plumbing and construction. PEX is flexible, resistant to scale and chlorine, and used primarily in water supply piping. It can handle high temperatures, making it suitable for hot and cold water lines. On the other hand, PVC is a rigid, versatile plastic used in various applications, including waste water pipes, irrigation, and electrical conduit. It cannot handle high temperatures well and is thus not suitable for hot water systems. Both materials offer durability and cost-effectiveness but are chosen based on specific project requirements.

Rayon is a semi-synthetic fiber made from cellulose, commonly derived from wood pulp, and is known for its silk-like feel. The production of rayon yarn involves several steps. Firstly, the purified cellulose is dissolved in a chemical solution, typically containing caustic soda and carbon disulfide, to form a viscous solution called viscose. This viscose solution is then aged, allowing it to ripen and reduce the molecular weight of the cellulose, which is necessary for the subsequent spinning process. After aging, the viscose is forced through a spinneret, a device with tiny holes, into a coagulating bath, which is a chemical bath that solidifies the viscose strands into continuous filaments. This solidification process is called wet spinning. The newly formed filaments are then drawn out to align the molecular chains and increase strength and elasticity. Finally, these continuous filaments can be cut into staple fibers or left as filaments, depending on the desired end product. The fibers are then twisted and spun into yarns, ready for weaving or knitting into fabrics. Despite its popularity, the environmental impact of rayon production, particularly the use of hazardous chemicals, has raised concerns and prompted a push towards more sustainable practices within the industry.

Epoxy, a versatile and durable material, undergoes significant changes when exposed to sunlight. UV radiation can cause epoxies to degrade over time, a process known as photodegradation. This can lead to discoloration, particularly yellowing, which affects the aesthetic qualities of clear or light-colored epoxies. Furthermore, prolonged exposure to sunlight can weaken the mechanical properties of the epoxy, such as its tensile strength and adhesion capabilities. To mitigate these effects, manufacturers often incorporate UV inhibitors into the epoxy formulation. These additives absorb harmful UV rays and prevent them from reaching the polymer matrix, thus preserving the integrity and longevity of the epoxy. For applications where UV resistance is critical, using epoxies with built-in UV inhibitors or applying a protective coating is recommended. Regular inspection and maintenance can also help manage any degradation caused by sunlight.