C. Answer the following questions in brief.
1. Why is rayon not a pure synthetic fibre?
2. List any three properties of nylon.
3. What are the disadvantages of synthetic fibres?
4. What are thermosetting plastics? Give two examples.
5. Why are plastics regarded as good storage materials?
Answers
Answer:
Answers to the following questions in brief.
Explanation:
1.It is made from purified cellulose from wood pulp which is converted into soluble compound which is chemically solidified to form synthetic fiber. Because rayon is manufactured from naturally occurring polymers, it is considered a semi-synthetic fiber.
2.The characteristic features of nylon 6,6 include:
Pleats and creases can be heat-set at higher temperatures.
Superior colorfastness.
Excellent abrasion resistance.
3.Most of synthetic fibers' disadvantages are related to their low melting temperature:
The mono-fibers do not trap air pockets like cotton and provide poor insulation.
Synthetic fibers burn more rapidly than natural.
Prone to heat damage.
Melt relatively easily.
Prone to damage by hot washing.
4.A thermosetting polymer, or plastic, often called a thermoset, is a polymer that is irreversibly hardened by curing from a soft solid or viscous liquid prepolymer or resin. Curing is induced by heat or suitable radiation and may be promoted by high pressure, or mixing with a catalyst.Examples of thermoset plastics include epoxy, silicone, polyurethane and phenolic.
5.Plastic containers are favoured for storing food due to the following reasons : Plastic containers are lightweight. They do not react with the food items and so safer to store unlike aluminium which reacts with lemon pickles. It has good strength,durability and quality.Plastic containers seem more convenient than metal containers. This is because of their light weight, lower price, good strength and easy handling.