What is PHBV? How is it useful to man?

Poly B-hydroxybutyrate — co-B-hydroxy valerate (PHBV) : It is obtained by the copolymerisation of 3 hydroxybutanoic acid and 3 — hydroxypentanoic acid. PHBV is used in speciality packaging, orthopaedic devices and in controlled release of drugs. PHBV undergoes bacterial degradation in the environment.

What is vulcanization of rubber?

Vulcanisation of rubber: Natural rubber becomes soft at high temperature (>335 K) and brittle at low temperatures (<283 K) and shows high water absorption capacity. It is soluble in non-polar solvents and is non-resistant to attack by oxidising agents. To improve upon these physical properties, a process of vulcanisation is carried out. This process consists of heating a mixture of raw rubber with sulphur and an appropriate additive at a temperature range between 373 K to 415K.

What is PDI (Poly Dispersity Index)?

Poly Dispersity Index (PDI): The ratio between weight average molecular mass ( M w ) and number average molecular mass ( M n ) of a polymer is called Poly Dispersity Index (PDI). PDI = M w M n The value of PDI for polymers is in between 1 and 1.5. Many polymers have PDI greater than unity. Polymers with PDI of near unity can be synthesized.

What are thermoplastic polymers? Give example.

Thermoplastic polymers: These are the linear or slightly branched long chain molecules capable of softening on heating and hardening on cooling. These polymers possess intermolecular forces of attraction intermediate in strength between those in elastomers and fibres. Some common thermoplastics are polythene, polystyrene, polyvinyls, etc.

What are polymers? Give example.

Polymers are high molecular mass substances consisting of a very large number of simple repeating structural units joined together through covalent bonds in a regular fashion. Polymers are also called macromolecules. Some examples are polythene, nylon-66, bakelite, rubber, etc.