Polymers
Some Important Terms
Polymers are formed in two general ways.
a) In chain-reaction polymerizationRad. + CH2 = CH2 → RadCH2CH2→ RadCH2CH2CH2CH2× → etc.b) In step reaction polymerization,c) Free-radical vinyl polymerization:At the doubly bonded carbons — the vinyl groups — and is called vinyl polymerization. A wide variety of unsaturated monomers may be used, to yield polymers with different pendant groups (G) attached to the polymer backbone. For example.
Download
Some Important Polymers:
a) Natural Rubber:Addition polymer of isoprene (2-methyl-1,3-butadiene)An average chain length of 5000 monomer units of isoprene.The rubber in which the arrangement of carbon chain is trans with respect to the double bond is known as Gutta Percha and this is the natural rubber obtained from bark of various trees.'Vulcanisation of rubber involves addition of sulphur to rubber and heating the mixture to increase the strength of natural rubber. sulphur forms short chains of sulphur atoms that link two hydrocarbon (isoprene) units together.Vulcanised rubber is thus stronger and less sticky than the natural rubber.b) Synthetic rubber:(Polychloroprene) or Neoprene)It is obtained by free radical polymerisation of chloroprene inA thermoplastic and need not to be vulcanised.It is a good general purpose rubber and superior to natural rubber as it is resistant to the reaction of aire, heat, light chemicals, alkalis and acids below 50% strength.It is used for making transmission belts, printing rolls and flexible tubing employed for conveyence of oil and petrol.c) Buna rubbers:i) Buna - N or GRA: it is synthetic rubber obtained by copolymerisation of one part of acryl nitrile and two parts of butadiene.It is more rigid responds less to heat and very resistant to swelling action of petorol, oils and other organic solvents.ii) Buna -S or GRS (General purpose Styrene rubber): It is a copolymer of three moles of butadiene and one mole of styrene and is an elastomer. It is obtained as a result of free radical copolymerisation of its monomers.It is generally compounded with carbon black and vulcanised with sulphur. It is extremely resistant to wear and tear and finds use in manufacture of tyres and other mechanical rubber goods.
d) Teflon: It is polymer of tetrafluorethylene (F2C=CF2) which on polymerisation gives Telfon.It is thermoplastic polymer with a high softening point (600K).It is very tough and difficult to work. It is inert to most chemicals except fluorine and molten alkali metals.It withstands high temperatures. Its electrical properties make it an ideal insulating material for high frequency installation.e) Nylon -66:A condensation polymer formed by reaction between adipic acid and hexamethylene diamine. It is a thermoplastic polymer.h) Phenol-formaldehyde polymer: E.g., Bakelite Novolac
Learn to create Machine Learning Algorithms in Python and R from two Data Science experts. Code templates included. This course includes: 41 hours on-demand video 34 articles 8 downloadable resources Full lifetime access Access on mobile and TV Certificate of completion What you'll learn Master Machine Learning on Python & R Have a great intuition of many Machine Learning models Make accurate predictions Make powerful analysis Make robust Machine Learning models Create strong added value to your business Use Machine Learning for personal purpose Handle specific topics like Reinforcement Learning, NLP and Deep Learning Handle advanced techniques like Dimensionality Reduction Know which Machine Learning model to choose for each type of problem Build an army of powerful Machine Learning models and know how to combine them to solve any problem. Description Interested in the field of Machine Learning? Then this course is for you! This course ha