por Daniel Mendez Gutierrez 2 anos atrás
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In this type of polymerisation, the molecules of the same monomer or diferent monomers add together on a large scale to form a polymer.
As this radical reacts with another molecule of ethene, another bigger sized radical is formed.
at some stage the product radical thus formed reacts
with another radical to form the polymerised product
Chain terminating step
For termination of the long chain, these free radicals can combine in different ways to form polythene
A variety of alkenes or dienes and their derivatives are polymerised in the presence of a free radical generating initiator (catalyst) like benzoyl peroxide, acetyl peroxide,tert-butyl peroxide, etc
These polymers are cross linked or heavily branched molecules,
which on heating undergo extensive cross linking in moulds and
again become infusible.
These are the linear or slightly branched long chain molecules
capable of repeatedly softening on heating and hardening on cooling.
These polymers possess intermolecular forces of attraction
intermediate between elastomers and fibres.
Ex:polythene
Fibers are thread-forming solids that possess high tensile
strength and high modulus. These characteristics can be
attributed to the strong intermolecular forces like hydrogen
bonding. These strong forces also lead to close packing of chains
and thus impart crystalline nature.
Ex:polyamides
(nylon 6, 6)
These are rubber – like solids with elastic properties. The polymer chains are held together by the weakest intermolecular forces in these elastomeric polymers. These weak binding forces permit the polymer to be stretched.
polymers are formed by repeated condensation
the reaction between two different bi-functional or tri-functional
monomeric units.In this reaction the elimination
of small molecules such as water, alcohol, hydrogen chloride
The addition polymers are formed by the repeated addition of
monomer molecules possessing double or triple bonds.
These polymers consist of long and straight chains.
Are found in plants and animals.
Cellulose derivatives as cellulose acetate (rayon) and cellulose nitrate.
It is applied the division of two bi-functional monomers by condensation.
Teflon is manufactured by heating tetrafluoroethene with a free radical or persulphate catalyst at high pressures. It is chemically inert and resistant to attack by corrosive reagents. It is used in making oil seals and gaskets and also used for non – stick surface coated utensils.
calvo lindo
It is formed when the addition polymerization of ethene takes place in a hydrocarbon solvent in the presence of a catalyst such as triethylaluminium and titanium tetrachloride (Ziegler-Natta catalyst) at a temperature of 333 K to 343 K and under a pressure of 6-7 atmospheres.
It's used for manufacturing buckets, dustbins, bottles, pipes, etc.
It is obtained by the polymerisation of ethene under high pressure of 1000 to 2000 atmospheres at a temperature of 350 K to 570 K in the presence of traces of dioxygen or a peroxide initiator.
Biodegradable polymers are defined as materials whose chemical and physical characteristics undergo deterioration and completely degrade when exposed to microorganisms, aerobic, and anaerobic processes.
https://www.sciencedirect.com/topics/materials-science/biodegradable-polymer
A polymer's molecular weight is the sum of the atomic weights of individual atoms that comprise a molecule.
https://www.sciencedirect.com/topics/engineering/polymer-molecular-weight#:~:text=A%20polymer's%20molecular%20weight%20is,or%20distribution%20of%20molecular%20weights.
Melamine formaldehyde polymer is formed by the condensation polymerisation of melamine and formaldehyde.
Phenol - formaldehyde polymers are the oldest synthetic polymers. These are obtained by the condensation reaction of phenol with formaldehyde in the presence of either an acid or a base catalyst.
These are the polycondensation products of dicarboxylic acids and diols. Dacron or terylene is the best known example of polyesters. It is manufactured by heating a mixture of ethylene glycol and terephthalic acid at 420 to 460 K in the presence of zinc acetate antimony trioxide catalyst as per the reaction given earlier
These polymers possessing amide linkages are important examples of synthetic fibres and are termed as nylons. The general method of preparation consists of the condensation polymerisation of diamines with dicarboxylic acids and also of amino acids and their lactams.
A large number of polymers are quite resistant to the environmental degradation processes and are thus responsible for the accumulation of polymeric solid waste materials.
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.
The word ‘polymer’ is coined from two Greek words: poly means many and mer means unit or part.
Is any of a class of natural or synthetic substances that have really large molecules, formed by smaller molecules called monomers, that are joined toguere by something called covalent bond.
polymer | Description, Examples, Types, Material, Uses, & Facts. (s. f.). Encyclopedia Britannica. https://www.britannica.com/science/polymer
Are formed by joining of repeating structural units on a large scale.
