2. What is Polymer?
Poly- means "many" and -mer means "part" or "segment". Mono means
"one". So, monomers are those itty bitty molecules that can join together
to make a long polymer chain.
The term polymer is commonly used today in the plastics
and composites industry, and it is often used to imply the meaning of
"plastic" or "resin". In actuality, the term polymer means much more.
3.
4. Difference between Thermoplastic
& Thermosettings
• Thermoplastics polymers get soften and melt on heating where
as thermosetting polymers don’t soften on heating but rather become
hard.
• The former can be reshaped while the later can’t be reshaped.
• Thermoplastics polymers are less brittle and soluble in organic solvents.
Thermosetting polymers are brittle and insoluble in organic solvents.
• One more difference between thermoplastic and thermosetting polymers
is thermoplastic polymers are usually linear structures while thermosetting
polymers have three dimensional cross linked structures.
•
5. Different types of Polymeraisation:-
• Bulk polymerization or mass polymerization is carried out by adding a soluble initiator
to pure monomer in liquid state. The initiator should dissolve in the monomer. The
reaction is initiated by heating or exposing to radiation.
• Suspension polymerization is a heterogeneous radical polymerization process that uses
mechanical agitation to mix a monomer or mixture of monomers in a liquid phase, such
as water, while the monomers polymerize, forming spheres of polymer.
• Solution polymerization is a method of industrial polymerization. In this procedure, a
monomer is dissolved in a non-reactive solvent that contains a catalyst. The reaction
results in a polymer which is also soluble in the chosen solvent.
• The most common type of emulsion polymerization is an oil-in-water emulsion, in
which droplets of monomer (the oil) are emulsified (with surfactants) in a continuous
phase of water. Water-soluble polymers, such as certain polyvinyl alcohols or
hydroxyethyl celluloses, can also be used to act as emulsifiers/stabilizers.
6. Biodegradable Polymers
Biodegradable polymers are a specific type of polymer that
breaks down after its intended purpose to result in natural
byproducts such as gases (CO2, N2), water, biomass, and
inorganic salts.
7. Bio Polymers
Biopolymers are polymers that are biodegradable. The
input materials for the production of
these polymers may be either renewable (based on
agricultural plant or animal products) or synthetic
8. Tacticity of Polymers
Tacticity (from Greek τακτικός taktikos "of or relating to
arrangement or order") is the relative stereochemistry of
adjacent chiral centers within a macromolecule. The
practical significance of tacticityrests on the effects on
the physical properties of the polymer.
9. Polydispersity index
.
Polydispersity Index is nothing but the ratio of Weight
average molecular weight to number average molecular
weight. The weight average MW is always higher than
Number average MW and hence the ratio starts from 1.
This dispersity index measures the deviation from the
uniformity of dispersion. For example if the weight
distribution is uniform then the ratio is 1. 1 to 1.1 it is
considered to be narrow distribution, 1–2 is moderate
distribution and more than 2 is noted as broad
distribution
10. Glass Transition Temperature
Semi crystalline solids have both amorphous and
crystalline regions. According to the
temperature, the amorphous regions can be
either in the glassy or rubbery state The
temperature at which the transition in the
amorphous regions between the glassy and
rubbery state occurs is called the glass
transition temperature.
11. Conducting Polymers
In general many organic polymers are used as electric insulators. (Ex:
polyethylene, PVC, Teflon etc.). The main reason for non-conducting nature
of organic polymers is due to the absence of conjugation in the backbone or
absence of conducting ingredients.Polyacetylene is the first example of
conducting polymer.Conducting polymers have backbones of
continuous sp2 hybridized carbon centers. One valence electron on
each center resides in a pz orbital, is orthogonal to the other three sigma-
bonds.
12. Rubber Polymer
Rubber is an example of an elastomer type polymer, where the polymer has the ability to
return to its original shape after being stretched . The elastic properties arise from the
its ability to stretch the chains apart, but when the tension is released the chains snap
back to the original position. Such conjugated diene monomers have a constructive
backbone of at least four carbon atoms with a double-single-double bond reactive
core (C=C-C=C ).. The diene's double bonds turn into single bonds, and the single
bond between them turns into a Z or E configured double bond, depending on the
polymerization conditions .
15. Ziegler nata Catalyst
Zegler-natta polymerization is a method of vinyl polymerization. it's important because it
allows one to make polymers of specific tacticity. it was discovered by two scientists,
and i think we can all figure out what their names were. ziegler-natta is especially
useful, because it can make polymers that can't be made any other way, such as
linear unbranched polyethylene and isotactic polypropylene. free radical vinyl
polymerization can only give branched polyethylene, and propylene won't polymerize
at all by free radical polymerization. so this is a pretty important polymerization
reaction, this ziegler-natta stuff.
