2. Polymer
Polymer - any of a class of natural or synthetic substances composed
of very large molecules, called macromolecules, that are multiples of
simpler chemical units called monomers.
Monomer - a single molecule that has the ability to combine with
identical or similar molecules, a process also known
as polymerization.
Polymerization - is the process in which monomer units are linked by
chemical reaction to form long chains. These long chains set polymers
apart from other chemical species and give them their unique
characteristic properties. The polymer chains can be linear, branched,
or cross-linked.
4. Polymerization
The two major types of polymerization are “Addition Polymerization” also
called Chain Reaction and “Condensation Polymerization” also called Step
Reaction.
Step reactions require bifunctional or polyfunctional monomers, while chain
reactions require the presence of an initiator.
5. Step & Chain Polymerization
Step polymerization requires that there is at least a reactive
functional group on each end of the monomer that will react
with functional groups with other monomers. For example,
6. Cont….
Chains (i.e., addition) polymerization requires an initiator
(I) and proceeds by adding one repeating unit at a time.
Example
7. Types of polymers
There are two types of polymers: synthetic and
natural. Synthetic polymers are derived from
petroleum oil, and made by scientists and
engineers.
Examples of synthetic polymers include nylon,
polyethylene, polyester, Teflon, and epoxy.
Natural polymers occur in nature and can be
extracted i.e. Starch, cellulose, proteins, natural
rubber.
9. Natural Polymers
Natural polymers occur in nature and can be extracted.
They are often water-based. Examples of naturally
occurring polymers are silk, wool, DNA, cellulose and
proteins.
There are four basic kinds of biological macromolecules.
They are carbohydrates,lipids, proteins and nucleic
acids. These polymers are composed of
differentmonomers and serve different
functions. Carbohydrates - molecules composed of
sugar monomers.
10.
11. Brief on Natural Polymers
Proteins and Polypeptides- Proteins are the basic type of natural polymers
which constitutes in almost all the living organisms. Proteins are said to be
most versatile in nature. They can also be as catalysts. Some of the proteins
are called as enzymes. These enzymes are responsible for various chemical
reactions occurring in our body and it happens about million times faster even
without these enzymes. One type of protein in our blood called as hemoglobin
carries the oxygen from lungs to the cells of a human body.
A protein is usually a naturally occurring type of polyamide. This polymer
consists of an amide group present in the backbone chain of human body.
Collagen– Collagen is one of the natural polymers and is a protein. It makes
up the connective tissue present in the skin of human beings. This Collagen-
polymer is also a fiber that creates an elastic layer below the skin and thus
helps in keeping it supple and smooth.
Latex- Latex is known to be a kind of rubber, and rubber is a natural polymer.
This latex occurs in both the forms either synthetic or natural. The natural
form of latex is mainly collected from the rubber trees and it is also found in
variety of plants which includes the milkweed. It can also be prepared
artificially by the process of building up long chains of molecules of styrene.
12. Cont..
Cellulose– Cellulose is one of the most abundant organic compounds found on
the Earth and moreover the purest form of natural cellulose is the cotton.
The paper manufactured from the woods of trees and also the supporting
materials in leaves and plants mainly comprise of cellulose. Like the amylose,
it is also a polymer which is made from the monomers of glucose.
Starch– Starch is the derivative of condensation polymerization and consists
of glucose monomers, which further split into water molecules when
combined chemically. Starch is also a member of basic food groups called
the carbohydrates and it is found in the grains, cereal and potatoes. Starch is
a polymer of monosaccharide glucose. The molecules of starch consists of 2
kinds of glucose polymers namely amylopectin and amylose which are the
main component of starch in most of the plants.
13. Synthetic Polymers
Synthetic polymers are those which are human-made polymers.
The eight most common types of synthetic-organic polymers, which are commonly
found in households are:
• Low-density polyethylene (LDPE)
• High-density polyethylene (HDPE)
• Polypropylene (PP)
• Polyvinyl chloride (PVC)
• Polystyrene (PS)
• Nylon, nylon 6, nylon 6,6.
• Teflon (Polytetrafluoroethylene)
• Thermoplastic polyurethanes (TPU)
15. Polymer Abbreviation Properties Uses
Low-density polyethylene LDPE Chemically inert, flexible, insulator
Squeeze bottles, toys, flexible pipes, insulation
cover (electric wires), six pack rings, etc.
High-density
polyethylene
HDPE
Inert, thermally stable, tough and
high tensile strength
Bottles, pipes, inner insulation (dielectric)
of coax cable (see also PTFE), plastic bags, etc.
Polypropylene PP
Resistant to acids and alkalis, High
tensile strength
Auto parts, industrial fibers, food containers,
liner in bags, dishware and as a wrapping
material for textiles and food
Polystyrene (thermocole) PS
Thermal insulator. Properties depends on
the form, expanded form is tough and
rigid
Petri dishes, CD case, plastic cutlery
Polytetrafluoroethylene PTFE
Very low coefficient of friction,
excellent dielectric properties,
chemically inert
Low friction bearings, non-stick pans, inner
insulation (dielectric) of coax cable (see also
HDPE), coating against chemical attack etc.
Polyvinylchloride PVC
Insulator, flame retardant, chemically
inert
Pipe ( mainly draining), fencing, lawn chairs,
hand-bags, curtain clothes, non-food
bottles, raincoats, toys, vinyl flooring,
electrical installation insulations, etc.
Polychlorotrifluoroethyle
ne
PCTFE
Stable to heat and thermal attacks, high
tensile strength and non wetting
valves, seals, gaskets etc.
16.
17. Polymers Used in Textile
Both synthetic and natural polymers used in textile field,
like nylon, polyester, gums such as xanthan and guar
gums and carrageenan.
Widely used polymers are synthetic polymers in textile
industries.
Mainly nylon ,polyester, acrylic.
18. Nylon
The synthetic polyamides are the urea-formaldehyde
resins, which are thermosetting. They are used to produce
molded objects and as adhesives and coatings for textiles
and paper.
Also important are the polyamide resins known as nylons.
They are strong, resistant to heat and abrasion,
noncombustible, and nontoxic, and they can be colored.
Their best-known use is as textile fibers, but they have
many other applications. It is a condensation
polymerization process.
21. Polyester
Polyester is a category of polymers that contain the ester functional
group in their main chain. As a specific material, it most commonly
refers to a type called polyethylene terephthalate (PET).
Synthesis of polyesters is generally achieved by a polycondensation
reaction. See "condensation reactions in polymer chemistry". The
general equation for the reaction of a diol with a diacid is :
(n+1) R(OH)2 + n R´(COOH)2 → HO[ROOCR´COO]nROH + 2n H2O
