POLYMER

• INTRODUCTION• POLYMER MATERIALS• CLASSIFICATION OF POLYMER• STRUCTURE OF LONG CHAIN POLYMERS • CRYSTAL OF LONG CHAIN POLYMER

• Polymer are long chain giant organic molecules assembled from many small molecules called monomers .

• More monomer molecules joined in units of long polymer.

• Example;polyethylene

INTRODUCTION

POLYMER MATERIALS

The polymers are a diverse group of engineering materials.

They are the main components of plastics, rubbers, resins, adhesives and paints.

These materials have distinctive microstructures built from macromolecular chains and networks of carbon and other light elements.

CLASSIFICATIONS OF POLYMERS

Thermoplastics Thermosets Long chain Polymers Natural polymers Homopolymer Copolymer

THERMOPLASTICS

• A type of plastic that can be softened by heat, hardened by cooling, and then softened by heat over and over again. Thermoplastics are not cross-linked.

• Thermoplastics such as polyethylene, Nylon, Polyvinyl chloride which soften on heating.

Example; Polyvinyl chloride

POLYVINYL CHLORIDEPipesElectric cablesClothing and furnitureUnplasticized polyvinyl chloride (uPVC) for constructionHealthcare(Components of dialysis installations and temporary blood storage devices)Flooring( buildings covering the home, hospitals, offices, schools, etc.)

thermoset - having the property of becoming permanently hard and rigid when heated or cured; "the phenol resins and plastics were the original synthetic thermosetting materials"

They are hard and rigid at room temperature and do not soften on heating.

Examples and uses of thermoset plastic materials: Epoxy resins - used as coating materials, caulks, manufacture of

insulating materials, etc ... Phenolic resins - tool handles, billiard balls, sprockets,

insulation, etc ... Unsaturated polyester resins - manufacture of plastics

reinforced fiberglass commonly known as polyester,fillers, etc ...

THERMOSET

NATURAL POLYMERS

The definition of a natural polymer is a polymer that results from only raw materials that are found in nature. Some of these natural polymers include DNA and RNA. These are critical in genes and life processes.

Cotton, DNA ,wool, wood etc. are some of the naturally occurring polymers.

Homopolymers

Homopolymers- consist of chains with identical bonding linkages to each monomer unit. This usually implies that the polymer is made from all identical monomer molecules.

These may be represented as : -[A-A-A-A-A-A]-

copolymer

A polymer of two or more different monomers. The synthetic rubber used to make tire treads and shoe soles, for example, is a copolymer made of the monomers butadiene and styrene

These may be represented as : -[A-B-A-B-A-B]-

STRUCTURE OF LONG CHAIN POLYMERS

A very long strand of repeating molecules linked together by primary bonds. Polymer chains orient themselves in lines as they enter a mold, but may be annealed so they can recoil.

Properties of PolymersThe physical properties of a polymer, such as its strengthand flexibility depend on:

• Chain length - in general, the longer the chains the stronger the polymer;

• Side groups - polar side groups give stronger attraction between polymer chains, making the polymer stronger;

• Branching - straight, un branched chains can pack together more closely than highly branched chains, giving polymers that are more crystalline and therefore stronger;

• Cross-linking - if polymer chains are linked together extensively by covalent bonds, the polymer is harder and more difficult to melt.

Characteristics of Polymers Low Density. Low coefficient of friction. Good corrosion resistance. Good mould ability. Excellent surface finish can be obtained. Can be produced with close dimensional tolerances. Economical. Poor tensile strength. Low mechanical properties.  Poor temperature resistance.  Can be produced transparent or in different colours

Applications of Polymers

Polymeric materials are used in and on soil to improve aeration, provide mulch, and promote plant growth and health.

Medicine Many biomaterials, especially heart valve replacements

and blood vessels, are made of polymers like Dacron, Teflon and polyurethane.

Consumer Science Plastic containers of all shapes and sizes are light weight

and economically less expensive than the more traditional containers. Clothing, floor coverings, garbage disposal bags, and packaging are other polymer applications.

Industry

Automobile parts, windshields for fighter planes, pipes, tanks, packing materials, insulation, wood substitutes, adhesives, matrix for composites, and elastomers are all polymer applications used in the industrial market.

Sports

Playground equipment, various balls, golf clubs, swimming pools, and protective helmets are often produced from polymers.