Polymers

Polymerization is the process of joining small molecules called monomers to form polymers. Polymers are relatively large molecules consisting of a chain or network of many identical or similar monomers chemically bonded to each other. Monomer is a relatively small molecule that can form covalent bonds with other molecules of this type to form a polymer. Polymers consist of many repeating monomer units in long chains, sometimes with branching or cross-linking between the chains.

Structures of Some Monomers

Classification of Polymers

A. Based on Origin of Source
1. Natural Polymers– from living things ( ex. Cotton, silk, rubber ) 2. Synthetic Polymers– man-made ( glue, PVC, Teflon )
B. Based on Structure
1. Linear – a polymer consisting of a single continuous chain of repeat units. 2. Branched-chain – a polymer that includes side chains of repeat units. connecting onto the main chain of repeat units. 3. Cross-linked – a polymer that includes interconnection between chains 4. Network – a cross linked polymer that includes numerous interconnection between chains.



C. Based on Molecular Forces
1) Thermoplastics are a type of polymer that become moldable and malleable past a certain temperature and they solidify upon cooling.
2) Thermosets are synthetic fibers that become hard and cannot change shape once they have set. They are often used in adhesives.
3) Elastomer is a term used interchangeably with rubber. It is a flexible polymer.
4) Fibers are fibers created by improving upon natural plant and animal fibers and make up a large category of polymers.

D. Based on Mode of Polymerization
1. Addition polymer – is formed when double bonds are broken in the individual molecules and these rebond to another molecule so that long chains are formed. Example is poly(phenylethene ).
. 2. Condensation polymer – is formed when molecules are joined together with the elimination of some other compound ( usually water ). Examples are nylon and polyester.



Various main chains and side chains are used to make different synthetic organic polymers. The backbones of common synthetic polymers are made of carbon-carbon bonds, whereas heterochain polymers have other elements (e.g. oxygen, sulfur, nitrogen) inserted along the backbone.
The seven most common types of synthetic organic polymers are: low density polyethylene (LDPE), high density polyethylene (HDPE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), nylon, Teflon, and thermoplastic polyurethane (TPU). Synthetic fibers are found in money, super glue, etc.

Synthetic Polymers in Everyday Us

Some familiar household synthetic polymers include nylons in textiles and fabrics, Teflon in non-stick pans, and polyvinyl chloride in pipes. The common PET bottles are made of a synthetic polymer, polyethylene terephthalate. The plastic kits and covers are mostly made of synthetic polymers like polythene, and tires are manufactured from Buna rubbers. Due to the environmental issues created by these synthetic polymers, which are often non-biodegradable and synthesized from petroleum, alternatives like bioplastics are also being considered. However, these bioplastics are often more expensive than synthetic polymers.. Types of Synthetic Polymers

1. Low Density Polyethylene
Low Density Polyethylene (LDPE) polymers are among the most common types of synthetic organic polymers, which are often found in households. LDPE is a thermoplastic made from the monomer ethylene. Despite competition from more modern polymers, LDPE continues to be an important plastic grade.

2. High Density Polyethylene
High Density Polyethylene (HDPE) or polyethylene high-density (PEHD) is a polyethylene thermoplastic made from petroleum.

3. Polypropylene
Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used packaging and labeling materials, textiles, stationery, plastic parts and reusable containers of various types, laboratory equipment, loudspeakers, automotive components, and polymer banknotes. An additional polymer made from the monomer propylene, it is rugged and unusually resistant to many chemical solvents, bases, and acids.

4. Polyvinyl Chloride
Polyvinyl Chloride (PVC) is the third-most widely produced plastic, after polyethylene and polypropylene. PVC is used in construction because it is cheaper and stronger than more traditional alternatives such as copper or ductile iron., PVC is used in clothing and upholstery, electrical cable insulation, inflatable products, and many applications in which it replaces rubber.

5. Polystyrene
Polystyrene (PS) is an aromatic polymer made from the monomer styrene, a liquid petrochemical. PS is a colorless solid that is used in disposable cutlery, plastic models, CD and DVD cases, and smoke detector housigs. Products made from foamed polystyrene include packing materials, insulation, and foam drink cups.

6. Nylon
Nylon,is a family of synthetic polymers known generically as polyamides . Nylon is one of the most commonly-used polymers. The amide backbone present in nylon causes it to be more hydrophilic. It would be noticed that nylon clothing will absorb water. This is because nylon can engage in hydrogen bonding with water, unlike the purely hydrocarbon polymers that make up most plastics.

7. Teflon
Teflon (Polytetrafluoroethylene or PTFE) is a synthetic fluoropolymer of tetrafluoroethylene. PTFE is a solid, high-molecular-weight compound consisting entirely of carbon and fluorine. PTFE is hydrophobic: neither water nor water-containing substances can interact with PTFE. PTFE is used as a non-stick coating for pans and other cookware because it has very low friction with other compounds. It is very non-reactive, partly because of the strength of carbon–fluorine bonds, so it is often used in containers and pipework for reactive and corrosive chemicals. Where used as a lubricant, PTFE reduces friction, wear, and energy consumption of machinery.

8. Thermoplastic Polyurethane
Thermoplastic polyurethane (TPU) is any of a class of polyurethane plastic. It has many useful properties, including elasticity, transparency, and resistance to oil, grease, and abrasion. Most of these properties are resultant of the fact that TPU is hydrophilic and can react with water. Technically, TPU is a thermoplastic elastomer consisting of linear segmented block copolymers made of hard and soft segments

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