Plastics

Plastic: A plastic material is any of a wide range of synthetic or semi-synthetic organic solids that are mouldable. Plastics are typically organic polymers of high molecular mass, but they often contain other substances. They are usually synthetic, most commonly derived from petrochemicals, but many are partially natural.

In general, plastics are manmade materials which are usually derived from a natural Material such as coal, oil, etc. These natural materials are subjected to various chemical Processes, additives put in, such as other chemicals, until they finally emerge as one certain type of plastics material, ready for processing.

This material can be processed by various method (of which we shall speak later) by   the application of heat and pressure, until it assumes the shape of whatever it has been pressed, formed, or moulded into. When this has happened, the heat and pressure is removed, and the plastic material will remain in this form, thereby making the plastic component.  

ADVANTAGES OF USING PLASTICS

1. Light in weight 

2. Higher strength to weight ratio 

3. Wider design freedom. 

4. Easy Processability 

5. Low Energy Required for  Manufacturing 

6. Minimum post finishing

7. Corrosion Resistant. 

8. Low creep

9. Better aesthetics look 

10. Wide colour range

COMMODITY PLASTICS

1. Low Density Polyethylene (LDPE)

2. Linear Low Density Polyethylene (LLDPE)

3. High Density Polyethylene (HDPE)

4. High Molecular High Density Polyethylene (HMHDPE)

5. Polypropylene (PP)

6. Polyvinylchloride (PVC

7. Polystyrene (PS)

8. High Impact Polystyrene (HIPS)

9. Poly Methyl Methacrylate (PMMA)

10. Ethylene Vinyl Acetate (EVA)

ENGINEERING THERMOPLASTICS

1. ACRYLO NITRILE BUTADIENE STYRENE (ABS)

2. STYRENE ACRYLONITRILE (SAN)

3. POLYMETHYL METHACRYLATE (PMMA)

4. POLYAMIDE - (PA) 

5. POLYETHYLENE TEREPHTHALATE- (PET)

6. POLYBUTYLENE TEREPHTHALATE- (PBT)

7. POLYOXYMETHYLENE - (POM)

8. POLY CARBONATE - (PC)

9. HIGH IMPACT POLYSTYRENE (HIPS)

SPECIALITY PLASTICS

1. POLYTETRA FLUOROETHYLENE (PTFE)

2. THEROPLASTIC POLYURETHANE (TPU)

3. POLY SULPHONE (PSO)

4. POLY ETHER SULPHONE (PES)

5. POLYPHENYLENE  SULPHIDE (PPS)

6. POLYPHENYLENE  ETHER (PPE)

7. POLY ETHER ETHER KETONE (PEEK)

8. POLY ACRYLATE

9. POLY AMIDE – IMIDE (PAI)

10. POLY ETHER – IMIDE (PEI)

11. LIQUID CRYSTAL POLYMERS (LCP)

THERMOSET PLASTICS

1. PHENOL FORMALDEHYDE (PF)

2. UREA FORAMLDEHYDE (UF) 

3. MELAMINE FORAMLDEHYDE (MF) 

4. EPOXY RESINS

5. UNSATURATED POLYESTER RESIN

6. POLYURETHANES

7. SILICONES

Polymerization: “The process by which, monomer combine to form polymers is known as polymerization”. 

Degree of Polymerization (DP): “The numbers of repeating unit present in it call degree of polymerization (DP)”. 

Addition Polymerization: ‘When molecules just add on to form the polymer, the process is called ‘addition polymerization’ 

In ‘addition polymerisation’ the molecular weight of the polymer is roughly equal, to that of all the molecules, which combine to form the polymer. Ex; Polyethylene, polypropylene.

Amorphous Polymers : An ‘amorphous polymers’ is characterized by completely random arrangement of molecules of polymer chain. While a crystalline region (called crystallites) embedded in amorphous random matrix. e.g. Polystyrene, polyvinyl acetate and polymethyl methacrylate (all are having bulky side groups attached at random to the main carbon chain) are typically amorphous.

Mplecular distribution: of molecular weights is caused by the statistical nature of the polymerization process e.g. methane (CH4) molecules have the same molecular weight (16), but all polyethylene do not have the same molecular weight because the statistical distribution of molecular weight may be different for the different grade of the polyethylene and the degree of polymerization may also be different. 

Number Average Weight (Mn) :The number average molecular weight is not too difficult to understand. It is just the total weight of all the polymer molecules in a sample, divided by the total number of polymer molecules in a sample.

Weight and degree of polymerisation: Number of repeating unit in a polymer called as degree of polymerisation (DP). DP provides the indirect method of expressing the molecular weight and the relation is as follows; => M = DP x m 

The influence of molecular weight on the bulk properties of polyolefin's, an increase in the molecular weight leads to 

Increase in: Melt viscosity, Impact strength

Lowers in: Hardness, Stiffness, Softening point, Brittle point, High molecular weight polymer does not crystallize so easily as lower molecular weight material crystallizes due to chain entanglement and that reflect in bulk properties of the high molecular weight polymer.

Composition: Almost invariably, organic polymers mainly comprise plastics. The vast majority of these polymers are based on chains of carbon atoms alone or with oxygen, sulphur, or nitrogen as well. The backbone is that part of the chain on the main "path" linking a large number of repeat units together. To customize the properties of a plastic, different molecular groups "hang" from the backbone (usually they are "hung" as part of the monomers before linking monomers together to form the polymer chain). The structure of these “side chains” influences the properties of the polymer. This fine tuning of the properties of the polymer by repeating unit's molecular structure has allowed plastics to become an indispensable part of twenty first-century world.