Unit IV: Non-Metallic Materials - Review and Summary

 In this unit, the non-metallic materials—polymers, ceramics, and composites have been discussed in detail.

REVIEW AND SUMMARY

✔ In this unit, the non-metallic materials—polymers, ceramics, and composites have been discussed in detail.

✔ Polymers are large, high-molecular-weight molecules produced by joining smaller molecules called monomers.

✔ Polymerisation is the process of forming a polymer by linking together of monomers.

✔ Two polymerisation mechanisms used are:

1. Addition polymerisation, and

2. Condensation polymerisation.

✔ Addition polymerisation, also known as chain reaction poly- merisation, is a process by which two or more chemically similar monomers are polymerised to form long chain molecules.

✔ Condensation polymerisation, also known as step-growth poly- merisation, is the formation of polymers by stepwise inter- molecular chemical reactions that normally involve at least two different monomers.

✔ Polymers use various additives to improve their properties and performance. Some of the polymer additives are: filler materials, plasticizers, stabilizers, colorants, flame retardants, reinforcements, and lubricants.

✔ A plastic may be defined as an organic polymer, which can be moulded into any desired shape and size with the help of heat, pressure, or both.

✔ The two broad groups of plastics are:

1. Thermoplastics, and 2. Thermosetting plastics.

✔ Thermoplastics, also known as thermoplasts, are the plastics whose plasticity increases with the increase in temperature. Thermoplasts can be repeatedly moulded and remoulded to the desired shape and hence they have a good resale/scrap value. 

✔ Thermosetting plastics, also known as thermosets, are plastics which become permanently hard when heat is applied and do not soften upon subsequent heating. They cannot be remoulded/ reshaped again and again.

✔ It may be noted that most of the thermoplastics are formed by addition polymerisations whereas most of the thermosetting plastics are formed by condensation polymerisations.

✔ Based on the usage, commercial value, and cost, plastics can be classified as commodity plastics and engineering plastics. 

✔ The characteristics and typical applications of some important thermoplastics such as PE, PP, PS, PVC, PTFE, PMMA, PAN, PA, POM, PC, PET, PEEK, PPO, PPS, PI, and PAI have been discussed in this unit.

✔ Also the characteristics and typical applications of some important thermosetting plastics such PF, UF, MF, polyesters, EP and PUR have been elaborated.

✔ Ceramics are non-metallic and inorganic solids that are processed and/or used at high temperatures. Typical ceramics are electrical and thermal insulators with good chemical stability and good strength in compression.

✔ Engineering ceramics, also known as industrial ceramics or advanced ceramics, are those ceramics that are specially used in engineering applications or in industries.

✔ Engineering ceramics are mainly oxides, carbides, sulphides, and nitrides of metals.

✔ In this unit, the properties and typical applications of some important engineering ceramics such as Al2O3, SiC, Si3N4, PSZ, and sialon have been presented.

✔ Composites are produced when two or more materials are joined to give a combination of properties that cannot be attained in the original materials.

✔ Composites are composed of two phases: matrix phase and dispersed phase.

✔ This unit gives a summary of the particulate-reinforced and fibre-reinforced composites.

KEY TERMS YOU SHOULD REMEMBER

Non-metallic materials

Polymers

Polymerisation

Addition

polymerisation 

Condensation 

polymerisation 

Polymer additives

Fillers 

Plasticizers 

Stabilizers

Colorants

Flame retardants

Reinforcements

Lubricants

Natural plastics

Synthetic plastics 

Thermoplastics

PE, PP, PS, PVC, PTFE, PMMA,

PAN, PA, POM, PC,

PET, PEEK, PPO, PPS, PI, PAI 

Thermosetting plastics

PF, UF, MF, 

Polyesters, EP, PUR

Commodity plastics

Engineering plastics,

Ceramics

Engineering ceramics 

Al2O3, SiC, Si3N4 

PSZ, Sialon

Composites

Particulate-reinforced

composites 

Dispersion- strengthened 

composites

Large-particle

composites 

Fibre-reinforced

Composites