Its play important role in our life, polymers form very important class of materials, without its, we can't imagine about life. We all are surrounded by them in daily life uses and also the are present in our body in the form of protein, enzymes etc. Other polymers which are naturally found such as wood, rubber, silk, and leather etc. Polymers are formed after reaction of monomers, and this reaction is called polymerization. Its have higher molecular weight.
Types Of Polymers: Classification of polymers are explained on various basis, such as on their molecular structures and synthesis. Such as linear polymer contains long molecular chains, but better way to classify polymers is their mechanical and thermal properties. In industry polymers are divided into two main group: a) Plastics, b) Elastomers.
Plastics: It is found either natural or synthetic, it is basically resins and moldable. And the process is forming and molding into shapes. It is play important role in engineering materials for many reasons. Because they have large range of properties, like few are unattainable from other materials, and they are cost effective. Properties of plastics are: Light weight, maximum number of colors, thermal and electrical conductivity is low, less brittle, toughness is good, good in acid resistivity, dielectric strength is high. Plastics are again classified into two groups: a) Thermoplast and b) Thermoset
Thermoplast: These are soften when heated and harden when cooled, and these processes are repeated and reversible. Fabrication of this materials is processed by heat and processed with simultaneously applied. These polymers are ideally linear polymers and here no crosslinks are found. Plasticity of these material is increasing when temperature is increased, and due to this secondary bond between them is breaks. Some examples are: polymethyl methacrylate, PVC, acrylic, nylons, polystyrene.
Thermoset: These are required heat and pressure to molding in shapes, and when they shaped then it is their permanent state or shaped or 'set' through chemical reaction such as cross-linking. It can not be remelted and reformed, but they can decompose on high temperature. It means they can not be recycled, and more stronger and more brittle then thermoplast. Thermoset are connected in 3D network with long chain. Advantages of its properties in engineering due to: maximum thermal stability, higher dimensional stability, rigidity is high, light weight, electrical and thermal insulating properties is high, and resistant to creep and deformation within load. Some examples are: Epoxise, vulcanized rubber, phenolics, unsaturated polyster resins etc.
Elastomers: It is also called rubber, it have property that it can undergo large elongation under load on room temperature and after this it will be returned in original shape when load is released. Here many man-made polymers are such as natural rubber