37.3.CLASSIFICATION ACCORDING TO APPLICATIONS

On the basis of applications, polymers can be further classified as –

i. Adhesives : Some polymers can be used for bonding . They are usually of the resin type and require some water resistance . Some common adhesives are -

Cellulose adhesives ; which consist of cellulose derivatives dissolved in a solvent. Eg. Duco cement.

Vinyls ; these are rubber base type water-emulsified latex adhesives.

Apart from these, some cheap natural products such as starch, dextrins, proteins and natural rubber may also be used for adhesive formulations.

ii. Coatings and films : A large bulk of the polymers produced are used for manufacturing coatings and films. Free films of polyethylene and cellulosic types, protective and decorative coatings are the products of the polymer industry.

Coatings can be manufactured by solvent evaporation followed by polymerization. Emulsion and casting or extrusion of free films by mechanical methods can also produce coatings and films.

iii. Fibers : These are formed by extrusion or spinning of linear monomer molecules into thin sections of diameter in the range of 10 – 50 microns. Fibers have excellent tensile strength , creep and resilience.

Fibers are extensively used in the textile industry . Cotton, wool etc. are the examples of some natural fibers.