Properties of Polymers

A thermoplastic, also known as thermosoft plastic, is a type of plastic polymer that becomes pliable or mouldable at a high temperature and hardens when cooled.

The polymer chains are bonded together via intermolecular forces, which reduce as the temperature increases, producing a viscous liquid. Thermoplastics may be reshaped in this state and are commonly utilised to manufacture parts using polymer processing techniques like injection moulding, compression moulding, calendering, and extrusion. 

Physical Properties of Polymer

The structure, kind of monomer units from which polymers are generated, and other elements all influence the qualities of a polymer. The following are some of the physical and chemical properties of polymers:

Tensile Strength – A polymer’s tensile strength is its ability to stretch without breaking. This feature of polymers determines their physical strength and durability.

Melting and Boiling Points – Polymers have extremely high melting and boiling points. Longer chains mean stronger intermolecular forces, and thus higher melting and boiling points.

Hardness – Hard polymers are resistant to hard substances penetrating them. They are employed in the construction of electronics and can tolerate wear and tear as well as scratches.

Density-Based on density differences, polymers are classed as high-density polymers or low-density polymers.

Heat Capacity / Heat Conductivity — This determines how effective a polymer is as a heat insulator. A polymer’s heat conductivity is determined by the stiffness of its molecules.

Thermal Expansion – This property determines how much a polymer expands or shrinks when exposed to heat or cold.

Crystallinity – Because polymers with less crystallinity are brittle, they are more useful. The sort of organisation of polymeric chains determines this feature.

Elasticity– Polymers with weak intermolecular linkages stretch more and are more pliable.

Chemical Properties of Polymer

Reactivity and bonding – The strong covalent link and various weak forces between polymer particles, such as hydrogen bonding, determine properties such as reactivity. Polymers are chemically robust in general due to their low reactivity.

Interaction between reactive groups – The dipole of the monomers determines the intermolecular pressures between them. The hydrogen bond is formed by the carbonyl group (amide group) located on the side chains of the monomers.

In the case of paints, the adhesion of polymers on the surface, their interaction with the coating, and the external environment all have an impact on their quality.

Biodegradability– Polymers can be decomposed by decomposers. Biodegradable polymers, such as rubber, are biodegradable, but synthetic polymers are not.

Mechanical Properties of Polymer

The mechanical property of a polymer refers to its ability to resist or withstand physical force. It is one of the most important considerations when deciding whether or not to employ a particular type of polymer. The following are some of these characteristics:

Strength – A polymer’s strength is defined as the minimal force or stress required to break a sample of that polymer. Tensile strength, torsional strength, compressibility, and flexibility are some of the different types of polymer strength. The increasing orders of different polymers’ strength are: linear < branched < cross-linked < network.

Proportion The measure of a polymer’s elongation to break is its elongation without deforming it.

Young’s Modulus– The ratio of tensile stress to tensile strain is known as Young’s Modulus. It determines a polymer’s ability to stretch and distort. It is a measurement of a polymer’s stiffness.

Toughness– The area under the stress-strain curve determines a polymer’s toughness.

Viscoelasticity – This metric evaluates both elasticity and viscosity. It occurs as a result of transient contacts between fibre particles. Polymers, when released after stretching, revert to their previous shape due to this characteristic.

Polymer Properties Contributing Factors

A polymer’s properties are primarily determined by three factors:

• Chemicals that are used to make polymers.

• Chain length, type of bonds between polymers, and nature of the functional group present at the end of the monomers are all factors that influence polymerization.

• One of the essential aspects that determines the properties of polymers is the type of monomer units polymerized to form the repeating units.

Factors that Affect Properties of a Polymer

• Temperature – Polymers are temperature sensitive; as the temperature rises, so does their flexibility and compressive strength. With the rising temperature, the kinetic energy of the molecules increases, but Young’s modulus drops.

• Polymer Chain Length – It can be assumed that as the chain length of polymers rises, so does their strength.

• Branching – The mechanical strength of polymers rises as branching increases. Linear polyethylene, for example, has a high degree of crystallinity but poor mechanical characteristics. As a result of branching, polymers become stiffer, tougher, and stronger.

• Cross-linking: When polymer chains are substantially cross-linked by strong covalent connections, their strength rises, making melting more difficult.

• Because of hydrogen bonding and other attractive forces, the presence of polar side groups improves the strength of attraction between polymeric chains, making them stronger.

Conclusion

Polymers are macromolecules that are created by the covalent bonding of monomer units. Polymers are employed in practically every aspect of life, including apparel, plastics production, industrial applications, medical, dentistry, and so on. Polymers are utilised in a variety of industries based on their physical and chemical qualities, such as strong ropes used to transport weights in factories and building sites. Polymers’ properties, such as tensile strength, strain, elasticity, and toughness, determine their use.