Discuss the classification of polymers based on... - SS3 Chemistry Organic Chemistry: Polymers Question

Polymers can be classified based on their origin, structure, and behaviour, leading to several distinct polymer classes.

1.    Classification based on Origin:

a.    Synthetic Polymers: These are artificially created polymers and constitute a significant portion of commercially available materials. Examples include polyethene (PE), polypropylene (PP), and polyvinyl chloride (PVC). Synthetic polymers offer a wide range of properties and find applications in various industries, such as packaging, construction, and textiles.

b.    Natural Polymers: These polymers are derived from natural sources and are often found in living organisms. One example is cellulose, found in plants and used to make paper and textiles. Another example is proteins, like silk and wool, which possess exceptional mechanical properties and are used in clothing and medical applications.

2. Classification based on Structure:

a.    Linear Polymers: These polymers have a simple linear structure with a straight chain of monomers. Polyethene and polypropylene are prime examples of linear polymers. Their linear nature results in relatively high density and melting points, making them suitable for strong and rigid applications.

b.    Branched Polymers: In these polymers, some branches or side chains are attached to the main chain of monomers. Low-density polyethene (LDPE) is a branched polymer. The presence of branches leads to a more amorphous structure, giving branched polymers increased flexibility and lower melting points compared to their linear counterparts.

c.     Cross-linked Polymers: These polymers have covalent bonds between polymer chains, forming a three-dimensional network. Cross-linking imparts superior mechanical strength and resistance to swelling, making them ideal for applications like rubber tires, adhesives, and dental fillings. Examples include vulcanised rubber and cross-linked polyethene (PEX).

3. Classification based on Behaviour:

a.    Thermoplastics: These polymers can be repeatedly softened and hardened through heating and cooling without undergoing significant chemical change. They have a linear or branched structure with weak intermolecular forces, allowing for easy processing and recycling. Polyethene, polypropylene, and polystyrene are common thermoplastics used in various consumer products.

b.    Thermosetting Polymers: These polymers undergo irreversible chemical cross-linking when exposed to heat or other curing agents. Once set, they cannot be reshaped or melted, which makes them highly durable and resistant to heat and chemicals. Epoxy resins and phenolic resins are examples of thermosetting polymers used in coatings, adhesives, and composites.

In summary, the classification of polymers based on origin, structure, and behaviour provides a comprehensive understanding of the diversity and versatility of these materials. Each polymer class offers unique properties that cater to specific applications in numerous industries. The continuous advancement in polymer science and engineering ensures the development of novel materials to meet evolving technological and societal needs.