Polymer Fundamentals
This term refers to a very large molecule formed by the repetition of small units
What is a polymer?
This type of polymerization involves monomers joining without the formation of any by-product.
What is addition polymerization?
This class of polymers softens on heating and hardens on cooling repeatedly.
What are thermoplastics?
This is the common trade name of polytetrafluoroethylene.
What is Teflon?
This high-performance polymer fiber is commonly used in bulletproof vests and helmets.
What is Kevlar?
These small repeating units combine chemically to form polymers.
What is degree of polymerization?
Polythene formed from ethene proceeds through this specific polymerization mechanism.
What is free-radical chain-growth (addition) polymerization?
PVC, polythene, and polypropylene belong to this polymer category
What are thermoplastics?
The strong C–F bond is primarily responsible for this key property of Teflon
What is chemical inertness?
Kevlar is synthesized by this type of polymerization.
What is condensation polymerization?
A polymer used for making tyres must belong to this class because it can stretch and recover its shape.
What are elastomers?
Nylon-6,6 is formed by stepwise reaction between diamines and dicarboxylic acids with elimination of small molecules.
Give an example for step-growth condensation polymerization.
Which class of polymers is more suitable for recycling, and why?
Thermoplastics, because they can be remelted and reshaped.
Why is Teflon widely used as a lining material in chemical reactors and pipes?
Because it resists chemical attack and corrosion
Why is Kevlar preferred over steel in protective gear and aerospace applications?
Because it is lightweight yet extremely strong
An engineer needs a lightweight but strong material for load-bearing applications. Which polymer class is most suitable and why?
Fibers, due to high tensile strength and molecular orientation
An engineer requires a polymer with strong intermolecular forces for high-strength fibers. Which polymerization route is preferred and why?
Condensation polymerization, because it forms polymers with polar functional groups.
Why are thermosetting plastics preferred for high-temperature structural applications?
Because cross-linking provides rigidity and thermal resistance
An engineer must choose between PVC and Teflon for handling concentrated acids at high temperature. Which should be selected and why?
Teflon, due to superior chemical and thermal resistance
An engineer must choose a material for making a high-strength rope that should not stretch much under load. Why is Kevlar suitable?
Because it has high tensile strength with minimal elongation
Evaluate this statement: “All polymers are plastics.” Is it correct? Justify.
No, polymers include plastics, elastomers, and fibers with different properties and uses
Evaluate this statement: “Condensation polymers are always inferior to addition polymers for engineering applications.”
False; condensation polymers like nylon and Kevlar have superior mechanical strength and thermal stability
Evaluate this statement: “Thermoplastics are always better than thermosets for engineering applications.”
False; thermosets are superior where high strength, rigidity, and thermal stability are required
Evaluate this statement: “Teflon is ideal for all plastic applications.”
False; its high cost and processing difficulty limit its use to specialized applications
Evaluate this statement: “Kevlar is the best material for all high-strength applications.”
False; cost, processing difficulty, and lack of flexibility limit its universal use