Addition Polymerisation Mechanism

Polymer Types and Formation

• A trifunctional monomer mixed with a bifunctional monomer leads to the formation of a branched polymer.
• A polymer with a main chain consisting of one type of monomer and branched chains consisting of another monomer is called a graft polymer.
• Polymers made up of different types of monomers are classified as copolymers.
• Polymers with different types of atoms in the main chain are classified as heterochain polymers.
• Polymers made up of the same type of monomers are called homopolymers.

Elastomers and Fibers

• Elastomeric polymers are held together by weak intermolecular forces.
• The property of elastomeric polymers that allows them to be stretched is elasticity.
• Polymers that can be converted into fibers when drawn into long filament-like material are called fiber-forming polymers.
• A characteristic feature of fibers that imparts high tensile strength and high modulus is orientation of molecules.
• Polymers that exhibit a crystalline nature due to strong intermolecular forces like hydrogen bonding are called crystalline polymers.

Polymerization

• Crosslinks play a crucial role in elastomeric polymers by providing elasticity.
• Polymerization involving the generation of a free radical initiator like benzoyl peroxide is called free radical polymerization.
• The first stage of the chain reaction in free radical polymerization is called initiation.
• A free radical is defined as a highly reactive molecule with an unpaired electron.
• Benzoyl peroxide is commonly used as a free radical generating initiator in polymerization reactions.
• The final stage of the chain reaction in free radical polymerization is called termination.

Specific Polymers and Their Properties

• Polythene polymer is obtained from the polymerization of ethene.
• Step-reaction polymerizations are characterized by slow reaction rates and high molecular weights.
• Styrene rubber is a type of polymer that exhibits a property of being soft and flexible.
• Vulcanization of Styrene rubber is different from natural rubber in that it involves the addition of sulfur to create crosslinks.
• Styrene rubber is commonly used in making tires and other automotive parts.
• A notable downside of Styrene rubber is its low resistance to heat and UV light.
• Silicones are characterized by their flexibility and low thermal conductivity due to the proportion of alkyl silicon halides used during their preparation.
• The property of silicones that is generally lower than that of other plastics is their mechanical strength.
• The range of specific gravity for silicones is 0.9-1.1.
• Liquid silicones or silicone oils are commonly used as lubricants and hydraulic fluids.
• Silicone greases are primarily used for lubricating and protecting surfaces.
• The key characteristic of conducting polymers is their ability to conduct electricity.