Chapter 5 - Polymers and Solid Structures Flashcards
What is Amorphous Solid
is a shapeless solid that takes place of its container
Glass temperature / TG
is a temperature where the molecules begins to obtain partial freedom of movement
Polymerization process - Chain Growth
chain growth is a polymerization process of monomer through a process of chain reaction that occurs after initation through free radicals agent that on heat decomposes into free radicals
Name of these compounds and chemical structure
PVC
PVAc
PMMA
PBA
PVC - Polyvinyl Chloride
PVAc - Polyvinyl Acetate
PMMA - Polymethyl Methacrylate
PBA - PolyButyl Acrylate
Propagation Sequence of growth steps Termination Occurance
3 Termination Occurances
- Combination - 2 polymer with free radicals satisfy each other free valencies
- Disproportionation - when one of the 2 polymers with free radicals donate hydrogen atoms to other and form doublebond to satisfy radical
- Chain Transfer - basically free radicals is transfered to another compound through the removal of monovalent atom.
4 ways to remove hydrogen
- another monomer molecule
- a solvent molecule
- another polymer molecule - which will grow further polymer
- a compound called a chain transfer agent
What is the function of Inhibitor in polymerization process
a reactive materials that hinders or prevent polymerization taking place or further polymerization
4 Purpose of inhibitors
Safe storage of monomers
Controlling the stability of UPR (unsaturated polyester resin)
Anti Oxidants
Stopping polymerization or further polymerization
Step Growth polymerization
is a polymerization process that yields out unneccessary byproduct, and this byproduct needs to be removed in order to use the polymer
For example dibasic acid + dihydric alcohol –> ester and water
Polymers characteristics of Polyacrylonitrile
Its a highly polar side groups, reinforced with hydrogen bonding and high TG
it is not suitable for paints, ideal property for synthetic fiber
Polymer characteristics of Polyethylene
Non polar, weak intermolecular forces, tg is between 105 - 115 C, homopolymer it is unsuitable for paints and fiber, can be used as monomer in emulsion polymer with vinyl acetate
Polymer Characteristics of PVC / Polyvinyl Chloride
Similar to Polyacrylonitrile, it is high tg, can be used as a copolymer PVC with PVAc to add toughness in coating, for plastisizing also
Polymer Characteristics of Polyvinyl Acetate
bulky and flexible polar side group with tg 70-125 C, found mostly in polymer emulsion for emulsion paint
weakness - acetate tend to hydrolyse, which makes copolymer less durable and less suitable where moisture is frequently encountered.
Polymer Characteristics of Polystyrene
Bulky side group, low polarity has ring, which contributes to yellowing. rigid groups which makes a polymer inflexible
weak and brittle, except at high molecule weights
