HS2004_2339 Week 4 Asyn_Mechansisms of Decay in polymers Flashcards
How free radicals create more free radicals
What is a free radical
Diagram showing how different energies are required for free radical production
Scheme of reaction of free radicals
Free radicals in polymer chains: stage one: Abstraction: free radicals
- an attack on the C-H bond, producing two free radicals, one on the carbon chain
Stage two of free radical production on polymer chains (formation of a peroxy radical)
- hydrogen abstracted, creating a free radical, this is how polymers decay
- this can react with oxygen, to stabilise via covalent bonding, but the oxygen remains a free radical (this is called a peroxy radical)
Stage three of free radical production in polymers: Abstraction
A weaker hydrogen bond is targeted, and pulled in
Free radical oxyl group causing chain scission (diagram)
- creates an oxyl radical
- reaction depends on energy and structure
Polymer decay reactions, which are non free- radical and non homolytic
Diagram showing side chain loss in polyvinyl acetate- what is the Physical change?
yellowing in polymer
Diagram of cyclisation in polymer decay
How heat and oxygen causes degradation of polymers and free radical formation