ADVANCED BIO-FRIENDLY POLYMERS
Jaroslav Mosnáček
What is degradation of polymers?
• Any change of the polymer properties relative to the initial, desirable
properties.
• In this sense, "degradation" is a generic term for any number of
reactions which are possible in a polymer.
• These reactions, in turn, lead to a change in the physical and optical
properties of the polymer.
• It is accompanied with change in molar mass of the polymers
Mode of initiation of degradation
Thermal*
Photo (light induced)*
Biological*
Chemical (Hydrolytic)*
Mechanical
High Energy Radiation
*Will be discussed
MECHANISTIC ASPECT OF POLYMER DEGRADATION
Mode of Initiation
Chain scission
Random Chain scission (Hydrocarbons)
Thermal
Norrish Type (I, II) chain scission (SSR)
Photochemical
Enzymatic or hydrolytic attack of esters, amides and glucosides (SSR)
Biological/hydrolytic
Norrish I and II
Random scisson
.+ .
+
+
Alkanes
Alkenes
Alkadienes
SSR= Single step reaction
MECHANISTIC ASPECT OF POLYMER DEGRADATION
Mode of Initiation
Side Chain elimination
Solvolysis (Hydrolysis) of ester linkage (SSR)
Chemical (hydrolytic)
Thermal
Elimination of HCl (PVC) (CR)
Side Chain Elimination
Hydrolysis of ester linkages
H
H
Cl
Cl
H
Cl
H
Cl
H
PVC
Cl
H
Cl
H
Cl
H
Cl
H
Cl
- HCl
Polyene
Aromatics
SSR= Single step reaction
CR = Chain reaction
MECHANISTIC ASPECT OF POLYMER DEGRADATION
Mode of Initiation
Thermal
Depolymerization
COOR
COOR
COOR
COOR
COOR
COOR
COOR
.
COOR
COOR
.+
COO
COOR
COOR
COOR
Cross-linking
COOR
Typical for Poly(methyl methacrylate and
mainly for other acrylate based polymers
Monomer
Thermal, Photochemical,
Mechanical, Chemical
Oxidation
PP with Oxygen
Beta-scission of
tertiary alkoxy
radicals