ADVANCED BIOFRIENDLY POLYMERS Jaroslav Mosnek What is degradation

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 SSR= Single step reaction

MECHANISTIC ASPECT OF POLYMER DEGRADATION Mode of Initiation Side Chain elimination Solvolysis (Hydrolysis) of ester linkage (SSR) Elimination of HCl (PVC) (CR) Chemical (hydrolytic) Thermal Hydrolysis of ester linkages SSR= Single step reaction CR = Chain reaction

MECHANISTIC ASPECT OF POLYMER DEGRADATION Mode of Initiation Depolymerization Thermal Typical for Poly(methyl methacrylate and mainly for other acrylate based polymers Cross-linking Thermal, Photochemical, Mechanical, Chemical Oxidation PP with Oxygen Beta-scission of tertiary alkoxy radicals