Polymer degradation Polymer

a plastic item thirty years of exposure heat , cold, brake fluid, , sunlight. notice discoloration, swelling, , crazing of material

polymer degradation change in properties—tensile strength, color, shape, or molecular weight—of polymer or polymer-based product under influence of 1 or more environmental factors, such heat, light, chemicals and, in cases, galvanic action. due scission of polymer chain bonds via hydrolysis, leading decrease in molecular mass of polymer.

although such changes undesirable, in cases, such biodegradation , recycling, may intended prevent environmental pollution. degradation can useful in biomedical settings. example, copolymer of polylactic acid , polyglycolic acid employed in hydrolysable stitches degrade after applied wound.

the susceptibility of polymer degradation depends on structure. epoxies , chains containing aromatic functionalities susceptible uv degradation while polyesters susceptible degradation hydrolysis, while polymers containing unsaturated backbone susceptible ozone cracking. carbon based polymers more susceptible thermal degradation inorganic polymers such polydimethylsiloxane , therefore not ideal high-temperature applications. high-temperature matrices such bismaleimides (bmi), condensation polyimides (with o-c-n bond), triazines (with nitrogen (n) containing ring), , blends thereof susceptible polymer degradation in form of galvanic corrosion when bare carbon fiber reinforced polymer cfrp in contact active metal such aluminium in salt water environments.

the degradation of polymers form smaller molecules may proceed random scission or specific scission. degradation of polyethylene occurs random scission—a random breakage of bonds hold atoms of polymer together. when heated above 450 °c, polyethylene degrades form mixture of hydrocarbons. other polymers, such poly(alpha-methylstyrene), undergo specific chain scission breakage occurring @ ends. literally unzip or depolymerize constituent monomer.

the sorting of polymer waste recycling purposes may facilitated use of resin identification codes developed society of plastics industry identify type of plastic.

product failure

chlorine attack of acetal resin plumbing joint

in finished product, such change prevented or delayed. failure of safety-critical polymer components can cause serious accidents, such fire in case of cracked , degraded polymer fuel lines. chlorine-induced cracking of acetal resin plumbing joints , polybutylene pipes has caused many serious floods in domestic properties, in usa in 1990s. traces of chlorine in water supply attacked vulnerable polymers in plastic plumbing, problem occurs faster if of parts have been poorly extruded or injection molded. attack of acetal joint occurred because of faulty molding, leading cracking along threads of fitting serious stress concentration.

ozone-induced cracking in natural rubber tubing

polymer oxidation has caused accidents involving medical devices. 1 of oldest known failure modes ozone cracking caused chain scission when ozone gas attacks susceptible elastomers, such natural rubber , nitrile rubber. possess double bonds in repeat units cleaved during ozonolysis. cracks in fuel lines can penetrate bore of tube , cause fuel leakage. if cracking occurs in engine compartment, electric sparks can ignite gasoline , can cause serious fire. in medical use degradation of polymers can lead changes of physical , chemical characteristics of implantable devices.

fuel lines can attacked form of degradation: hydrolysis. nylon 6,6 susceptible acid hydrolysis, , in 1 accident, fractured fuel line led spillage of diesel road. if diesel fuel leaks onto road, accidents following cars can caused slippery nature of deposit, black ice.