Crosslinking and thermal degradation

Figwre Photoinduced-acid catalyzed crosslinking and thermal degradation... 

Ageing and thermal degradation of crosslinked nadimide end-capped oligomers have been studied by means of solid infrared 13C NMR spectroscopy as well as by thermogravimetric measurements. They are mainly related to PMR and BBN families. 

PVC shrinkage is caused by several processes, such as release of frozen-in stresses, change of temperature, crosslinking, photodegradation, thermal degradation, and loss of additives. 

EFFECTS OF CROSSLINKING AND CHAIN DEGRADATION ON THE THERMAL CONDUCTIVITY OF POLYMERS. 

Cansarz, I. and Laskawski, W. 1979. Peroxide-initiated crosslinking of maleic anhydride-modified low-molecular-weight polybutadiene. II. Crosslinking degree and thermal degradation of cured polymers. Journal of Polymer Science, Polymer Chemistry Edition 17 1523-1529. 

KIO. — Yamamoto, O. Efiects of crosslinking and chain degradation on the thermal conductivity of polymers, KoUoid-Z. (1970) im Druck. 

Attractive blends for PEMs with high proton conductivity have been made from sulfonated PES, PSU, polyetherketone (PEK), PEEK or poly(2,6-dimethyl 1,4-phenylene ether) (PPE) blended with polybenzimidazole (PBI) or polyetherimide (PEI). To preserve the desired PEM performance, the blends are often crosslinked by radiation, chemical reaction of ionic interactions. For long-term PEM applications it is important that membranes resistance to mechanical, chemical and thermal degradation is maximized. Accelerated aging tests should follow several membrane functionalities, for example conductivity, membrane integrity and permeability. The tests should also identify a possible cross-correlation of effects, namely stress on thermal and/or chemical degradation. 

Phenolic networks are well known for their excellent thermal and thermo-oxidative stabilities. The mechanisms for high-temperature phenolic degradation include dehydration, thermal crosslinking, and oxidation, which eventually lead to char. 

Polyurethane materials are extremely versatile in that it is possible to produce a large variety of structures which range in properties from linear and flexible to crosslinked and rigid. The crosslinked PURs are thermosets, which are insoluble and infusible and therefore cannot be reprocessed by extrusion without suffering extensive thermal degradation. At present, the main sources of recyclable waste are flexible PUR foams and automobile waste. Waste and scraps of these materials may consist of 15-25% by weight of total PUR foam production. 

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