Radical Formation in Thermoplastics

The possibility of employing block copolymers as materials that might possess desirable properties was originally considered by Mark In the first period the effort in preparing block copolymers was directed to radical polymerization and it was only in 1956 that Szwarc obtained well-defined block copolymers by anionic polymerization . In block copolymers, the incompatibility between polymeric chains becomes an advantage a phase separation of the blocks occurs leading to the formation of microdomains which are responsible for the ecific properties of block copolymers. For instance, the presence in a molecule of an elastomeric block linked by its ends to thermoplastic blocks generates a polymer in which reversible physical multifunctional cross-links allow the behaviour of conventional vulcanized elastomers at room temperature, but the material remains easily moldable at elevated temperature just as normal thermoplastic resins ° ... 

Photoactive Additives.—Ferric compounds, in particular, the chloride, continue to attract much interest as photosensitizers for thermoplastics. " From e.s.r. work the mechanism appears to involve a redox reaction resulting in the formation of active hydroxy-radicals. Photodegradable polyethylene film has been developed by doping it with radiation-modified atactic polypropylene and hydroxyethyl-ferrocene. Several workers have studied the dye-sensitized photo-oxidation of polyisoprene and di-n-butyl sulphide embedded in Augustyniak and... 

ABS copolymer is a popular engineering thermoplastic because of its unique properties, which include an excellent mechanical response, chemical resistance, fine surface appearance, and easy processing characteristics. Its unique properties. It consists of a styrene-acrylonitrile (SAN) continuous phase partially grafted onto a dispersed polybutadiene phase of an elastomeric nature. ABS resin is its inherent flammability and lower thermal stability when it is exposed to heat, mechanical stress, and ionizing or ultraviolet radiation in the presence of oxygen because of the formation of reactive intermediates such as free radicals and hydroperoxides. 

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