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Light stabilizer are used to inhibit polymer photo-oxidation, which is the combined result of the action of light and oxygen. Like autoxidation this is a free radical process, hence the antioxidants described above are effective inhibiting agents, however additional classes of additives are also beneficial, such as UV absorbers, quenchers of ...
In industrial chemistry, a stabilizer or stabiliser is a chemical that is used to prevent degradation. [1] Above all, heat and light stabilizers are added to plastic and rubber materials because they ensure safe processing and protect products against aging and weathering.
Hindered amine light stabilizers (HALS) are chemical compounds containing an amine functional group that are used as stabilizers in plastics and polymers. [1] These compounds are typically derivatives of tetramethylpiperidine and are primarily used to protect the polymers from the effects of photo-oxidation; as opposed to other forms of polymer degradation such as ozonolysis.
UV-328 is a light stabilizer for a variety of plastics and other organic substrates. Its use is recommended for the stabilization of styrene homopolymers and copolymers, acrylic polymers, unsaturated polyesters, polyvinyl chloride, polyolefins, polyurethanes, polyacetals, polyvinyl butyral, elastomers and adhesives. [5]
The metal is heated into the austenite region of the iron-cementite phase diagram and then quenched in a salt bath or other heat extraction medium that is between temperatures of 300–375 °C (572–707 °F). The metal is annealed in this temperature range until the austenite turns to bainite or ausferrite (bainitic ferrite + high-carbon ...
Its primary crystalline structure is austenite (face-centered cubic). Such steels are not hardenable by heat treatment and are essentially non-magnetic. [2] This structure is achieved by adding enough austenite-stabilizing elements such as nickel, manganese and nitrogen.
In order for any transformation to take place, the microstructure of the metal must be austenite structure. The exact boundaries of the austenite phase region depend on the chemistry of the alloy being heat treated. However, austenitizing temperatures are typically between 790 and 915 °C (1,454 and 1,679 °F). [5]
ASA can be made by either a reaction process of all three monomers (styrene, acrylonitrile, acrylic ester) or a graft process, although the graft process is the typical method. A grafted acrylic ester elastomer is introduced during the copolymerization of styrene and acrylonitrile. The elastomer is introduced as a powder. [11]