Ultraviolet light stability polymers

Ultraviolet light stabilizers, for PVC polymers, 25 675 Ultraviolet lithography, extreme,... 

Ultraviolet-light stabilizers are of two types those that preferentially absorb UV, thus shielding the polymer structure from UV light and those that protect by quickly scavenging the free radicals as they form. The latter belong to a group of compounds known as hindered amine light stabilizers (HALS). 

Polymers that are unstable in sunlight and require ultraviolet light stabilizer, like poly(vinyl chloride), polypropylene, nylons, rubbers, and cellulose. 

Zhang, X., Pi, H., Guo, S. Photostabilizing efficiency of ultraviolet light stabilizers for rigid poly(vinyl chloride) against photo-oxidation. Polym. Eng. Sci. 53, 378-388 (2013)... 

There is the possibiUty of a chemical reaction between a plastic and a colorant at processing temperatures. Thermal stabiUty of both the polymer and colorant plays an important role. Furthermore, the performance additives that may have been added to the resin such as antioxidants, stabilizers, flame retardants, ultraviolet light absorbers, and fillers must be considered. The suitabiUty of a colorant in a particular resin must be evaluated and tested in the final apphcation after all processing steps to ensure optimum performance. 

The commercial polymers are of comparatively low molecular weight (M = 25 000-60 000) and whilst being essentially linear may contain a few branches or cross-links arising out of thermal oxidation. Exposure to ultraviolet light causes a rapid increase in gel content, whilst heating in an oven at 125°C causes gelation only after an induction period of about 1000 hours. Eor outdoor applications it is necessary to incorporate carbon black. The polymers, however, exhibit very good hydrolytic stability. 

This study was therefore undertaken to prepare and evaluate acrylonitrile—butadiene-styrene (ABS) and methyl methacrylate-butadiene-styrene (MBS) polymers under similar conditions to determine whether replacement of acrylonitrile by methyl methacrylate could improve color stability during ultraviolet light aging, without detracting seriously from the good mechanical and thermal-mechanical properties of conventional ABS plastics. For purposes of control, the study also included briefer evaluation of commercial ABS, MBS, and acrylonitrile-butyl acrylate-styrene plastics. 

Among the types of ultraviolet absorbers that may be used as stabilizers are salicylates, o-hydroxybenzophenones, o-hydroxyarylbenzotri-azoles, and certain acrylonitriles. The stabilization of polystyrene by other additives has also been reported. Matheson and Boyer (10) found that certain aliphatic amines and amino alcohols improved the light stability of the polymer. 

Certain phenolic antioxidants in combination with ultraviolet absorbers improve substantially the light stability of polystyrene. Combinations of this type can be used advantageously to prevent polymer discoloration in indoor fluorescent lamp fixture applications. However, studies of this type require further investigation, and an explanation must be sought for the striking differences in behavior of the various antioxidants tested. 

Stabilizer—A substance added to a polymer to inhibit the degrading effects of oxidizers, ultraviolet light, or electrical discharge. 

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