Light stabilizer, additive

The exterior durabiHty of relatively stable coatings can be enhanced by use of additives. Ultraviolet absorbers reduce the absorption of uv by the resins and hence decrease the rate of photodegradation. Eurther improvements can be gained by also adding free-radical trap antioxidants (qv) such as hindered phenols and especially hindered amine light stabilizers (HALS). A discussion of various types of additives is available (113). 

Further improvement in light stability may be achieved by addition of small quantities of ultraviolet absorbers. Typical examples include phenyl salicylate, 2,4-dihydroxybenzophenone, resorcinol monobenzoate, methyl salicylate and stilbene. 

Figure 13.21 shows the resolution of a dozen polymer additives at very high resolution using chloroform as the mobile phase. Tinuvin 622 will elute in pure chloroform whereas Chimassorb 944 and many other hindered amine light stabilizers (HALS) will not. With the addition of 1% triethyl amine to the chloroform, however, virtually all HALS will elute. 

Since the first plastic cellulosic was produced in 1868, there has been an evergrowing demand for specially compounded plastics. Using a post-reactor technique, plastics can be compounded by alloying or blending polymers in addition to using additives such as colorants, flame retardants, heat or light stabilizers, lubricants, fillers, and/or reinforcements (Fig. 6-6). With reinforcements the resulting reinforced compounds are usually referred to as reinforced plastics (RPs). 

An alternative mechanism by which additives may protect polymers from photo-oxidation is radical trapping. Additives which operate by this mechanism are strictly light stabilizers rather than antioxidants. The most common materials in this class are the hindered amines, which are the usual additives for the protection of poly (ethylene) and poly (propylene). The action of these stabilisers is outlined in Reactions 8.3-8.5. 

The UV method performs well in the absence of interferences of other additives or pigments but is liable to be in error owing to interference by highly absorbing impurities that may be present in the sample or in the solvent [56,57]. Commercial erucamides with variable light stability have been analysed by means of SEC-UV (254nm)/RI and UV absorption in MeOH [58]. 

In the present study possible modes of action of a relatively new class of light stabilizers, the Hindered Amine Light Stabilizers (HALS, tetramethylpiperidine derivatives, TMP) will be discussed. Certain members of this group have a light stabilizing effect superior in many fields of application to that of previous additives. They are effective in both thick layers and fibers13 12. 

Several additives are common in producing moldable ABS resins. These include lubricants, mold release agents, antistatic agents, heat stabilizers, light stabilizers and flame retardants (65). 

In addition to such general requirements as low volatility, temperature stability, light stability, little, or no odor, etc., there are a number of more basic requirements. 

As indicated above, considerable efforts in research and development have been deployed into the development of insoluble singlet oxygen sensitizers. Although, rose bengal chemically bound to chloromethylated copolymer of styrene and di vinyl benzene [14, 84] (and commercialized as Sensitox ) has shown excellent results as far as its light stability in solid matrices is concerned [85], the sensitizer is suffering, in addition to the drawbacks of the... 

Patents state that the addition products from 2,2,6,6-tetramethyl-piperidin-4-ol and tetrolic acid are heat and light stabilizers for polymers.276-277... 

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