Ultraviolet stabiliser

For outdoor applications, additives such as UV-absorbers and light stabilisers are generally used during compounding and are transparent to solar radiation but immune to the destructive effect of UV radiation. 

Crompton [59] has described a simple direct thin-layer method for the determination of UV 531 ultraviolet stabiliser in hot toluene extracts of HDPE. Interference was encountered from a number of additives, namely, dilauryl thiodipropionate, lonox 330, lonol CP, Topanol CA, Santonox R and Polygard. 

UV 531 is extracted from the polymer by precipitation of the polymer with ethanol from a hot toluene solution as described previously. An aliquot of the extract is applied to a thin-layer plate and chromatographed. The zone corresponding to UV 531 is removed from the plate and extracted with ethanol. The concentration of UV 531 is determined by measuring the UV absorption peak near 295 nm in ethanol solution and referring to a calibration graph. 

Other methods for the determination of UV absorbers in polymers are reviewed in Table 5.6. 

Benzophenone and salicylic acid types Solvent extraction, TLC [40] 

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Further variation in properties is obtained by incorporating such additives as antistatic agents, ultraviolet stabilisers and antioxidants. 

Comparatively little information is available concerning the use of additives in commercial grades of polycarbonate. Pigments, heat and ultraviolet stabilisers, blowing agents and fire retardants are used but the range of materials available... 

Besides resin and reactive diluent, additives are commonly incorporated into polyester resins. These include not only curing agents and fillers (see Section 25.2.3) but also ultraviolet stabilisers. The latter are particularly important for outdoor applications such as roof lighting, benzotriazoles being particularly effective. 

Table 2,6 Ultraviolet stabilisers for epoxy systems, with the chemical abstracts service (CAS) registry number...

Ultraviolet stabilisers for epoxies. The function of ultraviolet (UV) stabilisers is to retard light-induced polymer degradation which is caused by electromagnetic radiation emitted by the sun. Commonly used UV stabilisers for epoxy systems are given in Table 2.6 (Dexter, 1982). Only chemical names along with chemical abstracts services (CAS) registry numbers are mentioned commercially they are known by trade names. 

Ultraviolet stabilisers. Stabilisers based on hindered amines are effective. 

A further development of the OFB concept is erosion control and re vegetation blankets (ECRB). These are a combination of PA or PP staple fibre bound within two PP or PA nets. They have similar ground cover characteristics to the OFBs. However, the use of ultraviolet stabilised fibres provides for a much longer installation life than the organic blankets. 

A gas chromatographic method for the determination of antioxidants and ultraviolet stabilisers in low-density polyethylene was developed which involved a binary solvent... 

Lappin and Zannucci [5] concerned themselves with polypropylene additives such as hindered phenols and ultraviolet stabilisers which are stable at 350 °C. They used a gas chromatograph equipped with a flame ionisation detector. Copper columns, 6.4 mm x 1.5 m, packed with 10% SE-30 on 40- to 60-mesh Chromsorb V were used (the column may require silylation). The injection port and detector oven were held at a constant... 

Figure 9.19 Heat ageing of natural stabilised polypropylene in air in conjunction with an ultraviolet stabiliser. Source Author s own files)...

Resistance to ultraviolet radiation is limited. This is because of the strong absorption of ultraviolet by the aromatic species. It can be addressed by coating the PAEK components or to some extent by incorporating ultraviolet absorbers of reflectors. Unfortunately many standard ultraviolet stabilisers are too volatile or lack the thermal stability required to work well in PAEK. 

Table 5.1 gives the formulation of a polyethylene and a polystyrene used in some Uvitex OB extractability studies. In addition to the ultraviolet stabiliser, liquids obtained in extractability tests carried out on these plastics would contain various other substances, some of which are ultraviolet absorbers and which may be present in the extractant at higher concentrations than Uvitex OB. In this case the polymer also contained Santonox R, Wingstay T, phenolic antioxidant and styrene monomer. The presence of such ultraviolet absorbing substances in the extractant will interfere in the determination of Uvitex OB at 378 nm. In applying spectroscopic methods of analysis to extractants, consideration must always be given to the possibility of interference by any polymer additives present other than that which one is required to determine. 

THE EFFECT OF ULTRAVIOLET STABILISERS ON THE PHOTODEGRADATION OF POLY(ETHYLENE TEREPHTHALATE)... 

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