Additives UV absorbers

From the quantum yield data in Table I and the extent of sunlight absorption by each polymer (Table I and Figure l) it is apparent that although PET and PmPiPA absorb strongly, they have very low quantum yields for their primary reactions. PP on the other hand absorbs weakly due to low concentrations of chromophores but these chromophores give radical products by efficient processes. In addition photooxidation leads to a rapid build up of additional UV absorbing -OOH groups (discussed in Section III). 

Promotional additives (UV absorbers, natural oils, botanic extracts, protein hydrolytes) 0-2... 

These constituents may include additives antistatic additives, UV absorbers, antislip additives, slip additives, colourants, opacifiers, plasticisers, stabilisers, antioxidants, etc., which may be added at the compounding stage to provide specific or modified properties. However, other constituents may be present from the polymerisation and/or the converting processes. The polymerisation process may involve residues and processing aids. Residues (constituents which may remain from the polymerisation process) may include monomer(s), solvents, accelerators, catalysts, initiators, etc. Processing aids are additional substances to aid processing or restrain undesirable effects, e.g. antioxidants. 

Tinuvin . [Ciba-Geigy/Additives] Uv absorber, light stabiUzer for plastics, coatings. 

Topanex. [ICI Polymer Additives] Uv absorber, stabilize, antroxidant... 

Tinnvln . [Ciba<3dgy/Additives] Uv absorber, ItgiK stabitizer for friastics, coatings. 

Plastic Sheet. Poly(methyl methacrylate) plastic sheet is manufactured in a wide variety of types, including cleat and colored transparent, cleat and colored translucent, and colored semiopaque. Various surface textures ate also produced. Additionally, grades with improved weatherabiUty (added uv absorbers), mat resistance, crazing resistance, impact resistance, and flame resistance ate available. Selected physical properties of poly(methyl methacrylate) sheet ate Hsted in Table 12 (102). 

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). 

The alternative is to add a UV-absorbing material to the mobile phase. If a compound elntes from the HPLC colnmn that does not absorb UV radiation, the detector response will decrease. An additive should be chosen which has significant absorption in order that it may be added at low concentration and thus have minimal effect on the chromatographic separation. It is also important that reaction between the analyte(s) and additive does not occur. 

Polymer/additive analysis then usually proceeds by separation of polymer and additives (cf. Scheme 2.12) using one out of many solvent extraction techniques (cf. Chapter 3). After extraction the residue is pressed into a thin film to verify that all extractables have been removed. UV spectroscopy is used for verification of the presence of components with a chromophoric moiety (phenolic antioxidants and/or UV absorbers) and IR spectroscopy to verify the absence of IR bands extraneous to the polymer. The XRF results before and after extraction are compared, especially when the elemental analysis does not comply with the preliminary indications of the nature of the additive package. This may occur for example in PA6/PA6.6 blends where... 

The most important area for packed column use involves modified mobile phases (MPs). Consequently, pSFC needs detection systems in which the MP modifier and possible additive(s) do not interfere, and in which detection of low or non-UV-absorbing molecules is possible in combination with pressure/modifier gradients. The disadvantage of adding even small amounts of modifier is that FID can no longer be used as a detector. In the presence of polar modifiers in pSFC the detection systems are restricted basically to spectroscopic detection, namely UVD, LSD, MSD (using PB and TSP interfaces as in LC). ELSD can substitute FID and covers the quasi-universal detection mode, while NPD and ECD cover the specific detection mode in pSFC on a routine basis. As ELSD detects non-UV absorbing molecules dual detection with UV is an attractive option. 

Many industrial laboratories conducting significant amounts of additive analyses have developed a universal HPLC method which may be used to separate most of the additives of interest. Thomas [417] has reported a method that can separate over 20 common primary and secondary stabilisers. Verdurmen et al. [197] employ a gradient ranging from 60 % acetonitrile/40 % water to 100% acetonitrile subsequently, all components are eluted off the column in isocratic mode. Irganox 1063 is used as a suitable internal standard since this compound is not frequently encountered in commercial polymers, elutes without overlap to other additives and shows good UV absorbency. In order... 

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