Antioxidants melt processing variety

Phosphite polymer stabilizers were analyzed by combining LD/El/FTICR. Used to control molecular weight and color in melt processing, these antioxidants are difficult to analyze by extraction-LC, X-ray fluorescence, UV, or FTIR for a variety of reasons. Xiang et al. examined these additives individually and in mixed polymers that were prepared by hot pressing to form thin films that could be attached to the probe tip. Additives examined included Ultranox 626 (604 Da), XR-2502 (636 Da), and Weston 618 (732 Da). 

Another approach was developed by Scott in the 1970 s (7.8) which utilises the same mechanochemistry used previously by Watson to initiate the Kharacsh-type addition of substituted alkyl mercaptans and disulphides to olefinic double bonds in unsaturated polymers. More recently, this approach was used to react a variety of additives (both antioxidants and modifiers) other than sulphur-containing compounds with saturated hydrocarbon polymers in the melt. In this method, mechanochemically formed alkyl radicals during the processing operation are utilised to produce polymer-bound functions which can either improve the additive performance and/or modify polymer properties (Al-Malaika, S., Quinn, N., and Scott, 6 Al-Malaika, S., Ibrahim, A., and Scott, 6., Aston University, Birmingham, unpublished work). This has provided a potential solution to the problem of loss of antioxidants by volatilisation or extraction since such antioxidants can only be removed by breaking chemical bonds. It can also provide substantial improvement to polymer properties, for example, in composites, under aggresive environments. 

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