Unsaturated Carboxylic Acids and Related Compounds

The introduction of a reactive functionality into the polymer, such as unsaturation, offers the potential to use organic acids as coupling agents, but mixed results have been reported. A number of potentially suitable unsaturated products exist, notably, maleic acid and anhydride, acrylic and methacrylic adds, and unsaturated versions of fatty acids such as oleic acid. The acidities and double-bond reactivities of these compounds widely vary depending on their structures, and this probably accounts for the marked differences in their performance. Compounds such as acrylic acid have both high addity and high double-bond reactivity due to the proximity of the carbonyl group to the double bond. The only commercial products specifically developed for use with filled polymer systems are from Lubrizol Advanced Materials (SOLPLUS). 

The exad composition of these additives is not disdosed, but they are described as unsaturated oligomeric carboxylic acids. 

It has been demonstrated that effeds consistent with coupling can be achieved with at least some of these additives, although not all structures are effedive. It seems that the strength of the acid group and the reactivity and accessibility of the unsaturation are important fadors. 

Although not widely studied, the simplest case is that of peroxide cured or cross-linked systems, where unsaturation can take part in the curing readion. Mori has reported very good results with some unsaturated carboxylic acids (e.g., CH2=C(CH3)C00C2H4C00H) in a calcium carbonate-filled unsaturated polyester resin [15]. Some of the results are presented in Table 6.1. 

Some of the basic effeds obtained with aluminum hydroxide-filled EVA in the absence of peroxide and additional stabilizer are illustrated in Table 6.2, which contains a comparison between various unsaturated adds and three common organofimctional silane coupling agents. The silanes are all seen to significantly 

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