Polyesters, network film formation

Films can be formed from dihydroxydocosanoic acid [23] and appear to be formed as polyesters by intermolecular dehydration to form a network polymer. In contrast, monohydroxydocosanoic acid gives a linear polymer. Coefficients of friction are not exceptionally low, with jx of the order of 0.1, but wear properties are claimed to be comparable or better than those of ZDDP, albeit only in simple FourBall testing. However, this mechanism of film formation may be applicable in very low or zero phosphorus formulations if the mechanisms for film generation are applicable in fully formulated oils. 

Several applications of hyperbranched polymers as precursors for synthesis of crosslinked materials have been reported [91-97] but systematic studies of crosslinking kinetics, gelation, network formation and network properties are still missing. These studies include application of hyperbranched aliphatic polyesters as hydroxy group containing precursors in alkyd resins by which the hardness of alkyd films was improved [94], Several studies involved the modification of hyperbranched polyesters to introduce polymerizable unsaturated C=C double bonds (maleate or acrylic groups). A crosslinked network was formed by free-radical homopolymerization or copolymerization. 

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