Hyperbranched polyesters resins

Radiation curable epoxy functionahsed hyperbranched polyester resin has been synthesised from a hydroxy functional hyperbranched polyether polyol and an epoxy functional fatty acid, vernolic acid. The resin was cationically polymerised in the presence of differing amounts of vernolic acid methyl ester as a reactive diluent. Similarly, Mesua ferrea L. seed oil-based hyperbranched polyesters are prepared using anhydride-based... 

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. 

A combination of enhanced reactivity and reduced viscosity for alkyd resins has been achieved by using hyperbranched polyester structures as discussed in Sect. 4.2.3 [ 123]. This study clearly showed the benefits of using highly branched structures in coating applications to obtain improved properties. 

In the second part of this review, we report the synthesis of dendrimers and hyperbranched polyesters based on 2,2-bis(methylol)-propionic acid. An extensive study has also been made on the material properties of the hyperbranched polyesters both as thermoplastics and as cross-linkable resins. All characterization techniques and apparatus that have been used throughout this work are described in the Appendix. An outline of the material covered is shown in Figure 2. 

Three different acrylates have been synthesized and characterized. The same hydroxy-functional hyperbranched polyester (H3) was used as a base for all resins. Approximately 50% of the terminal hydroxyls were acrylated and the rest either... 

Another resin application based on the same hyperbranched polyester structure described herein is low-VOC alkyds, which have very low viscosity and high reactivity compared to conventional high-solid alkyds. Other resin structures are unsaturated polyesters, polyurethane dispersions, and epoxides. ... 

Nonlinear, dendritic or hyperbranched polymers have received considerable attention in recent years. These polymers have seen little use as supports for oligosaccharide synthesis compared to Merrifield or soluble MPEG resins. Nevertheless, some interesting applications of hyperbranched polymers such as hyperbranched polyester and poly(amidoamine) to oligsaccharide synthesis have been reported. 

The use of epoxidized hyperbranched polyesters as toughening additives in carbon-fiber reinforced epoxy composites has been demonstrated (Boogh et al., 1995). Since a hyperbranched resin has a substantially lower viscosity and much shorter drying time than a conventional (less branched) resin of comparable molecular weight, hyperbranched polymers have been used as the base for various coating resins (Pettersen and Sorensen, 1994). 

Polyesterpolyols (Boltom from Perstop, Sweden) - highly branched nanopolymers - allow for tailor-made duroplastic chemistry. Small amounts of epoxide-functionalized, hyperbranched polyesters increase the impact strength of epoxy resins without reducing rigidity. 

Wu Wu, H., Xu, J., Liu, Y., Heiden, P. Investigation of readily processable thermoplastic-toughened thermosets. V. Epoxy resin toughened with hyperbranched polyester. J. Appl. Polym. Sci. 72 (1999) 151-163. 

Xu Xu, G., Shi, W. F., Gong, M., Yu, F., Feng, J. P. Curing behavior and toughening performance of epoxy resins containing hyperbranched polyester. Polym. Adv. Technol. 15 (2004) 639-644. 

One of the recent advancements and interests in alkyd resin technology is hyperbranched alkyd resins, which, due to their unique highly branched polymer architecture, have low viscosities at higher MWs. An important characteristic of these alkyds is rapid drying. Generally they are prepared by reacting hyperbranched polyester polyols with fatty acids. The main limitation of such alkyds, however, is higher cost, due to the need for unique, more expensive raw materials in their synthesis. 

Polyester chemistry is the same as studied by Carothers long ago, but polyester synthesis is still a very active field. New polymers have been very recently or will be soon commercially introduced PTT for fiber applications poly(ethylene naph-thalate) (PEN) for packaging and fiber applications and poly(lactic acid) (PLA), a biopolymer synthesized from renewable resources (corn syrup) introduced by Dow-Cargill for large-scale applications in textile industry and solid-state molding resins. Polyesters with unusual hyperbranched architecture also recently appeared and are claimed to find applications as crosstinkers, surfactants, or processing additives. 

The dilution properties of hyperbranched polymers also differ from those of linear polymers. In a comparison between two alkyd resin systems, where one was a conventional high solid alkyd and the other based on a hyperbranched aliphatic polyester, the conventional high solid alkyd was seen to exhibit a higher viscosity [113]. A more rapid decrease in viscosity with solvent content was noted for the hyperbranched alkyd when the polymers were diluted. 

Amongst the first studies presenting the use of dendritic polymers for thermoset applications was the work of Hult et al. [62]. They modified hyperbranched hydroxy functional polyesters with various ratios of maleate-allyl ether/alkyl ester end groups. Dependent on this ratio, resins with different vis-... 

Pettersson and Sorensen have described a number of different thermoset resin structures based on hyperbranched aliphatic polyesters [123]. Their results can best be exemplified by a study on hyperbranched alkyd coating resins. A comparative study was performed between an alkyd resin based on a hyperbranched aliphatic polyester and a conventional high solid alkyd, which is a less branched structure. The hyperbranched resin had a substantially lower viscosity than the conventional resin of comparable molecular weight, that is, less solvent was needed to obtain a suitable application viscosity. The hyperbranched resin also exhibited much shorter drying times than the conventional resin, although the oil content was similar. These achievements would not have been possible without a change in architecture of the backbone structure of the resins (Figs. 12,13). 

Studies on acrylate resins [82, 124, 125] based on hyperbranched aliphatic polyesters have shown that it is possible to vary both the polarity (wetting be-... 

Another type of hyperbranched resins which has been studied is unsaturated polyesters as described in Sect. 4.2.3 [62]. 

Ranby and Shi also studied hyperbranched methacrylated polyesters and their use in photopolymerizations of films and fiber-reinforced polymer composites. The resins were found to have low viscosities and higher curing rates than those of corresponding linear unsaturated polyesters [131-133]. 

It is apparent that the mode of reaction of the hyperbranched polyesteramides must be distinctively different from those of the known commercial crosslinkers. In order to explain these results, the hyperbranched polyesteramides should in our view not be regarded as simply multifunctional polymeric crosslinkers but rather as precondensed forms of two-functional crosslinkers (the addition product of diisopropanolamine and the cyclic anhydride), as depicted in Fig. 22, left. Bearing in mind the chemical fate of benzoic acid (2.2.1, Fig. 11) which was condensed with a polyesteramide resin and which appeared to transesterify at least as fast as it esterified, the mode of reaction of polyesters comprising aromatic acid end groups must be in accordance and comprised of both transesterification and esterification. 

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