Polyesters, Maleate Unsaturation

Polyesters. Two unsaturated polyesters were employed, one of which was highly unsaturated (dipropylene glycol maleate) (P-373), while the other was more flexible, containing adipic acid in addition to maleic anhydride. Both were crosslinked by means of styrene monomer. 

Conjugated unsaturated bonds in unsaturated polyester resins are reduced at the dropping mercury electrode and the height of the wave, resembling maleic acid esters, is a measure of the maleate unsaturation in polyesters. 

Unsaturated polyester maleate/phthalate (1/1) of propylene glyconol and neopenty glycol crosslinked by 38%, by weight, of styrene. 

DADC may be polymerised industrially with small amounts of other miscible Hquid monomers. Some acryflc ester monomers and maleic anhydride may accelerate polymerisation. Copolymerisation with methacrylates, diaHyl phthalates, triaHyl isocyanurate, maleates, maleimides, and unsaturated polyesters are among the examples in the early Hterature. Copolymers of DADC with poly-functional unsaturated esters give castings of high clarity for eyeglass lenses and other optical appHcations (20). 

Vinyl ethers can also be formulated with acryHc and unsaturated polyesters containing maleate or fumarate functionaHty. Because of their abiHty to form alternating copolymers by a free-radical polymeri2ation mechanism, such formulations can be cured using free-radical photoinitiators. With acryHc monomers and oligomers, a hybrid approach has been taken using both simultaneous cationic and free-radical initiation. A summary of these approaches can be found in Table 9. 

Unsaturated Maleate/O-Phthalate/1,2-Propanediol Polyester Prepolymer... 

Ultralow-monol polyols, 223 Ultrapek, 327, 328 Ultraviolet (UV) radiation, 209 Ultraviolet spectroscopy, 490 Unimolecular micelle, 58 United States, phenolic production in, 375 Unsaturated maleate/O-phthalate/ 1,2-propanediol polyester prepolymer, 101-102 Unsaturated polyester resins (UPRs), 19, 29-30, 58-59... 

Variation of Maleate to Vinyl Ether Ratio. Variation of the stoichiometric ratio of vinyl ether double bond to maleate double bond should produce more flexible films due to plasticization by dangling end groups but also may reduce cure speed and mechanical properties. The curing of unsaturated polyester F with DVE-3 using 4% Darocur 1173... 

Maleate/vinyl ether formulations based on a model unsaturated polyester prepared from maleic anhydride and 1,5-pentane diol and triethylene glycol divinyl ether were studied. At molecular weights of less than about 10,000 the cured films were extremely brittle. When the equivalent weight of the unsaturated polyester was increased by replacing some of the maleic anhydride with succinic anhydride, measurable values for film elongation could be obtained but the cure speed was definitely slower. When either diethyl maleate or isobutyl vinyl ether were added as monofunctional diluents the cure dose needed to obtain 200 MEKDR was increased and the flexibility measured by pencil hardness increased as the amount of diluent was increased. A urethane vinyl ether was synthesized and used to replace DVE-3 and films with increased elongation were obtained at equivalent at dosages as low as 1 J/cm2. 

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. 

Unsaturated liquid polyester resins - oligo(ester maleates), and especially oligo(ester maleate fu-marates) - OEMF, are stable in storage for months and sometimes years at normal temperature. Their general formula is ... 

Using simple laboratory equipment, it is possible to detect variations of the density of the order of 1 kg m-3 therefore, density measurements would be useless for diglycidyl ether of bisphenol A and diamino diphenyl methane (DGEBA-DDM), because both components have close Ma values. They would be moderately sensitive for unsaturated polyesters of maleate/ phthalate (1/1) of propylene glycol crosslinked by styrene (36 wt%), and relatively sensitive for DGEBA cured by diamino diphenyl sulphone (DDS) or phthalic anhydride (PA), for which relative variations of the molar ratio y of about 5% could be detected. In certain cases, where some comonomer (PA or styrene) can be lost by evaporation during the cure, density measurements can constitute a simple and efficient method of control way (e.g., for non-filled materials). 

This approach can be illustrated by unsaturated polyesters based on an almost equimolar combination of maleate and phthalate of propylene glycol, crosslinked by styrene (45 wt%) (Mortaigne el al., 1992). Six samples differing by the prepolymer molar mass were analyzed. The chain-ends concentration, b, was determined by volumetric analysis of alcohols and acids in the initial reactive mixture. Then, the system was cured, elastic measurements were made in the rubbery state at Tg + 30° C, and the shear modulus G was plotted against chain-ends concentration (Fig. 14.7). The following relationship was obtained ... 

Photopolymerization of Powder Formulations Powder coatings are very attractive [314]. The powder is applied on the substrate and exposed to an IR source to get the coalescence of the solid particules then, the cross-linking reaction is carried out under UV (or visible) light in a very short time and at a temperature about 100-120°C. Largely encountered systems are based on, for example, polyesters (with maleates or fumarates unsaturations) and polyurethane vinyl ethers that copolymerize according to a radical process, amorphous polyesters and functionalized polyesters (with allyl ethers). 

Chemistry of TJnsaturated Polyester Resins. Polyester Component. This part of the composition is prepared first and is sometimes called the alkyd portion. The starting materials are glycols and unsaturated dibasic acids or anhydrides. By way of example, the first member of the series may be ethylene maleate, and its preparation can be represented by the equation... 

A simplified structure is often written for such polyesters as —G— M—G— M —G— M—, where G and M are glycol and unsaturated dibasic acid residues, respectively. Ethylene maleate is seldom used because of limited compatibility in the commonly used monomers. Propylene glycol is used most often in commercial rigid resins, while diethylene and dipropylene glycols are used to impart flexibility. 

Carothers repeated Vorlander s synthesis of ethylene glycol maleates— but found that the crosslinking reaction of these solid unsaturated polyesters was too slow to be of practical use. 

Among polar additions to unsaturated polymers are reactions of amines and ammonia with unsaturated polyesters in the form of a Michael condensation. Thus, for instance, additions to poly(l,6-hexanediol maleate) and poly(l,6-hexanediol fumarate) show a difference in the reactivity of the two isomers. The maleate polyester reacts with ammonia to yield a crosslinked product at room temperature, when stoichiometric quantities or an excess ammonia in alcohol is used. At the same reaction conditions, the fumarate isomer only adds a few percent of ammonia. In a 1 1 mixture of chloroform and ethanol, however, approximately half of the fumarate double bonds react. Also, the maleate polyester reacts differently with piperidine or cyclohexylamine. In butyl alcohol at 60 °C the polymer initially isomerizes and precipitates. After the isomerization is complete and the temperature is raised to 80 °C, the polymer redissolves. An exothermic reaction follows and Michael-type adducts form. ... 

Another rearrangement reaction is isomerization of unsaturated polyesters upon heating. Thus, for instance, maleate polyesters rearrange to the fumarate analogs at elevated temperatures ... 

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