Oligomers unsaturated

Microstructures of piperylene oligomers unsaturated part and polyisoprene were determined by IR-spectroscopy on "Specord M80". Absorption bands at 730, 750, 910 and 967 cm corresponding to CIS-1,2-, CIS-1,4-, 3,4- and rrans-(l,2 + l,4)-units of oligopiperylene accordingly were used as analytical. Polyisoprene microstructure was determined by absorption bands 840 and 889 cm ... 

Photopolymerizable monomers and oligomers can be classified under four main groups including radical monomers and oligomers, unsaturated polyester resins, thiol-ene systems, and cationic monomers. In addition to these systems, particular photopolymerizable systems are also available such as expanding monomers, liquid crystalline monomers, and some other miscellaneous monomers. 

The practical consequences of an auto-acceleration effect on exotherm and conversion are illustrated by the exotherm curves in Figure 9.1. The urethane methacrylate/methyl methacrylate resin that shows auto-acceleration at all oligomer/monomer ratios is compared with an unsaturated polyester/styrene resin, which only shows an autoacceleration (or gel effect ) at high alkyd/styrene ratios. The urethane methacrylate oligomer copolymerised with styrene shows virtually the same exotherm behaviour as the unsaturated polyester for equivalent styrene/oligomer unsaturation ratios. 

The freedom in monomer/oligomer unsaturation ratio in the all-acrylic functional resins allows crosslink density and hardness/softness properties of the cured polymer to be varied... 

In 2004 total consumption of radiation-curing raw materials in North America, Europe and Asia was around 255,000-260,000 tonnes. Of this, 47% went towards functional monomers for reducing the viscosity of binders and modifying the properties of the cured film, and 39% consisted of various acrylic oligomers. Unsaturated polyesters accounted for 8% of total raw materials consumption, while photoinitiators accounted for about 6% by volume. 

Unsaturated oligomers up to aHyl-penta PG from a pentane extraction of polyol have also been separated and identified (114). 

Cross-linking agents or oligomers with multifunctional unsaturation sites include the following ... 

Fig. 10. Generalized formulation design outline for radiation-curable coatings and adhesive systems. The cross-linker is a multifimctional unsaturated cross-linking agent or oligomer, rj = viscosity CR = cure rate S = shrinl ge H = hardness F = flexibility A = adhesion 7 = surface energy ...

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. 

Fatty acids, both saturated and unsaturated, have found a variety of applications. Brassilic acid (1,11-un-decanedicarboxylic acid [BA]), an important monomer used in many polymer applications, is prepared from erucic acid (Scheme 2), obtained from rapeseed and crambe abyssinica oils by ozonolysis and oxidative cleavage [127]. For example, an oligomer of BA with 1,3-butane diol-lauric acid system is an effective plasticizer for polyvinylchloride. Polyester-based polyurethane elastomers are prepared from BA by condensing with ethylene glycol-propylene glycol. Polyamides based on BA are known to impart moisture resistance. 

The free radicals then initiate curing by attacking residual double bonds in acrylic oligomers and monomers, or in styrene and unsaturated polyester resins. Since most pigments absorb u.v. radiation and can prevent it reaching sufficient photoinitiator molecules, this technique is best suited to transparent coatings or thin pigmented layers (e.g. inks). 

Coating materials may be based on short or medium-oil alkyds (e.g. primers for door and window frames) nitrocellulose or thermoplastic acrylics (e.g. lacquers for paper or furniture finishes) amino resin-alkyd coatings, with or without nitrocellulose inclusions, but with a strong acid catalyst to promote low temperature cure (furniture finishes) two-pack polyurethanes (furniture, flat boards) unsaturated polyester resins in styrene with free-radical cure initiated by peroxides (furniture) or unsaturated acrylic oligomers and monomers cured by u.v. radiation or electron beams (coatings for record sleeves paperback covers, knock-down furniture or flush interior doors). 

Unsaturated acrylic oligomers are made from unsaturated acrylic monomers. For example, an epoxy acrylate may be made by reaction of acrylic acid with epoxy resin. 

Although low-molar-mass aliphatic polyesters and unsaturated polyesters can be synthesized without added catalyst (see Sections 2.4.1.1.1 and 2.4.2.1), the presence of a catalyst is generally required for the preparation of high-molar-mass polyesters. Strong acids are very efficient polyesterification catalysts but also catalyze a number of side reactions at elevated temperature (>160°C), leading to polymers of inferior quality. Acid catalysts are, therefore, not much used. An exception is the bulk synthesis of hyperbranched polyesters reported in Section 2.4.5.1, which is carried out at moderate temperature (140°C) under vacuum in the presence of p-toluene sulfonic acid catalyst. The use of strongly acidic oil-soluble catalysts has also been reported for the low-temperature synthesis of polyester oligomers in water-in-oil emulsions.216... 

Poly(unsaturated ester)-siloxane segmented copolymers have been prepared by the polycondensation of epoxy-terminated polydimethylsiloxanes and carboxy-terminated poly(ethylene adipate-co-maleate) oligomers 243). Reactions have been conducted in cellosolve solvent, at 140-150 °C, in the presence of 2% by weight potassium hydroxide catalyst. The molecular weights reported were fairly low. The same group has also prepared poly(hexamethylene adipate)-polydimethylsiloxane copolymers con-... 

Cross-linking oligomers (mol wt -200-1000), containing multiple unsaturation, are used to promote rapid free-radical-induced propagation reactions leading to cross-linked strucmres [39]. 

The activity of PL was measured [23] from the formation of unsatured oligomers, during pectin degradation (5 g/L) in phosphate-citrate buffer 50 mM, pH 5.6 following the absorbance at 235 nm. The enzymatic activity was expressed as enzymatic units (EU), i.e. amount of enzyme that produces 1 pmol of product per minute. The extinction coefficient (5,550 M" cm was used for calculating product concentration. 

PL activity was tested [9] by detecting the formation of unsatured oligomer, derived from the enzymatic depolymerisation of 0.5% (w/v) buffered pectin solution through the absorbance increase at 235 nm. 

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