Acrylate resin systems, properties

Although the acrylate adhesives are readily available and studies have shown that they can produce reasonable bonding properties, they have the disadvantages of having high shrinkage, high fluid absorption, and low service temperatures. Acrylate adhesive applications would be limited. The development of EB-curable epoxy adhesives would have applications in the aerospace and automotive industry and potential wider uses. The most immediate application for these resin systems is composite repair of commercial and military aircraft. 

The characteristics of the three most common thermoset resin systems used in pultrusion are compiled in Table 11.2 [3]. It is noteworthy that unreinforced polyesters and vinylesters shrink 7-9% upon crosslinking, whereas epoxies shrink much less and tend to adhere to the die. These epoxy characteristics translate into processing difficulties, reduced processing speed, and inferior component surface finish. It is normal practice to use resin additives to improve processability, mechanical properties, electrical properties, shrinkage, environmental resistance, temperature tolerance, fire tolerance, color, cost, and volatile evaporation. It is normally the resin, or rather its reactivity, that determines the pulling speed. Typical pulling speeds for polyesters tend to be on the order of 10-20 mm/s, whereas speeds may exceed lOOmm/s under certain circumstances. Apart from the resins characterized in Table 11.2, several other thermosets, such as phenolics, acrylics, and polyurethanes, have been tried, as have several thermoplastics (as will be discussed in Sec. 11.2.6). 

The resin systems used in this process are mainly based on methacrylates and acrylates and epoxies.The selection of the resin system depends on the required physical properties. 

The properties of thermosetting and thermoplastic resin systems are continually improved to meet increasing performance requirements of end users. One way to enhance material properties is to incorporate nano-modifiers, based on elastomeric silicone particles, which are optionally grafted with other (acrylic) polymers to control dispersibility, viscosity, and other parameters. As an example, epoxy resin formulations have been modified with silicone nanospheres to improve low-stress behavior. Table 1 shows the outstanding fracture toughness improvement of silicone coreshell nanospheres, even at very low particle loading levels. 

Sec-butyl alcohol offered some promise with the trimellitic alkyd and the epoxy ester vehicles, judging from the preliminary phase of the investigation. Further work is needed to establish this fact. An approach involving mixed solvent systems is suggested. With the acrylic resin, the solution properties and deposition characteristics were poor. Isopropyl alcohol offered some promise with the alkyd and the acrylic resin, but further tests are needed to determine its ultimate utility. Diacetone alcohol may be of value with the alkyd and the acrylic. With these resins it... 

As mentioned earlier, UV-curable resin formulations are very attractive for fiber coating because of the rapid cross-linking rates that are achievable. Most commonly, epoxy- or urethane-acrylate resins are employed (18-22), and viscosity and cross-link density are controlled through the addition of reactive diluents. With these systems work has focused on producing low modulus, low T properties (20-22) through the incorporation of appropriate chemical constituents to enhance higher chain flexibility, for example, ether linkages. 

Only a limited amount of resin can be added to white paints due to its intrinsic color. Addition of these hard resins increases the hardness and the gloss of the paint films, accelerates and improves the drying of oxidatively cross-linking alkyd resins, and optimises sanding properties and corrosion protection in putties. Modified phenolic resins have lost much of their importance because they have been replaced by more efficient binder systems (e.g., thermoplastic and cross-linkable acrylic resins, polyurethane systems). Rosin-modified phenolic resins are, however, still extremely important in the production of resins for printing inks. 

Prepolymers. A broad range of acrylated resins (oligomers) are commercially available. The film-forming properties depend on the oligomer system. One of the most common is the acrylated epoxy system. In acrylated urethanes, an isocyanate-functional prepolymer with a polyol backbone can be reacted with a hydroxy-functional monomer (e.g., hydroxyethyl or hydroxypropyl acrylate). Many different resins can be synthesized by varying the polyol backbone, the isocyanate type, and the hydroxy-functional monomer. Polyester acrylates are another example of commercially important prepolymers. Acrylated acrylics have an acrylic backbone with pendant acrylate functionality. 

Chem. Descrip. Polysiloxane sol n. in cyclohexanone Uses Defoamer tor org. systems incl. chlorinated rubber, vinyl resin, acrylic resin, alkyds, solvent-based coatings Properties Pale to It. yel. Iiq. ether-like odor sp.gr. 0.95 g/cc dens. 7.90 Ib/gal vapor pressure 4 mm Hg flash pt. (Seta) 43 C ref. index 1.450 0.7% NV... 

Chem. Descrip. Acrylic resin in methoxy propyl acetate Uses Row aid, leveling agent for solv. and aq. systems Features Exc. recoatability and wide resin compat. similar to Carboflow 20 except with reduced solids for ease of handling Properties Dens. 8.3 Ih/gal vise. 200 cps 70% NV by wt. 

Uses Crosslinking agent flow control additive for oil-free polyester resin systems also rec. for TS acrylic and alkyd automotive topcoat finishes food-contact coatings, paper/paperboard Regulatory FDA 21 CFR 175.300,176.170 Properties Sp.gr. 1.01 dens. 9.7 Ib/gal (solids) vise. 5.5-10.7 poises acid no. 1 max. flash pt. (Seta) 43 C 64 02% NV by wt. 3% max. free formaldehyde... 

Uses Flow aid, leveling agent for p. coatings for polyesters, epo) resin systems, epoxy esters, crosslinking acrylics, polyurethanes Features Silicone-free Properties Powd. 

CAS 3775-90-4 EINECS/ELINCS 223-228-4 Uses Monomer, antistat, corrosion inhibitor for catephoretic metal primers, vinyl/acryl reactive resins, water-based resins, adhesive resins Features Multifunctional cation-active can be copolymerized with vinyl or acryl reactive systems exc. wet adhesion on metal low volatility Properties APHA 50 max. clear liq. m.w. 185 vise. < 10 mPa s 97.5% min. purity... 

These resins have many of the same properties as the epoxy, acrylic, and Bisphenol A fumurate resins. The vinyl ester resins have replaced polyester resins in mortars for bleach towers in the pulp and paper industry. The major advantage of these resin systems is their resistance to most oxidizing mediums and high concentrations of sulfuric acid, sodium hydroxide, and many solvents. Comparative resistances of the two types of vinyl ester mortars are shown in Table 7.13. 

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