Vinyl ester resins mechanical propertie

Vinyl ester resins generally offer mechanical properties superior to those of polyester matrices but at an increased cost. Vinyl esters are chemically similar to epoxy resins but are manufactured via a cold-curing process similar to that used in the manufacture of polyester resins. Vinyl esters offer superior resistance to water and chemical attack and are used in such appHcations as underground pipes, tank liners, and storage tanks (see Vinyl polymers). 

In the same way, ABS acts as a toughener for vinyl ester resins (34). Assessment of the mechanical properties suggest that a chemical reaction may have occurred between the constituents of the blends. The blends are intended as a toughening agent for interlayer toughened vinyl ester/glass composite materials. 

Epoxy vinyl ester resins are a special class of unsaturated resin. This resin is made by capping an epoxy resin with methacrylic acid and then dissolving in styrene monomer to the desired viscosity. This gives mechanical properties similar to epoxy resins, but the processibility (low viscosity allowing for resin infusion processes) of an unsaturated polyester resin. As with unsaturated vinyl esters, the most common fire retardant vinyl ester resin is based on a resin made from a halogenated system, tetrabromobisphenol A. The level of bromine in the resin and the presence of antimony will determine the fire performance of the resin. These resins are normally used for corrosion resistant equipment or when fire performance and high mechanical properties are required. It is very difficult to get a low smoke value with a brominated vinyl ester resin again due to the fact that bromine... 

The chemical reactivities of the unsaturated groups at the ends of vinyl ester resin and vinyl urethane resin chains are different in several respects from those of the same groups when situated in mid-chain positions, as they are in polyester resins. As a consequence of the different reactivity ratios, the two kinds of cured resin behave differently from moisture and chemical resistance points of view. The structural differences are also reflected in the mechanical properties, such as fracture toughness. 

Zia Ziaee, S., Palmese, G. R. Effects of temperature on cure kinetics and mechanical properties of vinyl-ester resins. J. Polym. Sci. B Polym. Phys. 37 (1999) 725-744. 

Alpha Owens-Coming offers a flame retardant vinyl ester resin that meets ASTM 84 Class 1 flame spread and smoke rating. The resin is a highly brominated bisphenol-A epoxy based vinyl ester. It provides a unique combination of good flame and smoke resistance and inherently good mechanical properties. The flexural strength of 34% glass composite is 5100 psi (35 MPa) and flexural modulus is 450 ksi (3.1 GPa). 

Vinyl ester resins The vinyl ester resins are essentially epoxide resins, normally the digly-cidyl ether of bisphenol A, that have been reacted with acrylic acid or its derivatives. The unsaturation in the acid residues provides sites for a cross-linking mechanism based on free radical polymerization. The retention of the bisphenol A backbone in the chain of the cross-linked polymer conserves most of the mechanical and physical properties associated with the parent epoxy. The resins thus provide a combination of ease of processing with good chemical resistance and mechanical behaviour. 

Compared with other thermosetting polymers (i.e. polyester or vinyl ester resins), epoxy resins are more expensive, but show both better mechanical properties and higher resistance to moisture absorption and to corrosive liquids and environments. These good physical properties and their durability in service help to provide a favorable cost-performance ratio when compared to other thermoset plastics. 

Seawater aging of epoxy and vinyl ester resins reinforced with different fibers (e g. glass and carbon) has also been investigated (Narasimha Murthy et al., 2010). The experimental results have evidenced that the vinyl ester composites retain better their mechanical properties than epoxy ones in particular, the flexural strength and ultimate tensile strength (UTS) dropped by about 35% and 27% for glass/epoxy, by 22% and 15% for glass/vinyl ester, by 48% and 34% for carbon/epoxy, and by 28% and 21% for carbon/ vinyl ester composites, respectively. In contrast, the authors have shown that the water uptake of the epoxy-based composites is lower than that of the vinyl ester ones. 

Tough, versatile, bisphenol-A epoxy based vinyl ester resins dissolved in styrene offering outstanding mechanical properties and excellent resistance to cracking, crazing, chemicals and heat, for use in hand-lay, spray/projection lamination, filament winding and pultrusion. Available in standard and low monomer... 

The mechanical properties and water diffusivity of vinyl ester/clay nanocomposites have been investigated by Shah et al. A vinyl ester resin (bisphenol A... 

A newly developed third class of vinyl ester resins is represented by the even higher quality VE urethanes based on bisphenol A epoxy. Here, the secondary OH groups of the VE react in polyaddition with polyisocyanates to produce urethane bridges, see Eigure 1.3. Vinyl ester urethane resins (VEU resin, vinyl ester urethane-hybrid resins) combine the good mechanical properties (stiffness) of VE resins with excellent high-temperature resistance (T approx. 220 °C and HDT approx. 210 °C) and excellent chemical resistance (the long-term durability of VEUH resin exceeds that of normal VE). 

Vinyl ester resins contain fewer ester groups than resins based on glycol fumarate, phthalic acid, or bisphenol. Therefore, VE resins hydrolyze much more slowly, and the molecular mass does not undergo essential changes during hydrolysis, so that the mechanical properties change very little. Vinyl ester resins are therefore considerably more resistant (especially to alkalis) than phthalic acid, isophthalic acid, or bisphenol resins [32]. 

Alkalis hydrolyze glass fiber-reinforced polyester resins, drastically changing their mechanical properties. Phthalic- and isophthalic-based glass fiber-reinforced polyester resins suffer property reductions at room temperature shortly after exposure begins. Bisphenol HEX type resins are more resistant vinyl ester resins are the most resistant [32]. 

The effects of solvent exposure on the viscoelastic properties of several vinyl ester resins (phenohc-novolac epoxy, propoxylated bisphenol-A fu-marate, urethane and bisphenol-A epoxy based) and various unsaturated polyester resins (terephthalic or isophthaUc acid with a standard glycol based) containing 10wt% glass fiber were studied [130]. The results of dynamic mechanical analysis showed that the influence of exposure time to the solvent as well as the influence of temperature depended on the styrene content and chemical composition of the studied resins, while the amount of cobalt octoate used for the synthesis as the accelerator had no influence on the viscoelastic properties of the prepared materials after solvent exposure. It was also found that not fully cured urethane vinyl ester and the terephthahc acid-based unsaturated polyester resins showed excellent resistance to sulfuric acid exposure. However, interactions between the tested resins and petroleum could possibly occur through intermolecular bonding between the non-polar chains of the cured resins and the solvent. 

Alkali treatment of jute fibers also improves the mechanical properties of thermoplastics. The vinyl ester resin reinforced with alkali-treated fibers shows improved mechanical properties. The maximum improvement was noted for the composites prepared with 4 h alkali-treated fibers at 35% fiber loading. The flexural strength improved by 20% and the modulus by 23%. The strength and modulus of the composites were found to be lower than the values estimated from the general rule of mixtures. For the jute/vinyl ester composites with 35% fiber content, the strength was decreased by 29% and 16% for the untreated and 4h alkali-treated fibers and the modulus was lower by 51% and 37% for the untreated and 4h alkali-treated fibers, respectively [154]. 

The term TS polyester covers a very large chemical family, of which the unsaturated resins (covering orthophthalic, isophthalic, vinyl esters, and blends) form the largest single group of fiber reinforced TSs (RTSs). Polyesters offer a good balance of mechanical, electrical and chemical-resistance properties, at relatively low cost (Table 3.15). They also have good dimensional stability and are relatively easy to handle. They are... 

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