Vinyl ester resin temperature

High-temperature cement formulations are basically polymer concrete. Mainly unsaturated polyesters or vinyl ester resins with allylphthalate as vinyl monomer are in use [927]. Cming is achieved with peroxides, which decompose sufficiently fast at temperamres between 120° and 200° C. Polymer concrete requires additional materials, which compensate shrinkage. 

The free-radical cure mechanism of the vinyl ester resins is well understood. In most respects, it is similar to that of the unsaturated polyester resins. To initiate the curing process, it is necessary to generate free radicals within Ike resm mass. Organic peroxides are tlie most common source of free radicals. These peroxides will decompose under the influence of elevated temperatures or chemical promoters, e.g., organometallics or tertiary amines, to form free radicals. Generation of free radicals also can be effected by ultraviolet or high-energy radiation applied directly to the resin system. The free radicals thus formed react to open the double bond... 

Two resins were used to do the first study on laminate construction. The first was a brominated epoxy vinyl ester resin with antimony pentoxide and the second was a brominated unsaturated polyester resin. They were both promoted to cure at room temperature with methyl ethyl ketone peroxide catalyst. The panels were then postcured at 250°F (121°C) for 8 h. Panels were prepared that varied in glass content from 25% to 70% and panel thickness varying from 0.05 in. to 0.25 in. and were tested at the same testing facility. A summary of the FSI test data for the first set of panels tested are shown in Figures 23.1 and 23.2. This graph in Figure 23.1 plots the FSI value versus the panel thickness. This data would indicate that the thickness of the test panel has no effect on the measured... 

These resins act more as polyester resins than they do as epoxy resins. They are easily processed, have fast cure rates at room temperature, and can be cured with peroxides. They effectively wet out glass fiber reinforcement and cure quickly. Therefore, vinyl ester resins are often used in the manufacture of composites such as filament- wound and pultruded structures. 

Heat generated versus isothermal cure temperature for (a) the Ashlemd polyester resin, emd (b) the Dow vinyl ester resin. 

It is seen that in both cases the use of gives rise to very high values for the degree of cure (approaching 1.0) at the end of each isothermal cure, compared to that obtained when was used. We know that the curing reaction cannot approach its completion at such low temperatures, say at 50 C, because the ratio of the residual heat (Q ) to the ultimate heat (Qxj ) is fairly large 0.376 for the Ashland polyester resin and 0.557 for the Dow vinyl ester resin. 

First, it is seen in Figure 3 that the meiximum value of dQ/dt (i.e., (dQ/dt)p) increases, and the time (tp) at which the mcucimum of dQ/dt occurs decreases, as the cure temperature (hence the rate of cure) increases. Over the range of temperatures investigated, the Ashlemd polyester resin exhibits higher values of (dQ/dt)p emd lower values of tp than the Dow vinyl ester resin, indicating that the former is more reactive than the latter. Second, although... 

As may be seen in Table II, in both resins the reaction rate constants kj emd k2 appearing in eq. (5) increase with the isothermal curing temperature. In most cases, the magnitudes of kj amd k2 (only at low temperatures) are greater for the Ashland polyester resin them for the Dow vinyl ester resin. 

Analyzer (DMA) module. Figure 9 gives the dynamic mechanical spectra of the Ashland polyester and Dow vinyl ester resins. It is seen in Figure 9 that the Ashland resin has a higher Young s modulus than the Dow resin, over a wide range of temperatures. 

The differences in prepolymer chemistry between the two resins investigated may be observed in their relaxation transitions at both low and high temperatures. Of particular interest is the existence of two major relaocation transitions observed in the Dow vinyl ester resin at high temperatures. We believe that the second releixation occurring at 80°C is not the same as the p transition reported in the literature (19.20). Furthermore, we speculate that the Dow vinyl ester resin employed in our study might have been a blend of two resins. This speculation will be tested in a future investigation. 

Waste incineration requires sophisticated scrubbers to contain corrosive volatiles which are in contact with the scrubber wall at elevated temperatures reaching 220°C. " Glass mat reinforced novolac epoxy vinyl ester resins have good performance in this application except that they are subjected to thermal stress due to the temperature difference between surface and wall, and they frequently crack. In order to improve performance, a two layer laminate was produced. The base layer is composed of resin reinforced with glass mat. The resin contains 15-20% graphite filler. The surface layer contains 100 g/m" of carbon fiber. The presence of these two fillers helps to distribute heat more evenly throughout the layer of laminate and prevents cracking even under extreme conditions. "... 

Vinyl ester resins (VERs, epoxy methacrylates) are a major class of styrenated, free radically curable, corrosion- and chemical-resistant thermoset resins. They are largely used in fiber-reinforced structural applications, and they have a substantial history of long-term service in numerous environments at elevated temperatures and pressures, usually under load. 

These electrolyzers are operated at about 80°C, as opposed to the 95°C common in the industry. This lower temperature allows the use of vinyl ester resins and other plastics for cell construction. Moreover, the Dow diaphragm cell is optimized for low current density ( 0.5 kA/m2 ). It consumes less electrical energy per unit of production than others in the industry. The cell voltage at low current density is only 300—400 mV above the thermodynamic decomposition voltage. Dow does not license its diaphragm cell technology and operating data for these cells are not available in the open literature. 

Mild steel may be suitable as a material of construction for handling caustic soda at ambient temperature. At elevated temperatures, >60°C (140°F), corrosion may occur. Nickel and/or its alloys are most suitable for caustic handling at all temperatures and concentrations, including anhydrous molten caustic up to 480°C (896°F) (Leddy et al. 1978). Polypropylene, fluorocarbon plastics, and flberglass/vinyl ester resins are being used for many applications. Aluminum, tin, zinc, and other amphoteric metals should not be used in construction materials. 

The vinyl ester resins have an upper temperature limit of approximately 225°F (107°C). Exceptions to this are the vinyl ester resins having a novolac backbone. These resins can be used at 325-350°F (163-177°C). 

Table 3.6 Chemical resistance of typical unsaturated polyester and vinyl ester resins as defined by a maximum use temperature (°C) [15]... 

In all cases, the resins used were Derakane epoxy vinyl esters (Fig. 9.4). In 64% of the cases the resin was one of the higher temperature type, that is an epoxy novolac vinyl ester resin (Derakane 470). This resin is particularly effective in containing acids and organic solvents. Its HDT of 150°C renders it the resin of choice for the higher temperature applications. Bisphenol A epoxy vinyl ester resins (Derakane 411) were used for 25% of the vessels, in particular for the high pH caustic and hypochlorite streams. The brominated epoxy vinyl esters (Derakane 510) were used for the remainder (11%) of the GRP vessels. These resins are important when both fire... 

The raw gas contains humid mixtures of SOj and SO3 and condensing sulfuric acid at temperatures of 80-100°C. The cleaned gas contains the same contaminants, but at much lower concentrations [6]. Both duct systems have been successfufly manufactured from GRP using an acid-resistant novolac epoxy vinyl ester resin. Large diameters are often used for... 

Significant cracking to a depth of 3-5 mm was found in the total circumferential area at the first and second spray nozzle levels, ft would have been only a matter of time, possibly another one to two more years, before the part of the structure exposed to high temperatures had failed. But the Derakane 470 novolac epoxy vinyl ester resin had held at temperatures far beyond its design limit. 

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. 

Vinyl ester resins derived from phenolic novolac epoxies are suitable for solvent resistant applications and use at higher service temperatures but have lower failure elongations of about 3%. 

Vinyl esters are thermosetting resins that consist of a polymer backbone with an acrylate or methacrylate termination. The backbone component of vinyl ester resins can be derived from epoxide, polyester or urethane but those based on epoxide resins have most commercial significance. Bisphenol A epoxy formed vinyl esters were designed for chemical resistance and commonly formulated for viscosity for use in filament winding of chemical containers. Typically styrene is used as a reactive dilutent to modify viscosity. Phenolic novolac epoxies are used to produce vinyl esters with higher temperature capability and good solvent resistance, particularly in corrosive environments, and their FRP composites have demonstrated initial economy and better life cycle costs compared with metals. 

---