"Decreasing the peak exotherm temperature could be done in a variety of ways, such as: 1) pre-cooling of components, 2) incorporation of phase change materials, 3) direct cooling during polymerization, 4) substitution of reactants having lower reactivity, 5) addition of fillers (in greater quantity and/or of higher heat capacity or thermal conductivity), etc. For certain applications several of these means of exotherm reduction are unacceptable. For instance, pre-cooling of components may raise viscosity and prevent good mixing, wetting, mold-filling, etc. Phase change materials may be expensive, chemically reactive, soluble once liquid, change at non-optimum temperatures, etc. Direct cooling is poorly effective in the thickest regions and may create additional residual stresses due to thermal expansion mismatches between components. Components having lower reactivity are also typically slower curing and require additional heat for full polymerization, thus they create a need for longer cycle times or higher bake temperatures. Filler incorporation greatly affects the mechanical properties and thus may be specified and fixed. Additionally, though higher filler levels decrease exotherm temperatures, there are practical upper limits of use level, based on both processing and performance, which cannot be exceeded.
"Reactive diluents have long enabled the use of epoxy formulations in new applications or as a way of achieving processing improvements in existing applications. In the case of amine-cured epoxy resin systems, such diluents have included low molecular weight epoxies, low molecular weight compounds with reactive unsaturation (such as acrylates), lactones, and cycloaliphatic carbonates (U.S. Pat. No. 3,305,527;
"Additionally, in some applications, such as the molding of large composite wind blades, decreasing or eliminating the use of common epoxy diluents (such as the diglycidyl ether of 1,4-butane diol) is beneficial to the thermal and mechanical properties of the cured resin but some minimum use level is necessary since viscosity reduction via heating is limited by the increase in maximum exotherm temperature that occurs when the temperatures of the reactive components are raised."
As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "A diluent that reduces the maximum exotherm temperature caused by the epoxy resin polymerization reaction would be of particular utility since it would allow one to increase the temperature of the reactants prior to blending. The ability to use higher resin formulation component temperatures reduces the need for diluents. Thus using a diluent that reduces the maximum exotherm temperature allows one to decrease the component viscosities by increasing the temperature(s) of the resin and hardener. At the same time this decreases the need for diluent, allowing a reduction in diluent level that improves the properties of the cured resin system, in particular by increasing the cured glass transition temperature.
"Embodiments of the present invention disclose a method for limiting peak exotherm temperatures in epoxy systems comprising the steps of: combining an amine hardener, an epoxy and a diluent to form an epoxy system, wherein the diluent is selected from the group consisting of: ethylene carbonate, propylene carbonate, butylene carbonate, delta-valerolactam, delta-valerolactone, gamma valerolactone, butyrolactam, beta butyrolactone, gamma butyrolactone, and combinations thereof.
"Embodiments of the present invention disclose an article of manufacture, such as a composite rotor blade for use in wind turbines, also termed a wind blade, produced by the method described above.
"Embodiments of the present invention further disclose the use of the method described above for producing a molded epoxy composite article.
"The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims
BRIEF DESCRIPTION OF THE DRAWINGS
"The following figure has been added to further clarify properties of the present invention.
"FIG. 1 shows the temperature rise during gel time testing."
For additional information on this patent application, see:
Keywords for this news article include: Anions, Alkalies, Carbonates, Carbonic Acid, Nanotechnology, Emerging Technologies, Phase Change Material,
Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2013, NewsRx LLC
Most Popular Stories
- American Airlines, US Airways Complete Merger
- ACA Delay Stresses Small Businesses
- Questions Remain in Jenni Rivera's Death
- Unemployed Wait as Lawmakers Debate
- General Dynamics Plans 200 New Jobs in N.M.
- Harley Issues Motorcycle Recall
- Dell Offers Undisclosed Number of Employee Buyouts
- Saab Gets Back into the Game; U.S. Auto Sales Soar
- Auto Dealer Builds Big Solar Project
- Authorities Close to Deal with JPMorgan Chase over Madoff Response