Epoxies viscosity

Cycloaliphatic Epoxy Resins. This family of aUphatic, low viscosity epoxy resins consists of two principal varieties, cycloolefins epoxidized with peracetic acid and diglycidyl esters of cycHc dicarboxyhc acids. 

T. R. Dartez and R. K. Jones. Method for selectively treating wells with alow viscosity epoxy resin-forming composition. Patent US 5314023, 1994. 

Spurr, A.R. (1969). A low-viscosity epoxy resin embedding medium for electron microscopy. Journal of Ultrastructural Research 26 31. 

UMEs used in our laboratory were constructed by sealing of carbon fibre into low viscosity epoxy resin (see Fig. 32.4) [118]. This method is simple, rapid and no specialised instrumentation is required. Firstly, the fibres are cleaned with this aim. They are immersed in dilute nitric acid (10%), rinsed with distilled water, soaked in acetone, rinsed again with distilled water and dried in an oven at 70°C. A single fibre is then inserted into a 100- iL standard micropipette tip to a distance of 2 cm. A small drop of low-viscosity epoxy resin (A. R. Spurr, California) is carefully applied to the tip of the micropipette. Capillary action pulls the epoxy resin, producing an adequate sealing. The assembly is placed horizontally in a rack and cured at 70°C for 8h to ensure complete polymerization of the resin. After that, the electric contact between the carbon fibre and a metallic wire or rod is made by back-filling the pipette with mercury or conductive epoxy resin. Finally, the micropipette tip is totally filled with epoxy resin to avoid the mobility of the external connection. Then, the carbon fibre UME is ready. An optional protective sheath can be incorporated to prevent electrode damage. 

Epoxies can cure in deep sections and are useful in potting and deep-section sealing applications. They adhere well to different substrates and therefore are used in the general assembly of many medical devices. A clear, medical-grade, low-viscosity epoxy adhesive has proved useful in the fabrication of access ports that are implanted beneath the skin of patients who require multiple infusions.21... 

Epoxy novolac resins also differ from standard DGEBA-based epoxy resins in their multifunctionality, which is about 2.5 to 6.0. The multiplicity of epoxy groups allows these resins to achieve increased crosslink density. The commercial epoxy novolac resins (e.g., DER 438, Dow Plastics, and EPON 164, Resolution Performance Products LLC) are semisolid to solid resins with EEW in the range of 170 to 230. Recently low-viscosity epoxy novolac resins have been produced (18,000 to 28,000 cP) to provide easy processing however, these generally have lower epoxy content. 

Next to viscosity, epoxy content and hydroxyl content are the prime properties of importance in formulating epoxy-based adhesive systems. Epoxy content allows one to determine the correct amount of curing agent to use. With certain curing agents it may also be important to know the hydroxyl content. These values determine the reactivity of the system. 

Spurr AR (1969) A low-viscosity epoxy embedding medium for electron microscopy J Ultrastruct Res 26 31-43... 

To circumvent the limitations described above, Plummer et al. have used a different method, suitable for observation of plastic zones in bulk samples [30]. They embedded a DCB sample in a low viscosity epoxy resin with the razor blade in place. The crack tip was therefore maintained under stress while the resin was left to cure at room temperature. The sample was then trimmed for thin sectioning, stained by immersion in a Ru04 solution, and microtomed in thin sections in the region of the plastic zone for observation by TEM. While this method gave particularly good results on ductile semicrystalline systems where a deformed thin film would not have been representative of the plastic deformation mechanisms taking place in bulk samples, it should in principle be applicable fairly generally. 

Table IX. Correlation of Viscosity, Epoxy Value, and Cure Time of Epoxide Coating Showing Dependence of Rapid Cure on Cycloaliphatic Epoxide...

Owing to their barrier resistance, durability and low viscosities, epoxy resins are widely used in the potting industry in applications such as electrical coils for transformers and electrical motors. Epoxy pottings are able to withstand extreme environments and have shown resistance to fungal growth and environmental resistance in arctic, desert and tropical conditions (Lee and Neville, 1957). 

Materials. A high viscosity epoxy diacrylate resin and an acrylate diluent were used to prepare the UV-cured films. The photoinitiator was 2,2-dimethoxy-2-phenylacetophenone, DMPA. Stabilizers are identified in Table I. All materials were from commercial sources and used as received from the suppliers. 

Fluid displacive embedding Displacing one fluid by another, usually water by acetone, and then adding low viscosity epoxy resin, which is then cured to produce a solid resin-embedded sample. 

Self-leveling floors are produeed from low-viscosity epoxy systems. Low-exotherm, unfilled systems are preferred. The entire floor should be cast in one operation, and thickness should preferably be at least 5 mm over the entire area. Because of their excellent chemical resistance to a wide range of chemicals, epoxies are often selected for flooring in chemical plants. Systems vary from trowelable to pourable or brushable and are usually filled. Choice of hardener and filler will depend on the specific chemicals encountered. Although tables of chemical resistance from suppliers will aid in selection of a suitable system, this system should always be tested using the chemicals that the floor is expected to withstand. 

FACC AG (Ried, Austria) fabricated a demonstration RP replacement part for a highly stressed aluminum spoiler center fitting on the Airbus A340-600. It used a low-viscosity epoxy resin in the resin transfer molding (RTM) process because the part s complex shape would be difficult to produce consistently and cost-effectively with hand lay-up. 

Transmission electron microscopy (TEM) is important to monitor cell-free sperm decondensation and nuclear formation. To prepare specimens for TEM, incubation mixture aliquots were fixed for 45 min in 2.5% (v/v) paraformaldehyde, 3.1% (v/v) glutaraldehyde, 0.02% (w/v) picric acid in 30 mAf NaHP04, pH 7.5. After fixation, samples were embedded in 2% (w/v) low-gelling-temperature agarose and postfixed for 15 min in 1% (w/v) OSO4. Samples may be dehydrated either in ethanol and propylene oxide or acetone and embedded for sectioning in Spurr s low-viscosity epoxy resin (Spurr, 1%9). Before examination, sections of about 70-nm thickness should be stained, e.g., with uranyl acetate and Reynolds lead citrate (Re)molds, 1%3). 

To speed the sample encapsulation/impregnation step using a slide warmer or hot plate, the technique described by Chromy (1992a) is helpful. A sample cup, the bottom of which was covered with 1.0 to 2.0 mm-diameter clinkers or crushed clinker particles, was heated to approximately 80 C. Freshly mixed low-viscosity epoxy resin was poured over the clinker particles and allowed to harden, requiring from 5 to 10 minutes. The encapsulation was then sawn to expose the clinker sections or, better, the bottom side was ground with a coarse grit (180 to 320) to quickly expose the particles. 

Photograph 7-28 Polished section of cement centrifuged in low-viscosity epoxy to produce a particle size and density gradation. Arrow on coarse particle near the base of the test tube (left) indicates alkali sulfate. Arrow on fine particle near the top of the cement (right) indicates gypsum. See Campbell (1986). (S A6648)... 

Spurr, A.R., "A Low-Viscosity Epoxy Resin Embedding Medium for Electron Microscopy,"/owma/ of Ultrastructure Research, Vol. 26,1969, pp. 31-43. 

To date only few dielectric relaxation studies have been reported on thermosetting nanocomposite systems. Kanapitsas et al. [109] reported isothermal dielectric relaxation studies of epoxy nanocomposite systems based upon three different clay modifications, a low viscosity epoxy resin based on the diglycidyl ether of bisphenol-A type (Araldite LY556, CIBA) and an amine hardener in a temperature range of 30-140 °C. Whilst details on the epoxy system investigated and the nanocomposite morphology were vague, it was reported that the overall mobility is reduced in the nanocomposite compared to the neat matrix resin. 

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