Epoxy resins 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. 

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. 

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). 

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. 

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. 

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. 

A variety of poly/dihydric oils are used for the preparation of glyddyl ether-type epoxy resins. These include bisphenols, namely bisphenol-A (BPA), bisphenol-F (BPF), bisphenol-S (BPS) and bisphenol-H (BPH) and so on. Other aromatic diols and polyols such as phenolic resin, MF resins and hyperbranched polyol may also be used in the preparation of vegetable oil-based epoxy resins. Bisphenol-A (2,2-bis(4-hydroxyphenyl)propane) is one of the most widely used aromatic diols for the synthesis of epoxy resin. The resins are commonly used as lacquers for coated metal products such as food cans, bottle tops and water pipes. There are also reports on the use of bisphenol-S (BPS) (bis(4-hydroxyphenyl) sulphone), in the synthesis of epoxy resin. The advantages of resistance to deformation by heat and improvement of thermal stability were observed for such epoxy resins. The presence of sulphone group (BPS-based epoxy resin) in the epoxy resin exhibits better gel time than BPA-based epoxy. Another important diol, namely bis(4-hydroxydiphenyl)methane or bisphenol-F (BPF) is used for the synthesis of low viscosity epoxy resins. BPF generally comprises several isomers such as bis(2-hydroxylphenyl)methane (i.e. ortho-ortho isomer), bis(4-hydroxylphenyl)methane (i.e. para-para isomer) and... 

A one part, low viscosity epoxy resin for resin transfer moulding or resin infusion, if necessary at room temperature. 

Repairing Termite-Damaged Wood. Wood that has been weakened or damaged by termite attack may be repaired without removing the wooden member from the structure. The procedure is similar to pressure-grouting cracks in concrete. For termite-damaged wood, a form sleeve must be built around the damaged wooden member then, a low-viscosity epoxy-resin... 

Epoxy resin systems of the bisphenol A-epichlorohydrin t)rpe and epoxy novalac type generally lack flexibility. There are a number of proprietary flexible, low viscosity epoxy resins used to modify the above types to provide better impact resistance, elongation, or flexibility. These flexible epoxy resins are true epoxies and react completely with epoxy curing agents and becomes a permanent part of the cured system. However, they do not contribute towards lowering costs. 

Glycidyl ethers of polyalkylene glycols are low viscosity epoxy resins that are useful as reactive diluents for conventional BPA epoxy resins. Their aliphatic ether backbone structure improves flexibility, elongation and impact resistance. However, heat, solvent, water, chemical and corrosion resistance are reduced. They are therefore frequently employed as a modifier rather than the sole binder. 

The impregnation of the sample is done with a low-viscosity epoxy resin (e.g. EPO-TEK 301). The sample is placed in a cylindrical mould, with the side slightly ground with SiC paper against the bottom of the mould. A label can be placed on top of the sample, as shown in Figure 8.13, but should be written using a pencil as ink will dissolve in the resin. The impregnation should be done under vacuum, ideally with about 1-10 mbar (or less) to remove most air in accessible porosity and thus better allow infiltration of the resin. 

---