Low-molecular-weight epoxy

The DP is dependent on the ratio of reactants. Generally an excess of the epichlorohydrin is used to produce cyclic ether end groups. Epoxies are formed from the reaction of diamines with low molecular weight epoxy resins that retain their cyclic ether end groups. Figure 4.9 shows the formation of this process. These materials are often sold as two-part, or two-pot, epoxy adhesives. Most use-at-home epoxy packages contain a part A of epoxy resin and a part B of hardener (typically a diamine). These two are mixed as directed and applied. They dry fast, so they can be handled in 5 10 min. Full strength occurs after 5 7 days. 

There are also one-part adhesives based on low molecular weight epoxy units that contain the unopened cyclic ether end groups. These materials can be cured when heated to about 200°C for 30 0 min. 

Different kinds of carbon-intense fibers are used, the most common being carbon and graphite fibers, and carbon black. As is the case with fibrous glass, surface voids are present. Carbon-intense fibers are often surface-treated with agents such as low molecular weight epoxy resins. Such surface treatments also aim at increasing the fiber-matrix adhesion. 

The overall procedure was similar for each sample (high molecular weight polystyrene, low molecular weight epoxy resin) and is outlined in Table I. 

Figure 8. GPC analysis of low molecular weight epoxy resin.

Bisphenol A diglycidyl ether is a contact allergen among people who have worked with low-molecular-weight epoxy resins (lARC, 1989). 

In situ derivatization of the crude epoxy alcohol product becomes a viable alternative to isolation when 5-10 mol % of catalyst is used for the epoxidation. This procedure is especially useful when the product is reactive or is difficult to isolate because of solubility in an aqueous extraction phase [15,16]. Low-molecular-weight epoxy alcohols such as glycidol are readily extracted from the reaction mixture after conversion to ester derivatives such as the p-nitrobenzoate or 3-nitrobenzenesulfonate [4,17]. This derivatization not only facilitates isolation of the product but also preserves the epoxide in a synthetically useful form. 

Diglycidyl ether of bisphenol 25 g, 73 mmol A (low molecular weight epoxy resins epoxy value ca. 

To a round-bottomed flask (250 ml) equipped with a long-necked adapter, reflux condenser, and a magnetic stirrer bar, add low molecular weight epoxy resin (25 g, 73 mmol), bisphenol-A (11 g, 48 mmol) and 2-methylimidazole (19 mg, 0.24 mmol). 

The primary reactive diluents are monoepoxy low-molecular-weight epoxy resins. These may be used at rather high concentration with little effect on cured properties. Often they are employed to make selective improvements on certain properties such as adhesion, thermal cycling resistance, and impact strength. Some lower-viscosity commercial epoxy resins are already reduced with these diluents. 

Another explanation of the increase in the major glass transition 126) of SIN s relates to the retention of low molecular weight polymer of one component by the other phase. In this case low molecular weight fractions of the epoxy may be trapped in the rubber. When the epoxy is at its gel point, there is still much low molecular weight epoxy resin that has not reacted. At the point when the n-butyl acrylate is still mostly... 

Organosol PVC dispersed in an appropriate varnish and conventionally stabilised with a low molecular weight epoxy, resin or epoxidised bean/seed oils Very good Very good Drawn cans Easy-open ends Closures Often used over epoxy-phenolic basecoat... 

The changes of molecular dynamics from the starting material of low-molecular-weight epoxy resins to the fully polymerized state during polymerization reaction are well brought out by the large number of experimental studies of the evolution of the primary and secondary relaxations over the past... 

Polyvinyl fluoride can be thermally stabilized with mixtures of phenyl phosphites (e.g., triphenyl phosphite) and low molecular weight epoxy resins. Other methods include the addition of the dolomite series and the zinc salt of an organic acid l or a dialkyltin bis 3> -sulfolanylmercaptide). PO... 

Now if a low molecular weight epoxy resin is used, e.g. Mn approx. 1000, (Epon 1001 or DER 661) there are about 2... 

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