Low molecular weight epoxy resin

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. 

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). 

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... 

The free hydroxyl groups of alkyds react with polyisocyanates. The products dry faster and have improved chemical and abrasion resistance. Alkyds with less than 45% fatty acids can be designed to be compatible with low molecular weight epoxy resins and certain melamine-formaldehyde resins. Pigmented systems based on this combination have excellent adhesion to metal, improved gloss and color retention, and excellent water and chemical resistance [26]. 

The synthesis of epoxyfumarate resins by adding an add ester of maleic acid to the commerdal low-molecular weight epoxy resin (Epidian 5) with simultaneous isomerization of maleate groups to fumarate ones was presented [9]. The resins were synthesized in the two-step procedure using the acid ester of maleic add prepared separately with epoxy resin or in the one-step synthesis (Fig. 1). The add ester of maleic acid was obtained in the reaction of maleic anhydride and cyclohexanol, although use of benzyl alcohol [10] and w-hexanol was also reported [llj. 

It was found that the obtained adducts accelerated the cure of UPRs. The efficiency of the tested accelerators was characterized by the gelation time and peak exotherm temperature. The shortest gelation time was obtained for the adduct of p-toluidine and bisphenol A or p,p -dihydroxydiphenylmethane based low-molecular weight epoxy resins. Adducts remained in the polyester resin as permanently bonded fragments and could not be extracted with methylene chloride from the cured UPR. Moreover, products extracted from the crossHnked resins were determined by the chromatographic and gravimetric methods. 

In turn, the synthesis of high-molecular-weight (solid) epoxy resins under PTC conditions was described. The method was based on the polyaddition of bisphenol A (PBA) to a low-molecular-weight epoxy resin or DGEBA in the presence of ammonium or phosphonium salts as well as imidazole derivatives as a catalyst (Figure 38). 

The synthesis of high-molecular-weight (solid) epoxy resins from PBA and a low-molecular-weight epoxy resin in a continuous microwave system that consists of four miaowave cavities with a rotating quartz tube (2.0 m x 0.12 m) was tested and developed (Figure 71). 

Alkyd resins cured with low molecular weight epoxy resins show excellent adhesion to metal, improved gloss and colour retention and excellent water and chemical resistance. Curing of carboxyl functional polyester (acid number 90) with an epoxy resin enhances the weatherability of the epoxy resins. Basic curing processes involve the reaction of—CO2H or —OH groups with epoxy groups. These reactions will be discussed later in Section 6.3.6. 

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