Epoxy Units Research Articles

Curing of epoxy resins with dicyandiamide and urones

AbstractThe curing of epoxy resins using dicyandiamide (DICY) and combinations of DICY with several uron accelerators as curing agents is investigated. DSC, FTIR, mechanical, and sorption measurements indicate complex multistage curing processes. There is no evidence that the curing reaction is catalyzed by DICY. The optimum stoichiometry is determined as 7 epoxy units per 1 molecule DICY. Contour plots for curing reactions with DICY in presence of Fenuron 3c or TDI‐uron 3d give some information for optimizing technical formulations. © 1993 John Wiley & Sons, Inc.

Kinetic models of pregelation stages for epoxy resins cured with mixed amine systems

The systems of epoxy resins cured with primary amines with the substitution effect and etherification have been analyzed by the kinetic method. The average molecular weight, witch changed with reaction time or conversion, and the gel time were calculated, and the results agree well with those by another combined kinetic and statistical theory and experimental data. Then a more complex system, epoxy resins cured with mixed amines, was analyzed for various reactivity ratio of two kinds of amines. For a system in witch the reactivity of one kind of amine unit is rather higher than another, the average degree of polymerization profile versus epoxy conversion is close to those system with only one kind of amine and excess epoxy units

Chemical epoxidation of a natural unsaturated epoxy seed oil fromVernonia galamensis and a look at epoxy oil markets

AbstractSince 1963, production of all epoxy esters has ranged from 60 to 150 million lb annually, a steady 7% of the 1 to 2 billion lb of annual plasticizer production. Growth rates in production averaged 4.3% for all plasticizers, 3.8% for all epoxy esters and 5.0% for epoxidized soybean oil (ESBO). ESBO accounted for 70–76% of total epoxy ester production (1963–1982). The natural liquid epoxy oil fromVernonia galamensis seed, with oxirane value (4.1%) and viscosity (100 cps) similar to some commercial epoxy fatty esters but with molecular weight similar to epoxidized vegetable oils, combines some of the properties of both commercial types. Chemical epoxidation ofVernonia oil raises the oxirane content to 8.2, intermediate between ESBO and epoxidized linseed oil (ELSO), while consuming less of the costly epoxidizing reagents. Epoxidation proceeds in stepwise fashion through partially epoxidized products, which are converted to final product. Since the major fatty components ofVernonia oil arecis‐12,13‐epoxy‐9‐octadecenoic (75%) and linoleic (13%) acids, further epoxidation produces fatty acids that are specifically epoxidized at the 9,10‐ and 12,13‐positions, and the major product has 6 epoxy units per triglyceride molecule. The resulting mixture of products has compositional and physical properties distinctly different from commercial samples of ESBO and ELSO.

Chromatographic studies of epoxy resins

Methods are given for the‘derivatisation’ of various of the components of epoxy resins: after fractionation by g.p.c. but before further analysis by h.p.l.c. or g.p.c. This paper describes the use of the following reagents for this purpose: concentrated HCl (to convert epoxy groups into chlorohydrin units); solid NaOH (to convert 1, 2-chlorohydrin groups into epoxy units); phenol (to open epoxy rings); N-methylaniline (to open epoxy rings); and KMnO4 (to oxidise —CH2 — and — OCH2CHOHCH2O — bridging units).

Rubber-modified epoxy resins: 1. Equilibrium physical properties

Dilatometry, thermal mechanical analysis, differential scanning calorimetry, electron microscopy and mechanical measurements are reported on a series of rubber-modified epoxy resins. The data obtained is discussed in terms of the interplay of molecular mobility, network and domain structure of the resins. Three transitions were identified; two being assigned respectively to the onset of motion of the acrylonitrile/butadiene units and epoxy units. The higher temperature transition is more difficult to assign, but appears to be associated with specific interactions involving the interface between the epoxy and acrylonitrile/butadiene interfaces or the crosslinked regions of the epoxy resin.