Different measurement methods of epoxy equivalent and epoxy value

epoxy iequivalent and epoxy value (epoxy equivalent s 100/ epoxy value), the main methods of measurement are based on hydrogen halide, sulphate (ester) and thiol, the addition reaction with epoxy-based measurement, or the ionization reaction for epoxy compound analysisSince 1984, many imported epoxy materials require the use of "hydrogen bromide-ice acetic acid non-water titration method" for quality control, this method than the long-term widespread use of hydrochloric acid acetone retration method fast, accurate, sensitive, not only to determine commonly used epoxy resin and suitable for fillers Or the rapid determination of dark epoxy materials, compared with acetone hydrochloride, the detection time is short, the end point is easy to determine, the data is more accurate and concentrated, the scope of application is wide, and the national standard GB/T4612 prescribed perchloric acid method effect is comparable, but the use of more safe, cheap and simpledomestic scientific research and production units in the production practice, the acetone hydrochloride method, hydrogen bromide-ice acetic acid method and high-chlorate method comparative testingThe national standard GB/T13657-1992 (bisphenol A epoxy resin) additional description, the national standard was formulated with reference to the use of ASTM1763-198l (epoxy resin standard specification), and the ASTM standard provides for the use of ASTMD1652 (brominated hydrogen-ice acetic acid method) to determine epoxy iethyleneThe main reason is because the acetone hydrochloride method uses back titration, only before titration needs to place the specimen 1h, and reagents need to be used now; In addition, in the import and domestic epoxy glue, a variety of potting materials and other analytical testing practices, most samples are not like E-51 (EP0144l-310 or CYD-128) and other transparent resins, but mixed with a large number of fillers, colored additives or dark products of the samplefor this researchers in the practical application of hydrogen bromide-ice acetic acid method, for different epoxy samples divided into 3 types of treatment: colorless transparent samples with l, 2 steps; 4000 centrifuge separation 5 to 10min, the liquid in the triangular flask for the next step test, the solution after centrifugal separation of the colored sample still contains color matter or due to the product dark interference titration, can be used for potential titration, after mapping from the curve to obtain the consumption volume, the same method to determine the blank sample 2 copiesCompared with perchloric acid, the principle is to add hydrogen bromide and epoxy metastasis, except that perchloric acid is converted by hydrochloric acid and bromide tetraethylamine reaction, converted hydrogen bromide and epoxy metastasisThe titration agent used in the 2 methods needs to be calibrated before use, and the calculation method and operation are similar (hydrogen bromide-ice acetic acid method usually does not take into account temperature/volume correction), and the error is small from the resultsAnd the bromide hydrogen one ice acetic acid method because the use of reagents is simpler and easy to obtain, practical betterall kinds of epoxy materials can be measured by potential titrationUnder normal circumstances, reagents can be directly tited, but due to the volatilization and oxidation of hydrogen bromide and other factors, ASTMD1052 standard provides for the use of perchloric acid and bromide tetraethylamine reaction for potential titration, for low-activity epoxy materials using iodized tetrabutylamine (as is the same as the national standard GB/T4610 perchlorate method)In fact, this perchloric acid method is another form of application of hydrogen bromide-ice acetic acid method, because the test principle is to use perchloric acid and bromide reaction in situ synthesis of primary ecological hydrogen bromide, and the resulting hydrogen bromide immediately equivalent to the epoxy group reactionThe calculation and test methods are the sameIn the test process due to volatile oxidation, the use of sealed automatic liquid titration tube, test results found that homemade reagents and imported reagents are equivalent, deviation of 1.5%, to meet the use requirements, in the analysis of 3 units of laboratory test personnel, the method and reagents can meet product quality control use requirements