Reversed-phase high performance liquid chromatography (HPLC), conventional gel permeation chromatography (GPC), and gel permeation chromatography coupled with a multiangle laser light scattering photometer (GPC-MALLS) were used for the analysis of epoxy resins based on bisphenol A. Compounds containing 2,3-dihydroxypropyl group were identified in HPLC chromatograms by means of the derivatization of sample by acetone. The presence of branched molecules was proved by GPC-MALLS using a molar mass versus root mean square (RMS) radius plot or molar mass versus elution volume plot. The molar mass distribution determined by HPLC was compared with that obtained by GPC-MALLS. Molar mass averages measured by means of GPC, GPC-MALLS, vapor pressure osmometry (VPO), and end group analysis (EG) were compared and the differences of results obtained by particular methods were discussed. An appropriate GPC calibration was found on the basis of literature data and the comparison of molar mass averages measured by GPC, VPO, and GPC-MALLS. The refractive index increment of epoxy resins was determined.
SynopsisA precipitation fractionation was carried out by the nonsolvent addition method of 60 g of an unsaturated polyester. The polyester was prepared by the generally known melt condensation of maleic anhydride, phtalic anhydride, ethylene glycol, and cyclohexanol. Number-average molecular weights of fractions were determined by vapor pressure osmometry in acetone a t 36°C. Polydispersities of fractions were evaluated by gelpermeation chromatography (GPC) measurements with tetrahydrofuran as solvent. They seem to be wider for fractions of higher molecular weights. By infrared spectroscopy the fractions were found not to have marked differences in chemical compositions. The obtained molecular weight distribution curve of the unsaturated polyester was found to be in good agreement with that expected from the theory of polycondensation kinetics. The small differences appear only in the low molecular weight range.
SynopsisThe zero-shear viscosities of the fractions of an unsaturated polyester were determined by using a rotation viscosimeter with cone-and-plate measuring system. The polyester was prepared by the generally known melt condensation of maleic anhydride, phthalic anhydride, ethylene glycol, and cyclohexanol. The viscosity-temperature relationship and the viscosity-molecular weight relationship are given. The low value of the critical molecular weight as well as rather high value of the inherent friction factor are probably caused by high forces between polar groups of the chains of an unsaturated polyester.
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