尿素-・ホルムアルデヒド樹脂のゲルクロマトグラフィー

概要

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The determination of the apparent number and weight average molecular weights (Mn and Mw) and the molecular weight distributions of urea-formaldehyde resins (UFR) was studied by gel chromatography. Samples studied were analyzed in an open column by descending gel chromatography. The operating parameters were as follows : solvent, dimethylformamide; temperature, 25°C±2°C; gel, Sephadex LH-20; column, Sephadex Column Model SR 25/100 available from Pharmacia Co., 80 cm; detector, Waters Associates, Differencial Refractometer Model 403; sensitivity, 16X; flow rate, 1 ml/min controlled with a Mariotte flask system; sample concentration, about 50 mg/2 ml. The calibration curve was obtained from free urea, mono- and dimethylol ureas, methylene diurea and standard monodispersed polystyrene and polydispersed polyethylene glycols available from Pressure Chemical Co. The peaks of water, methanol, monomethylol urea and methylene diurea in commercial UFR were not resolved separately. It was found that the Mn of commercial UFR adhesives ranged from 250 to 500 and the molecular weight distribution was broader than that of melamine- and phenol-formaldehyde resins. The calibration curve used is not strictly applicable to UFR etherificated with alcohols and that modified with melamine-formaldehyde resins.
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