Formaldehyde Resol Resins Research Articles

Physical structure of phenolaniline–formaldehyde resol resin and its kaolin–filled phenoplasts

AbstractAn investigation of the physical structure of samples of phenoaniline–formaldehyde resol resin in uncured and cured state, and of its phenoplasts containing different ratios of kaolin filler, was made with the aid of electron microscope pictures. The uncured and cured resin consists of microglobules of a size of 40–80 Å, which agglomerate to form larger‐sized globules of various dimensions. After a mathematical elaboration of the results of a large number of measurements, it was established that the diameters of the globules are casual values distributed in accordance with the normal (Gaussian) law. Both in the resin and in the kaolin‐filled phenoplasts (at a rate of 25 to 47 vol‐%), after curing at 170–180°C and a pressure of 300 kg/sq cm, the mean diameter of the observed globules was of a rather steady value and remained within the limits of 230–240 Å (with a standard deviation of 30–40 Å). A method was elaborated of determining the mean thickness of the adsorption coating of the resin on the filler particles. Calculations show that in the filling interval we have chosen, the thickness of the absorption coating is not below 1.8–0.6 times the mean thickness of the globules.

Investigation of the dependence of the properties of the phenoplasts of phenolaniline–formaldehyde resol resin on the degree of kaolin filling and on their physical structure

AbstractAn investigation was made of the dependence of 13 types of standard physical and mechanical and electric insulation properties of phenoplasts of phenolaniline–formaldehyde resol resin on their filler content in a broad range of 14 to 47 vol‐%. It is found that the respective curves have more than one maximum and periodically pass through several maximums and minimums. The periodicity is more clearly seen in the curves reflecting the dependences of the properties on the calculated mean thickness of the resin adsorption coating on the filler particles. With these curves the extremal values appear over more or less even intervals of the adsorption coating thickness. The periodicity relating to the change in this thickness is explained by the periodic formation of particles of a new type of filler in the points of a whole number of monoglobular adsorption coatings, and of a maximum amount of globules oriented toward them in the points of a whole number and a half monoglobular adsorption layer. The periodical appearance of an oriented (regarding the particles) globular layer determines the appearance of periodical positive and negative orientation effects in the properties of the phenoplasts. The diagram we propose is confirmed by the regular periodical change in the various properties as well as by the measured ratios of the mean thicknesses of the adsorption coating in the points of the extremums of the various types of curves, determined by the differential curves method.