The Linear Growth Rates of Pentaerythritol Crystals

Abstract

The linear growth rates of the (101) faces of single crystals of Pentaerythritol (Pe) in aqueous solutions have been measured as a function of temperature (10-50°C), and concentration difference (0.25 x 10° acs 2.60 x 10-2 KgPe/Kg Solution) under stagnant conditions in a batch cell. The effect on growth rate of the two main by-product impurities of Pe manufacture, di-Pe and a Formal, and several other impurities has been determined over a range of working conditions. It was found that the growth rate of the pure material varied with time and also from crystal to crystal. Due to the purification method used in preparing the solutions an impurity (X) was removed which resulted in these growth rates being at least two orders of magnitude greater than those previously reported. The pure material growth rate was kinetically controlled having a parabolic law over most of the range of conditions studied with an activation energy of 8.47 Kcal/mol. The effect of di-Pe was generally that it caused a slight reduction in the growth rate except at certain critical concentrations where the effect was an increase by up to a factor of two. The effect of the Formal was that it drastically reduced the crystal growth rate virtually to zero, when in concentrations greater than the order of 0.001 mass fraction. Of the other added impurities, only Formaldehyde, Sodium hydroxide, and 1,1,1,trimethylolethane had significant effects in reducing the growth rate. In the absence of (X) and Formal, Pe crystals were found to exhibit (110) and (001) faces in addition to the usually reported (101) faces. The phenomenon of secondary nucleation appears to be related to the magnitude of the crystal growth rate under the conditions investigated. It appears that (X) may be 1,1,1,trimethylolethane or similar compound.