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.

Date of Award	1973
Original language	English
Awarding Institution	Aston University