EFFECT OF PROCESS VARIABLES ON THE INITIATION TEMPERATURE AND EXOTHERMIC HEAT FOR THE COPOLYMERIZATION OF ACRYLONITRILE AND METHYLACRYLATE-I

Abstract

Differential scanning calorimetry (DSC) experiments were carried out on a set of laboratory-synthesized copolymers of acrylonitrile/methylacrylate precursors meant for the manufacture of hollow-fiber carbon membranes. This was done to determine the effect of the polymerization process variables on the exothermic heat and exothermic initiation temperature. Factors such as methylacrylate monomer and azo-bis-isobutyronitrile (AIBN) initiator concentrations, stirrer speed and polymerization temperature were investigated as functions of the exothermic heat and the exothermic initiation temperature. An empirical approach was adopted that employed statistical experimental designs that were used to recognize analytical and statistical methods that translate the process responses into comprehensible terms. It was established that hollow-fiber carbon membranes can be reproducibly made by exercising very strict control over the polymerization conditions when using co-monomers of acrylonitrile (AN) and methylacrylate (MA). Process variables such as stirrer speed, polymerization temperature methylacrylate and azo-bis-isobutylonitrile concentrations influence the properties of the copolymer produced and hence the properties of any carbon membranes produced from a precursor manufactured from the copolymer. The effects of the factors investigated, or the interactions of these factors on the variations observed in the initiation temperature, was rather inconclusive. This was ascribed to the unavoidable variation in the mass of the material used for the calorimetry experiments.

Keywords:

• acrylonitrile
• methylacrylate
• exothermic heat
• initiation temperature
• stirrer speed
• DSC

Permanent address of E.R. Sadiku is Tshwane University of Technology, Department of Polymer Technology, Postnet Suite 186, Private Bag X025, Lyhnwoodridge 0040, South Africa

Notes

llf = low level factor, hlf = high level factor.

llf = low level factor, hlf = high level factor.

DMF = Dimethylformamide, AN = Acrylonitrile, MA = Methylacrylate, AIBN = Azo-bis-isobutyronitrile.

Due to confounding, a true error variance can not be calculated. However, an estimate of the error of the variance can be assumed. This was done using the sum of squares of the two-factor interaction. This can be done because the two factor interactions are confounded with each other. The equation below shows how the estimate of error variance was calculated. The values of the SS used, are those in Table 7 above.

Estimate of error of variance = SS(AB≡CD + AD≡BD + AD≡BC)/3.