SOURCE:

Faculty: Engineering
Department: Chemical Engineering

CONTRIBUTORS:

Ojiabo, K.T;
Igbokwe, P.K;

ABSTRACT:

Kinetics and rheological behavior of washable paints produced from raw palm kernel oil (PKO) and Jatropha seed oil (JSO) were studied in this work. The kinetics study was carried out during the production of alkyd resins using the selected oils, phthalic anhydride, glycerol and benzoic acid as the major raw materials at a given ratio. The prepared alkyd resins were then emulsified using isopropyl alcohol as the surfactant. The alkyd resins used for the emulsions were first prepared byalcoholysis and polycondensation reactions. Response surface methodology (RSM) was used tooptimize the polycondensation reactions and emulsification of the alkyds. Thermodynamic study was also carried out during the polycondensation reaction by measuring the in-suit viscosity of the reactants at different temperatures. The prepared emulsions were analyzed for their physiochemical properties, film properties and volatile organic content (VOC) and Fourier transform infra-red spectroscopy (FTIR).These resins were used for comparative studies on washable paint samples. Nine samples of washable paints were produced from the alkyd emulsion samples. Two of the samples were produced using alkyd emulsion as the only binder, a sample was produced using only polystyrene acrylic binder, six other samples were produced using different proportion of alkyd emulsion and polystyrene acrylic. The proportions include; 25% polystyrene acrylic to 75% alkyd emulsion, 50% each for both binders, 75% polystyrene acrylicto 25% alkyd emulsion.These paint samples were analysed for the following performances; storage stability, sagging behaviour, levelling and applicator loading. These performances were determined through rheological properties which include dynamic viscosity, yield stress and shear rates.The dynamic viscosities were measured at three different shear rates; 06 rpm, 12 rpm, 30 rpm and 60 rpm respectively. Drying performance and volatile content were determined by ASTM (D1640-83, 1991) and weight difference according to ISO 11890-1:2007.Kinetics study of the polycondensation reactions showed that the esterification reaction was a second order reaction. The reaction order was of 10-4kgmol/KOH. The rate constants obtained at interval of 20mins show that the reaction rate increases as the reaction progresses. According to the viscosity profile, it was observed that the longer the reaction time, the more viscous the mixture is. Hence there was a sustained increase in the viscosity of the alkyd as the reactions progress. Thermodynamic study of the polycondensation reactions showed that the activation energy for PKOBR is Ea = -1.031 kJ/mol and the activation enthalpy is ΔH#=- 4349.25𝐾𝐽/𝑚𝑜𝑙, while that of JSOBR are Ea = -1.039 kJ/mol and ΔH#= -4349.26 kJ/mol respectively. The negative enthalpy of activation proves that the reactions proceeded by formation of stable intermediate.The FTIR spectra showed that polymerization reaction took place. While raw PKO and JSO can be polymerised and emulsified to produce low VOC resins, the usefulness of the products depend on their ability to meet certain performance evaluation. Also, the rheological study shows that polystyrene acrylic can be used to modify both the film and flow properties of washable paints but, this can only be achieved at a ratio below 25% of polystyrene acrylic to PKOBR and above 25% of polystyrene acrylic to JSBOR.