Rice Husk ash as Flatting Extender in Cellulose Matt Paint

摘要

The high silica content of rice husk ash (RHA) promotes its attractiveness as an abundant, cheap and renewable resource for various industrial applications such as surface coatings formulation. This study investigated the applicability of rice husk ash (RHA) as a flatting extender in cellulose matt paint and compared its flatting effect with those of two commercial extenders; fumed silica (the standard flatting agent) and silica flour. RHA was obtained by controlled incineration of rice husks at a temperature of 6500C and duration of 4hrs. The granular ash was then ground and sieved to obtain RHA flour with a particle size of ~32microns used in the formulation of the cellulose paints. Cellulose paint produced with fumed silica of 20μm-particle size was the reference standard while a sample produced with 0% extender served as the Control. The gloss values of the dry films of the paints were measured with a gloss meter at 200 angle of reflectance and their matt values calculated from their gloss values. The results showed that all three extenders substantially reduced the gloss levels of the cellulose paint samples with a resultant corresponding increase in their matt values. Although the flatting agents displayed varied degrees of flatting effect, their matt values were all over 100% higher than that of the Control. Fumed silica was highest in flatting performance, followed closely by RHA while silica flour ranked third. This trend was evident in the matt values (%) of 98.2±0.00, 94.7±0.06 and 86.9±0.11 obtained for cellulose matt paints produced with fumed silica, RHA and silica flour respectively. The Control had the lowest matt value of 42.9% showing its glossy nature due to the absence of a flatting agent.