Case Study of Fire Flame Resistance Improvement of a Plywood Board Coated with Paint Containing Added Rice Husk Amorphous Silica

Aims: Rice husks constitute an issue of concern for stakeholders interested in rice production; on the other hand, rice husk silica has been recognized as a valuable resource for industrial uses. Thermal insulation is a potential industrial benefit offered by silica. In this study, thermal resistance of rice husk silica, especially its resistance to fire flame, was investigated. It was found that rice husk ash should be ground for obtaining the desired effects.

Study Design: Time of burning out and the temperature increase rate were obtained for evaluating thermal resistance of rice husks. The former was the time from the launch of the fire flame to when the plywood board was burned. The latter was the temperature increase rate on the plywood board within 60 s.

Place and Duration of Study: Experiments were conducted at Toyama Prefectural University and the duration was between April 2016 and March 2017.

Methodology: Paints that contained 0%, 5%, 10%, 15%, 20%, 25%, and 30% of rice husk ash (as is) by weight were prepared and one side of plywood boards (2.5 mm in thickness and 100 mm x 100 mm in area) were coated with these paints. After painting, the boards were dried for one day at ambient temperature.　Each board was set in an upright position on a stable foundation and a fire flame (3.5 kW) was launched from a handheld burner from a distance of 0.1 m toward the board. The time from the launch of the fire flame to when the area demarcated by the red circle on the back side of the board was burned was measured and recorded.

Results: The following results were obtained in this study. Rice husk ash showed fire flame resistance. Ground rice husk ash was better than the as-is rice husk ash in terms of handling and offering fire flame resistance. The fire flame resistance increased as the ash contents increased up to 20% and it decreased drastically beyond 20%. The sample with 15% ash content showed the highest temperature resistance. The sample with 20% ash content showed resistance for the longest duration.

Conclusion: The fire flame resistance increased as the ash contents increased up to 20% in weight and decreased drastically beyond 20%. The optimal ash contents were in the range of 15–20%. Thus, rice husk silica can be a useful resource that provides further advantages to stakeholders involved in rice production globally.