# Performance of Polystyrene-Impregnated and CCA-Preserved Tropical Woods Against Subterranean Termites in PNG Field and Treatment-Induced Color Change

## TL;DR

This study compares polystyrene-treated and CCA-preserved tropical woods against termites in Papua New Guinea, finding polystyrene as a safer and effective alternative.

## Contribution

The study introduces polystyrene impregnation as a non-hazardous alternative to CCA for termite-resistant wood preservation.

## Key findings

- Polystyrene-impregnated wood showed minor color change and high termite resistance.
- CCA-preserved wood was effective against termites but caused significant color change and is hazardous.
- Polystyrene treatment increased wood density and reduced moisture content effectively.

## Abstract

Logs supplied in Papua New Guinea and Indonesia are predominantly sourced from fast-growing tree species of plantation forests. The timber primarily consists of sapwood, which is highly susceptible to biodeterioration. At a training center, CCA (chromated copper arsenate) is still used for wood preservation, while in the wood industry, ACQ (alkaline copper quaternary) is commonly applied to enhance the service life of timber. In the future, polystyrene impregnation or other non-biocidal treatments could potentially serve this purpose. This study aimed to determine the discoloration and resistance of polystyrene-impregnated and CCA-preserved woods. Wood samples, Anisoptera thurifera and Octomeles sumatrana from Papua New Guinea, and Anthocephalus cadamba and Falcataria moluccana from Indonesia, were used. The wood samples were treated with polystyrene impregnation, CCA preservation, or left untreated, then exposed at the PNG Forest Research Institute site for four months. After treatment, the color change in polystyrene-impregnated wood was minor, whereas CCA-preserved wood exhibited a noticeably different color compared to untreated wood. The average polymer loading for polystyrene-impregnated wood reached 147%, while the average CCA retention was 8.4 kg/m3. Densities of untreated-, polystyrene-, and CCA-wood were 0.42, 0.64, and 0.45 g/cm3, respectively, and moisture contents were 15.8%, 9.4%, and 13.4%, respectively. CCA preservation proved highly effective in preventing termite attacks; however, CCA is hazardous to living organisms, including humans. Polystyrene impregnation also significantly improved wood resistance to subterranean termites, as indicated by lower weight loss and a higher protection level compared to untreated wood. Additionally, polystyrene treatment is nonhazardous and safe for living organisms, making it a promising option for enhancing wood resistance to termite attacks in the future as an alternative to the biocides currently in use.