Influence of Zinc Oxide Nanoparticles on Flame Resistance in Wood Plastic Composites/Utjecaj nanocestica cinkova oksida na vatrootpornost drvno-plasticnih kompozita

The interest in wood plastic composites (WPCs) has increased in recent years. The utilization of environmentally friendly materials has been of great significance due to the overwhelming pressure on nature. As a widely used material, plastic is, however, easily combustible due to its structure. In this study, WPCs were reinforced with zinc oxide (ZnO) nanoparticles. The effect of higher content of ZnO nanoparticles (1, 3, 5, 10 %) on WPCs thermal stability and fire performance was investigated. Thermogravimetric analysis (TGA) clearly demonstrated that nanoparticles acted as a shield, which inhibited heat transfer and increased the degradation temperature thanks to covering the surface of materials. Free radicals accelerated the thermal degradation of neat-HDPE (high-density polyethylene) by oxidative reactions, while ZnO nanoparticles reduced the degradation velocity. Moreover, the increase in nanoparticle content significantly affected the residue. The fire performance of WPCs was also investigated by the limit oxygen index (LOI) test. While neat-HDPE flamed with dripping, ZnO nanoparticles made flaming difficult for WPCs. Therefore, the LOI values increased with increasing nanoparticle content up to 28.5 %, which indicated the need for more oxygen. The improvement reached up to 54 % compared to neat HDPE. Moreover, the char forming was also improved, which helped enhance the fire resistance. The scanning electron microscope (SEM) investigation indicated that nanoparticles were well dispersed in the matrix. However, the tendency to agglomerate increased with the increase of concentration. The ability of carbonization of wood fiber surface during the combustion also contributed to improving thermal stability and fire performance. KEYWORDS: ZnO nanoparticles; LOI test; TGA analysis; thermal resistance; WPC Zanimanje za drvno-plasticne kompozite (WPC) posljednjih je godina poraslo. Upotreba ekoloski prihvatljivih materijala ima veliko znacenje zbog golemog pritiska na okolis. Plastika je siroko rasprostranjen i vrlo cesto upotrebljavan materijal, ali je zbog svoje strukture lako zapaljiva. U ovom su istrazivanju drvno-plasticni kompoziti ojacani nanocesticama ZnO. Istrazivan je utjecaj veceg udjela nanocestica cinkova oksida (ZnO) (1, 3, 5 i 10 %) na toplinsku stabilnost i vatrootpornost WPC-a. Termogravimetrijska analiza (TGA) jasno je pokazala da nanocestice djeluju kao stit koji inhibira prijenos topline i povecava temperaturu razgradnje. Nadalje, slobod