A novel wood-plastic composite fabricated via modified steel slag: preparation, mechanical and flammability properties

A novel method was developed to enhance the utilization rate of steel slag (SS). By treating SS with phosphoric acid and aminopropyl triethoxysulane (KH550), we obtained modified steel slag (MSS), which was used to replace talcum powder (TP) in the preparation of modified steel slag/wood-plastic composites (MSS/WPCs). The composites were fabricated through melting blending and hot pressing. Their mechanical properties were systematically investigated as well as the combustion properties comprising heat release, smoke release, and thermal stability. The MSS could improve the mechanical strength of the composites through grafting reactions between wood powder and thermoplastics. Notably, MSS/WPC#50 (16wt% MSS) with a MSS-to-TP ratio of 1:1 exhibited an optimal comprehensive performance. Compared to WPC#0 without MSS, the tensile, flexural and impact strengths of MSS/WPC#50 were increased by 18.5%, 12.8%, and 18.0%, respectively. Moreover, the MSS/WPC#50 sample achieved the highest limited oxygen index (LOI) of 22.5% among all the samples, the highest UL-94 vertical burning rating at V-1, and the lowest horizontal burning (HB) rate at 44.2 mm/min. The enhanced thermal stability and significant reduction in heat and smoke release of MSS/WPC#50 can be attributed to the formation of a dense and stable char layer. However, partial replacement of TP with MSS slightly compromised the mechanical and flame-retardant properties, possibly due to weak grafting caused by SS powder agglomeration. These findings suggest that MSS/WPCs are suitable for high-value added applications as decorative panels indoors or outdoors.