Thermal degradation behavior of polypropylene base wood plastic composites hybridized with metal (aluminum, magnesium) hydroxides

Fire Behavior and Failure Model of Multilayered Wood Flour/HDPE/Polycarbonate Composites with a Sandwich Structure

The flame retardancy of wood–polymer composites significantly affects their potential applications. Thus, multilayered wood flour/high-density polyethylene (HDPE)/polycarbonate (PC) composites were prepared via thermocompression to improve the fire retardancy of wood–polymer composites in this paper. Thermal degradation behavior, flame retardancy, and flexural strengths of the resulting composites were investigated using a thermogravimetric analysis, cone calorimetry, and mechanical testing machine, respectively. Results revealed that the boric acid treatment reduced the heat release rate and total heat release of the wood flour/HDPE composites and increased their mass of residues. However, boric acid reduced the flexural strength of the resulting composites. The combustion test indicated that PC cap layers suppressed the combustion of the resulting composites via the formation of carbon layers. Adding PC layers reduced heat release and increased the flexural strength of the resulting composites. Finally, the failure mode of the multilayered wood flour/HDPE/PC composites in the three-point flexural test was simulated by finite element analysis.

Flame Retardant Polypropylene Composites with Low Densities

Polypropylene (PP) is currently widely used in areas requiring lightweight materials because of its low density. Due to the intrinsic flammability, the application of PP is restricted in many conditions. Aluminum trihydroxide (ATH) is reported as a practical flame retardant for PP, but the addition of ATH often diminishes the lightweight advantage of PP. Therefore, in this work, glass bubbles (GB) and octacedylamine-modified zirconium phosphate (mZrP) are introduced into the PP/ATH composite in order to lower the material density and simultaneously maintain/enhance the flame retardancy. A series of PP composites have been prepared to explore the formulation which can endow the composite with balanced flame retardancy, good mechanical properties, and low density. The morphology, thermal stability, flame retardancy, and mechanical properties of the composites were characterized. The results indicated the addition of GB could reduce the density, but decreased the flame retardancy of PP composites at the same time. To overcome this defect, ATH and mZrP with synergetic effect of flame retardancy were added into the composite. The dosage of each additive was optimized for achieving a balance of flame retardancy, good mechanical properties, and density. With 47 wt % ATH, 10 wt % GB, and 3 wt % mZrP, the peak heat release rate (pHRR) and total smoke production (TSP) of the composite PP-4 were reduced by 91% and 78%, respectively. At the same time, increased impact strength was achieved compared with neat PP and the composite with ATH only. Maintaining the flame retardancy and mechanical properties, the density of composite PP-4 (1.27 g·cm-3) is lower than that with ATH only (PP-1, 1.46 g·cm-3). Through this research, we hope to provide an efficient approach to designing flame retardant polypropylene (PP) composites with low density.

Synergistic influence of halogenated flame retardants and nanoclay on flame performance of high density polyethylene and wood flour composites

High density polyethylene and wood flour (HDPE/WF) composites containing three flame modifiers (FMs) (i.e., two fire retardants: 1,2-bis(pentabromophenyl) and ethylene bis(tetrabromophthalimide), and one nanoclay), maleic anhydride grafted polyethylene (MAPE) and other processing aids were prepared through twin-screw extrusion, and their properties were characterized.

Hybrid Composites from Wheat Straw, Inorganic Filler, and Recycled Polypropylene: Morphology and Mechanical and Thermal Expansion Performance

Reinforcing effect of hybrid filler including wheat straw (WS) and inorganic filler (heavy calcium carbonate, silicon dioxide, and fly ash) in recycled polypropylene (R-PP) has been investigated. The effects of individual filler (WS) and combined fillers (WS and inorganic filler) on morphological, mechanical, and thermal expansion and water absorption properties of hybrid composites were investigated. The flexural modulus and flexural strength were both reduced when reinforced with three kinds of inorganic fillers, respectively, which was possibly due to the poor interphase adhesion as observed in SEM. The high surface energy of heavy calcium carbonate due to its high acidic character provides an opportunity of better PP-heavy calcium carbonate interfacial interactions compared to PP-straw, PP-fly ash, and PP-SiO2interface. The water absorption at saturation increased markedly by introduction of WS in it. The hybrid composites from WS and inorganic fillers showed better water absorption compared to those WS/PP composites. The thermal expansion of composites decreased with the increase of WS loading. Heavy calcium and SiO2can obviously reduce the LCTE value of composite. At the 25% inorganic filler content, composites had the smallest LCTE values.

Thermal degradation and flammability properties of multilayer structured wood fiber and polypropylene composites with fire retardants

Single and multi-layer structured wood fiber and polypropylene composites filled with fire retardants were prepared. Fire retardant property of composites were determined by thermogravimetric analysis and cone calorimetry.