The influence of degree of fragmentation of Pinus sibirica on flammability, thermal and thermomechanical behavior of the epoxy-composites

In this study, lignocellulosic flour obtained through grinding of Pinus siberica wood (S) was used as a filler for developing epoxy-based (EP) composites characterized by reduced flammability. The influence of filler particle size on flammability, thermal and thermomechanical behavior of the natural composites was discussed in reference to the morphological analysis of final products as well as filler geometrical changes induced by processing. The structural analysis was realized with using 3D tomography. It was found, that introduction of 20 wt% of Pinus siberica wood caused a sharp drop in the heat release rate values, and the lowest results (2.5 times lower compared to EP) was determined for composite with the highest degree of fragmentation. The residue investigation confirmed the influence of particles size on the formation of the swelling structure of char, which effectively inhibits the combustion processes. Moreover, the analysis of gaseous products emitted during the thermal decomposition of composites was performed. The addition of investigated filler caused a decrease in the amount of degradation products, while the quantity of polycyclic aromatic hydrocarbons (PAHs) increased. •Epoxy-Pinus siberica (EP-S) composites were characterized by higher thermal stability.•The improved thermomechanical stability of composites independent of particle size of S.•Higher resistance to indenting point load at elevated temperature for EP-S with lower particle size was observed.•Quality of char have been influenced by the degree of fragmentation of S wood.•S caused a decrease in the amount of gases emitted during the thermal decomposition.