Incorporation of Fly Ash in Flame-Retardant Systems of Biopolyesters

The incorporation of fly ash in polybutyl succinate (PBS) and polybutyl adipate terephtalate (PBAT) in the partial replacement of ammonium polyphosphate and/or melamine polyphosphate is evaluated in the present work. Furthermore, the influence of the surface modification of fly ash with two silanes and titanate coupling agents was also studied. Cone calorimeter experiments, pyrolysis combustion flow calorimeters (PCFCs), and UL94V tests were used to assess the fire performance of the composites. Scanning electronic microscopy, X-microanalysis, and X-ray diffractometry analysis were carried out on cone calorimeter residues in order to access the fire-retardant mode of action. The formation of new components due to the presence of fly ash was highlighted by X-ray diffractometry, indicating the synergistic effects between the flame-retardant system and fly ash. The X-microanalysis results showed that the main fraction of initial phosphorous is present in the cone calorimeter residue, indicating that the proposed system acts in a condensed phase.

Dispersion characteristics of hydroxyl and carboxyl-functionalized multi-walled carbon nanotubes in polyester nanocomposites

Multi-walled carbon nanotube (MWCNT) reinforced polyester-based composites were prepared by mixed blending in a solvent. Orthophthalic unsaturated polyester was blended individually with different types of non-functionalized and functionalized MWCNTs. Two types of functional groups: hydroxyl (-OH) and carboxyl (-COOH) were introduced with MWCNTs for the nanocomposites. The mechanical properties of the composites, like tensile, three-point bending and impact energy were evaluated. Fourier transform infrared spectroscopy was used for the functional group analysis. The dispersion characteristics of the samples were observed by transmission electron microscopy and field-emission electron microscopy. In addition, the thermal decomposition and melting behavior of the samples was assessed by differential scanning calorimetry and thermogravimetric analysis. The properties were varied due to the variation of the functional groups. The result analysis showed that the entangled agglomerations of hydroxyl-functionalized MWCNTs were destroyed to relatively smaller clusters. The hydroxyl-functionalized MWCNTs were more effective for homogeneous dispersion and contributed for better mechanical properties of the composites, compared to non-functionalized and carboxyl group-functionalized MWCNTs.