Tensile properties and fire residue morphology of flame-retarded-polypropylene composites

The polypropylene (PP) composites filled with flame retardants (including aluminum hydroxide (Al(OH)(3)), magnesium hydroxide (Mg(OH)(2)), and zinc borate (ZB)) were prepared, and the composites were separately loaded with polyolefin elastomer (POE) and nanometer calcium carbonate (nano-CaCO3). The tensile properties and the fire residue morphology of the specimens after burning for these three groups of composites were measured. The results were shown that the tensile fracture strength and the Young's modulus increased while the tensile yield strength and the tensile elongation at break (delta (b)) decreased with increasing flame-retardant volume fraction. At the same flame-retardant content, the delta (b) values of the PP/Al(OH)(3)/Mg(OH)(2)/ZB/nano-CaCO3/POE composite were the highest in the three groups of composites. The fire residue in the pyrolysis zone of the specimens increased corresponding to the increased flame-retardant volume fraction and with loading the nano-CaCO3 and POE, especially at low-flame-retardant concentration. The reinforcing and the flame-retarded mechanisms of the composites were discussed.

Automated summary

This study investigated the properties of polypropylene composites filled with different flame retardants. The results showed that the tensile strength and Young's modulus increased with increasing flame-retardant volume fraction, while the tensile yield strength and elongation at break decreased. Among the composites with the same flame-retardant content, the one loaded with polyolefin elastomer and nanometer calcium carbonate exhibited the highest elongation at break. The addition of flame retardants, especially at low concentrations, increased the fire residue in the pyrolysis zone of the specimens.