Effect of DMDBS (3: 2, 4-bis(3,4-dimethyldibenzylidene) sorbitol) and NA11 (sodium 2,2′-methylene-bis(4,6-di-tertbutylphenyl)-phosphate) on electret properties of polypropylene filaments

Polypropylene (PP) composite filaments containing two different nucleating agents - DMDBS (3: 2, 4-bis(3,4-dimethyldibenzylidene) sorbitol) and NA11 (sodium 2,2′-methylene-bis(4,6-di-tertbutylphenyl)-phosphate) were melt spun to modify polymer electrostatic charging characteristics. Sample filaments were charged with a corona instrument and their surface potentials were measured. Initial surface potential as well as potential stability was monitored through an accelerated decay procedure. NA11 was found to be more efficient as an electret additive leading to a 50% increase in charge stability. Filaments with DMDBS exhibited a faster decay. Charging at elevated temperatures resulted in enhanced charge density and stability for both additives. The fiber microstructure was examined by Wide Angle X-ray Diffraction and Differential Scanning Calorimetry. Rather than reducing the crystal sizes, X-Ray diffractograms suggest that the crystal size increases with the addition of nucleating agents, while the degree of crystallinity appears to remain unaltered.