Ultrafine dispersion of a phosphate nucleating agent in a polypropylene matrix via the microemulsion method

To reduce the nucleator's size and improve its dispersion, microemulsions of sodium 2,2′-methylene bis-(4,6-di-tert-butylphenyl) phosphate (NA11) and NA11-sodium benzoate (SB) composite nucleators were prepared by choosing ethanol as NA11's solvent. NA11 nucleator within ethanol was dispersed on the interface of droplets, whose size is ca. tens of nanometers as characterized by dynamic light scattering and cryo-TEM. Investigations on PP's crystallization behavior as well as on the mechanical properties indicate that NA11's nucleation efficiency can be further improved using the microemulsion method. However, the blank microemulsion can adversely affect PP's crystallization and mechanical properties due to its residual oil and surfactant components in the PP matrix. A synergistic effect was found in the NA11-SB composite microemulsion, which shows a smaller size of the dispersed phase and an improvement to PP's stiffness. A possible dispersion mechanism of the nucleator microemulsions in the final PP matrix is proposed according to the microemulsions' structure and their nucleation effects.