Loading-Dependent Effects of J-AP on Polypropylene: Thermal Reinforcement and Electrostatic Charge Decay

Abstract Polypropylene (PP) blends containing 0.5, 1.0, and 3.0 wt% poly(7-amino-4-hydroxy-2-naphthalenesulfonic acid) (J-AP) were prepared by twin-screw melt compounding to assess the effect of additive loading on their structural, thermal, morphological, mechanical, electrical, and electrostatic charge-dissipation properties. FTIR-ATR confirmed the incorporation of J-AP, while XRD revealed predominantly α-monoclinic crystalline structures. Increasing the J-AP content enhanced crystallinity and thermal stability: the DSC-derived crystallinity rose from 34.3% for neat PP to 45.4% for the 3.0 wt% blend, and the degradation onset temperature increased from 431 to 449°C. The blends exhibited yellow fluorescence under 366 nm UV excitation, most pronounced at 3.0 wt% loading, and the elastic modulus increased from 456.1 MPa for neat PP to 1732.8 MPa for the 3.0 wt% blend. Thermal degradation kinetics were evaluated by six methods at four heating rates (5, 10, 15, and 20°C min⁻¹); all indicated higher apparent activation energies after J-AP incorporation. Experimental master plots agreed most closely with the D2 diffusion model for the 0.5 and 1.0 wt% blends and with the D1 model for the 3.0 wt% blend. Electrical conductivity increased from 7.6 × 10 − 10 to 1.7 × 10 − 9 S cm⁻¹ across the series. However, corona-induced charge-decay measurements showed that higher conductivity did not translate into faster charge dissipation: the 0.5 wt% blend gave the shortest decay times under both positive and negative polarization, although its ESD performance remained limited. These results identify J-AP as a multifunctional PP modifier with distinct loading requirements for thermal-mechanical enhancement and electrostatic charge dissipation.