Pulsed Electric Field Surface Engineering: A Reagent‐Free Technology for Valorising Biomass Fly Ash in Natural Rubber Composites

Fly ash is an abundant but weakly reinforcing filler for elastomers, owing to coarse particles, low surface activity and poor adhesion to rubber. Here, pulsed electric field (PEF) processing is explored as a reagent‐free treatment for biomass fly ash (BFA) from rubber‐wood combustion. Sieved BFA (< 250 μm) was dispersed in distilled water (1:2 by mass), exposed to 2.5 kV cm −1 pulses for 10–40 min (94–375 kJ per kg of ash), dried and compounded into natural rubber (NR) at 0–45 phr. X‐ray fluorescence identified an alumino‐ferric mixed‐oxide ash (Al 2 O 3 28.3, Fe 2 O 3 9.6, SiO 2 7.6 wt%). Two‐way analysis of variance showed that ash loading dominated the scorch time, optimum cure time and tensile strength, whereas the treatment dominated the hardness and elongation at break. The ash shortened the scorch and cure times; the treated ash raised the hardness by 3–8 Shore A, to a maximum of 58.6 Shore A at 94 kJ kg −1 , and increased the tensile strength at 45 phr from 15.0 to 18.5 MPa (+23%), while the elongation at break fell from 1051%–1133% to 943%–1044%. Fracture surfaces showed debonded untreated and textured treated particles; surface area and chemistry were not measured. Energy balances bound the bulk slurry heating to ≤ 41 K and show that drying, not the pulses, dominates the energy demand. Because the untreated reference was not slurried, the field, heating and aqueous contributions cannot yet be separated; PEF processing is a promising but provisional route to tailoring fly‐ash fillers for elastomers.