Mechanisms of enhanced electro-mechanical properties and thermal stability of PMA esterification-crosslinked insulation pressboard

A crosslinking modification method for cellulose pressboard via PMA is proposed. • Modification synergistically enhances electro-mechanical properties of pressboard. • Modified pressboard better retains multiple properties during thermal aging. • Structural evolution underlying PMA-induced performance improvement is revealed. Cellulose insulation pressboard serves as both electrical insulation and mechanical support in power transformers. Developing insulation pressboard with superior electrical, mechanical, and thermal stability properties is essential for reliable long-term transformer operation. This study proposes a crosslinking modification method using poly(maleic acid) (PMA) for cellulose insulation pressboard. Fourier transform infrared spectroscopy (FTIR) and dynamic mechanical analysis (DMA) confirm esterification between PMA and cellulose. This reaction forms a crosslinked network that restricts cellulose-chain mobility. After modification, the dielectric constant decreases by 10.60%, while the elongation at break increases by 9.21%. The modification also improves thermal stability of pressboard. After 30 days of accelerated thermal aging, the modified pressboard exhibits a 10.83% lower dielectric constant and a 13.54% higher elongation at break than the unmodified pressboard. Furthermore, the evolution of surface and pore structures is analyzed to elucidate the mechanisms underlying the enhanced electrical, mechanical, and thermal stability properties.