Implications of dry-heat ageing on the structure and mechanical properties of the special Chinese pulp fibre and its handsheets

Abstract The phloem fibres of wingceltis ( Pteroceltis tatarinowii ) are a key resource for traditional Chinese handmade paper. This study investigated changes in handsheets made from phloem fibres of wingceltis during dry-heat ageing. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) spectra indicated that mild oxidation occurred in cellulose. Though minimal, this oxidation could still induce cellulose degradation, leading to a decrease in the mechanical properties of individual phloem fibres. The analysis of the pore structure via nitrogen adsorption–desorption isotherms revealed a complex, hybrid variation mode, characterised by the reduction of larger pores and/or voids while micropores formed. By combining chemical, structural, and mechanical analyses, this study demonstrated a simultaneous occurrence of a decrease in fibre strength and an increase in inter-fibre bond strength. However, the modest enhancement in inter-fibre bond strength was insufficient to compensate for the decline in the mechanical strength of the individual fibres. This work attempted to evaluate the mechanical properties of paper from a microscale perspective, highlighting its potential for future non-destructive analysis of paper relics.