CHANGES IN THE OPTICAL PROPERTIES OF HEMP OFFICE PAPERS DUE TO ACCELERATED AGEING

This research observes alteration in optical properties of two commercially available hemp office papers exposed to various methods of accelerated ageing. Both handmade office papers, natural colored and non-chlorine bleached were formed from 100% hemp plant fiber. In order to establish their optical stability under controlled conditions two different accelerating ageing treatments were carried out for the period of 24 hours as a simulation of different degradation processes that naturally occurs in cellulosic materials: thermal oxidation (TO) and photo-oxidation (PO). Before and after ageing treatments the changes in the optical properties of papers were monitored by X-rite DTP 20 spectrophotometer and obtained differences in Reflectance index (R), Euclidean difference (ΔE00*) and Yellowness Index (YI E313) have been discussed. The results have shown how the paper optical stability is dependent upon manufacturing process. Namely, it was found that bleached hemp pulp provide better optical stability of papers than unbleached hemp pulp.