Title
UV stability of thermochromic ink on paper containing clinoptilolite tuff as a filler
Authors
MIRELA ROZIC RAHELA KULCAR SONJA JAMNICKI BRANKA LOZO and DIANA GREGORSVETEC

Published Volume 49 Issue 7-8 July-August
Keywords zeolite, clinoptilolite filler, thermochromic ink, photocatalytic oxidation

Abstract
The aim of the study was to analyse the possibility of using natural zeolite clinoptilolite as partial substitute of paper filler in order to improve the UV stability of thermochromic ink. Natural zeolite tuff was added to calcium carbonate in mass proportions of 0%, 20% and 60% and laboratory handsheets were prepared with 20% filler addition to fibre paperstock. The printability tester IGT A2 was used in the preparation of thermochromic prints on laboratory handsheets, which were exposed to the process of UV radiation in a Solarbox 1500e aging chamber (CO.FO.ME.GRA) for various time intervals during 40 hours. The measurements of the CIELab values (L*, a*, b* and C*) have shown changes as a function of accelerated aging time, which are very significant already after 1 hour. The smallest changes were obtained in the case of paper samples with 12% clinoptilolite (20% zeolite tuff addition). It was concluded that small proportions up to 20% of zeolite tuff in the paper filler act favorably on the UV stability of printed thermochromic ink, while higher proportions reduce the stability as an effect of photocatalytic oxidation features due the presence of Fe-oxides in the sample of natural zeolite tuff.