This paper deals with the determination of chemical composition and the study of the pulping potentialities of banana pseudo-stems growing in Madeira Island (Portugal). First, the raw material was both studied as a whole (type I) and as the outer bark part (type II), which is richer in cellulose fibres. Before starting the cooking of banana wastes, the main components of the two types of material were quantified, and showed that the polysaccharide content was high enough (about 60-70%) to justify the pulping investigations. Moreover, the lignin content was very low (approximately 12%). The only discouraging finding was the relative high amounts of ashes and extractives. The pulping of these residues was carried out using soda, kraft and soda-anthraquinone (AQ) cooking processes and the optimal pulping conditions were established. Thus, pulps with a yield of about 37-38% with a Kappa number (Kappa no.) about 30-32 were obtained when cooking in the presence of 0.25-0.35% of anthraquinone at 120 • C for a short cooking time, i.e. 30 min. The longer times and higher temperatures of cooking as well as the use of kraft pulping conditions did not give rise to better performances, comparing to those mentioned above. These severe conditions were detrimental to the hemicellulose preservation.
The photochromic behaviour of two series of 2,2'-bithiophene azo dyes in THF solutions was studied. The photochromic properties and colour constancy were strongly dependent on the substitution pattern of the dyes. Under visible irradiation (> 420 nm) while some dyes exhibited a significant change in the colour intensity others exhibited an almost stable absorption. The photokinetic parameters of these systems are described.
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