Strengthening of degraded cellulosic material using a diamine alkylalkoxysilane

Abstract

The physicochemical modifications in papers upon introducing AEAPMDMS (3 N-(2-aminoethyl)-3-aminopropylmethyl-dimethoxysilane) as a dry strength and deacidification agent were explored. The double amine functionality was shown to favor penetration in the cellulose fibers, with large uptakes being achieved at low concentration. In situ polymerization in the paper was demonstrated using ²⁹Si CP-MAS and ¹H NMR. The distribution of the compound inside and on the fibers' surface was evidenced with SEM-EDS and XPS. The deacidification efficacy was established. The strengthening effect was shown to arise from the interaction of AEAPMDMS with the fibers, and depended on the fiber composition (lignin content) and oxidation state, with a higher efficiency for the less degraded and less lignified fibers. In the most degraded papers, the occurrence of yellowing was interpreted as due to the formation of Schiff bases, where the amine functional group reacts with the carbonyl groups on the oxidized cellulose.