Strengthening naturally and artificially aged paper using polyaminoalkylalkoxysilane copolymer networks

Various parameters that may affect the efficiency of tri- and di-functional aminoalkylalkoxysilanes (AAAS) copolymer treatments to deacidify and mechanically strengthen aged complex papers (lignocellulosic pulp, additives) were studied. Three model papers were first hydrothermally aged (90 °C—50% RH) in order to achieve physicochemical characteristics similar to those of a naturally aged newsprint, and were then treated with AAAS copolymers. The chemical composition of the treatments varied from 50 to 5 wt% of tri-functional monomer APTES, the latter acting as cross-linker in the copolymer network. The respective ratio of tri- and di-functional monomers in the mixture was shown to greatly influence the mechanical properties of the treated papers in the case of APTES/DIAMINO but less so in the case of APTES/AMDES. If APTES/DIAMINO (50/50 wt%) did not strengthen the degraded papers, a higher proportion of DIAMINO (95 wt%) and lower proportion of APTES (5 wt%) led to improving the tensile strength and, more importantly for the function properties of paper, significantly enhancing the folding endurance. The treatment efficiency decreased at higher state of deterioration of the papers and in the presence of alum–rosin sizing. Lastly, the treatments developed for the artificially aged model papers were applied to the degraded newsprint paper specimen and successfully enhanced its mechanical properties. Graphical abstract