| Abstract: | SUMMARIES. The object of this article is to study the strengthening effect of amino silanes on degraded paper, an effect that has been observed in a previous study, focussed on amino silanes as deacidification agents. Several paper samples of different fiber composition from the beginning of the 20 cen¬tury were treated with ethanolic solutions of several amino alkyl alkoxy silanes and submitted to accelerated ageing 80°C dry (=room humidity). As parameters to describe mechanical strength, breaking length and folding endurance were measured. In the main the former is enhanced by several silane treatments, and the effect is stable during accelerated ageing. The chemical reac¬tions between reagent and cellulose that provide the strengthening effect are intensively dis¬cussed. Several questions arising from this discussion will be studied in following-up research.
CONCLUSION. To conclude on the effects amino alkyl trialkoxy silanes have on the mechanical properties of paper, it is clear that these effects can be assigned to the formation of a macromolecular network, interpenetrating the fibrous network. The general effect of such a reaction was demonstrated over twenty years ago16. In principle, to give mechanical reinforcement the network must not necessarily be covalently bound to the fiber network; the entanglement effect is sufficient for that. How¬ever, the slight yellowing effect that has been noticed, might be assigned to a chemical reaction of the amino group of the silanes with some chemical function of the cellulose, either with oxidized groups formed during ageing, or with the terminal units of the cellulose macromolecular chains. Actually, it can be as¬signed to the reaction of the amino groups with some carbonyl functions, most probably coming from the lignin content in the paper, which produces aromatic imine functions. These functions absorb light in the UV range. It was necessary to firmly understand the origin of this effect and to determine whether it could be possible to limit or to eliminate it. A future paper in this se¬ries will shed more light on this problem, and a deeper study on the excellent ageing behavior of the deacidified papers is also to be published. |
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