Trattamenti sostenibili per la protezione e il consolidamento di legno e carta

Preservation of lignocellulosic materials has been a concern for mankind since timber was first used for structural purposes and paper for writing. The increasing use of wood as a building material and paper as documentation support has implied an increasing interest in their decay and the development of numerous strategies for the preservation against abiotic agents (e.g., moisture, acidity, chemicals, sun radiation, and fire) and biotic agents (e.g., bacteria, algae, fungi, moulds, insects, and shipworms). At present, legislation on health and environmental risks is constantly restricting substances in wood preservative formulations, which means that eco-friendly, long-lasting, and more benign treatments are desired. In this context, a novel treatment based on polyamidoamines (PAAs) for the preservation of wood and paper against abiotic and biotic decay, with a broad protection functionality, low effective concentration, and low environmental impact, has been developed. PAAs are easily prepared by reacting diacrylamides with prim-amines or sec-diamines through the aza-Michael reaction. A lot of features make PAAs attractive for green-preservation: (i) they are functional linear polymers (oligomers) with tert-amine (basicity, coordination capability) and amide function (structural demands, coordination); (ii) they are functionalizable in order to modulate solubility, carrier properties, reticulation; (iii) they are non-volatile, safe, biocompatible materials; (iv) they are endowed with biostatic/biocidal properties against organisms responsible of biotic decay. In addition, PAAs are homogeneously vehiculable by acqueous media into lignocellulosic materials, are endowed with deacidfying power and, concerning ancient manuscripts, they are able to fix iron-gal ink by forming insoluble iron complexes. Further researches are ongoing on the use of crystalline nanocellulose (CNC, obtained from cellulose by acid hydrolysis) as sustainable material for the preservation of lignocellulosic artifacts, in particular for ancient wood consolidation.