Abstract
Since cleaning of artworks may cause undesirable physicochemical alterations and is a nonreversible procedure, it is mandatory to adopt the proper cleaning procedure. Such a procedure should remove undesired materials whilst preserving the original surface. In this regard, numerous gels have been developed and exploited for the cleaning of various artwork surfaces. Lately, agarose (AG) and polyvinyl alcohol-borax (PVA-B) hydrogels have been widely employed as cleaning tools by conservators. Both hydrogels show some limitations in specific cleaning practices. In this work, we investigated the influence of including increased levels of agarose into PVA-B systems. For this reason, we performed a detailed characterization on the double network (DN) hydrogel including the chemical structure, the liquid phase retention, the rheological behavior, and the self-healing behavior of various PVA-B/AG double network hydrogels. These new hydrogels revealed better properties than PVA-B hydrogels and obviated their limitations. The inclusion of AG into PVA-B systems enhanced the liquid retention capacity, shape-stability, and mechanical strength of the blend. Furthermore, AG minimized the expelling/syneresis issue that occurs when loading PVA-B systems with low polarity solvents or chelating agents. The resultant double network hydrogel exhibits relevant self-healing properties. The PVA-B/AG double network is a new and useful cleaning tool that can be added to the conservators’ tool-kit. It is ideal for cleaning procedures dealing with porous and complex structured surfaces, vertical surfaces and for long time applications.
Highlights
Cleaning of artworks is deemed to be one of the most important and critical actions undertaken by conservators owing to its irreversible nature
We investigated in greater detail various characteristics of the polyvinyl alcohol-borax (PVA-B)/AG double network hydrogel such as (a) its chemical structure, (b) liquid phase retention, (c) mechanical strength, (d) rheological properties, and e) self-healing behavior
In this study, we investigated the addition of agarose to the Polyvinyl alcohol (PVA)-B system and its effect on the chemical structure, liquid phase retention capacity, mechanical properties, rheology behavior, and self-healing properties of the blend
Summary
Cleaning of artworks is deemed to be one of the most important and critical actions undertaken by conservators owing to its irreversible nature. Agarose provides the gelling power for agar gels because of its high molecular weight. It is extracted from marine red seaweeds and is composed of ß-1, 3 linked-d-galactose, α-1, 4-linked 3,6-anhydro-l-galactose (see Additional file 1: Fig. S1a). Further cooling leads to the final gelation stage where thick bundles of double helices are formed (Gel II) (see Additional file 1: Fig. S1b). This gelation process is thermoreversible and creates the 3D network of rigid agarose gel due to the formation of hydrogen bonds among the bundles of double helices [1, 17]
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