Reversibility glue

Vos-Davidse, L. (1969). Note on the reversible glueing of broken glass objects. Studies in Conservation, 14, 183. 

The property of thermal, reversible gelation is obtained by the addition of water-soluble proteins and protein degradation products to an aqueous solution of poly (vinyl alcohol) 2). Protein products such as albumin, gelatin, glue, a-amino acids, and their condensation products—diketopiperazines—may be used. A typical formulation for the preparation of a thermally reversible gel is ... 

So-called peripheral neuropathies can result from excessive exposure to certain industrial solvents such as carbon disulfide (CS2, used in the rubber and rayon industries) and hexane (CgHn, once used in certain glues and cleaning fluids). Over-exposure to acrylamide, an important industrial chemical, and chronic alcohol abuse can also induce this effect. As the name implies, it involves attack of the chemical on and damage to axonal portions of neurons. Typical symptoms of peripheral neuropathies include weakness or numbness in the limbs, which are more or less reversible depending upon the specific agent and the intensity of exposure. 

Severe but reversible liver and kidney injury occurred in a person who was a glue sniffer for 3 years. The chief component of the inhaled solvent was toluene (80% vol/vol) other ingredients were not listed. In workers exposed for many years to concentrations in the range of 80-3 00 ppm, there was no clinical or laboratory evidence of altered liver function. ... 

Resorcinol differs from other phenols in that it reacts readily with formaldehyde under neutral conditions at ambient temperature. To make stable adhesives, which can be cured at the point of use, they are prepared with less than a stoichiometric amount of formaldehyde. About two thirds of a mole of formaldehyde for each mole of resorcinol will give a stable resinous condensation product. The resin is formed into a liquid of convenient solids content and viscosity. Such solutions have infinite stability when stored in closed containers. Glue mixes formed at the point of use from these solutions, on addition of paraformaldehyde-containing hardeners, will have a useful life of several hours due to two principal factors (1) the paraformaldehyde depolymerizes to supply monomeric formaldehyde at a slow rate, as determined by the pH (2) the availability of the formaldehyde is also controlled by the kind and amount of alcohol in the solvent. Formaldehyde reacts with the alcohol to form a hemiacetal. This reaction is reversible and forms an equilibrium which exerts further control on the availability of the formaldehyde. 

Figure 13.7 The adsorption and desorption of CD-functionalized nanoparticles onto and from a CD SAM with ferrocenyl dendrimers as a reversible supramolecular glue.

Immobilization is required for the stable imaging analysis in C. elegans neuron studies. Chaimel microfluidics provides a flexible, gentle, and reversible mechanical manner for worm immobilization instead of the conventional glue method [41, 42], thus avoiding the side-effects of glue or anesthesia. Currently, there are mainly... 

Fortunately, hollow fibers may be cleaned by back-washing which tends to compensate for their propensity to foul. Manufacturers of tubes, plate and frame units, and spiral wound modules do not recommend back-washing due to problems with membrane delamination and glue line seal rupture. Because hollow fibers are self-supporting and hold up well under the compression force of a reverse transmembrane pressure drop, they can easily withstand back-wash pressures of 15 to 20 psi. However, the back-wash fluid should be filtered to remove any particles which would tend to lodge in the porous wall of the fiber. 

Water-Soluble Starches, Gums, Cellulose Derivatives, and Synthetic Polymers. Water-soluble plant starches and gums have historically been used as glues and should be reversible. Some of the modern water-soluble polymers (e.g., cellulose ethers and esters and soluble nylon) should also be reversible. 

Water-Soluble Proteins. Historically, several water-soluble plant and animal proteins have been used as adhesives, both industrially and in conservation work. Currently, only the milk-based casein products are in significant industrial use. Casein glues have also been used in conservation work, but formulations designed for high water resistance could be difficult to reverse. Plant proteins, especially those from legumes such as soybeans and peanuts, have been used industrially, some until fairly recently. Presumably at least some forms of plant protein glues would be reversible enough to be of interest to conservators. 

Solvent-Soluble Natural Polymers. The exudate of the lac insect is dissolved in alcohol to yield shellac. This solution has adhesive properties and should be reversible by treatment with the appropriate alcohol or similar solvent, although it may present problems in other performance areas (8). Solvent-soluble plant gums, especially coniferous resins (e.g., from firs or pines) can be dissolved in organic solvents and used as adhesives. Solvent solutions of some plant waxes may also have limited utility in gluing. All such glues should be reversible by treatment with solvents similar to those they were dissolved in when applied. 

Plant Resin Formulations, Sometimes compounded with shellac, as in DeKhotinsky cement, these compounds have long been used as hot-melt glues. Likewise, waxes of plant and animal origin have also been used as hot-melt adhesives (22). They all should be reversible by application of heat, possibly in conjunction with solvent action in the more diflScult cases. 

In other cases, chemically curing glues may have been used with the realization that the opportunity for reversal may sometimes have to be sacrificed in deference to other bonding needs or objectives. This situation might be particularly true when the artifact must bear significant loads or manifest real durability. 

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