A STUDY OF ACRYLIC DISPERSIONS USED IN THE TREATMENT OF PAINTINGS
Michael C. Duffy
3 SAMPLE PREPARATION
EACH OF THE FIVE ACRYLIC DISPERSIONS were prepared as follows:
3.1 Cast Films
The undiluted adhesives were cast onto sheets of silicone release mylar using a doctor knife. This tool spreads an even film of uniform thickness (0.015″). When dry, these cast films could be peeled off for testing or left on the mylar carrier. The Plextol B500 had to be mixed with toluene (toluene 1:10 Plextol) to facilitate spreading; otherwise it beaded up on the mylar surface (for consistency, all samples were prepared using toluene “thickened” Plextol). The Plextol AC 33 and 489 HV dried down to a hard, clear film overnight, while the AC 234 and 360 HV remained tacky and soft. Samples not subjected to accelerated aging were kept under room conditions (approximately 68° F and 50% RH).
3.2 Wet Laminate Lining Mockups
The five adhesives were applied onto 9″ × 7″ pieces of polyester sailcloth10 fabric using a squeegee to achieve a film of uniform thickness (approximately 1/16″). Pieces of the same size polyester sailcloth were placed in contact with these samples to simulate a wet laminate lining. These samples were then placed on the vacuum table in a mylar envelope at 1″ Hg pressure for one hour to assure even adhesion. The mockups were allowed to air dry under room conditions over a 48-hour period and then cut into 1″ × 7″ strips in preparation for peel strength testing.
3.3 Reactivated Lining Mockups
The adhesives were applied to sheets of polyester sailcloth as described in section 3.2 and allowed to dry for 48 hours under room conditions. Toluene was sprayed repeatedly onto the adhesive surface to swell and reactivate the tack. Approximately 500 ml of toluene was required to reactivate five 9″ × 7″ samples. While the samples were still tacky, a second piece of sailcloth was applied to the surface. The samples were then placed under vacuum for one hour at 1″ Hg to simulate lining conditions. After “lining” the samples were cut into 1″ × 7″ strips.