3 FURTHER CONSIDERATIONS

WHILE POLYMETHYL ACRYLATE alone is flexible, and rather soft, leather impregnated with the resin is a composite material of which the hardness and other properties may not be easy to predict. The surface hardness of the composite would determine whether there is a tendency to pick up dust, in which case a surface coating might be needed. The composite's comparative strengths in tension versus compression would affect its resistance to cracking when folded sharply: if the inside surface of a fold does not compress easily, the outside may break in tension. Though only one formulation was tried—rather “rich” in monomer—the properties of composites made by treating different leathers varied widely.

Outline tracings of the samples indicated little or no shrinkage during treatment. Shrinkage might be observed in some cases, caused either by contraction within the polymer as it formed or dried, or as a direct effect on the leather of the heating needed to activate the polymerization initiator. Room-temperature initiation systems, such as those activated by ultraviolet light, might be useful.

An important consideration is reversibility of treatment. Polymethyl acrylate is a linear acrylic resistant to cross-linking and thus, theoretically, removable. The actual practicality of removal is another question, however, involving the molecular weight of the polymer, the effect of solvents on the leather, and stresses exerted by the polymer when swollen by solvent during removal.