The interaction of methyl methacrylate with wool under the catalytic influence of the hydrogen peroxide–thiourea redox system was studied under a variety of conditions. The degree of grafting depends upon the method empolyed; it is advantageous to first immerse wool in thiourea solution, monomer and hydrogen peroxide being then subsequently applied. Increasing the hydrogen peroxide concentration from 4 to 8 mmole/1. causes a significant enhancement in the graft yield. The latter remains practically unchanged upon further increment in hydrogen peroxide concentration within the range studied, i.e., up to 12 mmole/1. This was also observed with respect to thiourea concentration. On the other hand, increasing monomer concentration is accompanied by a significant increase in the graft yield. The polymerization reaction is temperature dependent; at the three temperatures examined, the graft yields follow the order 80° > 60° > 40°C. The rate of grafting is also dependent on the pH of the reaction medium over the range of 2 to 8, being decreased as the pH increased. Furthermore, the presence of traces of cupric ions in the polymerization system accentuates the graft formation. The alkali solubility as well as the urea bisulfite solubility of wool grafted with poly(methyl methacrylate) are much lower than those of physical mixtures of wool and poly(methyl methacrylate). This demonstrates that grafting of poly(methyl methacrylate) into wool has occurred.
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Hebeish et al. (1974) studied this question.