3.1. Monomer conversion and total solid content
The effect of the MAH proportion in the alkyd resins on monomer conversion and total solid content was investigated. As already postulated above, the Cdouble bond; length as m-dashC bonds of MAH are more accessible and prone to direct addition reaction with acrylate monomers and may have some effect on the polymerization behavior. The Properties of hybrid alkyd–acrylic latexes are given in Table 4 and the monomer conversion curves versus miniemulsion polymerization time are plotted in Fig. 1. From Table 4 and Fig. 1, it is clearly shown that the monomer conversions as well as total solid content are increasing with the increased content of MAH on the resin. The lowest monomer conversion is obtained for R-1 (40.54%) with 0% MAH and the highest monomer conversion (96.19%) for R-4 with 75% MAH and, with solid contents 14.44% and 48.09% respectively. This result suggests that the grafting of the alkyd resin to acrylate monomers is more favorable for the direct addition reaction of the Cdouble bond; length as m-dashC double bonds of MAH than those of the triple conjugated unsaturation of the α-eleostearic fatty acid chain. The direct addition of the acrylate to MAH of the alkyd resin is of great interest because it limits or avoids the use of triple conjugated diene of the R. heudelotii and will play a vital role during the auto-oxidation crosslinking reaction after application. The grafting of the unsaturated carbon–carbon double bonds of MAH onto the acrylate monomers has been recently studied [1] and [17] and furthermore MAH can graft to acrylate monomers through its single bondCOOH groups [17]. The effect of the alkyd–acrylate ratio on monomer conversion using Resin C was also investigated. With the increase of resin content (40% and 50%) in the preparation of the hybrid latexes, some anomalous behavior was observed on the monomer conversion. The monomer conversion decreased with the increase of alkyd content and the formed latex exhibited large particle size distribution leading to phase separation. Therefore, due to instability of the formed latexes containing more than 20% alkyd, the performance of the resins was not studied. Similar results have been reported for other alkyd–acrylate systems [1], [18] and [19].