Abstract
Purpose: Alkyd resins constitute a very high proportion of conventional binders used in
surface coatings. In order to enhance the quality of these alkyd resins methyl esters of rubber
seed oil (MERSO) were used in the preparation of the resins.
Methods: MERSO were obtained by in-situ alcoholysis of rubber seed. Alkyd resins having
oil lengths of 45, 50 and 55% were prepared with MERSO, phthalic anhydride and glycerol
using alcoholysis method. Lead (II) oxide and xylene were used as catalyst and refluxing
solvent, respectively. The physico-chemical characteristics of the MERSO and the resins
obtained were compared with the corresponding value of rubber seed oil (RSO) and its alkyd
resins. Chemical resistance of the alkyd resins was also determined.
Results: The acid value of the finished alkyd resins depends on the rate and extent of
esterification. Iodine value of the alkyd shows that the level of unsaturation depends on the
oil length of the resins. The free fatty acid (FFA) value (1.99%) of the MERSO was much
lower than that of the RSO (9.54%). This supports the choice of methyl ester as a preferred
alternative to the use of the raw RSO in alkyd resin preparation. All the alkyd samples were
fairly resistant to brine, acid and water but poorly resistant to alkali. However, the MERSO
alkyds were observed to have a better resistance than the RSO alkyd resins. The
scratch/gouge pencil hardness shows that the hardness of the alkyd films decreases with the
oil length.
Key words: Alkyd resins, rubber seed oil, methyl ester