Oil-Gelling Ability of the Mixture of Plant-Derived Highly Purified Paraffin Wax and Botanical Waxes

Oil gels composed of oils and waxes are used in stick cosmetics. Recently, modification of petroleum-derived waxes to botanical waxes has become desirable; however, the gel hardness of these gels is insufficient. Therefore, to improve the gel hardness of rice paraffin wax (RP-wax), a highly purified botanical wax, the mixing effect with other botanical waxes, namely carnauba wax and rice bran wax, was investigated. RP-wax has a lower gel hardness than petroleum-derived paraffin waxes because of the formation of large plate crystals in the gel. The gel hardness of carnauba wax is very low owing to the existence of spherical clusters composed of small crystallites in the gel. However, when RP-wax was mixed with 20% carnauba wax, its gel hardness significantly improved. This was due to the size reduction of plate crystals in the gel and the disappearance of the spherical clusters derived from carnauba wax. However, rice bran wax did not produce a similar effect.