Читать книгу Surface Science and Adhesion in Cosmetics - Группа авторов - Страница 39

To enhance the hardness of the low melting wax in oil, Endo and Shibata blended the high melting point alcohol (T_m= 80°C) with low melting point rice bran wax (T_m= 72°C) in macadamia nut oil [23]. The gel hardness improvement was explained by the disappearance of spherical clusters present in the gel and the creation of more uniform structure of the oil-wax blend compared to the single wax gel system as observed by SEM.

Tavernier et al. [24] investigated the crystallization behavior of high and low melting wax blend in the rice bran oil. The hardness of the oil-wax oelogel was much enhanced when a high T_m rice bran wax (RBW) or a high T_m sunflower wax (SFW) was combined with a low T_m berry wax (BEW) in oil. The synergistic property of the wax blend was discussed through crystal morphology and sequential crystallization of binary waxes, at which high T_m wax crystallized first with large size and low T_m wax crystallized later with much smaller size. The hardness enhancement of oil-binary wax blend system was explained through sintering effect at which small crystals formed bonding between large crystals of the high T_m waxes, creating a stronger cohesive oil-gel network.

Maru and Lahoti used sunflower wax (T_m=79°C) to replace the carnauba wax which was a hard wax in the standard lipstick formulation [4]. Their results showed that the quality of the lipstick containing sunflower wax was the same as the one containing the carnauba wax. The hardness of new lipstick was reduced and the deposit increased but not significantly.

Budai et al., studied the hardness of the lipsticks containing natural oils and natural waxes [6]. The natural oils were sunflower oil, castor oil, jojoba oil, and coconut oil. These oils were blended with either carnauba wax, or candelilla wax or yellow beeswax at various ratios. The results showed that the coconut oil, jojoba oil and carnauba wax had the strongest influence on the thermal parameters of the sticks such as softening point and drop point. The compression strength or hardness of the sticks could be achieved even with only 1% to 2% for both candelilla and carnauba waxes.