COLOUR COSMETICS
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■ Solvent based ■ F91-141B based on Sytran PC5620
Two types of plasticisers are used – permanent and fugitive (also referred to as coalescents). Permanent plasticisers are absorbed completely by the polymer upon drying and remain in the film to provide continuing plasticisation. Coalescents, which volatilise during drying process, are used to temporarily lower the MFFT of a nail polish during the drying phase. Therefore the amount and types of the various plasticisers required to produce an optimised nail polish film are of critical importance.
Testing and results The formulation F-91-141B was evaluated against commercially available water-based and solvent-based nail polishes.
Drying time
One of the main demands of consumers concerning nail enamels is a quick drying time. A trend in the cosmetic industry today is that consumers are looking for more convenient products which apply quickly and easily, and save them precious time. The drying time of a nail polish formulation containing 92% of the new acrylic polymer dispersion was evaluated against three water-based and one solvent- based competitor currently on the market. For this test a film with a thickness of 150 µm was applied on glass under controlled humidity (55% RH) and temperature (21˚C) and the drying time of the film was evaluated with a standardised method (ASTM D5895-03). This test allows one to determine the rate of dry film-formation of organic coatings using a straight line mechanical drying time recording device. In this test method, a rod with a hemispherical tip, fitted to a carriage, is brought into contact with the fresh film at one end of the test strip and moved lengthwise at a selected constant speed. The drying time is calculated from the distance travelled, measured using a graduated rule along the edge, corresponding to the various stages observed on the trace. Among all the water-based products, the formulation containing 92% of the
April 2012 PERSONAL CARE 141
Figure 3: Gloss measurement.
Specular gloss 20˚
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