298 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS TABLE 1 Water Solubility of Per Cent Sward Rocker Film Air Dried Neutralization Hardness Value 1 Week at 72øF. 0 44 Poor 50 42 Poor 70 40 Fair 80 32 Good 90 30 Excellent 100 24 Excellent 110 18 Excellent 125 16 Excellent Sward rocker is a method for measuring surface hardness of a film in relation to plate glass which is given a value of 100. It indirectly measures flexibility (i.e. materials which are soft are also generally flexible). Figure 10 depicts the solubility characteristics of cast films. Dye has been added to the coatings to make the properties more easily discernible. UNNEU•A•IZE.D: '•N•T•'ED. UNNEUTRALIZ[.• TAP ': .'•ATER [..:TAP •ATER: •5"• •N Figure 10.--Solubility characteristics of cast films. 'The first sample shows the relative insolubility of the unneutralized resin in tap water. The second sample is 90 per cent neutralized resin and it dis- solves readily in tap water. The third sample shows the solubility of the unneutralized resin in a typical shampoo solution.* This data is useful when considering the problems of formulating to meet .consumer requirements. Thus, while the film dissolves readily in shampoo, it is possible to build in an extra safety factor by neutralizing partially or ,completely to provide a measure of water solubility. * Author's Note: The difference in color between second and third solutions is caused color of shampoo combining with that of dye.

VINYL COPOLYMER IN THE COSMETIC COSMOS 299 WA"ER ABSOiIPTION V,• . TIME FCR VINYL :OPOLYMEF (UNNEUT•ALIZED) ,• ANI 90%NEI TRALIZED AND PVP AT 50% •H /•...-.- -- 0 IPVP T VINY COPOLYI•IER (90% NEUTRALIZED) _ () ( VIN'YL COPOLYI4ER (UNNE JTRALI•-•I•j -i'-- •, { ' 0 0 2 4 6 8 10 12 14 16 TIME IN HOURS ß Figure 11.--Moisture pick up rate at 50 per cent relative humidity for the 90 per cent neutralized resin rs. PVP. 6O 48 .• 24 WATER ABSORPTI DN VS. TII• E FOR VII•YL COPOLIfMER AT VARYIN, DEGREEI OF NEUTRALIZATION AND PVI AT 90%RH 125% N EU T.• ,,.•"'""• /•'• '• P V P // •- , % NEUT. ....... •NNEUT. 0 20 40 60 80 1DO 120 140 160 TIME IN HOURS Figure 12.--Moisture pick ups at 90 per cent relative humidit), of the vinyl copolymer at varying degrees of neutralization.