ItAIR SPRAY RESINS õ 30 • 20 •o Figure 4. PVP K-30 E-735 VEM- 9 VEM-5 / ß ,-,, •, •'•"• N.S-7_ • • ....... •'--'-•- N.S- 0 50 60 70 80 90 Relative Humidity (%) Moisture absorption o[ various resin fihns rs. relative humidity (3oøc) 599 5O 4O • 3o o • zo ,-- PVP K-30 50 60 70 80 90 Relative Humidity (ø/o) t'¾gure 5. Moisture absorption of various films with 3.5•'•½ plasticizer (Silicone oil DC 55,5) vs. relative humidity (30øC)

600 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS signed to meet U. S. Weather Bureau specification and which uses an air velocity of 5 m/sec past the wet and dry bulb, it was found that the air velocity in the chamber was high enough to obtain correct relative humidity readings. Method Approximately 1.25 g of a 40% solution of resin in anhydrous ethanol was placed evenly in an aluminum dish (diameter 5.1 cm) provided with a hanger and dried at room temperature over a period of two days. At the end of this time a uniformly dried film formed on the bottom of the dish. Final drying of the film was done at 105 øC for a 2-hour period in a circulating oven. In this way it was possible to obtain a resinous film weighing 0.5 :k 0.02 g in each dish with practically no surface bubbles, which might increase the surface in contact with air and probably would change the rate of conditioning. This arrangement made it possible to place eight dishes on hangers in the chamber for one run. For the determination of moisture pick-up or loss the dishes were placed on the hook of the Sauter Balance (Fig. 3), weighed, and then returned to the hangers. For Sward Hardness measurement three different films were cast on the polished glass plate from a 40% solution of the resin in anhydrous ethanol having a wet thickness of 3 X 10 -3 in. (1.2 X 10 -3 em). These films were then dried at room temperature outside of the chamber for two days. In this way the air in the chamber was not contaminated with alcohol vapor. Then the glass plate with the films was placed in the chamber and conditioned for two days under the humidity conditions desired for determining the hardness. It was found that this time period was sufficient to obtain equilibrium conditions of the films. Duplicate hardness measurements were taken about six hours later to check the results. RESULTS Data shown include results obtained with four resins commercially used as hair fixatives: National Starch Resyn 28-1310, G. Barr Co. VEM Resin, Arttara PVP/VA E-735, and Antara PVP K-30. The first two resins have carboxylic groups which, for hair spray purposes, usually are neutralized with an amino-alcohol. In the case of Resyn 28-1310, 90% (N.S-9) and 70% (N.S-7) neutralization with AMPD and also unneutralized resin (N.S-0) were used. The VEM resin was 90% neutralized (VEM-9) and 50% neutralized (VEM-5) with AMPD, as