HAIR SPRAY RESINS 603 7O 6O • •o • •o Io N.S-7 • I I I I I I I 5O 6O 70 80 Reinfive Humidity (%) l,'i,gure 10. Sward hardness of various resin films rs. relative humidity (B()øC) 7O 6O • 40 •_ •o '• 20 m I0 0 VEM-5 • '"" • •-- VEM-O i ' I I I I I I I 50 60 70 80 Relative Humidity (%) I 9o Figure 11. Sward hardness of various resin fiHns with 3.5•0 plasticizer (Silicone oil DC 555) rs. relative humidity (30øC) well as unneutralized (VEM-0). The percentage of water absorption is based on dry resin. All tests were made with films with and without plasticizer. Whenever a plasticizer was used, it was 3.5% Silicone Oil DC 555* based on dry resin. Figure 4 shows the moisture absorption at different relative hu- midities of various resin films at equilibrium. PVP K-30 shows the greatest moisture absorption, followed by PVP/VA 735. VEM has lower humidity pick-up. As can be anticipated, unneutralized resin has lower moisture absorption than does neutralized resin because of its lower water solubility. Resyn 28-1310 has the lowest moisture absorp- tion. Figure 5 shows the results with plasticized films. There is a decrease in the water absorption of the plasticized fihns in comparison with the nonplasticized films. * Dow Corning Corp., Midland, Mich.

6{)4 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Figure 6 shows the moisture absorption rate of these films conditioned at $0% relative humidity and then exposed to 90% RH. Both ear- boxylie types of resin have a much faster conditioning rate than PVP/VA 735 and finally PVP K-30. Plastieized films have approximately the same conditioning rate (Fig. 7), except that the initial and final ab- sorptions are lower than those of unplastieized films. The drying rate of films conditioned at 90% RH and then exposed to 50% RH is shown in Fig. $. Equilibrium is reached by all the films in two to four hours except PVP/VA 735 and PVP K-30. Figure 9 gives the results with films that have been plastieized. The drying rate curves of plastieized films are all displaced downward due to the hydrophobic character of the plastieizer. Figure 10 shows the variation of Sward Hardness with relative humidities from 50 to 90% at equilibrium. It can be seen that the unneutralized VEM-0 and 50% neutralized VEM-5 give the hardest films. These are followed by 90% neutralized VEM-9, except beyond 61% RH where the hardness is surpassed by the unneutralized Resyn 28-1310. It can be seen that the hardness of both the PVP K-30 and PVP/VA 735 decrease more rapidly. Figure 11 gives similar data using plasticized films. Hardness obtained with plastieized films with sili- cone oil could, of course, be affected by at least three factors: (a) plastieizer decreases the moisture pick-up which results in harder film (b) plastieizer itself decreases the hardness and (e) plastieizer lubri- cates the surface between the film and the Sward Hardness rocker, thereby increasing the Sward Hardness reading. Each of these factors may produce different effects, even on the same plastieized film at different humidities. CONCLUSIONS In conclusion, it can be seen from the foregoing that the greater the degree of neutralization the greater the hygroscopicity of the films of carboxylic types of resins. PVP/VA 735 and PVP K-30 films are more hygroscopic than any of the films made with VEM or the Resyn 28-1310 resins. Although moisture pick-up by the VEM resin is greater than that of Resyn 28-1310, the hardness of the former at any given humidity is greater. Greater hardness at high humidity means less tack. A hard film on the hair will break more easily when the comb is passed through, whereas a soft, tacky film will put drag on the comb. Soft, tacky films will also result in hair snagging with resultant difficulty in combing. A certain degree of moisture pick-up is perhaps desirable