868 JOURNAL OF THE SOCIETV OF COSMETIC CHEMISTS .g Figure 4. Strain gauge apparatus were dried slowly and thoroughly to prevent air or solvent entrapment. The dried films were approximately 0.0038 cm in thickness. From these, tensile pieces were cut in 1.26-cm wide strips, conditioned, and tested at 90% RH at 22øC on an Instron Model TM* at a crosshead speed of 0.5 cm/min. Equilibrium Moisture Content The equilibrium moisture content was determined on free films cast from anhydrous ethanol. The films were air dried for 2 hours at 22øC, 2 hours at 60øC, 15 minutes at 105øC, and then stored in a desiccator for 24 hours. The dried films were attached to a hulled pressure transducer or strain gauge (Fig. 4). A pressure transducer will con- vert mechanical motion or strain into electrical current when a stress changes the resistivity of one leg of the transducer circuit. The dry film weight was recorded as millivolts on the readout of a DC-Micro- Volt Aremeter (Model 425At). The film weight was then hulled by the precision potentiometer and the strain gauge assembly was inserted into an atmosphere of 90% RH at 22øC. The increase in weight was * Instron Corp., Springfield, N.J. t Hewlett Packard Corp., Paramus, N. J.

POLYMER PROPERTIES INFLUENCING CURL RETENTION 869 Figure $. z 0.09 GMS DE POSITED 0.05 GMS DEPOSITED 0 20 40 60 80 I00 NEUTRALIZATION,(%) Curl retention vs. neutralization with AMPD (2-amino-2-methyl-l,3-propanediol) for Polymer B after 30 minutes at 90% RH (22øC) continuously recorded as a change in voltage. The equilibrium milli- volt deflection could be converted to grams and the equilibrium mois- ture content calculated as' Grams water Grams polymer x ]oo (2) Film Hardness The relative hardness of films was determined with a Sward Rocker* apparatus. This device is set into a rocking motion on the film under test and the number o[ complete, standardized rocking cycles is counted. The value or number assigned is relative to glass which has an arbitrary value of 100. Therefore, the higher the Sward number the harder the film. Soft, tacky films have a Sward reading of zero. RESULTS Statistically designed experiments were conducted to determine the effect of neutralization with 2-amino-2-methyl-l,3-propanediol (AMPD), molecular weight, functionality, and copolymer composition upon curl retention, moisture permeability, tensile strength, and film hardness. Additionally, this study included various types of resins: carboxylated polymers, polyvinylpyrrolidone, t a polyvinylpyrrolidone/ vinyl acetate copolymer, t and dimethyl hydantoinformaldehyde resin. $ * Gardner Laboratory Inc., Bethesda, Md. ? PVP, PVP/VA, General Aniline and Film Corp., New York, N.Y. $ Dantoin 734, Glyco Chemicals, Div. of Chas. L. Huisking Co., Williamsport, Pa.