672 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table II Alkali Resistance of Polymid, Carboset, and Ethyl Cellulose Films Appearance of Film Plasticizer (%) Opalescence Erosion Performance Polymid 1155 Hexadecyl alcohol (10) 13 hours 2 days Poor Polymid 1155 Citroflex-4 (10) 13 hours 2 days Poor Polymid 1155 Amerchol L-101 (10) 13 hours 2 days Poor Carbose* 525 a . .. 3 days None Good Ethyl Cellulose N-10 Hexadecyl alcohol (10) None None Excellent Ethyl Cellulose N-10 Hexadecyl alcohol (20) 12 hours None Fair Ethyl Cellulose N-10 Hexadecyl alcohol (30) 12 hours None Fair a Carboset 525 is soluble in alkaline media and therefore the resistance of the film was determined in demineralized water. Film Hardness Film hardness was determined on films which had been cast upon a steel surface. A concentrated solution of the film-forming agent and plasticizer (35-50% w/w depending upon solubility in the alcohol sol- vent) was placed onto a steel plate (4 in. x 12 in.) and by means of a film casting knife* drawn into a thin film having a thickness of approxi- mately 0.0024 in. These plates with the cast film were placed in an oven at 45 _--+- 0.5øC for 3-4 hours. The exact thickness of the film was measured using a magnetic gauge.* Hardness of the applied film was measured as the number of oscilla- tions the Sward Hardness Rocker* completed on the smooth surface of the film compared to 100 oscillations on a polished plate glass. These results are shown in Tables III and IV and represent the average of three determinations for each film. Modulus of Elasticity Following determination of the Sward hardness, R, of the film, the modulus of elasticity, E, was calculated from the following equation: KR • E- * Gardner Film Casting Knife, Model •AG-3820, Gardner Laboratories, Inc., Bethesda. Md. * Elcometer Magnetic Gauge, Model •GG-6270, Gardner Laboratories, Inc., Bethesda, Md. ++ Model •C, Gardner Laboratories, Inc., Bethesda, Md.

INGREDIENT RELEASE FROM AEROSOL FILMS 673 Table III Effect of Plasticizer on the Physical Properties of Emerez Films Sward Modulus of Film Hardness Elasticity (E), Film Emerez Plasticizer (%) Rocks (R) psi Flexibility Appearance" 1533 Hexadecyl alcohol (10) 8 777 Very good Tack free 1536 Hexadecyl alcohol (5) 4 100 Fair Sticky 1536 ... 8 777 Slightly brittle Tack free 1540 Hexadecyl alcohol (10) 18 8,859 Good Tack free 1540 Hexadecyl alcohol (20) 14 4,100 Fair Soft and tacky 1540 Hexadecyl alcohol (30) 10 1,520 Fair Soft and tacky 1540 Citroflex-4 (10) 18 8,859 Good Tack free 1540 Amerchol L-101 (10) 24 21,000 Brittle Tack free All of the films were transparent and glossy. Table IV Effect of Plasticizer on the Physical Properties of Polymid, Carboset, and Ethyl Cellulose Films Sward Modulus Hard- of ness Elas- Plasticizer Rocks ticity Flexi- Film (%) (R) (E), psi bility Film Appearance Polymid 1155 Hexadecyl 10 1,520 Good Transparent, very glossy, alcohol (10) and tack free Polymid 1155 Citrofiex-4 10 1,520 Good Tramparent, very glossy, (10) and tack free Polymid 1155 Amerchol 14 4,100 Brittle Transparent, very glossy, L-101 (10) and tack free Carboset 525 ... 14 4,100 Excellent Translucent and tack free Ethyl Cellulose Hexadecyl 12 2,600 Good Clear and tack free N-10 alcohol (10) Ethyl Cellulose Hexadecyl 8 700 Very good Clear and tack free N-10 alcohol (20) Ethyl Cellulose Hexadecyl 4 100 Excellent Clear and tack free N-10 alcohol (30) The values of the constants (K) for three different illin thicknesses are tabulated below as they appear in the literature (8). Constant (K) Thickness (T), in. 1.73 X 10 -9 0.0012 2.1 X 10-8 0.0024 1.3 X 10 -7 0.004