HAIR-HAIRSPRAY JUNCTIONS 17 5 Table III Effect of Product (C2) Concentration on Knot Adhesion Dilution N robust Robust mean Standard deviation 0% 18 24.0 + 11.7 25% 16 28.3 +18.0 50% 9 20.9 + 10.1 75% 7 17.5 +5.4 The least significant difference in mean at 95% confidence is 12.1 by Duncan's multiple range test. have a large effect on the number of robust knots formed. At 50% and 75% dilutions, only nine and seven robust knots were formed, compared to 18 with undiluted product. We interpret this result in the following manner: The strength of an adhesive junction is determined by the bonding energy and the area of contact. This hairspray probably spreads uniformly throughout the area in which the hairs are in contact, due to Laplace forces. As long as there is sufficient polymer to fill the spaces, a good junction is formed. As the concentration is reduced, the odds of filling the necessary space to make a junction are reduced and N robust decreases. There is less effect on the mean force to break the junctions that do form. EFFECT OF RELATIVE HUMIDITY Three hairspray formulations were tested at 20%, 40%, and 60% RH: 1) A betaine formula (CTFA name: methacryloyl ethyl betaine/methacrylates copolymer) containing 4.5% polymer, 2) the betaine plasticized by 0.5% hydrogenated soy glyceride, and 3) a formula containing an acrylic polymer made by emulsion polymerization (7) (acrylates copolymer). Results are shown in Figure 5. Both the betaine and acrylic polymers showed the highest adhesive strength at 40% RH. The plasticized betaine showed slightly higher adhesion at 20% RH than at 40% RH. The unplasticized polymer films may be too brittle to give optimum adhesion at low RH. All three polymers may be too soft to give optimum adhesion at 60% RH. EFFECT OF POLYMERS AND MODIFIERS A number of different types of polymers appropriate for use in the formulation of hairsprays are available from suppliers to the industry. We have tested several of these for adhesion at a concentration of 3% solid polymer. Results are given in Table IV. The CTFA names of the ingredients are as follows: The betaines were variations of meth- acryloyl ethyl betaine/methacrylates copolymer. Acrylates I & II were acrylate/ acrylamide copolymers. Acrylate III was octylacrylamide/acrylates/butylaminomethyl acrylates copolymer. Acrylate IV was acrylates copolymer, which is an acrylate/ methacrylate copolymer made by an emulsion process (7). VA/CA refers to vinyl acetate/ crotonic acid copolymer. AMP refers to aminomethyl propanol, LMP is lauramidopropyl dimethylamine, and PGSA is PEG-10 stearamine. AMP, LMP, and PGSA are added as neutralizers.

176 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 7O 6O 50 4O 5O 2O 10 I I I N N x, 2O 4O 6O •beLaine •--• betainc + HSG • acrylic RELATIVE HUMIDITY Figure 5. Effect of relative humidity on knot strength. Error bars are at 95% confidence intervals. Table IV Knot Adhesion Testing of Hair Spray Polymers N Average Standard 95% Confidence Polymer (3.0%) Modifiers robust force deviation interval Betaine I 13 7.5 +6.3 ---3.8 Acrylic I 0.30 AMP 10 9.0 +7.2 4-5.1 Betaine II 18 11.4 4-6.0 4-3.0 Betaine III 32 12.7 4-6.2 4-2.2 Vinyl acetate 0.30 AMP 33 13.1 4-6.7 4-2.4 Vinyl ether I 0.13 AMP 28 13.7 4-8.8 4-3.4 Acrylic II 0.38 AMP 32 15.0 4-9.1 4-3.4 Vinyl ether II 0.13 AMP 20 15.0 4-7.5 4-3.5 Acrylic IV 0.30 AMP 27 15.2 4-17.7 4-7.2 Acrylic III 0.50 AMP 37 19.2 4-6.6 4-2.2 Acrylic IV 0.30 AMP q- 0.3 PGSA 36 22.0 4-9.0 +3.0 Acrylic IV 0.30 AMP q- 0.3 LMP 39 25.2 4-8.4 4-2.7 In this study 40 replicates of each treatment were run. N Robust and mean force varied from 13 and 7.5 grams for betaine I to 39 and 25.2 grams for acrylic IV + AMP and LMP. Sramek (7) obtained a patent based on use of long-chain amines as neu- tralizers with acrylic polymers and silicone surfactants to improve the adhesion and removability of hairspray. Here we see that acrylics III and IV gave the strongest