878 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS 200 160' • ,•o. z ,• 80' z o,/ "' 40' 0 2•) 40 60 80 I00 NEUTRALIZATION (%) Figure 20. Elongation (%) at 90 % RH rs. neutralization with AMPD for Polymer A (22øC) transmission and extremely low tensile strength. On the basis of moisture absorption alone, one might expect DMHF to have a curl re- tention greater than 46%. But, in this polymeric system, the moisture transmission and tensile strength have a more significant effect than equilibrium moisture content. SUMMARY AND CONCLUSIONS It is evident from the data presented that curl retention at elevated humidity is related to the degree of neuturalization of carboxylated polymers, the hydrophobic or hydrophilic nature of the polymer, and, to a large extent, the average molecular weight. The practical considerations of curl retention at high humidity should be examined in view of the data presented in Fig. 21 and Table I. The curl retention and high-humidity properties of various com- mercial hair spray resins are illustrated. It might be pointed out that these polymers offer a wide range of film properties. The more hygro- scopic or water-sensitive polymers, such as PVP and PVP/VA, may be suitable primarily for soft-holding hair sprays or in formulations marketed in less humid areas. These limitations are not apparent when less moisture sensitive polymers are utilized. They have in- creased curl-holding power, and the resins can be incorporated into both hard-to-hold and soft-holding formulations notwithstanding the climatic conditions.

POLYMER PROI•ERTiES INFLUENCING CURL RETENTION 879 IOO 90. 80. • 7'0, :::,. _0 60. • SO. • 40, 30' Figure 21. ••'• POLYM"A" opvP-K30 3'0 60 9b I•o I•o i•o (TIME-MIN.) Curl retention at 90% RII as a function of time for several commercial hair spray resins (0.06 g deposited) A most important property of the carboxylated polymers is their ability to be varied by reaction of the polymeric acidity. Film hard- ness, moisture transmission, tensile strength, and elongation, and ultimately curl retention may be modified to cover a wide range of applications. For carboxylated vinyl acetate polymers, the following conclusions can be made from the data presented. (a) Curl retention is inversely related to neutralization with AMPD. (b) Moisture transmission rate is increased as the neutralization is changed from 0 to 100% of the theoretical acidity. (c) Molecular weight affects the curl retention properties in a direct relationship, i.e., the higher molecular weight polymers exhibit higher retention at elevated humidity. (d) Tensile strength and elongation are a function of degree of neutralization. The former property decreases as neutraliza- tion is raised, while the latter property increases. In general, it may be concluded that the high-humidity curl reten- tion of a given polymeric composition is a complex function of its equilibrium moisture content, moisture transmission rate, and tensile strength.