202 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS q/A-10 9 (C.em -2) -2 -4 -6 (a) Rubbing against PC (b) Rubbing against Teflon Root to Tip Time [rain] Tip to Root Time [mini .2.4. .81.0 Root toT• Time [min] ß . .6 .81.0 Tip to Root Time [min] q/A.iO ½ (C.em -2) 6 (e) Rubbing against Stainless Steel Root to Tip Tip to Root • Decyl ß Dodecyl Q Hexadecyl 0 Steralkonium 00ctadecyl Time [m• .2 .4 .6 .81.0 0 Time [min] .2 .4 .6 .81.0 -2 -4 -6 Figure 6. Kinetic curves of charge generation by rubbing alkyltrimethyl ammonium bromide treated fibers against polycarbonate, teflon, and stainless steel. fibers treated with various long chain alkyl quaternary ammonium salts. Longer chain alkyl quats exhibit much higher ability to increase conductivity than their short chain alkyl analogues. This dependence is similar to the one observed in charging experiments in which long chain alkyl cationic surfactants were found to be more effective in

TRIBeELECTRIC CHARGING OF HAIR 203 modifying electrochemical surface potential. It should also be noted that very fast decays recorded for octadecyltrimethyl ammonium iodide are non-exponential. Lunn and Evans (21) in their study on the mechanism of static charging of hair also measured half times of charge decay and stated that the increase in fiber conductivity produced by treating hair with a creme rinse containing a quat and then rinsing was not sufficient to account for their antistatic action. This may be true, as it is possible that half times of charge decay, even of the order of 1 minute (Table II), could still not be sufficiently small to prevent electrostatic charging under practical combing conditions. Lunn and Evans also evaluated the reduction in combing forces produced by the same treatment and observed that such a decrease is accompanied by reduced electrostatic charging during the passage of a comb through a hair tress. As a result of these observations, they concluded that the mechanism of action of these agents is primarily based on their lubricating effect on hair. In our opinion, however, this explanation ignores the electronic nature of charge transfer phenomena and cannot fully account for the observed features of this process. While reduced combing forces should decrease the rate of charge generation (rate coefficient K in Eq. 7 was found to be dependent upon frictional coefficient and slip velocity), it should not affect the value of the equilibrium charge density cry. This parameter, according to Eq. 10 and as demonstrated by our data, is determined by the difference in work function of the contacting surfaces. A diminished driving force for electron transfer, i.e. a decrease in 02 - 0], and in some cases increased conductivity should thus be responsible for the suppression of static charges in fibers treated with quaternary ammonium salts. EFFECT OF ADSORBED CATIONIC POLYMER Figure 7 shows the kinetic curves of charge generation of hair fibers, treated with PMAPTAC at various concentrations, obtained by rubbing against PC film. In this 0/^.10 9 (C.cm -2) Q/A.10 9 (C. em -2) 7 6 5 3 2 1 0 -2 -3 -4 -5 -6 -7 Root to Tip 7 _......o 6 3 2 Time [mini 1 • I ., ,! - - 0 o.a 0.6 o.8 f. 6 -i -2 - • -6 -7 e 0.001% ß 0.01% 0 O. 1% e 1.0% Tip to Root Time [mini I I : : : --• IX 0.2 0.0, 0.6 0.8 1.0 t ' Figure 7. Kinetic curves of charge generation by rubbing PMAPTAC-treated fibers against polycarbonate.