0 Copyright 1993 American Chemical Society
NOVEMBER 1993 VOLUME 9, NUMBER 11
Letters Reduction of the Friction Coefficient of Liquid Paraffin by Novel Fluorosilicones Masahiko Abe,*J**Kenji Matsuda,t Keizo Ogino,tJ Hideo Sawada,! and Katsuhiro Nishiyamat Faculty of Science and Technology, Science University of Tokyo, 2641 Yamazaki, Noda, Chiba 278, Japan, Institute of Colloid and Interface Science, Science University of Tokyo, 1-3 Kagurazaka, Shinjuku, Tokyo 162, Japan, and Department of Chemistry, Nara National College of Technology, 22 Yata, Yamatokoriyama, Nara 639-11, Japan Received June 11,1993. In Final Form: September 10,199P We have synthesized novel fluorosilicone oligomers having different fluorooxaalkyl chain lengths and siloxane chain lengths, and have measured the reduction of their friction coefficients of liquid paraffii. The fluorosiliconeoligomers were able to reduce the friction coefficient of liquid paraffin from 0.086 to 0.015 (about an 82.6% reduction). Moreover, the friction coefficient was almost independent of the fluorooxaalkylchain lengths, but decreased with increasing siloxane chain lengths. Recently, it has become generally known that, although organosiliconesdissolve in nonaqueoussolution,they show unique physical properties such as heat resistance, chemical resistance, water repellence,and an antifoamingeffect.' On the other hand, organic compounds containing fluorocarbon chains exhibit a good oil repellence. Therefore, the introduction of fluorocarbonchains to organosilicones has become of great interest in recent years.24 In this paper, we report the effectiveness of novel fluorosilicone oligomers in reducing the friction coefficient of liquid paraffin. The fluorosilicone oligomers used in this experiment were synthesized by the reaction of vinyl-containing
* To whom correspondenceshould be addressed at the Faculty of Science and Technology, Science University of Tokyo. t Faculty of Science and Technology,ScienceUniversityof Tokyo. t Institute of Colloid and Interface Science, Science Universityof Tokyo. 8 Department of Chemistry,Nara National Collegeof Technology. Abtractoubhhedin Advance ACSAbstracts. October15.1993. (1) Okemotb, H.Kobunshi 1978,27,677. ( 2 ) Michael, J. 0.;Julianne, G. J. Appl. Polym. Sci. 1990, 40, 789. (3) A b , M.; Matauda, K.; Morikawa, K.; Ogino, K.; Sawada, H.; Mataumoto, T. J . Jpn. Soc. Colour Mater. 1992i65, 760. (4) Sawada, H.; Mitani, M.; Nakayama, M.; Yoshida, M.; Kamigata, N. Polym. Commcln. 1990,31, 63.
dimethylpolysiloxanes(VPS)with bis(fluorooxaalkanoy1) peroxides (FAP) as shown in Scheme I. The synthetic method and preparation of fluorosilicones were followed accordingto our previous methods.= Materialswere three sorts of VPS having different siloxane chain lengths (-(SiO),,-, n = 10,21,63),and fluorooxaalkylatingreagents were two sorts of FAP having different RFgroups (RF= CF(CFS)OCF~CF(CF~)OC$~, CF(CF3)0C$7). The products obtained were polydispersant mixtures of oligomers (M,IM,, > 1)as shown in Table I. A small amount (less than 1.0 w t % 1 of organosilicones (VPSs and/or fluorinated VPSs) was added into liquid paraffin (reagent grade from Shudzui's Pure Chemicals, Tokyo), after which the mixture was vortexed for a few minutes. The dispersion stability of mixtures of liquid paraffin with the VPS was not good, but that with the fluorinated VPS was extremely good. Lubrication effects of samples were tested with a reciprocating sliding apparatus. A schematic diagram of the apparatus for the friction test used in this experiment is shown in Figure 1. Details of this apparatus have been (5) Sawada, H.; Gong, Y-P.;Mataumoto, T.;Nakayama, M.; Ko~ugi, M.; Migita, T. J. Jpn. Oil Chem. SOC.1991,40,730.
0143-7463193/2409-2155$04.00/00 1993 American Chemical Society
2756 Langmuir, Vol. 9,No.11,1993
Letters
Table I. Fluorooxaalkylation of Vinyl-Containing Dimethylpolysiloxane (VPS) with Bis(fluorooxaalkanoy1) Peroxides (FAP) substrate
product Cl+=CH
0
RF-~CH~CH-S;;RF
I
I
Me-Si--fOSiMe2pOSiMe3
0
II I1
Me-Si -( OSiM@
\ OSiM
\0SiMe2pOSiMe3
R+XOG&
OSiMe
a y OSiMa
5
30.0
9600
1.12
94
17 500
2.11
CFOCF2CFoC,F7 I I CF3 CF3
5
30.0
9600
1.12
95
24 400
2.84
CFOQF7
4
24.5
3400
1.34
98
4 400
1.75
4
24.5
3400
1.34
97
14 200
3.06
4
17.9
1790
1.27
98
3 400
1.54
CFOGF7
I
CF3
I
CF3 CFOCF,CFoC,F7
I
CF3
I
CF3
CFOCF2CFGF7
I
CF3
I
CF3
(a) Blank
Scheme I. Fluorooxaalkylationof Vinyl-Containing Dimet hylpolysiloxane (VPS) with Bis( fluorooxaalkanoyl) Peroxides (FAP)
(b) Pure liq.paraffin (c) (b) + Fluorosilicone (n=63)
CHFCH
A
A0SiMez)nOSiMes + ~d~~yOSiMez)nOSiMe,
R&-O$~~
(4 .
. I
.d
Bis(fluoroalkanoy1) peroxide ;FAP
Vinyl-containing dimethyl polysiloxane ; VPS
(n=10,21,63)
40°C l 5 h
CF,ClCFCl,
- ..-"
.
p---
'-
Friction force Base line
F
". - .c 5 10mV=10g weight
Q)
g
RF-(CH2-CH);;;RF \ AOSiMez)nOSiMe3 M;" YOSiMez)nOSiMe3
(b)
--.f-WLSL'
I .-t
(c)
-.-
2-y-C
RF= FOCFz IF, 0 0
Speed control unit
I1
'
FOCiF7 ER '
--E! F,A--:*,.."L.a, ita1 multi meter
Ill
H
2sec.
Figure 2. chart at room temperature. 0.14
electrical
R p CF(CF3)OCF2CF(CF3)OC3F, @ ; Improved
VPS
c)
Motor
Figure 1. Schematic diagram of the apparatus for the friction test.
described in our patent.6 Briefly speaking, the friction coefficients of the stainless ball (SUS 304) pins sliding on a glass plate were measured at a maximum velocity of 1.36 m/min in a reciprocating sliding period, in other words, the smallest change of the plots, at a load of 120 g. Experimental errors were *7%. The sliding distance dependenceon the frictionalcoefficientwas not recognized below at least 2 m. Typical data (electrical chart) obtained from this experiment are shown in Figure 2 (at room temperature). In Figure 2, the bending points and their interval show stationaryand dynamic frictionstates, respectively. When the direction of the friction force changed, the potential, which correspondsto the height from the base line,changed (6) Nomiyama,Y.;Nishiyama,K.; Ab, M.; Mataukawa,K.; Yamanaka, A.; Nakayama, K. Japanese Patent Application No. 78968,1993.
-00.0
0.0 0.2 0.4 0.6 0.8
1.0
2
CONC. of silicone (%)
Figure 3. Comparison of the concentration dependence of the friction coefficient between W S and its fluorooxaalkylated product.
from negative to positive. The friction coefficient ( p ) can be calculated by dividing friction force (F)by the load ( W). As can be seen in Figure 2a, the potential without any liquid is high, resulting in afriction coefficient of 0.15. For the case with pure liquid paraffin (Figure 2b), the friction coefficient became 0.086. It should be noted that the addition of a small amount of fluorosilicone oligomer results in reducing the friction coefficientto 0.015 as shown in Figure 2c.
Letters
Q
:n=21 ;n=63
Q ; n=21
pure liqqaraffin
.-
0.04
o.o+ 0. $0
I
0.2 0.4 0.6 0.8 1.0 1.2 CONC. of silicone (96)
Figure 4. Effecta of fluorooxaalkyl chain length on the friction coefficient.
Figure 3 depicts the relationship between the friction coefficient and organosilicone concentration at room temperature. The friction coefficient was almost independent of VPS (M, = 9600) concentrations, but decreased with increasingfluorinated VPS concentrations, and then showed a minimum in the vicinity of 0.7 wt 9%. Figure 4 shows the effects of fluorooxaalkylchain lengtha in the organosilicones on the friction coefficient at room temperature. Each friction coefficientshowed a minimum value with increasing concentration, but almost no effect of fluorooxaalkyl chain length on the friction coefficient was recognized. Figure 5 demonstrates the effects of siloxane chain lengths in the organosilicones on the friction coefficient
0.02 "02t 0.001 I I I I I 1 1 0 0 .00.0 0.2 0.4 0.6 0.8 1.0 1.2 0.0 0.2 0.4 0.6 0.8 1.0 1.
CONC. of silicone (%)
CONC. of silicone (%)
Figure 6. Comparison of the influence of siloxane chain length on the friction coefficient between VPSs and those fluorooxaakylatad producta.
at room temperature. For the case of VPS, the friction coefficient decrease was quite small with increasing concentration and siloxane chain length. However, in the case of fluorinated VPS, each friction coefficient showed a minimum value with increasing concentration, and then decreased with increasing siloxane chain length. In particular fluorinated VPS containing large amounts of siloxane (n = 63) was especially effective in reducing the friction coefficient. The unique friction coefficient reduction caused by fluorosilicone oligomers cannot be explained in detail at this time. Further studies are in progress, and the results will be published in the near future.
