(65) Vol. 41, No. 5 (1985) T-211 - JST
Transcript of (65) Vol. 41, No. 5 (1985) T-211 - JST
(65) Vol. 41, No. 5 (1985) T-211
Technical Section
(Received July 10, 1984)
THE COEFFICIENTS OF FRICTION OF VARIOUS FIBERS
BY ROEDER'S METHOD
By Waichiro Tsuji, Kyoko Yoshida and Shigeko Asahara
(Faculty of Home Economics, Mukogawa Women's University, Ikebiraki-cho, Nishinomiya, Hyogo Pref., 663 Japan)
Synopsis
The static and kinetic coefficients of friction of various fibers were systematically measured by Roeder's method at the velocity ranging from 0 to 20m/min. Fibers tested were viscose rayon, cupra, polynosic, acetate, nylon 4, nylon 6, nylon 11, Nomex, Kevlar, polyester, alkali treated
polyester, polyethylene, polypropylene, vinylon having cocoon-like or circular cross-section, silk, and wool, respectively. In order to confirm the effect of shape of cross-section, the coefficients of friction of polyester and nylon filaments having various shapes such as circular, trilobal, pentagonal,
pentalobal and octalobal were also measured. All fibers tested except wool moved in scale direction, showed similar relation of the coefficient of friction with the circumferential velocity of the cylinder, i.e. the value decreased with increasing velocity at the initial stage and showed a minimum at the velocity 1m/min., gradually increased and levelled off at around 10 to 20m/min. Wool gave different values depending on the direction of rubbing. The effect of alkali treatment of polyester fiber was also examined.
Introduction
The coefficient of friction of fiber is the im
portant property related either to spinning and weaving processes and to the handling touch of textile fiber and fabric. Although various methods of measuring the coefficient of friction have been reported, the method developed by Roeder1)
possesses many advantages as following;(1) The construction of the apparatus is simple.(2) Short staple fiber can be used as sample.(3) The quantity of sample fiber required is small.(4) Both static and kinetic coefficients of friction
can be measured by the same apparatus.
(5) Kinetic coefficient of friction can be measured at various velocities.
(6) Reproducibility of data is high.(7) By selecting the material of the cylinder, the
coefficient of friction of fiber to any other material can be measured. Tsuji2) has already constructed the apparatus,
examined Roeder's method and particularly discussed on the measurement of the static coeffi
cient of friction.
In recent years, many kinds of new fiber have
been developed, however, the coefficient of fric
tion of these new fibers measured systematically
by the same apparatus seems not to be reported.
In this work, the static and kinetic fiber-to-fiber
coefficients of friction of various fibers including
such new fibers were measured using Roeder's
method and effects of fiber structure were dis
cussed.
Experimental
Measurement of the Coefficient of Friction
The experimental apparatus of Roeder's method
used in this research is schematically shown in
Figure 1. The surface of a short cylinder made of
bakelite, diameter of which is 8mm, is covered in
the following way with fibers arranged parallel to
the cylinder axis.
Short cut fibers are arranged parallel on a paper
frame and both ends of the parallel laid fibers are
fixed to the paper frame with adhesive tape. This
parallel fiber layer is wound around the cylinder
T-212 SEN-I GAKKAISHI (•ñ•¶) (66)
Fig. 1. The schematic diagram of the apparatus
of Roeder's method.
and fixed with adhesive tape. This short cylinder,
covered with fibers parallel to the cylinder axis,
is fixed to the end of a shaft which can be rotated
at different velocities by gear change mechanism.
One filament is hung transversely over the
cylinder hanging 100 mg weight on both fiber
ends. The weight of one end is fixed to the hook
of a torsion balance. Test condition was deter
mined referring to JIS L 1074-1977 which desig
nated Roeder's apparatus to measure the coefficient
of friction of synthetic fibers.
For measuring the static coefficient of friction,
the cylinder is not rotated and the arm of the
torsion balance is moved until the filament start
to slip. The indication of the torsion balance
(a mg) is read. For measuring the kinetic coeffi
cient of friction, the cylinder is rotated at the
circumferential velocities of 1, 2, 5, 10 and 20
m/min., and the arm of torsion balance is moved
to keep the hook of the torsion balance at rest.
The indication at this equilibrium state (a mg)
is read.
In this way the static and kinetic coefficient of
friction can be calculated by the classical formula
T1=T0exp(ƒÊƒÆ), where ƒÊ is the coefficient of
friction, ƒÆ=ƒÎ, T1=100mg, T0=(100-a)mg in
this case. In each one series of experiment three
cylinders covered with fibers were used and for
each cylinder ten filaments were tested. Total
number of measurements were thirty, and an
average value and standard deviation were calcu
lated. Most experiments were carried out at about
20•Ž and 55-65% RH.
Experiment on Wool
Sample fibers except wool are long filament,
but wool fiber is too short to hang a single fiber
over the cylinder. Therefore, one filament of Kevlar was attached by adhesive to each end of a wool fiber and carried out the measurement contacting the part of wool with the cylinder and hanging 200mg weight on each end of Kevlar filament. As wool fiber has crimps, it is difficult to cover evenly the cylinder, so in this case the cylinder was covered with degummed silk filaments, and the initial load of 200mg was hung to each end of Kevlar filament to extend the crimps of wool fiber contacting with the cylinder.
As well known, wool fiber has scale on the surface and the frictional force depends on the direction of the rubbing motion (the differential frictional effect). Therefore, in the experiments on wool, the direction of wool fiber hung on the cylinder was reversed after one series of experiment and measurements were repeated.Experiment on Polyethylene Monofilament
As the polyethylene monofilament (50 d) was thick, the initial load of 200mg was applied. The kinetic coefficient of friction could be measured by this apparatus, although the variation of coefficient value was larger than those of other fibers. In the measurement of the static coefficient of friction, the initial load larger than 200mg seemed to be needed to obtain even data, but it was inconvenient to use such a large initial load in this apparatus. Then another method3) was used as follows.
As shown in Figure 2, over the two polyethylene monofilaments parallel laid under tension T, one
polyethylene filament was laid across at right angle and weights T0 were hung at each end. Then the weight at one end was gradually increased by
Fig. 2. The experimental method used for the
measurement of the static coefficient of
friction of polyethylene monofilament.
(67) Vol. 41, No. 5 (1985) T-213
adding additional loads carefully by hand, and the
load T1 was measured at which the filament
started to slip. The static coefficient of friction
was calculated by the following formula.
T1=T0exp(ƒÊƒÎ). In this case, the weights of
20 and 1g were used as T and T0, respectively.
Scouring of the Sample Fibers
Most sample fibers were extracted by benzene
ethanol mixture (wt. ratio 1:1) for 10 hours using
Soxhlet's extractor. Acetate, nylon 4 and poly
ethylene were scoured by benzene-ethanol mixture
at room temperature and in 0.3-1.0% aqueous
solution of Monogen (sodium sulfate of higher
alcohol) at 40•Ž for 1 hour. Polypropylene was
extracted by benzene-ethanol mixture at room
temperature for 6 hours. Wool was scoured with
aqueous solution of Monogen at 40•Ž.
Degumming of Silk
Raw silk was immersed into warm water for
30 minutes and treated with aqueous solution of
soap (15-20% owf, liquor ratio 30-50:1) at
about 95•Ž for 1-2 hours. Further treatment was
given with new aqueous solution of soap (10-15%
owf) at about 95•Ž for 1 hour and washed 2-3
times with 0.1% aqueous solution of sodium
carbonate. The weight decrease in degumming
was 22%.
Causticizing (Alkali Treatment) of Polyester Fiber
As the finishing method to increase the pliability
of the fabric, the treatments with NaOH aqueous
solution at high temperature are sometimes given
to polyester fabrics. The surface of the polyester
fiber is partially hydrolized, the weight of the
fabric decreased and pliability of the fabric in
creased. To examine the effect of this treatment
on the coefficient of friction, polyester filament
(2.5 d) was treated with 5% NaOH aqueous solu
tion at 98•Ž for 10, 20, 30 and 40 minutes. The
weight decreases were 7.50, 12.68, 19.26 and
25.47%, respectively.
Results and Discussion
1. The Coefficients of Friction of Various Fibers
The static and kinetic coefficients of friction
measured by the methods above described are
shown in the following tables and figures.
Rayon and Acetate. As shown in Table 1 and
Figure 3, the coefficients of friction of viscose
rayon, cupra, polynosic and acetate show similar
relation with the circumferential velocity of
cylinder. Minimum value appears at low velocity
(1m/min.). This is presumed to be the result of
the boundary contribution to the friction which
decreases at high velocity, and the viscodynamic
contribution which increases at high velocity.
Similar behaviors are seen in all other following
fibers except wool rubbed in scale direction.
Viscose rayon and polynosic showed nearly the
Fig. 3. Coefficients of friction of rayon and
acetate.
•› Viscose rayon •¢ Cupra
•¬ Polynosic • Acetate
Table 1. Coefficients of friction of rayon and acetate.
a) Tufcel made by Toyobo Co.
T-214 SEN-I GAKKAISHI (•ñ•¶) (68)
Table 2. Coefficients of friction of nylon and polyester fibers.
same values of coefficients of friction. Cupra gave
somewhat higher values. Acetate showed lower
values at low velocity. It may be caused by the
decrease of intermolecular attraction force dues
to the substitution of hydroxyl groups by acetyl
groups.
Synthetic Fibers. The results for various ali
phatic and aromatic nylons are shown in Table 2 and Figure 4. Among three kinds of aliphatic
nylon, nylon 4 gave the highest value of coefficient
of friction and nylon 11 showed the lowest value.
It seemed that the increase of the number of
methylene group contributed to the decrease of
the coefficient of friction.
Aromatic nylons, Nomex and Kevlar, gave lower
values than aliphatic nylon. The results for poly
ester fiber are also shown. The values came
between those of nylon 6 and 4.
Some polyolefin and vinyl fibers gave the results
shown in Table 3 and Figure 5. The coefficients
of friction of polyethylene filament were markedly
Fig. 4. Coefficients of friction of nylon and
polyester fibers.
•› Nylon 4 •œNylon 6 •¬ Nylon 11
•£ Nomex •¬ Kevlar • Polyester
low as was expected. On the other hand, it was
noted that the values for polypropylene fiber
were high.
Acrylic and ordinary vinylon (polyvinyl alcohol
fiber partially acetalized with formaldehyde) fila
ments gave values similar to nylon 6. Vinylon
Table 3. Coefficients of friction of polyolefin and vinyl fibers.
a) The static coefficient of polyethylene monofilament was measured by the hanging weight method 3).b) Pewlon Filament made by Asahi Kasei Co .c) Ordinary vinylon made by Kuraray Co .; the degree of formalization is 27.5 mole%.d) Vinylon filament having circular cross-section made by Kuraray Co. using the coagulating bath
containing alkali and sodium sulfate; formalization is not given.
(69) Vol. 41, No. 5 (1985) T-215
Fig. 5. Coefficients of friction of polyolefin and
vinyl fibers.
•¢ Polyethylene •› Polypropylene
• Acrylic •¬ Vinylon (cocoon-like)
•¬ Vinylon (circular)
Fig. 6. Coefficients of friction of silk and wool.
•¢ Silk (degummed)
•œ Wool (scale direction)
•› Wool (anti-scale direction)
Table 4. Coefficients of friction of silk and wool.
a) Rubbed against the degummed silk filament.
filament having circular cross-section showed lower
values than that of ordinary vinylon which had
cocoon-like cross-section.
The results obtained for silk and wool fibers are
shown in Table 4 and Figure 6. The static coef
ficient of friction of silk is lower than various
nylon and polyester fibers, but the kinetic
coefficients are rather high.
As above described, wool fiber shows the
differential frictional effect. Therefore, in the
experiments on wool fibers sliding on the cylinder
covered with degummed silk, each wool fiber
hung on the cylinder was reversed its direction
and the measurement was repeated. As shown in
Table 4, the values obtained were separated dis
tinctly into high and low values at each cylinder
velocity. Thereupon, it was presumed that the
high values corresponded to the anti-scale direction.
The static coefficient in scale direction is lower
than kinetic coefficient. This is only one ex
ception among all fibers used in this study.
The reason is unknown at present.
The coefficients of variation of the measured
values were generally low (about 5% or less) for
all fibers except polyethylene monofilament, for
which the values exceeded 10% in some case of
measuring the kinetic coefficient as described
above.
2. Causticized (Alkali Treated) Polyester Fiber
Polyester filaments (2.5 d) were treated with
5% NaOH aqueous solution at 98•Ž. The results
obtained are shown in Table 5 and Figure 7.
The coefficients of friction decreased at first
with the increase of the treating time. Minimum
values were seen at the treating time of 20-30
minutes, and afterward the coefficients increased
with the increase of the treating time.
Electron micrographs (Figure 8) show the ero
sion on fiber surface increases with the increase
of treating time. The roughness of the fiber surface
especially increases when the treating time exceeds
30 minutes. Some literature4, 5) described that
T-216 SEN-I GAKKAISHI (•ñ•¶) (70)
Table 5. Coefficients of friction of the causticized (alkali treated) polyester fiber.
a) 5% NaOH aqueous solution at 98•Ž.
Fig. 7. Coefficients of friction of the causticized
(alkali treated) polyester fiber.
Treating times:
•› 0min. •¬ 10min. •¬ 20min.
• 30min. •¢ 40min.
the increase of the roughness of surface decreased the friction. It may be presumed that in above case the roughness of the fiber surface decreases the coefficient of friction until it reaches to some extent. The coefficients of variation of the values of the coefficient of friction increased distinctly at the treating time over 30 minutes (Table 6).3. Polyester and Nylon Fibers Having Different
Shapes of Cross-SectionThe results shown in Table 7 and Figure 9 were
obtained on the polyester and nylon filaments which had various fiber cross-sections.
In both cases, the coefficients of friction remarkably decreased between circular and pentalobal cross-sections, and then the decrease was little in the case of fibers with more complicated cross-section. This roughness effect is seemed to be similar to the case of the alkali treated polyester fiber as above described. The coefficients of variation of the measured values of the coefficient of friction were generally low as shown in Table 8.
Table 6. Coefficients of variation of the coefficient of friction of the causticized
(alkali treated) polyester fiber (%).
a) 5% NaOH aqueous solution at 98•Ž.
(71) Vol. 41, No. 5 (1985) T-217
Fig. 8. Electron micrographs of the polyester filaments causticized (alkali treated) with
5% NaOH aqueous solution at 98•Ž for various minutes. Sample filaments are
the same as described in Table 5 and Fig. 7. (Taken by Prof. Y. Fujiwara at
our faculty).
T-218 SEN-I GAKKAISHI (•ñ•¶) (72)
Fig. 7. Coefficients of friction of the polyester and nylon fibers having different shapes
of cross-section.
a) Dyeable with basic dyes (semidull) .b) Dyeable with disperse dyes (* semidull
, ** superbright).
c) Containing no anti -static agent.d) Containing anti-static agent .
Fig. 9-1. Coefficients of friction of the polyester
fibers having different shapes of cross
section (corresponding to polyester I in
Table 7).
•› Circular •¢ Trilobal • Pentagonal
•ž Pentalobal •¬ Octalobal
Fig. 9-2. Coefficients of friction of the polyester
fibers having different shapes of cross
section (corresponding to polyester II in
Table 7).
•› Circular •¢ Trilobal •ž Pentalobal
•¬ Octalobal
Fig. 9-3. Coefficients of friction of the nylon
fibers having different shapes of cross
section (corresponding to nylon I in
Table 7).
•› Circular •¢ Trigonal (T type, 3d.)
• Trilobal (Y type)
•ž Trigonal (T type, 30d.)
Fig. 9-4. Coefficients of friction of the nylon
fibers having different shapes of cross
section (corresponding to nylon II in
Table 7).
•› Circular •¢ Trigonal (T type)
• Pentalobal
(73) Vol. 41, No. 5 (1985) T-219
Table 8. Coefficients of variation of the coefficient of friction of the polyester and nylon fibers having different shapes of cross-section (%).
a) Dyeable with basic dyes (semidull) .b) Dyeable with disperse dyes (* semidull , ** superbright).
c) Containing no anti-static agent .d) Containing anti-static agent .
Conclusions
The static and kinetic coefficients of friction
of various fibers were measured by Roeder's
method. The circumferential velocities of the small
cylinder covered with fibers laid parallel to the cylinder axis were changed between 0 and 20
m/min. One filament of the same fiber was hung
transversely on the cylinder and the coefficients
of friction of fiber-to-fiber crossed at right angle were measured.
All fibers tested except wool moved in scale
direction showed similar relation of the coefficient
of friction with the circumferential velocity of the cylinder. Minimum value appeared at low velocity
(1m/min.).Acetate showed somewhat low coefficient of
friction at low velocity compared with viscose rayon, polynosic and cupra. Among three kinds
of aliphatic nylon, nylon 4 showed fairly higher
coefficient than nylon 6, and the values for nylon 11 were somewhat lower than nylon 6. Aromatic
nylons, Nomex and Kevlar, gave lower values than
those of aliphatic nylons. The values for polyester fiber came between nylon 4 and 6.
Polyethylene filament showed markedly low
coefficient. On the contrary, polypropylene gave high values. Acrylic and polyvinyl alcohol fiber
with cocoon-like fiber cross-section showed values
similar to nylon 6. The values for polyvinyl alcohol
fiber with circular cross-section were lower than
those.The coefficients of friction of the degummed
silk were lower than polyester and nylon 6 at low
velocity, but were higher at high velocity. The coefficients of wool were divided distinctly into
high and low values at each velocity according to
the direction of rubbing (differential frictional
effect).By the NaOH treatment the coefficients of
polyester fiber decreased at first until the treating time of about 30 minutes, but when the treating time exceeded this, the erosion of the fiber surface
became severe and the coefficients increased. Polyester and nylon fibers having different shapes
of cross-section were examined. The fibers with
circular cross-section showed the highest values of coefficient. The values decreased when the shapes
of fiber cross-section became more complicated.
Acknowledgment: The authors wish to express
appreciation to Toray Co., Kuraray Co. and Toyobo Co. for the presentation of the fiber
samples.
This paper was presented at the Annual Meeting
of the Japan Research Association for Textile End-Use, June 2, 1983, Okayama, Japan.
T-220 SEN-I GAKKAISHI (•ñ•¶) (74)
References
1) H. L. Roeder, J. Textile Inst., 44, T247 (1953).
2) W. Tsuji and M. Imai, Annual Rep. Inst. Chem. Fibers, Kyoto Univ., 14, 53 (1957).
3) I. Sakurada and W. Tsuji, Rayon World
(Jinkenkai), 7, 620 (1939).
4) H. G. Howell, K. W. Mieszkis and D. Tabor,
•g Friction in Textiles•h, Butterworths Scientific
Publications, London, p. 74 (1959).
5) F. L. Scardino and W. J. Lyons, Textile Res. J.,
37, 874 (1967).
レーダー法 による種 々の繊維 の摩擦係 数
武庫用女子大学家政学部 辻 和一郎,吉 田恭子,浅 原成子
種 々の 繊維 の静 的 及び動 的 摩 擦係数 を レー ダー法 によ
り, 0~20m/min.の 範 囲 で 系統的 に測定 した。 繊維 は,
ヴ ィス コー ス レー ヨ ン,キ ュプ ラ,ポ リノ ジ ック,ア セ
テー ト,ナ イ ロ ン4, 6, 11,ノ ーメ ッ クス,ケ プ ラー,
ポリ エス テル,ア ル カ リ処 理 ポ リエ ス テル,ポ リエチ レ
ン,ポ リプ ロ ピレ ン,ま ゆ型 また は 円型断 面 を もつ ビニ
ロ ン,絹 及 び羊 毛を 用 いた 。断 面 の形 状効 果 を み るた め
に,種 々の 形状(円,ト リローバ ル,ペ ンタゴ ナル,ぺ
ンタ ローバ ル,オ ク タ ローバ ル)を もつ ポ リエ ステル お
よ びナ イ ロン単 繊維 も測定 した 。用 い た すべ て の 繊維 は,
ス ケー ル の方 向 に測定 した羊毛 を除 き,摩 擦 係 数 と シ リ
ンダー 表 面 速度 の間 に は筒 じよ う な関係 が あ った。 す な
わ ち,値 は 速度 の増加 と と もに初 期 に 減少 し, 1m/min.
で最小 値 を 示 し,徐 々に増 加 し, 10~20m/min.で 飽和
した 。 羊毛 の摩 擦 方 向 によ り値 が 異 った。 ポ リエ ステル
繊 維 の アル カ リ処 理 につ い て も検 討 した。