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Latex deposition on fibers. VI. Deposition state and interaction energy
Latex Deposition on Fibers Vl. Deposition State and Interaction Energy ~
HISASHI TAMAI, YOSHINOBU NAGAI,
AND
TOSHIRO SUZAWA
Department of Applied Chemistry, Faculty of Engineering, Hiroshima University, Senda-machL Naka-ku, Hiroshima, Japan Received March 8, 1982; accepted June 3, 1982 The deposition of polystyrene latex particles on polyamide fiber (Nylon 6) and polyacrylonitrile fiber (Vonnel) was studied by observing the deposited latex particles with a scanning electron microscope as a function of deposition time and pH. The latex particles on Nylon fiber at low pH were connected to each other, e.g., like a rosary, with increasing deposition time. The deposition of the latex particles onto Vonnel fiber seemed to proceed along the many grooves, which were present on the fiber surface, and it was scarcely influenced by pH. On the Nylon fiber, the deposition states as a function of time and pH were conveniently interpreted by the interaction energy estimated from the Hogg, Healy, and Fuerstenau theory using a sphere-plate model and the consideration of the heterogeneous distribution of surface groups of the fiber. On the Vonnel fiber, the interaction energy of electrical double layers calculated by regarding the fiber surface as a plate possessing cylindrical holes correctly accounted for the deposition phenomena. INTRODUCTION
In previous papers (1-5) the deposition of monodispersed latex particles onto various fibers, viz. polyamide fiber (Nylon 6), polyacrylonitrile fiber (Vonnel), polyethylene terephthalate fiber (Tetoron), and cotton fiber, has been reported. We interpreted the deposition phenomena, e.g., deposition rate in terms of the interaction energy estimated using a sphere-plate model by the Hogg, Healy, and Fuerstenau (HHF) theory (6). Those results suggested that the deposition of latex particles on fibers was influenced by the surface characteristics of the fiber, in addition to the interaction energy. Regarding the deposition of colloidal particles onto solid surface, in addition to the estimated energy of interaction by HHF the1 This paper is Part VI in a series "Interfacial electrical studies on the deposition of polymer latexes onto fabrics and the removal of these deposited latexes." Part V: H. Tamai, A. Hamada, and T. Suzawa, J. Colloid Interface Sci. 88, 378 (1982).
ory, the influence of the roughness of solid surface has been treated by Marshall and Kitchener (7), and the influence of charge heterogeneity has been treated by Hull and Kitchener (8). Boughey et al. (9) have suggested that the deposition of polystyrene latex particles on Nylon fiber is influenced by a polyelectrolyte type layer on the Nylon surface. Considering these points of view, the authors thought that it is important to study the relation between the deposition phenomena of latex particles on fibers and the fiber surface. For this subject, it was thought that one effective method is to determine the depositing state of the latex particles as a function of time and the interaction energy between a latex particle and fibers. In this study, the depositing states of polystyrene latex particles on Nylon and Vonnel fiber were observed with a scanning electron microscope, and they were studied as a function of time and pH. Further, the change of coverage of fibers by the latex particles was also obtained.
464 0021-9797/83/020464-08503.00/0 Copyright© 1983by AcademicPress,Inc.
All rightsof reproductionin any formreserved.
Journalof Colloidand InterfaceScience,Vol.91, No. 2, February1983
465
D E P O S I T I O N OF L A T E X O N FIBERS
It is reported that the deposition on Nylon is conveniently interpreted by the interaction energy estimated by using a sphere-plate model and the consideration of heterogeneous distribution of surface groups of the fiber, and that the deposition on Vonnel is favorably interpreted by the interaction energy of electrical double layers calculated by regarding the fiber surface as a plate possessing cylindrical holes. EXPERIMENTAL
Materials . Styrene was distilled three times under reduced pressure and potassium persulfate was recrystallized twice from water. Sodium chloride, sodium l~ydroxide, and hydrochloric acid were all analytical grade materials and were used without further purification. Distilled and deionized water was used throughout the experiments. The polystyrene latex particles were prepared in the absence of emulsifier (10) and purified by the procedure described previously (1, 2). The average diameter of latex particles was 0.607 #m with electron microscopy. Two kinds of fabrics, viz. polyamide fiber (Nylon 6; Toyobo Co., Ltd.) and polyacrylonitrile fiber (Vonnel; Mitsubishi Rayon Co., Ltd.) were used as fibers after purification by the procedure described previously (2).
Methods Latex deposition. Five grams of weighed fabric (about 1 x 2-cm cloths) was immersed in a 200 ml latex dispersion (1 g/liter solid content) adjusted to required pH. The deposition was carded out without stirring or rotating. Two cloths were withdrawn at each deposition time after immersion of fabric, and these withdrawn cloths were rinsed instantly with the solution of the same composition (pH and electrolyte concentration) without latex particles for 1 rain to remove undeposited free particles. In order to con-
sider the state of latex particles deposited on fibers, these cloths were observed with a scanning electron microscope (JEOL JSM T-20) after air drying. The deposition experiments were carried out in various pH dispersions of latex at 10 -3 constant ionic strength. The pH was varied with hydrochloric acid and sodium hydroxide. The ionic strength was adjusted with aqueous sodium chloride. Coverage. From the scanning electron micrographs of fiber mentioned above, the number of deposited particles was determined by counting the deposited particles per 10 X 10 ~m area of the fiber surface. This counting was carried out at 4 to 10 different places on the fiber, and the average number of deposited particles N was calculated. The coverage was expressed in the form of the fractional coverage 0. According to Vincent et al. (11), O was obtained by N/Nmax, where Nmax is the maximum number of latex particles that can be accommodated in a hexagonal close-packed array on the 10 X 10 #m area of the fiber surface. ~-Potential. In order to investigate the interaction energy of electrical double layers between latex particles and fiber, ~'-potentials of latex particles and fibers were measured as a function of pH at I 0 -3 constant ionic strength and 25°C by the methods of microelectrophoresis and streaming potential (1, 2), respectively. R ES U LTS
State of Latex Particles Figure 1 shows typical scanning electron micrographs of Nylon fiber deposited with polystyrene latex particles at pH 3.0 as a function of deposition time. Figure 2 shows those of Vonnel fiber at pH 11.0. These photographs demonstrate that the deposition behavior of the latex particles on these two kinds of fibers is obviously different at the initial stage of deposition. As shown in Fig. 1, the latex particles deposit on Nylon fiber connected to each other, e.g., like a rosary, Journal of Colloid and Interface Science, Vol. 91, No. 2, February 1983
466
TAMAI, NAGAI, AND SUZAWA
FIG. 1. Scanning electron micrographs of Nylon fiber deposited with latex particles as a function of time at pH 3.0, 25°C, and 10-3 ionic strength. (A) 10 rnin; (B) 20 min; (C) 30 min; (D) 40 min; (E) 50 min; (F) 60 rain.
with increasing deposition time. The deposition of latex particles on Vonnel fiber proceeds along the m a n y grooves which are present on the fiber surface, with increasing deposition time. Though the photographs are not shown for various pH, the deposition state o f latex particles on Vonnel fiber was scarcely influenced by pH. On the other hand, the depositing Journal of Colloid and Interface Science, Vol. 91, No. 2, February 1983
latex particles on N y l o n fiber decreased with increasing pH. It is necessary to consider the influence of the rinse by the solution without latex particles on the deposition state, because the deposited latex particles m a y be removed by a rinse. The fibers after deposition were observed without the rinse. Those results were almost the same as those m e n t i o n e d above.
DEPOSITION OF LATEX ON FIBERS
467
FIG. 2. Scanning electron micrographs of Vonnel fiber deposited with latex particles as a function of time at pH 11.0, 25°C, and 10-3 ionic strength. (A) 10 rain; (B) 20 min; (C) 30 rain; (D) 40 min; (E) 50 min; (F) 60 min.
Coverage Figure 3 shows the fractional coverage 0 of Nylon fiber with the latex particles at the constant ionic strength l0 -3 as a function o f time and pH. The coverage of Nylon fiber with the latex particles reaches a constant value with increasing deposition time at p H 3.0. The coverage o f Nylon fiber decreases
with increasing pH, and the latex particles scarcely deposit at high alkaline pH. As shown in Fig. 4, the initial coverage o f Vonnel fiber scarcely changes with increasing pH.
F-Potential Figure 5 shows ~'-potentials of polystyrene latex particles and two kinds o f fibers at the Journal of Colloid and Interface Science, Vol. 91, No. 2, February 1983
468
TAMAI, N A G A I , A N D S U Z A W A
-10C - 8C
0.6
0.5 0.4
~~
- 6c > ~ - 4c ,¢x - 2(
~o.3 ~0.2 0.1 1
2 3 time(hr)
constant ionic strength 10 -3 as a function of pH. ~'-Potentials of the latex particles are negative at all pH, and approximate the constant value with increasing pH. ~'-Potentials of Nylon fiber are positive in an acidic solution and negative in an alkaline one, and the isoelectric point is pH 4.0. ~'-Potentials of Vonnel fiber are negative at all pH, and the negative values increase with increasing pH. DISCUSSION
Since the surface of a Nylon fiber has acidic groups and basic groups, viz - C O O H and -NH2, respectively, a Nylon fiber possesses an isoelectric point. At either more acidic or alkaline pH than the isoelectric point, the surface charge and potential will be influenced by the dissociation equilibria of these surface groups. As the isoelectric point of Nylon fiber used in this study is pH 4.0, the scanning electron micrographs shown in Fig. 1 show the deposition state of the latex particles on Nylon
o
aQ w _
6
FIG. 3. Coverage o f Nylon fiber with latex particles as a function o f time a n d p H at 10 -3 ionic strength a n d 25°C. ©, p H 3.0; B, p H 4.0; A, p H 5.7.
O.E 0.5 0.4 ~0,3
0 q ~ O -~ ?
o
8 0.2
0.1 time(hr) FIG. 4. Coverage of Vonnel fiber with latex particles as a function of time a n d p H at 10 -3 ionic strength a n d 25°C. O, p H 3.0; n , p H 5.7; A, p H 11.0. Journal of Colloid and Interface Science, Vol. 91, No. 2, February 1983
pH FIG. 5. ~'-Potentials of fibers a n d latex particles as a function o f p H at 10 -3 ionic strength a n d 25°C. ©, Nylon; A, Vonnel; 0 , latex particles.
fiber under the condition that the surface potentials of Nylon fiber and the latex particles are opposite in sign as shown in Fig. 5. Under this condition, the number of positively charged sites (-NH~-) on the fiber surface is more than that of the negative sites (-CO0-). Supposing that the distribution of these positive and negative sites is heterogeneous, the results shown in Fig. 1 may be interpreted. That is to say, the latex particles will deposit readily on the surface which has more positive sites than other surfaces, and, as a result of this effect, the latex particles may deposit on Nylon fiber connected to each other, e.g., like a rosary, with increasing deposition time. As shown in Fig. 3, the coverage of Nylo n fiber decreases with increasing pH. From the results of ~'-potentials of Nylon fiber and the latex particles shown in Fig. 5, this behavior is mainly influenced by the change of surface potential, which is due to the dissociation equilibria of the surface groups of the Nylon fiber. Hogg et al. (6) have shown that interaction energy of electrical double layers between parallel planes--Vwis expressed by the following equation [ 1], ~K
V = ~ [ ( ~ + ~])(1 - coth Kd) + 2~1~b2 cosech ~d]
[1]
D E P O S I T I O N O F L A T E X O N FIBERS
3001
,,' 52 ",
20o
~10C
pH5.7"-..
"..~ "'."-.
,
100
Ho(,&)
200
FIG. 6. Total interaction energy between latex particles a n d fibers as a function of p H a n d separation distance at 10 -3 ionic strength a n d 25°C. - - - , Nylon; ..... , Vonnel.
where ~ is the dielectric constant, K is the Debye-Hiickel parameter, ¢/ is surface potential and d is the distance between two planes. As described in the previous paper (4), the interaction energy of electrical double layers between a sphere (a latex particle) and plate (fiber surface)--VE--WaS estimated by using the expression derived from Eq. [ 1]. VE was calculated by using f-potentials shown in Fig. 5 as surface potentials of the latex particles and the fibers. The interaction energy of van tier Waals forces between a latex particle and the fiber-VA--WaS calculated by the equation described by Hamaker (12). The Hamaker constant was calculated by the procedure described in the previous papers (1, 2). In these calculations, the value of the Hamaker constant for polystyrene in water used was 5 × 10 -21 J (13), and those for Nylon and Vonnel were 4.1 × 10-2o and 6.1 × 10 -20 J (1, 2), respectively. The total interaction energy between a latex particle and the fiber-- VT--was obtained by the summation of VE and VA. The results of VT are shown in Fig. 6. Since VTbetween Nylon fiber and the latex particles is attractive at a pH lower than the isoelectric point of Nylon fiber and is repulsive at higher pH, these Vv explain roughly that the coverage of Nylon fiber decreases
469
with increasing pH. However, the latex particles deposit on Nylon fiber at pH 5.7 in spite of the large Vv. This phenomenon cannot be explained precisely only by VT. This experimental result may be explained more successfully by supposing a heterogeneous distribution of surface groups of the Nylon fiber mentioned above. This supposition may be substantiated by the fact that the rosarylike deposition of the latex particles decreases with increasing pH, though these scanning electron micrographs are not illustrated in this report. On the other hand, the coverage of Vonnel fiber is scarcely influenced by pH, although Vx increases with increasing pH as shown in Fig. 6. Thus the coverage of Vonnel fiber as a function of pH cannot be explained by VT obtained using the equations mentioned above. This may be attributed to VE calculated by assuming the fiber surface of Vonnel as a plane. That is to say, VE between the latex partic!es and Vonnel fiber may be influenced by many grooves which are present on the fiber surface as shown in Fig. 2. Consequently, we attempted to estimate VE between the latex particles and the fiber surface which has many grooves. In order to simplify and facilitate the calculation of VE, many grooves were approximated by the cylindrical holes. When the plate, i.e., fiber surface, possesses a cylindrical hole as shown in Fig. 7, the interaction energy of electrical double layers between a sphere and plate--V~-may be assumed to be made up of contributions from infinitesimally small parallel tings each of which can be considered as a flat plate from r to infinity with respect to h.
FIG. 7. Model used for the calculation o f the interaction energy o f electrical double layers between spheres a n d plate which possesses a cylindrical hole. Journal of Colloid and Interface Science, Vol. 91, No. 2, February 1983
470
TAMAI, NAGAI, AND SUZAWA
V~
=
50O
oo
i
[2]
2~rhVdh
400
300
where V is defined by Eq. [ 1], h is the radius of the ring as shown in Fig. 7, and r is the radius of a cylindrical hole. In a similar m a n ner as described by Derjaguin (14), from the geometry of Fig. 7,
~2oo
-
o -}00
o
H = Ho + a - f ~ - h 2.
h dH
=
,6o
[3]
Differentiation yields [4]
dh
-222==:
H~(/~)
2~o
FIG. 8. Interaction energy of electrical double layers between latex particlesand Vonnel fiber calculated using the model shown in Fig. 7 as a function of separation distance and radius of a cylindrical hole (r) against the radius of latex particles (a) at 10-3 ionic strength, pH 5.7, and 25°C. - - , r = 0; ..... , r = a/6; - - - - - , r = a/4; . . . .
, r = a/2.
which, for a ,> h, reduces to
Substituting for V~ =
[5]
adtI
= hdh.
hdh
in Eq. [2], then
f.
+a-J,2-r2
[6]
2~raVdH.
Ho is identical to the distance d between the planes in Eq. [ 1] so that the above integral can be evaluated analytically giving V~ ~-- ~ -
(1~¢12Jr ~ )
In
exp2K(Ho + a - ~ ×
r 2) - - 1
exp2r(Ho+a-~-r
2)
+2~1
energy VT shown in Fig. 6 is m u c h larger than VA. The results are shown in Fig. 9 as a function of r and the separation distance H0. With increasing r, V~ decreases remarkably similarly to V~, and F~ b e c o m e even negative values when r is equal to one-half of the radius of a latex particle. In this case, therefore, the latex particles are supposed to deposit readily on Vonnel fiber. Consequently, it m a y be interpreted conveniently by the above-mentioned model of plate possessing cylindrical holes that the deposition o f the latex particles on Vonnel fiber proceeds along the m a n y grooves, which
expK(H0 + a - ~/~ - r 2) _+ 11 ×~k~lnexpr(H0+a
V~
r 2)
1 " [7] 20(
between the latex particles and Vonnel fiber was calculated using Eq. [7]. Figure 8 shows the results at p H 5.7 as a function of r and the separation distance Ho. V~ decreases remarkably with increasing r. F r o m these V~ and VA calculated by the equation described above, the total interaction ene r g y - - V ~ - was obtained. The influence of the grooves on VA m u s t be also considered. However, VA between a sphere and plate was used in this study, because the influence o f the large repulsive VE on the total interaction Journal of Colloid and Interface Science,
Vol. 91, No. 2, February1983
~10(
"~'~
"'"-. "
0 -I00
f"
i _ I00 H.(~,)
---Z'.~=
200
FIG. 9. Total interaction energy between latex particles and Vonnel fiber calculated using the model shown in radius of a cylindrical hole (r) against the radius of latex particles (a) at 10-3 ionic strength, pH 5.7 and 25°C. - - . , r = 0; ..... , r = a/6; - - - - - , r = a/4; ....
,r=a/2.
DEPOSITION OF LATEX ON FIBERS
are present on the fiber surface. In addition, it is also understandable that the initial coverage of Vonnel fiber scarcely changes by pH as shown in Fig. 4. REFERENCES 1. Suzawa, T., Tamai, H., Shirahama, H., and Yamamoto, K., Nippon Kagaku Kaishi 1979, 16. 2. Tamai, H., Hakozaki, T., and Suzawa, T., Colloid Polym. Sci. 258, 870 (1980). 3. Tamai, H., and Suzawa, T., ColloidPolym. Sci. 259, 1100 (1981). 4. Tamai, H., and Suzawa, T., J. Colloid Interface Sci. 88, 372 (1982). 5. Tamai, H., Hamada, A., and Suzawa, T., J. Colloid Interface Sci. 88, 378 (1982).
471
6. Hogg, R., Healy, T. W., and Fuerstenau, D. W., Trans. Faraday Soc. 62, 1638 (1966). 7. Marshall, J. K., and Kitchener, J. A., J. Colloid Interface Sci. 22, 342 (1966). 8. Hull, M., and Kitchener, J. A., Trans. Faraday Soc. 65, 3093 (1969). 9. Boughey, M. T., Duchworth, R. M., Lips, A., and Smith, A. L., J. Chem. Soc. Faraday Trans. 174, 2200 (1978). 10. Kotera, A., Furusawa, K,, and Takeda, Y., KolloidZ. 239, 677 (1970). 11. Vincent, B., Young, C. A., and Tadros Th. F., Faraday Disc. Chem. Soc. 65, 296 (1978). 12. Hamaker, H. C,, Physica 4, 1058 (1937). 13. Ottewill, R. H., and Shaw, J. N., Disc. Faraday Soc. 42, 154 (1966). 14. Derjaguin, B. V., Kolloid-Z. 69, 155 (1934); Acta Physicochim. 10, 333 (1939).
Journal of Colloid and Interface Science, Vol. 91, No. 2, February 1983
HISASHI TAMAI, YOSHINOBU NAGAI,
AND
TOSHIRO SUZAWA
Department of Applied Chemistry, Faculty of Engineering, Hiroshima University, Senda-machL Naka-ku, Hiroshima, Japan Received March 8, 1982; accepted June 3, 1982 The deposition of polystyrene latex particles on polyamide fiber (Nylon 6) and polyacrylonitrile fiber (Vonnel) was studied by observing the deposited latex particles with a scanning electron microscope as a function of deposition time and pH. The latex particles on Nylon fiber at low pH were connected to each other, e.g., like a rosary, with increasing deposition time. The deposition of the latex particles onto Vonnel fiber seemed to proceed along the many grooves, which were present on the fiber surface, and it was scarcely influenced by pH. On the Nylon fiber, the deposition states as a function of time and pH were conveniently interpreted by the interaction energy estimated from the Hogg, Healy, and Fuerstenau theory using a sphere-plate model and the consideration of the heterogeneous distribution of surface groups of the fiber. On the Vonnel fiber, the interaction energy of electrical double layers calculated by regarding the fiber surface as a plate possessing cylindrical holes correctly accounted for the deposition phenomena. INTRODUCTION
In previous papers (1-5) the deposition of monodispersed latex particles onto various fibers, viz. polyamide fiber (Nylon 6), polyacrylonitrile fiber (Vonnel), polyethylene terephthalate fiber (Tetoron), and cotton fiber, has been reported. We interpreted the deposition phenomena, e.g., deposition rate in terms of the interaction energy estimated using a sphere-plate model by the Hogg, Healy, and Fuerstenau (HHF) theory (6). Those results suggested that the deposition of latex particles on fibers was influenced by the surface characteristics of the fiber, in addition to the interaction energy. Regarding the deposition of colloidal particles onto solid surface, in addition to the estimated energy of interaction by HHF the1 This paper is Part VI in a series "Interfacial electrical studies on the deposition of polymer latexes onto fabrics and the removal of these deposited latexes." Part V: H. Tamai, A. Hamada, and T. Suzawa, J. Colloid Interface Sci. 88, 378 (1982).
ory, the influence of the roughness of solid surface has been treated by Marshall and Kitchener (7), and the influence of charge heterogeneity has been treated by Hull and Kitchener (8). Boughey et al. (9) have suggested that the deposition of polystyrene latex particles on Nylon fiber is influenced by a polyelectrolyte type layer on the Nylon surface. Considering these points of view, the authors thought that it is important to study the relation between the deposition phenomena of latex particles on fibers and the fiber surface. For this subject, it was thought that one effective method is to determine the depositing state of the latex particles as a function of time and the interaction energy between a latex particle and fibers. In this study, the depositing states of polystyrene latex particles on Nylon and Vonnel fiber were observed with a scanning electron microscope, and they were studied as a function of time and pH. Further, the change of coverage of fibers by the latex particles was also obtained.
464 0021-9797/83/020464-08503.00/0 Copyright© 1983by AcademicPress,Inc.
All rightsof reproductionin any formreserved.
Journalof Colloidand InterfaceScience,Vol.91, No. 2, February1983
465
D E P O S I T I O N OF L A T E X O N FIBERS
It is reported that the deposition on Nylon is conveniently interpreted by the interaction energy estimated by using a sphere-plate model and the consideration of heterogeneous distribution of surface groups of the fiber, and that the deposition on Vonnel is favorably interpreted by the interaction energy of electrical double layers calculated by regarding the fiber surface as a plate possessing cylindrical holes. EXPERIMENTAL
Materials . Styrene was distilled three times under reduced pressure and potassium persulfate was recrystallized twice from water. Sodium chloride, sodium l~ydroxide, and hydrochloric acid were all analytical grade materials and were used without further purification. Distilled and deionized water was used throughout the experiments. The polystyrene latex particles were prepared in the absence of emulsifier (10) and purified by the procedure described previously (1, 2). The average diameter of latex particles was 0.607 #m with electron microscopy. Two kinds of fabrics, viz. polyamide fiber (Nylon 6; Toyobo Co., Ltd.) and polyacrylonitrile fiber (Vonnel; Mitsubishi Rayon Co., Ltd.) were used as fibers after purification by the procedure described previously (2).
Methods Latex deposition. Five grams of weighed fabric (about 1 x 2-cm cloths) was immersed in a 200 ml latex dispersion (1 g/liter solid content) adjusted to required pH. The deposition was carded out without stirring or rotating. Two cloths were withdrawn at each deposition time after immersion of fabric, and these withdrawn cloths were rinsed instantly with the solution of the same composition (pH and electrolyte concentration) without latex particles for 1 rain to remove undeposited free particles. In order to con-
sider the state of latex particles deposited on fibers, these cloths were observed with a scanning electron microscope (JEOL JSM T-20) after air drying. The deposition experiments were carried out in various pH dispersions of latex at 10 -3 constant ionic strength. The pH was varied with hydrochloric acid and sodium hydroxide. The ionic strength was adjusted with aqueous sodium chloride. Coverage. From the scanning electron micrographs of fiber mentioned above, the number of deposited particles was determined by counting the deposited particles per 10 X 10 ~m area of the fiber surface. This counting was carried out at 4 to 10 different places on the fiber, and the average number of deposited particles N was calculated. The coverage was expressed in the form of the fractional coverage 0. According to Vincent et al. (11), O was obtained by N/Nmax, where Nmax is the maximum number of latex particles that can be accommodated in a hexagonal close-packed array on the 10 X 10 #m area of the fiber surface. ~-Potential. In order to investigate the interaction energy of electrical double layers between latex particles and fiber, ~'-potentials of latex particles and fibers were measured as a function of pH at I 0 -3 constant ionic strength and 25°C by the methods of microelectrophoresis and streaming potential (1, 2), respectively. R ES U LTS
State of Latex Particles Figure 1 shows typical scanning electron micrographs of Nylon fiber deposited with polystyrene latex particles at pH 3.0 as a function of deposition time. Figure 2 shows those of Vonnel fiber at pH 11.0. These photographs demonstrate that the deposition behavior of the latex particles on these two kinds of fibers is obviously different at the initial stage of deposition. As shown in Fig. 1, the latex particles deposit on Nylon fiber connected to each other, e.g., like a rosary, Journal of Colloid and Interface Science, Vol. 91, No. 2, February 1983
466
TAMAI, NAGAI, AND SUZAWA
FIG. 1. Scanning electron micrographs of Nylon fiber deposited with latex particles as a function of time at pH 3.0, 25°C, and 10-3 ionic strength. (A) 10 rnin; (B) 20 min; (C) 30 min; (D) 40 min; (E) 50 min; (F) 60 rain.
with increasing deposition time. The deposition of latex particles on Vonnel fiber proceeds along the m a n y grooves which are present on the fiber surface, with increasing deposition time. Though the photographs are not shown for various pH, the deposition state o f latex particles on Vonnel fiber was scarcely influenced by pH. On the other hand, the depositing Journal of Colloid and Interface Science, Vol. 91, No. 2, February 1983
latex particles on N y l o n fiber decreased with increasing pH. It is necessary to consider the influence of the rinse by the solution without latex particles on the deposition state, because the deposited latex particles m a y be removed by a rinse. The fibers after deposition were observed without the rinse. Those results were almost the same as those m e n t i o n e d above.
DEPOSITION OF LATEX ON FIBERS
467
FIG. 2. Scanning electron micrographs of Vonnel fiber deposited with latex particles as a function of time at pH 11.0, 25°C, and 10-3 ionic strength. (A) 10 rain; (B) 20 min; (C) 30 rain; (D) 40 min; (E) 50 min; (F) 60 min.
Coverage Figure 3 shows the fractional coverage 0 of Nylon fiber with the latex particles at the constant ionic strength l0 -3 as a function o f time and pH. The coverage of Nylon fiber with the latex particles reaches a constant value with increasing deposition time at p H 3.0. The coverage o f Nylon fiber decreases
with increasing pH, and the latex particles scarcely deposit at high alkaline pH. As shown in Fig. 4, the initial coverage o f Vonnel fiber scarcely changes with increasing pH.
F-Potential Figure 5 shows ~'-potentials of polystyrene latex particles and two kinds o f fibers at the Journal of Colloid and Interface Science, Vol. 91, No. 2, February 1983
468
TAMAI, N A G A I , A N D S U Z A W A
-10C - 8C
0.6
0.5 0.4
~~
- 6c > ~ - 4c ,¢x - 2(
~o.3 ~0.2 0.1 1
2 3 time(hr)
constant ionic strength 10 -3 as a function of pH. ~'-Potentials of the latex particles are negative at all pH, and approximate the constant value with increasing pH. ~'-Potentials of Nylon fiber are positive in an acidic solution and negative in an alkaline one, and the isoelectric point is pH 4.0. ~'-Potentials of Vonnel fiber are negative at all pH, and the negative values increase with increasing pH. DISCUSSION
Since the surface of a Nylon fiber has acidic groups and basic groups, viz - C O O H and -NH2, respectively, a Nylon fiber possesses an isoelectric point. At either more acidic or alkaline pH than the isoelectric point, the surface charge and potential will be influenced by the dissociation equilibria of these surface groups. As the isoelectric point of Nylon fiber used in this study is pH 4.0, the scanning electron micrographs shown in Fig. 1 show the deposition state of the latex particles on Nylon
o
aQ w _
6
FIG. 3. Coverage o f Nylon fiber with latex particles as a function o f time a n d p H at 10 -3 ionic strength a n d 25°C. ©, p H 3.0; B, p H 4.0; A, p H 5.7.
O.E 0.5 0.4 ~0,3
0 q ~ O -~ ?
o
8 0.2
0.1 time(hr) FIG. 4. Coverage of Vonnel fiber with latex particles as a function of time a n d p H at 10 -3 ionic strength a n d 25°C. O, p H 3.0; n , p H 5.7; A, p H 11.0. Journal of Colloid and Interface Science, Vol. 91, No. 2, February 1983
pH FIG. 5. ~'-Potentials of fibers a n d latex particles as a function o f p H at 10 -3 ionic strength a n d 25°C. ©, Nylon; A, Vonnel; 0 , latex particles.
fiber under the condition that the surface potentials of Nylon fiber and the latex particles are opposite in sign as shown in Fig. 5. Under this condition, the number of positively charged sites (-NH~-) on the fiber surface is more than that of the negative sites (-CO0-). Supposing that the distribution of these positive and negative sites is heterogeneous, the results shown in Fig. 1 may be interpreted. That is to say, the latex particles will deposit readily on the surface which has more positive sites than other surfaces, and, as a result of this effect, the latex particles may deposit on Nylon fiber connected to each other, e.g., like a rosary, with increasing deposition time. As shown in Fig. 3, the coverage of Nylo n fiber decreases with increasing pH. From the results of ~'-potentials of Nylon fiber and the latex particles shown in Fig. 5, this behavior is mainly influenced by the change of surface potential, which is due to the dissociation equilibria of the surface groups of the Nylon fiber. Hogg et al. (6) have shown that interaction energy of electrical double layers between parallel planes--Vwis expressed by the following equation [ 1], ~K
V = ~ [ ( ~ + ~])(1 - coth Kd) + 2~1~b2 cosech ~d]
[1]
D E P O S I T I O N O F L A T E X O N FIBERS
3001
,,' 52 ",
20o
~10C
pH5.7"-..
"..~ "'."-.
,
100
Ho(,&)
200
FIG. 6. Total interaction energy between latex particles a n d fibers as a function of p H a n d separation distance at 10 -3 ionic strength a n d 25°C. - - - , Nylon; ..... , Vonnel.
where ~ is the dielectric constant, K is the Debye-Hiickel parameter, ¢/ is surface potential and d is the distance between two planes. As described in the previous paper (4), the interaction energy of electrical double layers between a sphere (a latex particle) and plate (fiber surface)--VE--WaS estimated by using the expression derived from Eq. [ 1]. VE was calculated by using f-potentials shown in Fig. 5 as surface potentials of the latex particles and the fibers. The interaction energy of van tier Waals forces between a latex particle and the fiber-VA--WaS calculated by the equation described by Hamaker (12). The Hamaker constant was calculated by the procedure described in the previous papers (1, 2). In these calculations, the value of the Hamaker constant for polystyrene in water used was 5 × 10 -21 J (13), and those for Nylon and Vonnel were 4.1 × 10-2o and 6.1 × 10 -20 J (1, 2), respectively. The total interaction energy between a latex particle and the fiber-- VT--was obtained by the summation of VE and VA. The results of VT are shown in Fig. 6. Since VTbetween Nylon fiber and the latex particles is attractive at a pH lower than the isoelectric point of Nylon fiber and is repulsive at higher pH, these Vv explain roughly that the coverage of Nylon fiber decreases
469
with increasing pH. However, the latex particles deposit on Nylon fiber at pH 5.7 in spite of the large Vv. This phenomenon cannot be explained precisely only by VT. This experimental result may be explained more successfully by supposing a heterogeneous distribution of surface groups of the Nylon fiber mentioned above. This supposition may be substantiated by the fact that the rosarylike deposition of the latex particles decreases with increasing pH, though these scanning electron micrographs are not illustrated in this report. On the other hand, the coverage of Vonnel fiber is scarcely influenced by pH, although Vx increases with increasing pH as shown in Fig. 6. Thus the coverage of Vonnel fiber as a function of pH cannot be explained by VT obtained using the equations mentioned above. This may be attributed to VE calculated by assuming the fiber surface of Vonnel as a plane. That is to say, VE between the latex partic!es and Vonnel fiber may be influenced by many grooves which are present on the fiber surface as shown in Fig. 2. Consequently, we attempted to estimate VE between the latex particles and the fiber surface which has many grooves. In order to simplify and facilitate the calculation of VE, many grooves were approximated by the cylindrical holes. When the plate, i.e., fiber surface, possesses a cylindrical hole as shown in Fig. 7, the interaction energy of electrical double layers between a sphere and plate--V~-may be assumed to be made up of contributions from infinitesimally small parallel tings each of which can be considered as a flat plate from r to infinity with respect to h.
FIG. 7. Model used for the calculation o f the interaction energy o f electrical double layers between spheres a n d plate which possesses a cylindrical hole. Journal of Colloid and Interface Science, Vol. 91, No. 2, February 1983
470
TAMAI, NAGAI, AND SUZAWA
V~
=
50O
oo
i
[2]
2~rhVdh
400
300
where V is defined by Eq. [ 1], h is the radius of the ring as shown in Fig. 7, and r is the radius of a cylindrical hole. In a similar m a n ner as described by Derjaguin (14), from the geometry of Fig. 7,
~2oo
-
o -}00
o
H = Ho + a - f ~ - h 2.
h dH
=
,6o
[3]
Differentiation yields [4]
dh
-222==:
H~(/~)
2~o
FIG. 8. Interaction energy of electrical double layers between latex particlesand Vonnel fiber calculated using the model shown in Fig. 7 as a function of separation distance and radius of a cylindrical hole (r) against the radius of latex particles (a) at 10-3 ionic strength, pH 5.7, and 25°C. - - , r = 0; ..... , r = a/6; - - - - - , r = a/4; . . . .
, r = a/2.
which, for a ,> h, reduces to
Substituting for V~ =
[5]
adtI
= hdh.
hdh
in Eq. [2], then
f.
+a-J,2-r2
[6]
2~raVdH.
Ho is identical to the distance d between the planes in Eq. [ 1] so that the above integral can be evaluated analytically giving V~ ~-- ~ -
(1~¢12Jr ~ )
In
exp2K(Ho + a - ~ ×
r 2) - - 1
exp2r(Ho+a-~-r
2)
+2~1
energy VT shown in Fig. 6 is m u c h larger than VA. The results are shown in Fig. 9 as a function of r and the separation distance H0. With increasing r, V~ decreases remarkably similarly to V~, and F~ b e c o m e even negative values when r is equal to one-half of the radius of a latex particle. In this case, therefore, the latex particles are supposed to deposit readily on Vonnel fiber. Consequently, it m a y be interpreted conveniently by the above-mentioned model of plate possessing cylindrical holes that the deposition o f the latex particles on Vonnel fiber proceeds along the m a n y grooves, which
expK(H0 + a - ~/~ - r 2) _+ 11 ×~k~lnexpr(H0+a
V~
r 2)
1 " [7] 20(
between the latex particles and Vonnel fiber was calculated using Eq. [7]. Figure 8 shows the results at p H 5.7 as a function of r and the separation distance Ho. V~ decreases remarkably with increasing r. F r o m these V~ and VA calculated by the equation described above, the total interaction ene r g y - - V ~ - was obtained. The influence of the grooves on VA m u s t be also considered. However, VA between a sphere and plate was used in this study, because the influence o f the large repulsive VE on the total interaction Journal of Colloid and Interface Science,
Vol. 91, No. 2, February1983
~10(
"~'~
"'"-. "
0 -I00
f"
i _ I00 H.(~,)
---Z'.~=
200
FIG. 9. Total interaction energy between latex particles and Vonnel fiber calculated using the model shown in radius of a cylindrical hole (r) against the radius of latex particles (a) at 10-3 ionic strength, pH 5.7 and 25°C. - - . , r = 0; ..... , r = a/6; - - - - - , r = a/4; ....
,r=a/2.
DEPOSITION OF LATEX ON FIBERS
are present on the fiber surface. In addition, it is also understandable that the initial coverage of Vonnel fiber scarcely changes by pH as shown in Fig. 4. REFERENCES 1. Suzawa, T., Tamai, H., Shirahama, H., and Yamamoto, K., Nippon Kagaku Kaishi 1979, 16. 2. Tamai, H., Hakozaki, T., and Suzawa, T., Colloid Polym. Sci. 258, 870 (1980). 3. Tamai, H., and Suzawa, T., ColloidPolym. Sci. 259, 1100 (1981). 4. Tamai, H., and Suzawa, T., J. Colloid Interface Sci. 88, 372 (1982). 5. Tamai, H., Hamada, A., and Suzawa, T., J. Colloid Interface Sci. 88, 378 (1982).
471
6. Hogg, R., Healy, T. W., and Fuerstenau, D. W., Trans. Faraday Soc. 62, 1638 (1966). 7. Marshall, J. K., and Kitchener, J. A., J. Colloid Interface Sci. 22, 342 (1966). 8. Hull, M., and Kitchener, J. A., Trans. Faraday Soc. 65, 3093 (1969). 9. Boughey, M. T., Duchworth, R. M., Lips, A., and Smith, A. L., J. Chem. Soc. Faraday Trans. 174, 2200 (1978). 10. Kotera, A., Furusawa, K,, and Takeda, Y., KolloidZ. 239, 677 (1970). 11. Vincent, B., Young, C. A., and Tadros Th. F., Faraday Disc. Chem. Soc. 65, 296 (1978). 12. Hamaker, H. C,, Physica 4, 1058 (1937). 13. Ottewill, R. H., and Shaw, J. N., Disc. Faraday Soc. 42, 154 (1966). 14. Derjaguin, B. V., Kolloid-Z. 69, 155 (1934); Acta Physicochim. 10, 333 (1939).
Journal of Colloid and Interface Science, Vol. 91, No. 2, February 1983