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Surface tension of silane treated natural zeolite
Materials Chemistry and Physics 63 (2000) 251±255
Surface tension of silane treated natural zeolite J.Y. Leea, S.H. Leeb, S.W. Kima,*
b
a Department of Chemical Engineering, The University of Seoul, 90 Jeonnong-Dong, Dongdaemun-Gu, Seoul, 130-743, South Korea Department of Environmental Engineering, Anyang University, 708-113 Anyang 5-Dong, Manan-Gu, Anyang City, Kyungki-Do 430-714, South Korea
Received 14 May 1999; received in revised form 30 September 1999; accepted 20 October 1999
Abstract To investigate the surface tension of the natural zeolite to be used in polymer composites, wicking method was employed on the base of Washburn's equation and that of the zeolite treated with 0.5 wt.% -aminopropyltriethoxysilane ( -APS) was also studied and compared. LW AB The apolar component SV of the untreated natural zeolite was 19.22 mJ/m2 and the polar one, SV was 15.27 mJ/m2. The polar component 2 LW AB LW
SV of the treated zeolite with 0.5 wt.% -APS was 27.08 mJ/m and the polar one SV was 12.23 mJ/m2. The value of SV component AB increased, while that of SV component decreased with -APS treatment and it was due to the increasing effect of alkyl group (hydrophobic) in -APS coupled on the zeolite surface. # 2000 Elsevier Science S.A. All rights reserved. Keywords: Natural zeolite; Surface tension; Silane coupling agent; Wicking method
1. Introduction Many researchers have investigated to characterize the surface of clay minerals and polymer matrix, and the interface between them in order to use the clay minerals as inorganic ®llers in polymer composite, paint, cosmetic, etc., and they have found that the surface of solid materials are divided into two categories [1±4]. One is hydrophilic solid whose surface tension is high and the other is hydrophobic solid whose surface tension is low [5±7]. To facilitate the adhesion of two different materials, the apolar surface should be modi®ed into a high-energy polar surface or the polar surface should be changed to apolar surface by a number of modifying methods. So, the information about solid surface tension is very important for better insight in the processes occurring at the interfaces, both in pure and applied science. To get the surface characteristics of solids, the contact angle method has been used. When a liquid drop is put on the solid surface at equilibrium as shown in Fig. 1, the interfacial tensions of solid/liquid, SL solid/vapor, SV, and liquid vapor, LV are expressed by the following Young's equation [8±11].
LV cos SL ÿ SV
(1)
where, is contact angle. However, the contact angle for a particle can't be measured by the same method in Fig. 1. To * Corresponding author. Tel.: 82-2-2210-2447; fax: 82-2210-2310. E-mail address: [email protected] (S.W. Kim).
get the contact angle formed between a liquid and a fine powder, column wicking method is used at constant temperature by determining the rate of penetration of probe liquids (usually methylene iodide, water and formamide) through the packed beds of the powder, using the following Washburn's equation [8,11]. h2
tR LV cos 2
(2)
where, h(cm) is the penetrated distance of the probe liquid in a selected time t(sec), R(cm) is the effective interstitial pore radius between the packed particles in column and (cP) is the viscosity of the probe liquid. Eq. (2) has a fundamental dif®culty that there are two unknowns (R and cos). So, R should be ascertained independently before determining the cos and this dif®culty can be easily solved by using the spreading liquids which can completely wet the solid surface, so that the contact angle 0, that is cos 1. Generally, n-alkanes are used as spreading liquids and Eq. (2) can be changed as follows [2,8]. R
2h2 =t
LV
(3)
After ascertaining the value of R, the contact angle for each probe liquid with the solid powder is calculated via Eq. (2) and the surface tension can be determined. Inorganic materials of many species such as silica, alumina, talc, mica, etc. have been investigated to characterize
0254-0584/00/$ ± see front matter # 2000 Elsevier Science S.A. All rights reserved. PII: S 0 2 5 4 - 0 5 8 4 ( 9 9 ) 0 0 2 3 1 - X
252
J.Y. Lee et al. / Materials Chemistry and Physics 63 (2000) 251±255
Fig. 1. Contact angles between liquid and solid surface.
the surface tension, however, we can ®nd few papers concerned with natural zeolite. In this study, the surface tension of a natural zeolite was studied to use as an inorganic ®ller in epoxy composites [12]. It is well-known that zeolite are crystalline aluminosilicate minerals whose surface areas are so high due to the channels and pores in which metal ions are located [13±15]. To improve the wettability between the epoxy matrix and the inorganic ®ller, the natural zeolite was treated with silane coupling agent and the effect of silane treatment on the surface characteristics was investigated. 2. Experiment The natural zeolite from Kampo area in Korea was found to be a clinoptilolite type zeolite whose average particle size was 9.89 mm. -aminopropyltriethoxysilane (A-1100, APS) was supplied by Union Carbide and the formulation was H2 Nÿ CH2 3 ÿSiÿ OC2 H5 3 ÿaminopropyltriethoxysilane The silane treatment process of the natural zeolite was as follows. 0.5 wt.% silane coupling agent to the natural zeolite was hydrolyzed in the mixture of ethanol/water 95/5 (vol%) for 15 min at room temperature, and then the natural zeolite was treated with the hydrolyzed solutions for 30 min at 508C and dried for 24 h at 1208C. The dried zeolite was ground and sieved into 325 mesh under. They were stored at desiccator to prevent water molecules from being adsorbed. The sample was analyzed by FT-IR spectroscopy at a resolution of 2 cmÿ1 from 4000 cmÿ1 to 400 cmÿ1. Column wicking experiment was carried out in the following manner. Glass tube with 100 mm long and 9 mm diameter was plugged at the bottom with a small wad of cotton wool. 3 g of well-dried zeolite powder was ®lled into the tube with the packing height of 7 cm by means of a hypodermic syringe. The packed zeolite was wicked with n-hexane to promote further settling and the tube was vertically placed in an oven at 1108C overnight to remove the hexane. Wicking was done with n-alkanes (hexane, heptane, octane and decane), methylene iodide, water and formamide at 208C, and the penetration rates of the liquids were measured.
Fig. 2. Plots of h2 versus t obtained by wicking with n-alkanes on the untreated natural zeolite.
3. Results and discussion Fig. 2 shows the penetrated distances squared, h2 as a function of time, t for untreated natural zeolite wicked with a series of n-alkanes. The linear relationship between h2 and t in Eq. (2) should go precisely through the origin. However, all lines do not so in practice, and it would appear in most cases owing to various hydrodynamic disturbances at the moment of immersion [8]. So, the best approach is to make a plot of h2 versus t as shows in Fig. 2. n-Alkanes are known as spreading liquids whose contact angles with a solid surface is 0, that is cos 1. To determine the value of R, the surface tension components,
LV and the viscosities, of n-alkanes in Table 1 are joined to Eq. (3) and the relationships between 2h2/t and LV are displayed in Fig. 3. This shows the straight line and the value of R is obtained from the slope, which is 6.10 10ÿ5 cm. The contact angles between the untreated natural zeolite and the probe liquids in Eq. (2) are obtained from each slope of the straight line in Fig. 4 by joining the value of R and the data of Table 2. The contact angles for methylene iodide, water and formamide are 76.78, 68.88 and 54.28, respectively. The relationships between 2h2/t and LV for the liquids (nonspreading liquids) are compared with those of nalkanes in Fig. 3 and they fail to meet with the straight line of the spreading n-alkanes. So, it is found that only Table 1 LW ÿ Viscosity, LV, LV , LV and LV of n-Alkanes at 208C [8] n-Alkanes
(cP)
LV (mJ/m2)
LW
LV (mJ/m2)
AB
LV (mJ/m2)
LV (mJ/m2)
ÿ
LV (mJ/m2)
n-Hexane n-Heptane n-Octane n-Decane
0.326 0.409 0.542 0.907
18.4 20.1 21.6 23.8
18.4 20.1 21.6 23.8
0 0 0 0
0 0 0 0
0 0 0 0
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253
The Lewis acid component, SV acts as an electron acceptor ÿ is electron donor site and the Lewis base component, SV site [9,11]. To get the values of these components, the values of the probe liquids in Table 2 were applied to Eq. (4) [9]. Methylene iodide was used as a probe liquid to determine LW component of the zeolite surface tension, and water the SV ÿ and SV components. and formamide were for SV q q LW LW ÿ
SV LV
SV
LV 1 cos 2 LV q ÿ (4) SV LV
Fig. 3. 2h2/t versus LV for wicking with n-alkanes and probe liquids on the untreated natural zeolite.
LW ÿ , LV and LV for Using the contact angle 76.78, LV 2 LW methylene iodide in Table 2, SV 19.22 mJ/m was cal ÿ and SV values, two culated from Eq. (4). To determine SV equations from Eq. (4) for water and formamide were rewritten and the solutions of the equations were ÿ 4.28 mJ/m2 and SV 13.63 mJ/m2. The polar com SV 2 AB ponent, SV is 15.27 mJ/m obtained from Eq. (5) and the total surface tension is calculated from Eq. (6) and it is 34.49 mJ/m2. qp AB ÿ (5) 2 SV
SV
SV LW AB SV
SV SV
(6)
The apolar component is a little larger than the polar and this means that the characterization of the untreated natural zeolite surface is some hydrophobic. It is interesting that this result is different from the general surface characteristics of zeolites whose surface is hydrophilic due to the hydroxyl groups located on the surface of the zeolite in the form of Al-OH, Si-OH, etc. This result may be attributable to the decomposition of the zeolite structure by grinding. Work of adhesion between solid and liquid was proposed by Dupre as follows [16]. WSL SV LV ÿ SL 2
Fig. 4. Plots of h versus t obtained by wicking with probe liquids on the untreated natural zeolite.
spreading liquids must be used to determine the value of R and it is due that the spreading liquids appear to pre-wet the solid surfaces over which they are subsequently spreading [8]. It has been well-known that the surface tension of a solid, LW for
SV consists of Lifshitz-van der Waals component, SV AB for polar. apolar and the Lewis acid-base component, SV Table 2 LW ÿ , LV and LV of probe liquids at 208C [8] Viscosity, LV, LV Probe liquids
LW AB ÿ (cP) LV
LV
LV
LV
LV 2 2 2 2 (mJ/m ) (mJ/m ) (mJ/m ) (mJ/m ) (mJ/m2)
Methylene iodide 2.80 Water 1.00 Formamide 4.55
50.8 72.8 58.0
50.8 21.8 39.0
0 51.0 19.0
0 25.5 2.28
0 25.5 39.6
(7)
Combining Eqs. (1) and (7), we can get the well-known Young±Dupre equation [16] and the work of adhesion between the untreated natural zeolite and the probe liquids is calculated. WSL LV 1 cos
(8)
Those values of WSL for water and formamide (polar liquids) are 99.13 mJ/m2 and 91.93 mJ/m2 and that for methylene iodide (apolar liquid) is 62.49 mJ/m2. Fig. 5 shows the penetrated distances squared, h2 as a function of time, t obtained by wicking of a series of nalkanes on 0.5 wt.% -APS treated natural zeolite. The slopes for all n-alkanes are wholly decreased compared with those of untreated natural zeolite and the trend of slope is similar. The values of Table 1 are joined to Eq. (3) to determine the value of R and the relationships between 2h2/ t and LV are displayed in Fig. 6. The value of R calculated from the slope is 3.72 10ÿ5 cm.
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J.Y. Lee et al. / Materials Chemistry and Physics 63 (2000) 251±255
Fig. 5. Plots of h2 versus t obtained by wicking with n-alkanes on the natural zeolite treated with 0.5 wt.% -APS.
Fig. 7. Plots of h2 versus t obtained by wicking with probe liquids on natural zeolite treated with 0.5 wt.% -APS.
To get the contact angles between the 0.5 wt.% -APS treated natural zeolite and the probe liquids by using Eq. (2), each slope of the straight line in Fig. 7 are joined to R value and the data in Table 2. The contact angles for methylene iodide, water and formamide are 62.68, 68.48 and 64.28, respectively. LW , LV and By introducing the contact angle 62.68, LV ÿ
LV of methylene iodide on Table 2, to Eq. (4), the apolar LW component, LV 27.08 mJ/m2 was obtained and the polar ÿ 9.09 mJ/m2 components, SV 4.12 mJ/m2 and SV were also obtained from Table 2 and Eq. (4). By substituting ÿ AB the value of SV and SV to Eq. (5), SV 12.23 mJ/m2 was obtained and the total surface tension, SV 39.31 mJ/m2 is calculated from Eq. (6). The apolar component is 2.2 times as large as the polar component and this means that the
characterization of the surface of 0.5 wt.% -APS treated natural zeolite is hydrophobic. Work of adhesion, WSL for water and formamide (polar liquids) are 99.60 mJ/m2 and 83.24 mJ/m2 and that for methylene iodide (apolar liquid) is 74.18 mJ/m2. The surface tension components for the zeolite are put LW component increased, together on Table 3. The value of SV AB while that of SV component decreased with -APS treatment. It is due to that the surface of the zeolite is more affected by alkyl group (hydrophobic) than amine or hydroxyl groups (hydrophilic) as shown in Fig. 8. Fig. 8A shows the FT-IR spectra of the natural zeolite. The strongest vibrations in the range of 1294±837 cmÿ1 are for the internal tetrahedron symmetric stretch of Si (or Al)O. The Si (or Al)-O bending appears at 474.1 cmÿ1 and the band of 525.4 cmÿ1 is related to the presence of the double rings in the framework structures. The band of H2O bending is observed at 1635 cmÿ1, the band of hydrogen-bonded OH is shown at 3453.2 cmÿ1 and the sharp band of isolated OH is shown at 3645.5 cmÿ1. The effect of -APS treatment is shown in Fig. 8B. The characteristic peaks mentioned above are similar in two spectra, however, the new bands appeared at 3187 cmÿ1 and 1697 cmÿ1 which are related to the presence of amine groups in -APS. Therefore, it was found that the surface of the zeolite is coupled with -APS, so the surface tension was affected by alkyl group and amine or hydroxyl groups explained above. Table 3 Surface, tension components for the natural zeolite at 208C
Fig. 6. 2h2/t versus LV for wicking with n-alkanes and probe liquids on natural zeolite treated with 0.5 wt.% -APS.
Samples
LW AB ÿ
LV
LV
LV
LV
LV (mJ/m2) (mJ/m2) (mJ/m2) (mJ/m2) (mJ/m2)
Untreated zeolite
-APS treated zeolite
34.49 39.31
19.22 27.08
15.27 12.23
4.28 4.12
13.63 9.09
J.Y. Lee et al. / Materials Chemistry and Physics 63 (2000) 251±255
255
Fig. 8. FT-IR spectra of natural zeolite untreated (A) and treated (B) with 0.5 wt.% -Aps.
4. Conclusions
References
The effects of -APS treatment on the surface tension of the natural zeolite used for polymer composites were studied by wicking method using the Washburn's equation. The components of surface tension for the LW 19.22 mJ/m2, SV 4.28 mJ/ natural zeolite were SV 2 2 ÿ AB m , SV 13.63 mJ/m , SV 15.27 mJ/m2 and SV 34.49 mJ/m2. Those for the -APS treated zeolite were LW ÿ 27.08 mJ/m2, SV 4.12 mJ/m2, SV 9.09 mJ/
SV 2 2 AB m , SV 12.23 mJ/m and SV 39.31 mJ/m2. The LW AB component increased, while that of SV value of SV component decreased with -APS treatment. It was due to that the surface of the zeolite was more affected by alkyl group (hydrophobic) than amine or hydroxyl groups (hydrophilic).
[1] H. Malandrini, F. Clauss, S. Partyka, J.M. Douillard, J. Colloid Interface Sci. 194 (1997) 183. [2] A. Ontiveros-Ortega, M. Espinosa-Jim nez, E. Chibowski, F. Gonz lez-Caballero, J. Colloid Interface Sci. 202 (1998) 189. [3] G. Fourche, Polym. Eng. Sci. 35 (1995) 957. [4] W. Wu, R.F Giese Jr., C.J. Van Oss, Powder Tech. 89 (1996) 129. [5] E. Chibowski, J. Adhesion Sci. Tech. 6 (1992) 1069. [6] C.J. Wu, C.Y. Chen, E. Woo, J.F. Kuo, J. Polym. Sci. Part A: Polym. Chem. 31 (1993) 3405. [7] J.S. Shukla, S.C. Tewari, G.K. Sharma, J. Appl. Polym. Sci. 34 (1987) 191. [8] C.J. Van Oss, R.F. Giese, Z. Li, K. Murphy, J. Norris, M.K. Chaudhury, R.J. Good, in: K.L. Mittal (Ed.), Contact Angle, Wettability and Adhesion, VSP, 1993, p. 269. [9] R.J. Good, in: K.L. Mittal, (Ed.), Contact Angle, Wettability and Adhesion, VSP, 1993, p. 3. [10] M. Salou, S. Yamazaki, N. Nishimiya, K. Tsutsumi, Colloids Surfaces A: Physicochem. Eng. Aspects 139 (1998) 299. [11] E. Chibowski, in: K.L. Mittal (Ed.), Contact Angle, Wettability and Adhesion, VSP, 1993, p. 64. [12] J.Y. Lee, M.J. Shim, S.W. Kim, Mater. Chem. Phys. 48 (1997) 36. [13] H.K. Lee, M.J. Shim, J.S. Lee, S.W. Kim, Mater. Phys. 44 (1996) 79. [14] B.C. Lee, C.H. Cho, J. Ind. Eng. Chem. 4 (1998) 298. [15] J.R. Sohn, J.H. Park, J. Ind. Eng. Chem. 4 (1998) 308. [16] M.E. Schrader, Langmuir 12 (1996) 3728.
Acknowledgements This work was supported by Jeong Moon Information Co. Ltd. and Keuk Dong Design & Communication Co. Ltd. in Korea.
Surface tension of silane treated natural zeolite J.Y. Leea, S.H. Leeb, S.W. Kima,*
b
a Department of Chemical Engineering, The University of Seoul, 90 Jeonnong-Dong, Dongdaemun-Gu, Seoul, 130-743, South Korea Department of Environmental Engineering, Anyang University, 708-113 Anyang 5-Dong, Manan-Gu, Anyang City, Kyungki-Do 430-714, South Korea
Received 14 May 1999; received in revised form 30 September 1999; accepted 20 October 1999
Abstract To investigate the surface tension of the natural zeolite to be used in polymer composites, wicking method was employed on the base of Washburn's equation and that of the zeolite treated with 0.5 wt.% -aminopropyltriethoxysilane ( -APS) was also studied and compared. LW AB The apolar component SV of the untreated natural zeolite was 19.22 mJ/m2 and the polar one, SV was 15.27 mJ/m2. The polar component 2 LW AB LW
SV of the treated zeolite with 0.5 wt.% -APS was 27.08 mJ/m and the polar one SV was 12.23 mJ/m2. The value of SV component AB increased, while that of SV component decreased with -APS treatment and it was due to the increasing effect of alkyl group (hydrophobic) in -APS coupled on the zeolite surface. # 2000 Elsevier Science S.A. All rights reserved. Keywords: Natural zeolite; Surface tension; Silane coupling agent; Wicking method
1. Introduction Many researchers have investigated to characterize the surface of clay minerals and polymer matrix, and the interface between them in order to use the clay minerals as inorganic ®llers in polymer composite, paint, cosmetic, etc., and they have found that the surface of solid materials are divided into two categories [1±4]. One is hydrophilic solid whose surface tension is high and the other is hydrophobic solid whose surface tension is low [5±7]. To facilitate the adhesion of two different materials, the apolar surface should be modi®ed into a high-energy polar surface or the polar surface should be changed to apolar surface by a number of modifying methods. So, the information about solid surface tension is very important for better insight in the processes occurring at the interfaces, both in pure and applied science. To get the surface characteristics of solids, the contact angle method has been used. When a liquid drop is put on the solid surface at equilibrium as shown in Fig. 1, the interfacial tensions of solid/liquid, SL solid/vapor, SV, and liquid vapor, LV are expressed by the following Young's equation [8±11].
LV cos SL ÿ SV
(1)
where, is contact angle. However, the contact angle for a particle can't be measured by the same method in Fig. 1. To * Corresponding author. Tel.: 82-2-2210-2447; fax: 82-2210-2310. E-mail address: [email protected] (S.W. Kim).
get the contact angle formed between a liquid and a fine powder, column wicking method is used at constant temperature by determining the rate of penetration of probe liquids (usually methylene iodide, water and formamide) through the packed beds of the powder, using the following Washburn's equation [8,11]. h2
tR LV cos 2
(2)
where, h(cm) is the penetrated distance of the probe liquid in a selected time t(sec), R(cm) is the effective interstitial pore radius between the packed particles in column and (cP) is the viscosity of the probe liquid. Eq. (2) has a fundamental dif®culty that there are two unknowns (R and cos). So, R should be ascertained independently before determining the cos and this dif®culty can be easily solved by using the spreading liquids which can completely wet the solid surface, so that the contact angle 0, that is cos 1. Generally, n-alkanes are used as spreading liquids and Eq. (2) can be changed as follows [2,8]. R
2h2 =t
LV
(3)
After ascertaining the value of R, the contact angle for each probe liquid with the solid powder is calculated via Eq. (2) and the surface tension can be determined. Inorganic materials of many species such as silica, alumina, talc, mica, etc. have been investigated to characterize
0254-0584/00/$ ± see front matter # 2000 Elsevier Science S.A. All rights reserved. PII: S 0 2 5 4 - 0 5 8 4 ( 9 9 ) 0 0 2 3 1 - X
252
J.Y. Lee et al. / Materials Chemistry and Physics 63 (2000) 251±255
Fig. 1. Contact angles between liquid and solid surface.
the surface tension, however, we can ®nd few papers concerned with natural zeolite. In this study, the surface tension of a natural zeolite was studied to use as an inorganic ®ller in epoxy composites [12]. It is well-known that zeolite are crystalline aluminosilicate minerals whose surface areas are so high due to the channels and pores in which metal ions are located [13±15]. To improve the wettability between the epoxy matrix and the inorganic ®ller, the natural zeolite was treated with silane coupling agent and the effect of silane treatment on the surface characteristics was investigated. 2. Experiment The natural zeolite from Kampo area in Korea was found to be a clinoptilolite type zeolite whose average particle size was 9.89 mm. -aminopropyltriethoxysilane (A-1100, APS) was supplied by Union Carbide and the formulation was H2 Nÿ CH2 3 ÿSiÿ OC2 H5 3 ÿaminopropyltriethoxysilane The silane treatment process of the natural zeolite was as follows. 0.5 wt.% silane coupling agent to the natural zeolite was hydrolyzed in the mixture of ethanol/water 95/5 (vol%) for 15 min at room temperature, and then the natural zeolite was treated with the hydrolyzed solutions for 30 min at 508C and dried for 24 h at 1208C. The dried zeolite was ground and sieved into 325 mesh under. They were stored at desiccator to prevent water molecules from being adsorbed. The sample was analyzed by FT-IR spectroscopy at a resolution of 2 cmÿ1 from 4000 cmÿ1 to 400 cmÿ1. Column wicking experiment was carried out in the following manner. Glass tube with 100 mm long and 9 mm diameter was plugged at the bottom with a small wad of cotton wool. 3 g of well-dried zeolite powder was ®lled into the tube with the packing height of 7 cm by means of a hypodermic syringe. The packed zeolite was wicked with n-hexane to promote further settling and the tube was vertically placed in an oven at 1108C overnight to remove the hexane. Wicking was done with n-alkanes (hexane, heptane, octane and decane), methylene iodide, water and formamide at 208C, and the penetration rates of the liquids were measured.
Fig. 2. Plots of h2 versus t obtained by wicking with n-alkanes on the untreated natural zeolite.
3. Results and discussion Fig. 2 shows the penetrated distances squared, h2 as a function of time, t for untreated natural zeolite wicked with a series of n-alkanes. The linear relationship between h2 and t in Eq. (2) should go precisely through the origin. However, all lines do not so in practice, and it would appear in most cases owing to various hydrodynamic disturbances at the moment of immersion [8]. So, the best approach is to make a plot of h2 versus t as shows in Fig. 2. n-Alkanes are known as spreading liquids whose contact angles with a solid surface is 0, that is cos 1. To determine the value of R, the surface tension components,
LV and the viscosities, of n-alkanes in Table 1 are joined to Eq. (3) and the relationships between 2h2/t and LV are displayed in Fig. 3. This shows the straight line and the value of R is obtained from the slope, which is 6.10 10ÿ5 cm. The contact angles between the untreated natural zeolite and the probe liquids in Eq. (2) are obtained from each slope of the straight line in Fig. 4 by joining the value of R and the data of Table 2. The contact angles for methylene iodide, water and formamide are 76.78, 68.88 and 54.28, respectively. The relationships between 2h2/t and LV for the liquids (nonspreading liquids) are compared with those of nalkanes in Fig. 3 and they fail to meet with the straight line of the spreading n-alkanes. So, it is found that only Table 1 LW ÿ Viscosity, LV, LV , LV and LV of n-Alkanes at 208C [8] n-Alkanes
(cP)
LV (mJ/m2)
LW
LV (mJ/m2)
AB
LV (mJ/m2)
LV (mJ/m2)
ÿ
LV (mJ/m2)
n-Hexane n-Heptane n-Octane n-Decane
0.326 0.409 0.542 0.907
18.4 20.1 21.6 23.8
18.4 20.1 21.6 23.8
0 0 0 0
0 0 0 0
0 0 0 0
J.Y. Lee et al. / Materials Chemistry and Physics 63 (2000) 251±255
253
The Lewis acid component, SV acts as an electron acceptor ÿ is electron donor site and the Lewis base component, SV site [9,11]. To get the values of these components, the values of the probe liquids in Table 2 were applied to Eq. (4) [9]. Methylene iodide was used as a probe liquid to determine LW component of the zeolite surface tension, and water the SV ÿ and SV components. and formamide were for SV q q LW LW ÿ
SV LV
SV
LV 1 cos 2 LV q ÿ (4) SV LV
Fig. 3. 2h2/t versus LV for wicking with n-alkanes and probe liquids on the untreated natural zeolite.
LW ÿ , LV and LV for Using the contact angle 76.78, LV 2 LW methylene iodide in Table 2, SV 19.22 mJ/m was cal ÿ and SV values, two culated from Eq. (4). To determine SV equations from Eq. (4) for water and formamide were rewritten and the solutions of the equations were ÿ 4.28 mJ/m2 and SV 13.63 mJ/m2. The polar com SV 2 AB ponent, SV is 15.27 mJ/m obtained from Eq. (5) and the total surface tension is calculated from Eq. (6) and it is 34.49 mJ/m2. qp AB ÿ (5) 2 SV
SV
SV LW AB SV
SV SV
(6)
The apolar component is a little larger than the polar and this means that the characterization of the untreated natural zeolite surface is some hydrophobic. It is interesting that this result is different from the general surface characteristics of zeolites whose surface is hydrophilic due to the hydroxyl groups located on the surface of the zeolite in the form of Al-OH, Si-OH, etc. This result may be attributable to the decomposition of the zeolite structure by grinding. Work of adhesion between solid and liquid was proposed by Dupre as follows [16]. WSL SV LV ÿ SL 2
Fig. 4. Plots of h versus t obtained by wicking with probe liquids on the untreated natural zeolite.
spreading liquids must be used to determine the value of R and it is due that the spreading liquids appear to pre-wet the solid surfaces over which they are subsequently spreading [8]. It has been well-known that the surface tension of a solid, LW for
SV consists of Lifshitz-van der Waals component, SV AB for polar. apolar and the Lewis acid-base component, SV Table 2 LW ÿ , LV and LV of probe liquids at 208C [8] Viscosity, LV, LV Probe liquids
LW AB ÿ (cP) LV
LV
LV
LV
LV 2 2 2 2 (mJ/m ) (mJ/m ) (mJ/m ) (mJ/m ) (mJ/m2)
Methylene iodide 2.80 Water 1.00 Formamide 4.55
50.8 72.8 58.0
50.8 21.8 39.0
0 51.0 19.0
0 25.5 2.28
0 25.5 39.6
(7)
Combining Eqs. (1) and (7), we can get the well-known Young±Dupre equation [16] and the work of adhesion between the untreated natural zeolite and the probe liquids is calculated. WSL LV 1 cos
(8)
Those values of WSL for water and formamide (polar liquids) are 99.13 mJ/m2 and 91.93 mJ/m2 and that for methylene iodide (apolar liquid) is 62.49 mJ/m2. Fig. 5 shows the penetrated distances squared, h2 as a function of time, t obtained by wicking of a series of nalkanes on 0.5 wt.% -APS treated natural zeolite. The slopes for all n-alkanes are wholly decreased compared with those of untreated natural zeolite and the trend of slope is similar. The values of Table 1 are joined to Eq. (3) to determine the value of R and the relationships between 2h2/ t and LV are displayed in Fig. 6. The value of R calculated from the slope is 3.72 10ÿ5 cm.
254
J.Y. Lee et al. / Materials Chemistry and Physics 63 (2000) 251±255
Fig. 5. Plots of h2 versus t obtained by wicking with n-alkanes on the natural zeolite treated with 0.5 wt.% -APS.
Fig. 7. Plots of h2 versus t obtained by wicking with probe liquids on natural zeolite treated with 0.5 wt.% -APS.
To get the contact angles between the 0.5 wt.% -APS treated natural zeolite and the probe liquids by using Eq. (2), each slope of the straight line in Fig. 7 are joined to R value and the data in Table 2. The contact angles for methylene iodide, water and formamide are 62.68, 68.48 and 64.28, respectively. LW , LV and By introducing the contact angle 62.68, LV ÿ
LV of methylene iodide on Table 2, to Eq. (4), the apolar LW component, LV 27.08 mJ/m2 was obtained and the polar ÿ 9.09 mJ/m2 components, SV 4.12 mJ/m2 and SV were also obtained from Table 2 and Eq. (4). By substituting ÿ AB the value of SV and SV to Eq. (5), SV 12.23 mJ/m2 was obtained and the total surface tension, SV 39.31 mJ/m2 is calculated from Eq. (6). The apolar component is 2.2 times as large as the polar component and this means that the
characterization of the surface of 0.5 wt.% -APS treated natural zeolite is hydrophobic. Work of adhesion, WSL for water and formamide (polar liquids) are 99.60 mJ/m2 and 83.24 mJ/m2 and that for methylene iodide (apolar liquid) is 74.18 mJ/m2. The surface tension components for the zeolite are put LW component increased, together on Table 3. The value of SV AB while that of SV component decreased with -APS treatment. It is due to that the surface of the zeolite is more affected by alkyl group (hydrophobic) than amine or hydroxyl groups (hydrophilic) as shown in Fig. 8. Fig. 8A shows the FT-IR spectra of the natural zeolite. The strongest vibrations in the range of 1294±837 cmÿ1 are for the internal tetrahedron symmetric stretch of Si (or Al)O. The Si (or Al)-O bending appears at 474.1 cmÿ1 and the band of 525.4 cmÿ1 is related to the presence of the double rings in the framework structures. The band of H2O bending is observed at 1635 cmÿ1, the band of hydrogen-bonded OH is shown at 3453.2 cmÿ1 and the sharp band of isolated OH is shown at 3645.5 cmÿ1. The effect of -APS treatment is shown in Fig. 8B. The characteristic peaks mentioned above are similar in two spectra, however, the new bands appeared at 3187 cmÿ1 and 1697 cmÿ1 which are related to the presence of amine groups in -APS. Therefore, it was found that the surface of the zeolite is coupled with -APS, so the surface tension was affected by alkyl group and amine or hydroxyl groups explained above. Table 3 Surface, tension components for the natural zeolite at 208C
Fig. 6. 2h2/t versus LV for wicking with n-alkanes and probe liquids on natural zeolite treated with 0.5 wt.% -APS.
Samples
LW AB ÿ
LV
LV
LV
LV
LV (mJ/m2) (mJ/m2) (mJ/m2) (mJ/m2) (mJ/m2)
Untreated zeolite
-APS treated zeolite
34.49 39.31
19.22 27.08
15.27 12.23
4.28 4.12
13.63 9.09
J.Y. Lee et al. / Materials Chemistry and Physics 63 (2000) 251±255
255
Fig. 8. FT-IR spectra of natural zeolite untreated (A) and treated (B) with 0.5 wt.% -Aps.
4. Conclusions
References
The effects of -APS treatment on the surface tension of the natural zeolite used for polymer composites were studied by wicking method using the Washburn's equation. The components of surface tension for the LW 19.22 mJ/m2, SV 4.28 mJ/ natural zeolite were SV 2 2 ÿ AB m , SV 13.63 mJ/m , SV 15.27 mJ/m2 and SV 34.49 mJ/m2. Those for the -APS treated zeolite were LW ÿ 27.08 mJ/m2, SV 4.12 mJ/m2, SV 9.09 mJ/
SV 2 2 AB m , SV 12.23 mJ/m and SV 39.31 mJ/m2. The LW AB component increased, while that of SV value of SV component decreased with -APS treatment. It was due to that the surface of the zeolite was more affected by alkyl group (hydrophobic) than amine or hydroxyl groups (hydrophilic).
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Acknowledgements This work was supported by Jeong Moon Information Co. Ltd. and Keuk Dong Design & Communication Co. Ltd. in Korea.