Evaluation
Water Repellency
Oil Repellency
Soil Release Property
Dry Soil Test on Carpet

Literature
Basic
Application
Topics

Index

Perfluoroalkyl acrylate homopolymer

1. "Wetting Properties of Acrylic and Methacrylic Polymers Containing Fluorinated Side Chains",
   M.K.Bernett, W.A.Zisman, J.Phys.Chem., 66, 1207(1962)
   
   
2. "Polymers Derived from Fluoroketones. II. Wetting Properties of Fluoroalkyl Acrylates and Methacrylate",
   A.G.Pittman, D.L.Sharp, B.A.Ludwig, J.Polymer Sci., Part A-1, 6, 1729(1968)
   
   
3. "Effect of Polymer Crystallinity on the Wetting Properties of Certain Fluoroalkyl Acrylates",
   A.G.Pittman, B.A.Ludwig, J.Polymer Sci., Part A-1, 7, 3053(1969)
   
   
4. "Fluoropolymers of Very Low Surface Energies",
   R.Ramharack, T.H.Nguyen, J.Polymer Sci., Part C, 25, 93(1987)
   
   
5. "The Relationship between Structures and Dynamic Surface Properties of Perfluoroalkyl Containing Polymer",
   T.Maekawa, S.Kamata and M.Matsuo, J.Fluorine Chem., 54, 84(1991)
   
   
6. "Aggregation State and Mesophase structure of comb-shaped polymers with fluorocarbon side groups",
   A.Takahara, T.Kajiyama et al., Polymer, 33, 1316(1992)
   
   
7. "Surface Structures Analysis of Polyacrylate Thin Films",
   T.Katsuragawa, E.Chiba, K.Okada, K.Tani, H.Tomono, Jpn.J.Appl.Phys., 34, 649(1995)
   
   
8. "Surface Property of Polymer Films with Fluoroalkyl Side Chains",
   Y.Katano, H.Tomono and T.Nakajima, Macromolecules, 27, 2342(1994)
   
   
9. "Ordered Structure of Poly(1H, 1H-fluoroalkyl alpha-fluoroacrylate)s",
   T.Shimizu, Y.Tanaka, S.Kutsumizu, S.Yano, Macromolecules, 29, 156(1996)
   
   
10. "Structure Studies of Poly(1H, 1H-fluoroalkyl alpha-fluoroacrylate)s by Infrared Spectroscopic Analysis",
    T.Shimizu, Y.Tanaka, M.Ohkawa, S.Kutsumizu, S.Yano, Macromolecules, 29, 3540(1996)
    
    
11. "Self-Dewetting of Perfluoroalkyl Methacrylate Films on Glass",
    S.Sheiko, Eva Lermann, M.Moller, Langmuir, 12, 4015(1996)
    
    
12. "Surface Properties and Structure of Poly(Perfluoroalkylethyl Methacrylate)",
    I.J.Park, S.B.Lee, C.K.Choi, K.J.Kim, J.Colloid Interface Sci., 181, 284(1996)
    
    
13. "Dewetting of Poly(Fluoroalkyl Acrylate) Films on PET",
    M.Ishikawa, M.Morita, T.Sakashita, M.Kubo, 216th ACS National Meeting(Boston) Polymer Preprints, 39, 968(1998)
    
    

Perfluoroalkyl acrylate random copolymer

1. "Surface Properties of Perfluoroalkylethyl acrylate/n-alkyl acrylate Copolymers",
   M.Morita, H.Ogisu, M.Kubo, The 14th International Symposium on Fluorine Chemistry, 1C14(1994)
   
   
2. "Surface Property of Poly(perfluoroalkylethyl methacrylate)/Poly(n-alkylethyl methacrylate)s Mixtures",
   I.J.Park, S.B.Lee, C.K.Choi, J.Appl.Poly.Sci., 54, 1449(1994)
   
   
3. "Molecular organization of polystyrene and polymethylmethacrylate with fluorocarbon side chains",
   S.Sergei, T.Alexei, H.Jens et al.,Macromol.Eng.[Proc.Int.Conf.Adv.Ploym.Macromol.Eng.], 219(1995)
   
   
4. "Lngmuir-Blodgett films of random copolymers of fluoroalkyl(meth)acrylate and methacrylic acid : fabrication and X-ray diffraction study",
   V.Safronov, L.A.Feigin, L.D.Budovskaya, V.N.Ivanova, Materials Sci.Eng., C2, 205(1996)
   
   
5. "Surface Properties of Networks Containing Fluorinated Acrylic Monomers",
   R.Bongiovanni, N.Pollicino et al., Polymer for Adv. Tech., 7, 403(1996)
   
   
6. "Morphology of Perfluoroalkylacrylate/Stearyl Methacrylate Polymers and Their Effect on Water/Oil Repellency",
   I.I. Chen, Y.L.Sheu et al., J.Applied Polym.Sci., 63, 903(1997)
   
   
7. "Surface molecular mobility for copolymers having perfluorooctyl and /or polyether side chains via dynamic contact angle",
   S.Takahashi, T.Kasemura et al., Polymer, 38, 2107(1997)
   
   
8. "Surface Properties of Perfluoroalkylethyl acrylate/n-alkyl acrylate Copolymers",
   M. Morita, H. Ogisu, M.Kubo, J.Appl.Polym.Sci., 73,1741(1999)
   
   

Perfluoroalkyl acrylate block and graft copolymer

1. "Synthesis and Application of Fluorine Containing Graftcopolymers",
   Y.Tamashita, Y.Tsukahara, K.Ito, K.Okada, Y.Tajima, Polymer Bulletin, 5, 335(1981)
   
   
2. "Surface Modification of Polymethyl Methacrylate by Graft Copolymers",
   Y.Tamashita, Y.Tsukahara, H.Ito, Polymer Bulletin, 7, 289(1982)
   
   
3. "Synthesis of Fluorine-Containing Graft Copolyamides by Using Condensation-Type Macromonomers",
   Y.Chujo, A.Hiraiwa, H.Kobayashi, Y.Tamashita, J.Polymer Sci, Part A, 26, 2991(1988)
   
   
4. "XPS Studies of Fluorinated Acrylate Polymers and Block Copolymer with Polystyrene",
   C.M.Kassis, J.K.Steehler, D.E.Betts et al., Macromolecules, 29, 3247(1996)
   
   
5. "Synthesis of fluorine-containing graft copolymers of perfluoroalkylethyl methacrylate)-g-poly(methyl methacrylate) by the macromonomer technique and emulsion copolymerization method",
   I.J.Park, S.B.Lee et al., Polymer, 38, 2523(1997)
   
   
6. "Surface Properties of the Fluorine-Containing Graft Copolymer of Poly((perfluoroalkyl)ethyl methacrylate)-g-poly(methyl methacrylate) ",
   I.J.Park, S.B..Lee, C.K.Choi, Macromolecules, 31, 7555(1998)
   
   
7. "Synthesis, characterization and surface analysis using dynamic contact angle measurements of graft copolymers: poly(methyl methacrylate)-g-poly(dimethylsiloxane) and poly(methyl methacrylate)-g-poly(trifluoropropylmethylsiloxane)",
   A.E. Meraa, M.Goodwin, J.K. Pike, K.J.Wynne, Polymer, 40, 419(1999)
   
   

Others

1. "Properties of Films Adsorbed Fluorinated Acids",
   E.F.Hare, E.G.Shafrin, W.A.Zisman, J.Phys.Chem., 58, 236(1954)
   
   
2. "Constitutive Relations in the Wetting of Low Energy Surface and the Theory of Retraction Method of Preparing Monolayers",
   E.G.Shafrin, W.A.Zisman, J.Phys.Chem., 64, 519(1960)
   
   
3. "Polymers Derived from Fluoroketones. IV. Poly(1, 4-Bis(heptafluoroisopropoxy)-2-butene Oxide)",
   A.G.Pittman, W.L.Wasley, J.N.Roitman, Polymer Letters., 8, 873(1970)
   
   
4. "Side Chain Effect on Surface Properties of Poly(alkylfumarate) and Poly(fluoroalkylfumarate)",
   A.Takahara, S.B.Choi, N.Amaya, Y.Murata, T.Kajiyama, Rept.Progr.Polym.Phys., Japan, 30, 187(1987)
   
   

Index

Water and Oil Repellency Agent

1. "Fabric Oil Repellency as Related to the Critical Surface Tension and Stiffness of Coating Material",
   J.N.Roitman, A.G.Pittman et al., Tex. Res.J., 44,500(1974)
   
   
2. "The effect of washing and heat treatment on the surface characteristics of fluorocarbon resin-treated polymer",
   T.Wakida, H.Li et al., J.Soc.Dyers Color, 109,Sep.292(1993)
   
   
3. "An XPS Investigation of Polymer Surface Dynamics.I. A Study of Surfaces Modified by CF4 and CF4/CH4 Plasmas",
   J.Wang, D.Feng et al., J.Appl.Polym.Sci., 50,585(1993)
   
   
4. "The Quantitative Analysis of Fluorocarbon Polymer Finishes on Wool by FT-IR Spectroscopy",
   J.S.Church, D.J.Evans et al., J.Appl.Polym.Sci., 57,1585(1995)
   
   
5. "Introduction of Water Molecules into Water Repellent Fabrics by Rubbing",
   Y.Onogi, A.Yabuuchi et al., Sen'i Gakkaishi, 52,488(1996)
   
   
6. "An Investigation into the Effect of Laundering on the Repellency Behaviour of a Fluorochemical-treated Cotton Fabric",
   S.Arunyadej, R.Mitchell et al., J.Text.Inst., 89 Part 1,696(1998)
   
   
7. "Surface Properties of Perfluoroalkylethyl acrylate/n-alkyl acrylate Copolymers",
   M. Morita, H. Ogisu, M.Kubo, J.Appl.Polym.Sci., 73,1741(1999)
   
   

Soil Release Agent

1. "Textile Characteristics Affecting the Release of Soil During Laundering Part II",
   P.O.Sherman, S.Smith et al., Tex.Res.J., 39, 449(1969)
   
   

Surface Characteristics of Fluoroalkyl Acrylate Polymer and Their Application Motonobu Kubo, Surface(Hyoumen), 33, 185(1995)
R & D Department No.2 Chemical Division Daikin Industries Ltd.

Polymers exhibit various surface characteristics. Among these characteristics, the surface rearrangement(mobility) of the polymer molecules at various interfaces has recently attracted considerable attention. The fluoroalkyl acrylate polymer, therefore, is exclusively used for water- and oil-repellent agents due to its excellent surface characteristics. This document describes the results of our research on this polymer from the above viewpoint.

Index

1. Introduction

2.Effects and Surface Characteristics of Fluorine Atom

3. Surface Characteristics of Fluoroalkyl Acrylate Polymer

3.1 Surface characteristics of homopolymers

3.2 Characteristics and water-repellency of copolymers

3.3 Copolymers used for soil-release agents

 

4. Conclusion

5. Reference

1. Introduction

Fluoroalkyl compounds that contain fluorine atoms exhibit various characteristics. Among these characteristics, surface characteristics, such as water- and oil-repellency, are especially useful1). These compounds, therefore, are widely used, for example, fiber processing. In 1950, 3M company in the U.S. announced that they had developed an fluoroalkyl compound "Scotchgard" as a water-repellent agent for fibers. Since then, fluoroalkyl compounds have found practical use for fiber.Following 3M, other companies, such as DuPont, Daikin Industries, and Asahi Glass, developed various water-repellent agents containing fluoroalkyl compounds. These fluorine-based water-repellent agents also exhibit oil-repellency, and the agents do not damage the texture of the fibers because even a small amount is very effective. For these reasons, the demand for fluoroalkyl compounds increased rapidly, and the compounds are now the main water-repellent agents in wide use.

It is now estimated that tens of thousands of tons of emulsion-type and solution-type products containing fluoroalkyl compounds are used every year as fiber-finishing agents. Most of the fluoroalkyl compounds used for the above purposes are long-chain fluoroalkyl-acrylate-based polymers. The thermal resistance and dynamic characteristics of these polymers depend on the characteristics of the hydrocarbon based acrylate main chains. On the other hand, the surface characteristics of these polymers depend on the characteristics of the perfluoroalkyl(Rf) group side chains. This heterogeneity in molecules represents one of the differences between perfluoropolymer[polytetrafluoroethylene (PTFE)] and long side chain fluoroacrylate based polymers. The surface characteristics are particularly important because they affect the structure and functions of the products, such as water-repellent agents. From the above point of view, the surface characteristics of fluoroalkyl-acrylate-based polymers and their influence on the products are described below along with the results of our recent research:

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2.Effects and Surface Characteristics of Fluorine Atom

Table 1 shows the physical constants of the fluorine atom and those of the hydrogen and chlorine atoms. The radius and polarizability of the fluorine atom are small, and the negative charge of this atom is the largest of all the atoms. In addition, the polarizability in carbon-fluorine bonding is also small2, 3, 4). Compounds containing many carbon-fluorine bonds, therefore, exhibit low inter-molecular cohesion and have low surface free energy. As a result, these compounds have extremely low wettability for various types of liquid and extremely low adhesiveness. Note that these characteristics greatly depend on the microstructure of each compound. As examples, the characteristics of PVdF (polyvinylidene fluoride) and PPFMA are shown below:

(CH2CF2)n PVdF

[CH2C(CH3)COOCH2CH2C7F15]n PPFMA

The fluorine contents of these polymers are 59.3% and 59%, almost equal to each other. However, the critical surface tension value of PVdF is 25 mN/m, and that of PPFMA is 11 mN/m greatly different from each other. From this fact, you can see the great influence of the Rf group side chains.

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3. Surface Characteristics of Fluoroalkyl Acrylate Polymer

In the 1950's, Zisman studied the surface wettability of various fluorine compounds and obtained critical surface tension of various surfaces. Table 25) shows the results of their study.

The monomolecular film of perfluorolaulic acid was used to obtain the value of -CF3. This value shows that the surface of a substance has an extremely low critical surface tension when covered with -CF3. In the 1960's, Pittman5) clarified the characteristics of the acryl-based polymers having Rf group side chains. They also studied the influence of the Rf chain length and reported that crystalline substances have smaller critical surface tension than amorphous substances. Table 3 shows a portion of the results obtained. These results show that the critical surface tension depends on the structure of the Rf group. There is no difference between acrylate and methacrylate critical surface tension; therefore, it seems that the structures of the main chains of these two components do not have any influence on the surface characteristics.

It is, however, interesting that methacrylate has a lower critical surface tension than 2-fluoroalkyl acrylate, although both are acryl-based polymers having the same Rf group6). The fluorine concentrations on the surfaces of these polymers were measured using XPS(X-ray photoelectron spectrometry)7). The measurement results show that the fluorine concentration depends on the critical surface tension, although the influence of the second-position fluorine of the main chain is unknown. This is because the surface orientation of the Rf group cannot be distinguished from the influence of the fluorine in the main chains.

It is not enough to consider only the static characteristic values when utilizing the surface characteristics, such as water- or oil-repellency, for products. For example, the static contact angle of water should be considered to ensure water repellency; a large contact angle is a necessary condition, but it is not a sufficient condition to ensure water-repellency. Let's think about water-repellent cloth. After application of the water-repellent agent to the cloth, water is sprayed on the cloth and then the surface condition of the cloth is checked to evaluate the water-repellency of the cloth8). As a result, the water-repellency increases as the receding contact angle is increase.

Van Damme and his staff studied the polymer surface wettability from the viewpoint of surface rearrangement and molecular mobility9). They measured the dynamic contact angles of various types of poly(alkyl methacrylate), and clarified that the change in hysteresis depends on the alkyl chain length. They explained this fact by clarifying the relation between the interplasticity increased by the chain length and the surface mobility of molecules. This point of view is important in studying the surface characteristics of polymers: therefore, it is also important for the fluorine polymers described in this paper. Recent data on the fluoroalkyl acrylate polymer is described below:

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3.1 Surface characteristics of homopolymers

To obtain more practical indexes, Ohgawara studied the characteristics of perfluoroalkyl acrylate(PFAA) homopolymers having Rf group chains of various lengths using various dynamic contact angles of water10,11,12).

CxF2x+1C2H4OOCH=CH2 PFAA

Fig.112) and Fig.2 12) show the results. The advancing contact angle did not depend on the Rf group chain length, but if the number of Rf group carbons was less than 8, the receding contact angle was much smaller than the advancing contact angle. On the contrary, if the number of Rf group carbons was 8 or more, the receding contact angle was close to the advancing contact angle(see Fig.1). Regarding X-ray diffraction, crystallization was at its peak when 2 theta = 18 degrees, and this value was equal to the angle of PTFE(polytetrafluoroethylene) crystals (having 1 0 0 faces). The above results shows that the water-repellency depends on the crystallization of the side chains, and that the mobility of the molecular chains greatly affects the water-repellency10,11,12). In addition, Katano et al.13) reported that when the PFAA (Rf : C=8) polymer film was heated and then immediately cooled in water, the receding contact angle was greatly reduced. They assumed that the Rf groups is tumbled under such condition, and the electrical screening effect of the Rf groups is decreases. As a result, the polymer film gets wet more easily.

On the other hand, it is well known that the 2-fluoroalkyl acrylate polymer shows high crystallization (when measured by X-ray diffraction) even if the number of Rf group carbons is 1 (minimum value)14). Compared with acrylate and methacrylate, this polymer has more interesting characteristics. It is, therefore, necessary to study this polymer further. The relation between the main chain structure and side chain crystallization and surface characteristics, etc. should be studied in the future.

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3.2 Characteristics and water-repellency of copolymers

When the surface characteristics of PFAA are utilized, PFAA is rarely used in the homopolymer form, but is in the form of a copolymer that contains various non-fluorine-based vinyl monomers. This is because the copolymer ensures excellent film-forming properties and is highly adhesive to substrate. We studied PFAA and PFAA/n-alkyl acrylate(AA) copolymers with the various length of side chains of the AA to further clarify the relation between the copolymer characteristics and water-repellency15,16).

Fig. 3 shows the structure of the copolymer we studied. Considering the copolymerization reactivity ratio of the monomers, the copolymer is a random copolymer. The Rf group of the PFAA homopolymer we studied was crystallized to a high degree. On the contrary, the copolymer was not crystallized when the number of side-chain carbons was 8 or less. This was due to the influence of AA. Table 4 shows these results and the DSC results. Using a cast film of the copolymer, we measured the advancing and receding contact angle and the sliding angle of water using the sliding method. Fig. 4 shows the measurement conditions, and Fig. 5 shows the results we obtained. The advancing contact angle was approximately 120 degrees regardless of the side chain length of AAs. On the other hand, the receding contact angle was very low (approximately 50 degrees) when the side chain length of AAs was less than 8. When n numbers was 12, however, the receding contact angle were rapidly increased, becoming close to the advancing contact angle. The sliding angle decreased as n numbers increased. This means that if the Rf group is not crystallized, the receding contact angle is very small and the sliding angle is very large, causing the polymer to exhibit high wettability.

In addition, to obtain data on the interfacial conditions between the polymer and water, we measured the peak area ratio of Fls to Cls using freeze-dried XPS17). Fig. 6 shows the results. The results show that in a wet condition (indicated as "hydration" in the figure), more fluorines were concentrated on the polymer surface as n numbers increased (Rf group is more crystallized), but in dry conditions, the fluorine concentration is kept constant.

Fig. 7 shows the surface free energy of copolymers measured in the air and water respectively. If the copolymer has a small n numbers and the side chains are not crystallized, the surface free energy in water is high: 40 to 50 mN/m. This value is almost equal to the reported value for poly(methyl methacrylate)18) and other non-fluorine-based polyacrylates measured in air. This is because if the non-crystallized Rf group has 8 or less carbons in the AA side chain, the Tg of the copolymer will be less than the measurement temperature of the contact angle; therefore,the Rf group will regress in the water to minimize the interfacial tension value between the polymer and water.

Fig. 8 shows the temperature dependency of the receding contact angle when stearyl acrylate(C = 18) is used as the AA, and also shows the Fls/Cls value on the copolymer surface measured after being dipped into water at the measurement temperature of receding contact angle and then immediately cooled. From Fig. 8, you can see that if the copolymer is heated above the melting point of the Rf group, the receding contact angle is almost equal to that of the copolymer having low side chain length of AAs. The same phenomenon is also seen in the Fls/Cls value.Considering the above results, it can be said that to ensure high water-repellency of the PFAA/AA copolymer, the motion of the molecular chains should be limited so that the interfacial condition between the water and copolymer can be kept at the same condition as the interfacial condition between the polymer and air.When water comes in contact with the copolymer surface, there is a change in the copolymer surface condition, and this change depends on the number of carbons in the side chain of AA. Fig. 9 shows this change in the surface condition.

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3.3 Copolymers used for soil-release agents

Water-repellency is used for the water-repellent agents. On the other hands, the mobility of the molecular chains are utilized for SR(soil-release) agents. If clothes processed with an SR agent are soiled by oil, the oil can be easily washed off. In the water, the contact angle is reduced as the critical surface tension is reduced. In the air, however, the opposite reaction can be seen19). This means that the polymer surface is highly oil-repellent in the air, but highly lipophilic in water. Let's think about how the oil is removed from the textile surface in the water. Assume that the interfacial tension between the oil and cleaning solution is Gow(G shows Gamma of Greak alphabet),that between the oil and the textile is Gos, and that between the cleaning agent and the textile is Gws. The following formula express the unit area work (W) necessary for washing oil off the textile surface using the cleaning solution20): W = Gws + Gow - Gos To remove the oil, the W should be smaller than 0 (W < 0); therefore, the Gos value should be larger than the "Gws + Gow" value (Gos > Gws + Gow).

If the oil type is the same, the Gow value will be constant. In this case, to satisfy the above formula, the Gws value should be reduced. In other words, a hydrophilic property is needed. To ensure water- and oil-repellency in the air and also ensure hydrophilic property and oil-repellency in the water, the SR agent should have both the Rf group and the hydrophilic group. The A-B-A type block copolymer21) and the copolymer22,23) consisting of PFAA and a hydrophilic monomer having poly(ethylene oxide) as the side chain are well known as SR agents. Fig. 10 shows the changes in the surface of the block copolymer when in contact with air and water. Fig. 11 shows an example of the effect of the SR agent.

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4. Conclusion

To develop polymer-surface-function materials, it is necessary to consider the surface rearrangement of molecules on various interfaces in addition to the static characteristics of the molecules. Moreover, we think that the surface morphology should be studied in addition to the molecular structures. This is why further study of polymer surface structures and functions are needed.

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5. Reference

1) E.J.Grajeck, W.H.Petersen, Text.Res.J., 32, 320(1962)

2) R.D.Chambers, "Fluorine in Organic Chemistry", Wiley, p-5(1973)(1982)

3) L.Pauling, "The Nature of the Chemical Bond", 3rd., Cornel Univ. Press(1960)

4) D.R.Lide, "CRC Handbook of Chemistry and Physics", 76th Ed., CRC Press, 10-192(1995-1996)

5) Leo A.Wall Ed.,"Fluoropolymers", A.G.Pittman, Chap13 Surface Properties of Fluorocarbon Polymers,Wiley Interscience,New York(1972)

6) K.Ishiwari, A.Ohmori, S.Koizumi, Nihon Kagakukaishi, 1985(10),1924

7) S.Koizumi, A.Ohmori, T.Shimizu, M.Iwami, Surface Chemistry(Hyoumen Kagaku), 13(7),428(1992)

8) JIS L1902

9) H.S.Van Damme, A.