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Water resistance improvement of filter paper by a UV-grafting modification with a fluoromonomer
2019-2-15 15:59:58
  • a Politecnico di Torino, Dipartimento di Scienza Applicata e Tecnologia, Corso Duca degli Abruzzi, 24, 10129 Torino, Italy
  • b Centre Technique du Papier (CTP), Domaine Universitaire, BP 251, 38044 Grenoble Cedex 9, France
  • c Università di Catania, Dipartimento di Ingegneria Industriale e Meccanica. v.le A.Doria 6, 90125 Catania, Italy
  • d OMNOVA Solutions, 2990 Gilchrist Rd., Akron, OH 44305, USA
Corresponding author contact information
Corresponding author at: Dipartimento di Scienza Applicata e Tecnologia, Corso Duca degli Abruzzi, 24, 10129 Torino, Italy. Tel.: +39 011 5644619.
Received 13 June 2012
Revised 22 October 2012
Accepted 1 November 2012
Available online 10 November 2012

1. Introduction

2. Experimental

3. Results and discussion

4. Conclusions

Appendix A. Supplementary data

References

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Abstract

This work describes the surface modification of filter paper by a photoinduced grafting process involving a poly(oxetane) acrylic oligomer with short perfluoroalkyl chains. This modifier avoids the safety, environmental and health concerns of conventional long perfluoroalkyl-chain chemistries, without sacrificing their key performance features. Therefore the work provides an alternative to existing processes aiming to make the paper hydrophobic: the chemicals used are safe, the proposed functionalization process is rather simple and inexpensive, moreover can be adapted to paper making plants.

The experiments show that the grafting induced by UV irradiation changes the surface composition of the samples as assessed by surface spectroscopies and other measurements. As a result of the surface modification, water contact angles on treated paper surfaces were as high as 143° approaching superhydrophobicity. Also oleophobicity was improved (ϑ = 57°), guaranteeing grease and antistain resistance. Surface tension was strongly reduced and water resistance was improved. XPS, static and dynamic contact angles and capillary wetting studies indicate a substantial gradient in surface energy normal to the treated paper surface.

Graphical abstract

Modification of filter paper by a photoinduced grafting of a fluoromonomer.

 

Highlights

► UV-induced grafting of cellulose is a successful strategy for paper modification ► A short (single bondC2F5) perfluoroalkyl chain acrylate was grafted on filter paper ► Its surface composition was changed as assessed by surface spectroscopies ► Quasi superhydrophobicity and oleophobicity was imparted to paper ► Grease resistance and water resistance of paper were improved.

Keywords

  • Cellulose;
  • Photografting;
  • Surface modification;
  • Fluoromonomer;
  • Hydrophobicity;
  • Oleophobicity

Figures and tables from this article:

Full-size image (14 K)

Fig. 1. Structure of fluorinated monomer, PolyFox PF-3510.

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Full-size image (36 K)

Fig. 2. Fluorine weight percentages by potentiometric titration. Fluorine weight percentage (vs paper mass) as a function of irradiation time (0, 0.5, 2 min), photoinitiator (PI = benzophenone 0–1.5 wt%) and fluoromonomer PF-3510 concentration (1–4 g/L); irradiation under nitrogen, Iflux = 51 mW/cm2.

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Full-size image (16 K)

Fig. 3. Hexadecane (□) and water (○) capillary wetting data for Sample 9. In this particular example, the wetting slope yields θ ≈ 44° for hexadecane and ∼37° for water.

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Fig. 4. Capillary wetting slope (■) with time and resultant contact angles (○) using water as probe liquid for Sample 9 using data from Fig. 3 and Eq. (2).

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Fig. 5. Dynamic contact angles and volumes for treated paper samples. Data for Samples 5A (□), 2A (○), 9 (▵), 7A (▿) and 8 (♢) are shown.

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Full-size image (42 K)

Fig. 6. ATR-FTIR spectra of treated samples. (A) Photoinitiator PI = 1.5 wt%, irradiation time = 1 min under nitrogen, fluoromonomer concentration = 4 g/L; spectra taken from three different points. Arrow indicates region of carbonyl stretch and unique to the fluorinated monomer/polymer. (B) Fluoromonomer concentration: 4 g/L (top spectrum), 2 g/L (middle spectrum), and 1 g/L (bottom spectrum) with ellipse showing carbonyl region of interest.

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Scheme 1. Photodissociation of the photoinitiator and hydrogen abstraction from the cellulose.

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Scheme 2. Photografting of monomer M onto cellulose and its photopolymerization.

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Table 1. Contact angles of filter papers UV-grafted with fluoromonomer PolyFox PF-3510 (photoinitiator, PI = benzophenone, irradiation under nitrogen at Iflux = 51 mW/cm2 unless stated otherwise).

Sample PI (wt% vs monomer) Monomer (g/L) Irradiation time (min) θ water (°) θ hexadecane (°)
1a 0 0 0 0 0
2A 1.5 4 2 143 37
2B 1.5 4 1 137 36
2C 1.5 4 0.5 136 33
3A 1.5 2 2 138 35
3B 1.5 2 1 137 33
3C 1.5 2 0.5 131 29
4A 1.5 1 2 136 27
4B 1.5 1 1 130 27
4C 1.5 1 0.5 129 26
5A 0 4 2 134 32
5B 0 4 1 135 32
5C 0 4 0.5 132 30
6A 0 2 2 135 27
6B 0 2 1 135 31
6C 0 2 0.5 131 29
7A 0 1 2 129 26
7B 0 1 1 129 29
7C 0 1 0.5 126 29
8b 1.5 4 2 134 32
9c 1.5 4 2 138 35
a

Control, untreated.

b

In air.

c

Iflux = 25 mW/cm2.

Full-size table
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Table 2. Capillary wetting and dynamic contact angle data for treated paper samples (photoinitiator, PI = benzophenone, irradiation under nitrogen at Iflux = 51 mW/cm2 unless stated otherwise).

Sample Irradiation time (min) Monomer (g/L) PI (wt% vs monomer) Gas atmosphere Capillary wetting contact angle
Dynamic contact anglee Static contact anglef
          θHexadecane (°) θWater (°) θWater (°) θWater (°)
1a and b – – – – 0 69.3 ± 0.7 –d –
5Ab 2 4 0 N2 46.0 ± 5 43.4 ± 31 119.7 118
2Ab 2 4 1.5 N2 8.83 ± 15 68.2 ± 9 117.9 122
9c 2 4 1.5 N2 35.8 ± 14 71.9 ± 30 112.4 117
7Ab 2 1 0 N2 46.8 ± 7 66.4 ± 6 109.8 114
8b 2 4 1.5 Air 34.8 ± 8 74.7 ± 13 92.94 118
a

Control, untreated.

b

Iflux = 51 mW/cm2.

c

Iflux = 25 mW/cm2.

d

Too rapid to measure.

e

Initial values.

f

After application of Wenzel correction.

Full-size table
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Table 3. XPS results: F/C, O/C and F/O ratios at different take off angles (t.o.a.) as a function of the fluoromonomer PolyFox PF-3510 concentration and photoinitiator composition (PI = benzophenone). Irradiation time = 2 min and flux = 51 mW/cm2.

Sample Monomer (g/L) PI (wt% vs monomer) Gas atmosphere F1s/C1s
O1s/C1s
F1s/O1s
        t.o.a. (°)
t.o.a. (°)
t.o.a. (°)
        80 45 25 80 45 25 80 45 25
1 – – – – – – 0.66 0.64 0.60 – – –
5A 4 0 N2 0.36 0.39 0.40 0.33 0.33 0.35 1.10 1.18 1.14
2A 4 1.5 N2 0.42 0.47 0.46 0.29 0.30 0.30 1.43 1.56 1.56
7A 1 0 N2 0.31 0.34 0.36 0.44 0.40 0.38 0.70 0.84 0.94
8 4 1.5 Air 0.39 0.41 0.44 0.37 0.35 0.35 1.05 1.19 1.24
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Table 4. Monomer content at the paper surface (estimated on the basis of the XPS data at t.o.a. = 25°). irradtiation time = 2 min I = 51 mW/cm2.

Sample Monomer (g/L) PI (wt% vs monomer) Gas atmosphere Mole faction of monomer at paper surface Molecules of monomer/ten glucosidic units
5A 4 0 N2 0.20 3
2A 4 1.5 N2 0.40 6
7A 1 0 N2 0.14 2
8 4 1.5 Air 0.23 3
Full-size table
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Corresponding author contact information
Corresponding author at: Dipartimento di Scienza Applicata e Tecnologia, Corso Duca degli Abruzzi, 24, 10129 Torino, Italy. Tel.: +39 011 5644619.
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