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Article The current location: Home > References and Applications > Water resistance improvement of filter paper by a UV-grafting modification with a fluoromonomer

Water resistance improvement of filter paper by a UV-grafting modification with a fluoromonomer

Number of hits:15097 Release time:2020-08-25 00:00:00

^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 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

http://dx.doi.org/10.1016/j.colsurfa.2012.11.003, How to Cite or Link Using DOI

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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.

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Highlights

► UV-induced grafting of cellulose is a successful strategy for paper modification ► A short ( single bond C₂F₅) 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:

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

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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, I_flux = 51 mW/cm².

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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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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 I_flux = 51 mW/cm² unless stated otherwise).

Sample	PI (wt% vs monomer)	Monomer (g/L)	Irradiation time (min)	θ water (°)	θ hexadecane (°)
1^a	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
8^b	1.5	4	2	134	32
9^c	1.5	4	2	138	35

a: Control, untreated.

b: In air.

c: I_flux = 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 I_flux = 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 angle^e	Static contact angle^f
					θ_Hexadecane (°)	θ_Water (°)	θ_Water (°)	θ_Water (°)
1^{a and b}	–	–	–	–	0	69.3 ± 0.7	–^d	–
5A^b	2	4	0	N₂	46.0 ± 5	43.4 ± 31	119.7	118
2A^b	2	4	1.5	N₂	8.83 ± 15	68.2 ± 9	117.9	122
9^c	2	4	1.5	N₂	35.8 ± 14	71.9 ± 30	112.4	117
7A^b	2	1	0	N₂	46.8 ± 7	66.4 ± 6	109.8	114
8^b	2	4	1.5	Air	34.8 ± 8	74.7 ± 13	92.94	118

a: Control, untreated.

b: I_flux = 51 mW/cm².

c: I_flux = 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	F_1s/C_1s			O_1s/C_1s			F_1s/O_1s
				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

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: 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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Sample	PI (wt% vs monomer)	Monomer (g/L)	Irradiation time (min)	θ water (°)	θ hexadecane (°)
1^a	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
8^b	1.5	4	2	134	32
9^c	1.5	4	2	138	35

Sample	PI (wt% vs monomer)	Monomer (g/L)	Irradiation time (min)	θ water (°)	θ hexadecane (°)
1^a	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
8^b	1.5	4	2	134	32
9^c	1.5	4	2	138	35

Sample	PI (wt% vs monomer)	Monomer (g/L)	Irradiation time (min)	θ water (°)	θ hexadecane (°)
1^a	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
8^b	1.5	4	2	134	32
9^c	1.5	4	2	138	35