ORIGINAL PAPER

Hydrorepellent finishing of cotton fabrics by chemicallymodified TEOS based nanosol

Monica Periolatto • Franco Ferrero •

Alessio Montarsolo • Raffaella Mossotti

Received: 15 June 2012 / Accepted: 1 November 2012 / Published online: 10 November 2012

� Springer Science+Business Media Dordrecht 2012

Abstract Hydrorepellency was conferred to cotton

fabrics by an hybrid organic–inorganic finishing via

sol–gel. The nanosol was prepared by co-hydrolysis

and condensation of tetraethoxysilane (TEOS) and

1H,1H,2H,2H–fluorooctyltriethoxysilane (FOS), or

hexadecyltrimethoxysilane (C16), as precursors in

weakly acid medium. The application on cotton was

carried out by padding with various impregnation

times, followed by drying and thermal treatment,

varying the FOS add-on from 5 till 30 % on fabric

weight or C16 add-on from 5 to 10 %. Treated samples

were tested in terms of contact angles, drop absorption

times, washing fastness and characterized by SEM,

XPS and FTIR-ATR analyses. In the case of FOS

modified nanosol applied with an impregnation time

of 24 h or C16 modified nanosol, water contact angles

values very close or even higher than 150� were

measured, typical of a superhydrophobic surface. The

application of the proposed sol–gel process yielded

also a satisfactory treatment fastness to domestic

washing, in particular for FOS modified nanosol.

Keywords Sol–gel � Nanosol � Cotton �Hydrophobicity � Hybrid alkoxides

Introduction

Improvement of existing properties and the creation of

new material properties are the most important reasons

for the functionalization of textiles (Gowri et al. 2010).

Recently, as markets in leisure and outdoor sporting

textiles have been expanded, the needs for superhy-

drophobic and self-cleaning fabrics have increased.

Cotton has always been the principal clothing fabric

due to its attractive characteristics such as softness,

comfort, warmness and biodegradability. However the

high concentration of hydroxyl groups on cotton

surface makes the fabrics water-absorbent and easily

stained by liquids. Therefore, additional finishes are

required to impart superhydrophobicity and self-

cleaning properties to cotton fabrics.

There have been some reports on the improvement of

hydrophobic properties of several kinds of fabrics using

nanostructures achieved by nanotechnology (Bae et al.

2009; Liu et al. 2011; Simoncic et al. 2012). It was

demonstrated that superhydrophobicity depends not only

on the surface chemistry but also on the surface topology.

Two distinct theoretical models (Wenzel and Cassie–

Baxter) have inspired how to engineer superhydrophobic

surfaces by either roughening the same through micro- or

M. Periolatto � F. Ferrero (&)

Dipartimento di Scienza Applicata e Tecnologia,

Politecnico di Torino, C.so Duca degli Abruzzi 24,

10129 Turin, Italy

e-mail: franco.ferrero@polito.it

A. Montarsolo � R. Mossotti

CNR ISMAC, Istituto per lo Studio delle Macromolecole,

C.so Pella 16, 13900 Biella, Italy

123

Cellulose (2013) 20:355–364

DOI 10.1007/s10570-012-9821-2

nano-structures or lowering the surface free energy thanks

to waxy materials applied on top of the rough structures, or

both. An example is a microprocessing technique to

produce rough surface and subsequent chemical treatment

with silane or fluoro-containing polymers to reduce the

surface free energy (Wang et al. 2008).

Recently, roughened surfaces have been commonly

obtained by introducing nano-size particles onto the

pristine surface and the sol–gel technique has been

reported as a promising tool for preparation of water

repellent coatings especially versatile for application on

paper, textiles or wood (Tomsic et al. 2008; Cunha and

Gandini 2010; Cappelletto et al. 2012). In many research

works sol–gel formulations of fluoroalkylsilanes in com-

bination with other silanes to obtain co-condensates are

used. These materials are called ORMOCER� (‘‘organi-

cally modified ceramics’’) or CERAMER (‘‘ceramic

polymers’’). The solvents are mostly alcohols, but some

water-based systems have been described. In these

nanocomposites, the organic and the inorganic network

are covalently bound and homogeneously intermingled at

the nanometer-scale, so that the resulting coatings show

enhanced mechanical stability (Pilotek and Schmidt 2003).

These materials have a pronounced gradient struc-

ture, with a high concentration of fluoroalkyl groups at

the coating-air interface so that only a small amount

(1.7 mol %) of fluoroalkyl silane is necessary to obtain

an effective repellency (Pilotek and Schmidt 2004).

Moreover, it accounts for an excellent adhesion of the

coatings on various substrates such as glass, metals and

polymers. The gradient is due to the accumulation of

surface-active fluorosilanol molecules and condensates

at the interface (Tomsic et al. 2008).

The use of nanoparticles together with suitable

silane precursors, solvents and additives allows to

obtain NANOMERs� (‘‘nano-polymers’’) materials

with many different additional properties. The homo-

geneous incorporation of nanoparticles enhances the

densification and improves the mechanical scratch

resistance and chemical durability of the nanocompos-

ites and may confer additional features such as anti-

microbial, UV protection and flame retardant functions

(Alongi et al. 2011a). Due to the nanometer size of the

particles, the coatings maintain a high transparency

between 400 and 1,000 nm. Nanomers can also be

tailored by curing at low temperature or even by UV

light (Han et al. 2007; Alongi et al. 2011b).

Employing organically modified alkoxysilanes con-

taining long-chained aliphatic or highly fluorinated

groups, sol–gel offers far reaching possibilities to

prepare water- as well as oil- repellent textiles (Textor

and Mahltig 2010). Hydrophobic and oleophobic

properties comparable to that of PTFE can be obtained

by using fluoroalkyl-substituted alkoxysilanes such as

(perfluorooctyl)ethyltrialkoxysilane or (perfluorohexyl)

ethyltriethoxysilane (Vilcnik et al. 2009). The high

effectiveness of fluorinated polymer coatings for water

and oil repellency is associated with their ability to

lower the surface energy due to the presence of long

perfluoroalkyl chains [-(CF2)n, -CF3] (Satoh et al. 2004;

Gowri et al. 2010). In fact superhydrophobic and self-

cleaning cotton was prepared by Erasmus and Bark-

huysen 2009 using 20 % add-on of 1H,1H,2H,2H-

fluorooctyl-triethoxysilane (FOS).

A low required add-on is of great interest for textile

applications, because the typical hand and breathabil-

ity of fabrics are not compromised. Furthermore, most

fluorinated materials are very expensive and may often

cause serious risks for the human health in case of skin

contact and for the environment in case of emissions of

fluorine compounds during and after the treatment

process. Therefore, it is necessary to minimize the use

of fluorinated materials (Bae et al. 2009).

Transparency and durability of surface coatings are

particular requirements for textiles. Currently, one

major barrier to widespread commercial use of silane

chemistry is the poor durability, in terms of washing

and abrasion fastness, of the resultant hydrophobic

surfaces. The durability of water-repellent coatings

after washing, especially for those produced on cotton,

remains a challenge, because a post-treatment is

usually required to restore the hydrophobic properties.

Laundering in fact can reduce the hydrophobicity of

treated fabric surfaces by damaging the links formed

by silanes and introducing impurities such as residual

surfactants and moisture. An additional heat-drying

step not only helps to remove residual moisture, but

also works to re-crystallize the long-chain alkyl

groups on the fabric surface, which enhances the

ability of the fabrics to repel water (Roe and Zhang

2009; Daoud et al. 2004).

The formation of highly hydrophobic surfaces on

cotton by silica sols from TEOS and hexadecyltri-

methoxysilane (C16) was reported by Gao et al. 2009,

but in the proposed procedure the fabric was treated in

two steps: firstly by impregnation for 20 min with

silica sol from hydrolyzed TEOS in basic medium

followed by drying at 80 �C; then the fabric was

356 Cellulose (2013) 20:355–364

123

impregnated with hydrolyzed C16 at pH 5, dried at

room temperature and finally cured at 120 �C for 1 h.

Obviously this procedure is too long for practical

purposes. In fact more recently Zhu et al. 2011

proposed a one-step procedure by fabric impregnation

for 30 s in silica sol modified, after TEOS hydrolysis

in basic medium, by addition of alkyltrialkoxysilanes,

followed by drying and curing as before. Moreover the

further addition of an epoxy modifier yielded the

coatings more durable to multiple launderings.

The aim of the present work was to confer a solid

highly hydrophobic behavior to cotton fabrics by one-

step deposition of modified silica based coatings by

sol–gel technique. These were prepared by co-hydro-

lysis and condensation in weakly acid medium of

TEOS-based sols with low amounts of hydrophobic

additives such as C16 or FOS. Textile finishing by C16

can just confer water repellency while FOS enables to

confer both water and oil repellency thanks to the

fluorine presence, but the work was focused on

hydrorepellency and its durability to washing.

Treated fabrics were characterized by SEM, FTIR-

ATR and XPS analyses while their wettability was

evaluated by measuring the water contact angle and

the permanence times of the drops on treated fabrics.

These properties were tested also after five washing

cycles to asses the durability of the treatments to

laundering.

Experimental part

Cotton functionalization

Treated fabrics were EMPA plain-weave pure cotton

(105 g/m2) used as received without scouring. In each

test, 1 g samples were treated. All chemicals were

purchased by Sigma Aldrich.

The sol solution for obtaining silica nanoparticles

was prepared by co-hydrolysis and condensation of

two silane precursors, tetraethylorthosilicate (TEOS)

and 1H,1H,2H,2H–fluorooctyltriethoxy-silane (FOS)

or hexadecyltrimethoxysilane (C16) in ethanol-H2O-

HCl solution. The preparation was carried out by

vigorously stirring, for 24 h at room temperature, of a

mixture of 60 ml of ethanol, 15 ml of TEOS, 15 g of

FOS or C16 and 4 ml of 0.01 N HCl solution,

obtaining sol solutions 17 % w/w of TEOS and

18 % w/w of FOS or C16.

In the sol–gel process, TEOS is hydrolyzed and

condensed according to well known reactions. How-

ever, using C16 or FOS as a co-precursor in the sol–gel

processing stage, the Hs from the OH groups on the

silica clusters are partially replaced by the hydrolyt-

ically stable :Si–C16H33 or :Si–C11H10F13 through

–O–SiC16H33 or –O–SiC11H10F13 bonds respectively.

During acid catalyzed hydrolysis labile silanol

groups are formed, which are enable to promote the

silane adsorption onto the OH-rich cellulose structure

of cotton fibers through hydrogen bonding. According

to the desired water-repellent finishing add-on, proper

amounts of nanosol solution were used to impregnate

the cotton fabrics: the investigated add-on range of

FOS was between 5 till 30 % on fabric weight while

C16 add-on was 5 or 10 % on fabric weight .

For each sample the add-on was calculated accord-

ing to the formula:

msol ¼%add � msample

Caddð1Þ

where msol was the amount of nanosol solution (17 %

w/w TEOS and 18 % w/w additive) to be taken to

obtain the desired add-on percentage (%add), msample

the sample mass and Cadd the mass fraction of the

additive in the nanosol (0.18). Impregnation was

carried out dipping the fabrics in the solution, suitably

diluted by ethanol, at ambient temperature, for differ-

ent times: 1 min, 2 or 24 h.

Then by heat treatment at 120 �C for 1 h silica

nanoparticles adhered onto cotton fibers, thanks the

formation of siloxane bonds between hydroxyl groups

of cellulose and the silanes of modified nanoparticles.

For comparison, two reference samples were also

prepared thermally curing fabrics impregnated with

FOS or C16 without incorporation into silica nanosol, in

order to highlight the nanosol influence on treated

fabrics. The add-on was 5 % in both cases and samples

were prepared by impregnation of the cotton in an

ethanol solution of additive for 2 h at ambient temper-

ature, followed by thermal curing at 120 �C for 1 h.

Characterization

Hydrophobic properties of the cotton fabrics surfaces

were estimated by measuring contact angles using a

DSA20E ‘‘Easydrop standard’’ drop shape analysis

Cellulose (2013) 20:355–364 357

123

system from Kruss, Germany. The measurements

were carried out by the sessile drop method, with

Young–Laplace curve fitting, using HPLC grade water

(72.8 mN/m surface tension), averaging 5 measures

on each fabric side to obtain a representative contact

angle value for each sample with standard deviation of

about 2�.

Moreover, after the drop deposition, also its

permanence time on the fabric before complete

adsorption was evaluated. All measurements were

carried out at ambient temperature.

On finished fabrics, treatment fastness to domestic

washing with standard ECE detergent according to

UNI-EN ISO 105-C01 was evaluated measuring the

contact angle value and permanence time of the drop

after 5 washing cycles. Each sample was treated in a

sealed test tube with a solution of 5 g/l of ECE

detergent maintaining a fabric to bath mass ratio of

1:50. The tubes were fixed on oscillating plane

plunged in a thermostatic bath at 40 �C and agitated

for 30 min. Finally the samples were rinsed in cold

water and dried in air oven at 80 �C. Each sample was

subjected to the same treatment five times.

The surface morphology of the fabrics was exam-

ined by SEM with a Leica (Cambridge, UK) Electron

Optics 435 VP scanning electron microscope with an

acceleration voltage of 15 kV, a current probe of

400 pA, and a working distance of 20 mm. The

samples were mounted on aluminum specimen stubs

with double-sided adhesive tape and sputter-coated

with gold in rarefied argon using an Emitech K550

Sputter Coater with a current of 20 mA for 180 s.

Chemical composition of the fabrics before and

after the treatment was analyzed by X-ray photoelec-

tron spectroscopy (XPS) and by FTIR-ATR.

XPS analyses were performed with a PHI 5000

Versa Probe system (Physical Electronics, MN) using

monochromatic Al radiation at 1486.6 eV, 25.6 W

power, with an X-ray beam diameter of 100 lm. The

energy resolution was about 0.5 eV. XPS measure-

ments were performed at a pressure of 1 9 10-6 Pa.

The pass energy of the hemisphere analyzer was

maintained at 187.85 eV for survey scan and 29.35 eV

for high-resolution scan while the takeoff angle was

fixed at 45�. Since the samples are insulators, an

additional electron gun and an Ar? ion gun for surface

neutralization were used during the measurements.

Binding energies of XPS spectra were corrected by

referencing the C1s signal of adventitious hydrocarbon

to 285 eV. XPS data fittings were carried out with PHI

multipackTM software using the Gauss-Lorenz model

and Shirley background.

FTIR-ATR analyses were performed on a Nicolet

FTIR 5700 spectrophotometer equipped with a Smart

Orbit ATR single bounce accessory mounting a

diamond crystal. Each spectrum was collected directly

on differently treated or untrated samples by cumu-

lating 128 scans, at 4 cm-1 resolution and gain 8, in

the wavelength range 4,000–500 cm-1.

Results and discussion

Water repellency

Firstly a test was carried out on a cotton sample treated

only with TEOS nanosol, without any additive for its

chemical modification. In this case, as expected, no

water repellency was conferred as silica is not

hydrophobic due to the large amount of hydroxyl

groups on its surface.

Water repellency, on the other hand, was conferred

to cotton by the nanosol prepared with TEOS and FOS

or with TEOS and C16, regardless the process condi-

tions. It is evident by the contact angles measured with

water on treated fabrics before washing, reported in

Tables 1 and 2, clearly higher than 90�. These values

have to be compared with the 0� contact angle

Table 1 Water repellency of FOS treated samples before and

after washing (CA : contact angle)

FOS on

fabric

weight

(%)

Impregnation

time

Water

CA

before

washing

(�)

Water

CA after

washing

(�)

Water drop

sorption

time after

washinga

5 1 min 138 139 4 min

10 1 min 137 131 2 h

20 1 min 140 139 90 min

30 1 min 138 136 2 h

5 2 h 138 140 2 h

10 2 h 144 138 [2 h

5 24 h 142 138 [2 h

10 24 h 140 138 [2 h

20 24 h 146 125 [2 h

30 24 h 146 141 [2 h

a Water drop sorption time before washing was in any case

higher than 2 h

358 Cellulose (2013) 20:355–364

123

measured on untreated cotton, due to the immediate

absorption of water drops by the fabric.

In particular, in the case of FOS modified nanosol

applied with an impregnation time of 24 h or C16

modified nanosol, values very close or even higher

than 150� with water were measured, typical of a

superhydrophobic surface. The highest measured

value with water was 169�, conferred by C16 modified

nanosol with 10 % add-on after 1 min impregnation or

with 5 % after 24 h. This result is even higher than that

obtained with C16 by Zhu et al. 2011.

Generally an increase in finish add-on should yield

higher contact angle values at the same impregnation

time. This was observed on samples treated with FOS

modified nanosol for long impregnation times and

even more on C16 treated for 1 min only.

Another evaluated parameter was the permanence of

the drop on the treated fabric, measuring the time till its

complete adsorption. In all cases, after 2 h the water

drops remained unchanged on the fabric surface;

moreover, the same drops rolled away from the textiles

without leaving any traces, as typically performed by

the so-called Lotus effect.

Water drop contact angle and absorption times were

determined also on the reference samples thermally

cured after impregnation with FOS or C16 alone

without silica nanosol, finding a contact angle value of

just 140� and an absorption time lower than 2 h. Hence

these results confirmed the importance of the hybrid

nanosol on the repellency of the fibers.

Washing fastness

Contact angle and absorption time evaluations were

carried out on washed samples differently treated

highlighting, in this case, relevant differences as

shown also in Tables 1 and 2. A slight decrease of

contact angle was measured but the values obtained

were still typical of water repellent finishes. Moreover,

the sample finished by 5 % C16 modified nanosol with

an impregnation time of 24 h showed superhydropho-

bic behavior, while cotton treated with C16 modified

nanosol by Zhu et al. 2011 showed lower water contact

angle values. Such difference could be due to the

different treatment proposed by Zhu: TEOS hydrolysis

in alkaline medium followed by C16 addition and

fabric immersion in the modified silica sol for 30 s

only.

The importance of a prolonged impregnation time

is clear in particular considering the absorption times

of water drops. Washed samples treated with the FOS

modified nanosol showed absorption times quite

comparable with those of the unwashed samples

([2 h), in particular if 24 h of impregnation time

was adopted. On the contrary, times evaluated on C16

nanosol treated samples dramatically decreased to few

minutes of drop permanence on fabric surface, before

its absorption. Evidently the FOS modified silica

nanoparticles are involved in stronger bonds with

cotton than those modified with C16 which could easier

undergo hydrolysis by washing, leaving more free OH

groups. This fact could justify the strong decrease of

drop adsorption times although the contact angle

values were substantially maintained.

Results related to FOS gain even more importance

if compared with the reference sample without nano-

sol. On cotton fabric treated with FOS alone, in fact,

the finish is completely lost after washing as

denounced by the immediate absorption of the water

drop. On C16 reference sample, after washing the

water drop stays on the surface for about 30 s with a

measured contact angle of 135�, so the nanosol

enhances, even if not so strongly as in the case of

FOS, the washing fastness of the treatment.

SEM analysis

SEM micrographs at magnification of 10009 on

cotton samples treated with FOS or C16 modified

nanosol are compared in Fig. 1a–h. The presence of

the finishing on treated fibers is evident comparing

their images with that of untreated cotton (Fig. 1a). In

the samples treated with FOS modified nanosol the

roughness of the fiber surface clearly increases the

Table 2 Water repellency of C16 treated samples before and

after washing (CA: contact angle)

C16 on

fabric

weight

(%)

Impregnation

time

Water

CA

before

washing

(�)

Water

CA after

washing

(�)

Water drop

sorption

time after

washinga

(min)

5 1 min 147 134 5

10 1 min 169 133 2

5 24 h 169 156 5

10 24 h 157 133 5

a Water drop sorption time before washing was in any case

higher than 2 h

Cellulose (2013) 20:355–364 359

123

360 Cellulose (2013) 20:355–364

123

more as higher the add-on. Nevertheless the finish is

gradually taking the shape of a coating adherent to the

each fiber and even at the highest add-on (30 %) the

fibers appear not glued each other and the interfibral

holes remain well open so the fabric breathability

should be not compromised. However lower add-ons

are preferable to obtain fabrics with softer hand.

Comparing washed and unwashed fabrics the

additive presence is evident in both cases meaning

that the finishing was only partially removed by the

mechanical action during washing or by the surfac-

tants. It confirms the results in terms of washing

fastness obtained by contact angle evaluation.

XPS analysis

The results of XPS analyses are reported in terms of

survey scan and high resolution C1s peak in Tables 3

and 4, referring to FOS modified nanosol and in

Tables 5 and 6, referred to C16 modified nanosol.

On all treated samples the presence of the finishing

is revealed by the detection of fluorine and/or silicon

on the fiber surface. The detected amounts are higher

at higher add-ons while, in accordance with the

measured contact angles, decrease after washing on

all treated samples. Nevertheless, considering the FOS

modified nanosol, this decrease is lower on sample 6,

prepared with 24 h of impregnation, confirming the

importance of the impregnation time for the treatment

fastness. In this case, in fact, more finishing agent is

retained after washing, probably thanks to a better

penetration of the same inside cotton fibers and an

intimate bond on them.

On C16 treated samples, more than 50 % of surface

Si was lost after washing. It can be the cause of the low

permanence times of the water drop on the fabric

surface after washing and of the decrease of the

measured contact angle.

Evaluation of the C/Si and O/Si ratios reveals the

organic nature of the finishing. From literature data

related to pure cellulose, high resolution C1s peak

should show only two contributions due to C–OH and

O–C–O groups with a relative intensity about 5:1.

Nevertheless there is always the presence of C–C and

C–H contribute, due to the presence of some surface

impurities, even when analyzing pure cellulose paper

filters. On a purged cotton the value found for C–C and

C–H is usually about 22 % (Mitchell et al. 2005), in

good agreement with the value found on our untreated

cotton sample.

On all the treated samples an increase of this

percentage was found, revealing the presence of the

finishing agent. Moreover, the increase was as higher

as the measured contact angle.

In particular, from the high resolution C1s peak

related to FOS modified nanosol, it can be observed

that, on unwashed samples, the presence of fluorine is

above all in form of CHF. Nevertheless after washing

these groups are lost, leaving just the contribution of

C=O to the related peak, while CF2 and CF3 groups are

less affected by washing, although the ratio F/C

decreased from 1.29 of sample 6 to 0.81 of sample 7.

Sample 6 gave the best performance in terms of

contact angles and absorption times before and after

washing; these values can be related to the XPS results

obtained on the same sample, where the highest

fluorine content as CF2 was detected, before and after

washing. It means that CF2 together with CF3 are the

groups of greater importance to confer water repel-

lency to the substrate rather than CHF group. However

it can be observed that CF2 (%) in sample 7 is higher

than before washing (sample 6), while CF3 (%),

belonging to the same chemical chain, is lower. This

variation can be justified by a rearrangement of the

residual fluorinated groups which could induce the

migration of CF2 groups towards the fabric surface.

Finally, on all C16 treated samples there is a decrease

of the C–OH groups detected with respect to untreated

cotton, confirming the involvement of these groups on

grafting reactions between nanosol and fabric surface.

FTIR-ATR analysis

In Fig. 2 the FTIR-ATR spectra of the fabrics treated

with 30 % FOS and 10 % C16 are compared with the

spectrum of the untreated cotton in the range

4,000–2,500 cm-1. A significant decrease of the

absorbance peak at 3,284 cm-1 assignable to OH

groups is observed, clearly indicating the involvement

of the OH groups of cellulose in the condensation

reactions. Moreover in the spectrum of sample treated

Fig. 1 SEM micrographs at magnification ratio 10009 of

cotton: a untreated; b treated with FOS modified nanosol, 5 %

FOS add-on, 2 h impregnation; c 10 % FOS add-on, 2 h

impregnation; d sample c washed; e 30 % FOS add-on, 24 h

impregnation; f sample e washed; g treated with C16 modified

nanosol, 10 % C16 add-on, 24 h impregnation; h sample g

washed

b

Cellulose (2013) 20:355–364 361

123

with C16 modified nanosol there are two evident peaks

at 2,920 and 2,849 cm-1 due to C–H groups, while the

same peaks are lower and fused in the spectra of

untreated cotton and FOS treated.

In the range 1,500–650 cm-1 (Fig. 3), the presence

of fluorosilane on cotton treated with FOS modified

nanosol is indicated by absorbance increase at

1,150–1,250 cm-1 where C–F stretching occurs

Table 3 XPS analysis. Survey Scan. FOS modified nanosol

N FOS add-on Impregnation time (h) C (%) F (%) O (%) Si (%) Ca (%) C/Si O/Si

1 Untreated cotton – 60.6 – 39.4 – – – –

2 5 % 2 36.6 36.6 20.7 6.1 – 6.0 3.6

3 5 % washed 2 45.5 26.5 22.6 5.0 0.4 6.0 3.4

4 10 % 2 36.6 35.4 21.9 6.1 – 9.1 4.5

5 10 % washed 2 48.0 23.0 23.4 4.6 0.3 10.4 5.1

6 30 % 24 31.1 40.1 20.4 8.4 – 3.7 2.4

7 30 % washed 24 39.3 31.8 21.5 7.4 – 5.3 2.9

Table 4 XPS analysis. C1s peak, high resolution. FOS modified nanosol

N. FOS add-on Impregnation time (h) C–C C–H (%) C–OH (%) O–C–O (%) C=O CHF* (%) CF2 (%) CF3 (%)

1 Untreated cotton – 27.0 62.2 10.8 – – –

2 5 % 2 35.6 22.8 20.4 12.7 6.2 2.3

3 5 % washed 2 57.1 18.7 13.3 4.7 5.2 1.0

4 10 % 2 46.8 31.5 12.7 6.4 2.4 0.2

5 10 % washed 2 38.3 48.7 7.2 3.6 1.5 0.7

6 30 % 24 15.7 38.7 11.2 23.2 7.6 3.6

7 30 % washed 24 33.6 37.9 9.7 6.4 10.4 2.0

* in presence of fluorine

Table 5 XPS analysis. Survey Scan. C16 modified nanosol

N. C16 add-on Impregnation time C (%) O (%) Si (%) Ca (%) C/Si O/Si

1 Untreated cotton – 60.6 39.4 – – – –

2 5 % 1 min 71.9 21.1 7.0 – 10.3 3.0

3 10 % 1 min 66.1 23.7 10.2 – 6.5 2.3

4 5 % 24 h 61.9 25.7 12.4 – 5.0 2.0

5 10 % 24 h 62.0 26.2 11.9 – 5.2 2.2

6 10 % washed 24 h 73.6 19.2 5.8 1.5 12.7 3.3

Table 6 XPS analysis. C1s peak, high resolution. C16 modified nanosol

N. C16 add-on Impregnation time C–C C–H (%) C–OH (%) O–C–O (%) C=O (%)

1 Untreated cotton – 27.0 62.2 10.8 –

2 5 % 1 min 33.9 29.0 30.3 6.8

3 10 % 1 min 23.2 45.0 28.6 3.2

4 5 % 24 h 55.2 30.9 11.8 2.1

5 10 % 24 h 89.9 3.1 5.7 1.3

6 10 % washed 24 h 68.8 22.8 6.0 2.4

362 Cellulose (2013) 20:355–364

123

(Erasmus and Barkhuysen 2009), while a peak at

790 cm-1 is observed in the spectra of samples treated

with both modified nanosols and could be due to Si–C

stretching according to Gao et al. 2009. However the

most significant peaks of the coating are overlapped to

those typical of cellulose substrate.

Conclusions

From the obtained results it can be concluded that the

chemical modification of TEOS nanosol by co-

hydrolyzed FOS or C16 in weakly acid medium and

the following application on textiles substrates is a

promising method to confer high hydrophobicity to

cotton fabrics. In this way, silica and fluorine based

compounds can be homogeneously nano-dispersed on

the fabric surface with the consequence of an increase

of the surface roughness coupled with the lowering of

the surface free energy.

Water contact angles, in many cases close to 150�or even higher, were measured on treated fabrics with

an important increase with respect to the C16 or FOS

thermally treated samples without nanosol.

The application of the proposed sol–gel process

yielded also a satisfactory treatment fastness to

domestic washing, in particular for FOS modified

nanosol, while that modified with C16 was partially

removed from fabric surface by washing, as revealed

by XPS analysis.

The water drop absorption times showed the

importance of the impregnation time on the durability

to washing with the best results ([2 h) after 24 h

impregnation in the case of FOS modified nanosol.

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