Impregnation of cotton fabric with pyrethrum extract in supercritical carbon dioxide

The Journal of Supercritical Fluids 128 (2017) 66–72

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Impregnation of cotton fabric with pyrethrum extract in supercritical carbon dioxide

MARK

Jelena Pajnika, Marko Stamenićb, Maja Radetićb, Snežana Tomanovićc, Ratko Sukarac, ⁎ Darko Mihaljicac, Irena Zizovicb, a b c

Innovation Center of the Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, Belgrade, Serbia Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, Belgrade, Serbia Department for Medical Entomology, Institute for Medical Research, University of Belgrade, Belgrade, Serbia

A R T I C L E I N F O

A B S T R A C T

Keywords: Supercritical carbon dioxide Pyrethrum extract Pyrethrin Solubility Supercritical solvent impregnation Tick repellent activity

This study discusses a possibility of cotton fabric impregnation with pyrethrum extract as a tick repellent in supercritical carbon dioxide. A solubility of pyrethrum extract in supercritical carbon dioxide has been determined at 35 and 40 °C and pressures ranging from 8 to 20 MPa. The highest solubility of 48.69 kg/m3 was obtained at temperature of 35 °C and pressure of 20 MPa. Density-based equations of Chrastil, Adachi-Lu and del Valle-Aguilera were employed to correlate the experimental data. Based on the solubility data, conditions for the impregnation of cotton fabric were selected. Conditions at 40 °C and 8 MPa provided targeted quantities of the impregnated extract of 0.5% and 1% after 1 h and 2 h of the impregnation, respectively. The presence of pyrethrins on the cotton fabric’s surface was confirmed by FTIR analysis. Repellent activity of both impregnated cotton fabrics (pyrethrum extract contents of 0.5% and 1%) was proven against ticks.

1. Introduction Pyrethrum is one of the oldest natural insecticides which was first mentioned in ancient China. It is believed that it was brought to Europe along the silk roads [1]. Pyrethrum is obtained in a process of drying and powdering of flower heads of a white-flowered perennial plant, Chrysanthemum cinerariaefolium [1]. Pyrethrum extract is a highly viscous liquid [2] and it is produced from pyrethrum through different kinds of extraction [3,4]. Pyrethrins are components of pyrethrum extract that possess strong insecticidal activity [1]. Pyrethrins are esters of chrysanthemic acid (pyrethrins I) and pyrethric acid (pyrethrins II). According to the alcohol type, they are further classified into pyrethrin I and II, cinerin I and II and jasmolin I and II [5]. Among all, the best insecticidal activity is achieved by combining pyrethrin I and II due to their different properties. Pyrethrin I exhibits higher lethality and pyrethrin II higher knockdown activity [6]. Pyrethrins are widely used as insecticides for cold-blooded animals as they target the voltage-gated sodium channels of insect neuronal membranes, initiating paralysis and death [7]. On the other hand, the great advantage of pyrethrins is their low mammalian toxicity [8]. Ticks are the most significant arthropod vectors of human pathogens in temperate regions of the world, and only second to mosquitoes in tropics and subtropics [9]. The list of tick-borne pathogens is long

⁎

including viruses (Flaviviruses, Coltiviruses and Nairovirus), bacteria (Spirochetes, Rickettsiae, Francisella spp.) and protozoa (Babesia spp.) [10]. Pyrethroids, synthetic derivatives of pyrethrins, were found to be effective repellents against different species of ticks [11–15]. Additionally, Kapoor et al. [16] reported that ticks were the most susceptible to pyrethrins, among all tested insecticides. Different methods for impregnation of fabrics with repellents have been previously reported: dipping [17], spraying [18–20], polymercoating [21,22] and microencapsulation methods [23,24]. A coating of textile surfaces with different polymers in the presence of repellents provides the opportunity to improve the washing fastness of impregnated fabrics [21,22]. Microencapsulation technique [23,24] is performed by microencapsulation of appropriate repellent through the complex coacervation method. Afterwards, the microcapsule suspension is bound to fabrics in the presence of fixing agent. Most of the listed techniques exploit pyrethroids as active substances. Their wide use over the last decades resulted in development of a resistance in some insects species [25,26]. Pyrethrins are known as very efficient insecticides against various insect pests such as cockroaches, mosquitoes, fleas etc. [27]. Major drawbacks of pyrethrins, photo- and air degradation, can be successfully overcome by mixing them with proper substances like antioxidants in order to prolong their self-life [28]. Sum et al. [29]

Corresponding author at: Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11120 Belgrade, Serbia. E-mail address: [email protected] (I. Zizovic).

http://dx.doi.org/10.1016/j.supflu.2017.05.006 Received 17 March 2017; Received in revised form 5 May 2017; Accepted 6 May 2017 Available online 09 May 2017 0896-8446/ © 2017 Elsevier B.V. All rights reserved.

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Košutnjak forest (Belgrade, Serbia) during September 2016. Prior to testing, ticks were kept for 24 h at 21 °C, 80% humidity and 16:8 (L:D) h in the tick rearing chamber at the Department for medical entomology, Institute for medical research University of Belgrade.

investigated efficiency of nets impregnated with stabilized pyrethrins by the dipping method against three days old female mosquitoes (Anopheles gambiae). Pyrethrins content of 375–400 mg/m2 for polyester fabric and 250 mg/m2 for nylon fabric were needed to reach the mortality level of 80% during three minutes. On the other hand, cotton fabric required much larger doses of pyrethrins (> 1000 mg/m2) [29]. The same group of authors demonstrated that polyester bednets impregnated with 500 mg/m2 of stabilized pyrethrins exhibited high bio-efficacy against Anopheles gambiae after six months period, including three wash cycles [30]. Supercritical carbon dioxide (scCO2) has been recognized as a green solvent and an attractive alternative to organic solvents due to its numerous advantages [31,32]. Unique properties of scCO2 have directed attention towards supercritical solvent impregnation (SSI) technology which exploits the benefits of supercritical fluids to transfer and incorporate solute molecules into a polymer network [33–36]. In order to achieve optimum impregnation rate, it is of the utmost importance to determine solubility of the solute in scCO2. Various models have been utilized to predict and correlate the solubility of liquids and solids in supercritical fluids. The most used are semiempirical density based models for solubility data correlation as they do not require solute properties for calculations [37–39]. Supercritical fluid technology has been proven to be efficient in delivering of biocides into wood and wood composites whereby SSI with carbon dioxide has been applied on industrial scale [40–42]. Impregnation of timber with permethrin using scCO2 was found to be very efficient in a control of termites [43]. Several papers reported the SSI of solids with essential oils and their components possessing repellent properties. Wood beads aimed for tick-repellent collars for animals were impregnated with eucalyptus oil using the SSI technique [44]. Poly(L-lactide-ran-cyclic carbonate), poly(LLA-ran-cyclic monomer) and L-lactide-ε-caprolactone were impregnated with d-limonene and α-pinene as repellents, using the same technique [45–47]. Although the supercritical fluid technology has been utilized on industrial scale in textile dyeing [31], to the best of our knowledge, there are no reports in the open literature dealing with impregnation of textile fabrics with a repellent in scCO2. The most important advantage of SSI over conventional textile finishing processes is the absence of waste water generation. In this study, SSI of cotton fabric with a commercial pyrethrum extract was studied. In the interest of selecting optimum process parameters, solubility of the commercial pyrethrum extract in scCO2 was investigated first using the static method. Modeling of the obtained solubility data was performed by employing semi-empirical models of Chrastil, Adachi-Lu and del Valle and Aguilera. Repellent activity of the impregnated cotton fabrics against ticks was investigated.

2.2. Solubility determination Solubility of pyrethrum extract was evaluated in a high-pressure view cell (Eurotechnica GmbH, 25 ml), using a static method. Detailed description of the high-pressure view cell was given elsewhere [48]. Briefly, a glass container with pyrethrum extract (1.00 g) was placed inside the view cell. To prevent precipitation of the pyrethrum extract during decompression, the stainless steel filter was placed above the glass container. Once the required temperature was attained, the system was pressurized by pumping CO2 into the view cell. Experiments were carried out at temperatures of 35 and 40 °C and pressures in the range of 8–20 MPa or scCO2density range 426.85–841.00 kg/m3 [49]. Higher temperatures than 40 °C haven’t been considered because of the pyrethrins’ thermal instability [3,50]. At the end of each experiment CO2 was released from the view cell at decompression rate of 0.33 MPa/min. The amount of dissolved pyrethrum extract was calculated as the mass difference of the pyrethrum extract before and after the solubilisation process (quantified on analytical scale with accuracy ± 0.0001 g). 2.3. Correlation of solubility data Semi empirical equations of Chrastil, Adachi-Lu and del ValleAguilera were used for correlation of the solubility data in order to determine which model provides the highest accuracy. One of the first density-based models was defined by Chrastil using the linear relationship between logarithm of solubility and density of pure supercritical fluid [37]:

⎛A ⎞ S = d k exp ⎜ + B⎟ ⎝T ⎠

(1)

where S is the solubility of solute (g/l), d is the density of pure solvent (g/l) and T is the temperature (K). The coefficient k is the association number which represents the number of gas molecules associated with one molecule of solute in a state of equilibrium. Parameter A is a function of the enthalpies of solvation and vaporization of the solute. Parameter B depends on the molecular weights of the solute and solvent. Adachi and Lu modified Chrastil’s model by making the association number to be density dependent as shown in Eq. (2) [38]:

⎛A ⎞ 2 S = d e0 + e1⋅⋅ d + e2 ⋅ d exp ⎜ + B⎟ ⎝T ⎠

2. Materials and methods

(2)

2.1. Materials Another approach of modifying Chrastil’s equation was proposed by del Valle and Aguilera Eq. (3) [39]. Dependence of the vaporization heat on temperature was included while the parameter k remained temperature independent.

Commercial pyrethrum extract was supplied by Ekosan (Serbia). Total pyrethrin content in the extract was 65.1%, whereby there were 38.2% of pyrethrins I (3.6% of cinerin I, 31.8% of pyrethrin I and 2.8% of jasmolin I) and 26.9% of pyrethrins II (3.2% of cinerin II, 21.7% of pyrethrinII and 2.0% of jasmolin II). Commercial CO2 (purity 99%) was purchased from Messer–Tehnogas (Serbia). Desized and bleached cotton (CO, 117.5 g/m2, 52 picks/cm, 27 ends/cm, thickness of 0.26 mm) woven fabric was used as a substrate in this study. In order to remove surface impurities, the CO fabric was washed in the bath (liquor-to-fabric ratio of 50:1) containing 0.5% nonionic washing agent Felosan RG-N (Bezema) for 15 min at 50 °C. After the single rinsing with warm water (50 °C) for 3 min and triple rinsing (3 min) with cold water, the samples were dried at room temperature. Ixodes ricinus ticks used for assessments of repellent characteristics of the impregnated cotton were collected from vegetation by flagging at

⎛A C⎞ S = d k exp ⎜ + B + 2 ⎟ ⎝T T ⎠

(3)

The model parameters were calculated by minimizing the AARD function given by Eq. (4), applying the excel solver tool:

AARD =

1 n

n

∑ i =1

Si,exp − Si, cal Si,exp

⋅100% (4)

where n is the number of experimental data points, while indexes ‘exp’ and ‘cal’ refer to the experimental and calculated values of the solubility at point i, respectively. 67

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2.4. Supercritical impregnation of cotton fabrics Impregnation of CO fabric with pyrethrum extract was performed in the Autoclave Engineers high pressure vessel (150 ml). Detailed description of the equipment was reported elsewhere [48]. Pyrethrum extract was placed in the glass container at the bottom of the vessel, below porous barrier to prevent possible splashing on the fabric’s surface during filling the vessel and decompression. CO fabric was cut into 9 cm × 15 cm samples, rolled around the stainless steel support and placed above the porous barrier. CO fabric/pyrethrum extract mass ratio was 1.70 ± 0.05 g/g. After reaching the process temperature, CO2 was pumped into the system until the desired pressure was attained. The system was kept at the operating conditions for desired time intervals. Based on the solubility data, temperature of 40 °C and pressures of 8 and 10 MPa were selected for the impregnation of CO fabric. Experiments were carried out with different durations from 1 to 24 h. At the end of each experiment, CO2 was released from the vessel at decompression rate of 0.33 MPa/min. Mass of the impregnated extract (mex) was determined gravimetrically as the mass difference of the CO fabric after and before the impregnation (quantified on analytical scale with accuracy ± 0.0001 g). Impregnation yield (I) was calculated as the mass ratio of the impregnated extract and impregnated CO fabric (micf) multiplied by 100% (Eq. (5)).

I=

mex ⋅100% micf

Fig. 1. Mass of dissolved pyrethrum extract in scCO2 in the system versus time at 40 °C and 8 MPa. Table 1 Solubility of pyrethrum extract in scCO2. P (MPa)

S (kg/m3)

σ

d CO2 (kg/

P (MPa)

S (kg/m3)

σ

m3)

(5)

m3 )

35 °C 8 10 20

2.5. Characterization of the cotton fabric Fourier-transform infrared (FT-IR) spectra of impregnated and control cotton fabrics samples were recorded in the ATR mode between 500 and 4000 cm−1 using a Nicolet 6700 Spectrometer(Thermo Scientific) spectrometer with a resolution of 2 cm−1.

23.57 39.28 48.69

d CO2 (kg/

40 °C 0.94 1.40 0.53

426.85 712.82 865.72

8 10 15 20

15.09 34.4 43.28 46.98

σ - standard deviation (corrected sample standard deviation

0.75 1.46 1.83 1.49

277.91 629.75 780.30 841.00

∑ (xi − x )2 /(n − 1) ).

determined solubility of commonly used pyrethroid permethrin in scCO2 at temperatures between 35 and 60 °C and pressures ranging from 8.1 to 28.37 MPa with and without methanol as a co-solvent [43]. Higher solubility was obtained at higher density (temperature of 35 °C compared to 40 °C), which is in accordance with the results from this study. The solubility values of permethrin in scCO2 without co-solvent were reported to be in the range of 0.17- 30.1 kg/m3 [43]. Those values are lower compared to the solubility of the pyrethrum extract obtained in this study, especially at lower pressures (0.17 kg/m3 for permethrin at 8.1 MPa and 23.57 kg/m3 for the pyrethrum extract at 8 MPa), while at higher pressures this difference is not so profound (11.83 kg/m3 for permethrin at 20.3 MPa and 48.69 kg/m3 for the pyrethrum extract at 20 MPa). This finding led to an assumption that the SSI with the pyrethrum extract would be feasible even at lower pressures around 8 MPa. Both experimental and correlated data on the pyrethrum extract solubility in scCO2 are presented in Figs. 2 and 3, while the calculated parameters of the applied density based models are shown in Table 2. It is evident that Adachi-Lu model gave the least accurate results, regardless of the largest number of parameters used (five). It is possible that this model would be more accurate with additional experimental data whereby the number of degrees of freedom would be larger. On the other hand, Chrastil and del Valle and Aguilera models showed good agreement with the experimental data, the latter one being slightly more accurate. Since the difference in obtained results between the two models is practically insignificant, conclusion can be made that Chrastil’s model, since it has less parameters, can be used for correlating pyrethrum extract solubility in scCO2. In order to show tendencies, modelling results in Fig. 2 are shown in the broaden range of pressure and temperature (for which there are no experimental data). Results are shown for pressure range from 7.5 to 35 MPa, while the temperature range was broaden to include temperature of 50 °C. These results confirm that for obtaining higher solubility

2.6. Repellent activity of impregnated CO fabrics Representative sample of 60 ticks (30 males and 30 females) was selected for testing. Repellent activity of the impregnated fabrics was evaluated by exploiting tick natural behaviour of questing against gravity, in the presence of host-associated attractant stimuli within in vitro vertical bioassay [51]. Two concentrations of the impregnated pyrethrum extract on CO fabric were evaluated, 0.5 and 1%. 3. Results and discussion 3.1. Determination and correlation of the solubility data In the first experiments, the rate of the pyrethrum extract solubilisation in the view cell was examined. Higher temperature (40 °C) and the lowest pressure (8 MPa), corresponding to the lowest scCO2 density, were selected for the experiments. Obtained results are presented in Fig. 1. As can be seen, the equilibrium (solubility) in the system was reached after 18 h. Therefore, the time of 18 h was selected for the subsequent solubility determination experiments. Obtained solubility data are presented in Table 1. According to the results, it could be concluded that the solubility of pyrethrum extract was scCO2 density driven at tested pressure and temperature conditions. Increase of vapour pressure due to temperature increase from 35 to 40 °C did not cause the solubility increase. The higher the density of scCO2, the higher the solubility. In other words, higher solubility was obtained at lower temperature and higher pressure, whereby the highest solubility of 48.69 kg/m3 was achieved at temperature of 35 °C and pressure of 20 MPa at the conditions of the highest scCO2 density (865.72 kg/m3). The results presented indicated that the density of scCO2 had the ultimate influence on the solubility by assembling influences of pressure and temperature. Cookson et al. 68

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Fig. 2. Solubility of the pyrethrum extract in scCO2 at various pressures correlated by: (a) Chrastil, (b) Adachi–Lu and (c) del Valle and Aguilera equation.

the lowest solubility) were selected for further experiments. The temperature of 35 °C was not taken into consideration for the SSI because even higher rate of the SSI was expected due to the higher solubility of the pyrethrum extract. The experiments of SSI at 8 MPa and 40 °C were performed in triplicate and the average values of the impregnation yield are presented in Table 3. As can be seen, the target values of impregnation yield of 0.5% and 1% were reached after one and two hours of impregnation, respectively. The SSI kinetics at 40 °C ad pressures of 8 and 10 MPa is presented in Fig. 4.

it is recommended to operate at higher pressures and lower temperature. Moreover, it is obvious that in the lower pressure area, the increase in temperature drastically influences the decrease in solubility, while at higher pressures these differences are significantly less pronounced. 3.2. Impregnation of CO fabric in scCO2 In the preliminary experiments with short impregnation times we obtained negative impregnation yields which led us to conclusion that moisture content of cotton fabric influenced the process. Thus, cotton fabric was exposed to pure scCO2 at 40 °C and 8 and 10 MPa to determine the content of extractables. The experiments were performed in triplicate and an average mass reduction of 1.6% was used for the correction of the obtained impregnation yields in the subsequent experiments. Recommended permethrin concentrations in textiles are limited to maximum 1250 mg/m2 by the United States Environmental Protection Agency (US EPA) and to 1300 ± 300 mg/m2 by the German Federal Institute for Risk Assessments (GFIFRA) [52–54]. In addition, pyrethrins contents in fabrics of 100, 250, 500 and 1000 mg/m2 were tested for the repellent efficiency in the previously published studies [29,30]. Based on these data, the target impregnation yields in this study were set to 0.5% and 1% which correspond to the concentration of pyrethrum extract on cotton fabric of 645 and 1290 mg/m2, respectively. First experiments were performed at pressure of 10 MPa and temperature of 40 °C. The results revealed considerably high rate of impregnation (Table 3). After just one hour of the batch SSI, impregnation yield of 2.42% was achieved, which exceeded the target values. Therefore, pressure of 8 MPa and temperature of 40 °C (conditions of

3.3. CO fabric characterization The presence of pyrethrins on the surface of the CO fabric was confirmed by FTIR analysis. Fig. 5 shows the FTIR spectra of control CO fabric and the cotton fabric impregnated with the pyrethrum extract (impregnation yield of 0.98%, CO + Pyr 0.98%). Characteristic bands of the cellulose in the control CO sample which fit well to literature data can be clearly observed: a broad band in the region between 3500 and 3200 cm−1 (the stretching vibrations of OH group) [55–58]; a broad band with a peak centered at 2898 cm−1 (CeH asymmetric stretching) [55]; the bands at 1429, 1368, 1317 and 1281 cm−1 (CeH in plane bending vibrations, CeH bending (deformation stretch) vibrations, CeH wagging vibrations and CeH deformation stretch vibrations, respectively) [55,56]; the bands at 1335, 1248 and 1204 cm−1 (OH in-plane bending vibrations) [55]; the bands at 1160 and 1108 cm−1 (asymmetric bridge CeOeC) [55]; the band at 1053 cm−1 (asymmetric in plane ring stretching) [55]; the band at 1030 cm−1 (CeO stretching) [55] and band at 900 cm−1 (asymmetric out-of-phase ring stretching at C1eOeC4 β glucosidic bond) [55–59]. The presence of CO2 (doublet at 2362 and 2334 cm−1) was also detected [55–59]. 69

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Fig. 3. Pyrethrum extract’s solubility in scCO2 vs. scCO2 density. Data correlated by: (a) Chrastil equation, (b) Adachi–Lu equation and (c) del Valle and Aguilera equation. Table 2 Parameters of the applied density based models: Chrastil (1), Adachi-Lu (2) and del Valle and Aguilera (3).

(1) (2) (3)

T (°C)

k

A

B

C

e0

e1·104

e2·107

AARD (%)

AARD(%)(%)

35 40 35 40 35 40

1.02

−156.60

−2.51

–

–

–

–

0.73

–

−160.00

−3.32

–

1.40

−7.70

5.50

1.02

−160.68

−2.95

41296.60

–

–

–

0.93 0.52 5.10 13.99 0.48 0.43

Table 3 Impregnation yield (I) in the SSI of CO fabric with pyrethrum extract at 40 °C. I (%) t (h) 1 2 4 8 18 24

8 MPa 0.50 1.01 3.93 8.02 9.60 9.90

σ 0.19 0.21 0.29 0.30 0.31 0.25

10 MPa 2.42 – – 9.68 11.2 11.4

σ 0.30 0.19 0.41 0.25 0.29 0.35

σ - standard deviation (corrected sample standard deviation ∑ (xi − x )2 /(n − 1) ).

After impregnation, several new bands likely originating from pyrethrin appeared in the FTIR spectrum. The band centered at 1715 cm−1 corresponds to C]O group while the band at 1647 cm−1 is assigned to C]C group of pyrethrins [60]. In addition, pyrethrins obviously contribute to slight increase of the band intensity at 2898 cm−1 compared to control CO fabric due to CeH asymmetric stretching. The other specific bands corresponding to these esters could not be distinguished as they overlap with bands originating from CO

Fig. 4. The SSI kinetics at 40 °C.

70

9.55 0.46

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as a durability of the repellent potential of the impregnated fabrics is needed. The results demonstrated that it was possible to obtain high impregnation yields using SSI due to the high solubility of the pyrethrum extract in scCO2 and penetration ability of the supercritical fluid. Therefore, application of SSI in finishing of other textiles with repellents, apart from clothes, like nets, tents and different textiles for civil, medicinal and military application especially in tropical areas should be investigated. Acknowledgment Financial support of the Ministry of Education, Science and Technological Development of the Republic of Serbia (Projects III45017 and ON173006) is gratefully acknowledged. References Fig. 5. FTIR spectra of control cotton fabric (CO) and cotton fabric impregnated with pyrethrum extract (CO + Pyr 0.98%).

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fiber. Additionally, a doublet band located at 2360 and 2341 cm−1 corresponding to presence of CO2 can be observed. It can be attributed to the sorption of CO2 during scCO2 impregnation [61]. 3.4. Tick repellent activity Both samples of impregnated CO fabric (pyrethrum extract contents of 0.5% and 1%) showed repellent activity. All the ticks, regardless of sex, have altered a motion compared to the natural questing activity. In negative controls, with non-impregnated CO fabrics used in the bioassay, ticks were moving upwards toward the host associated stimuli, passing freely the zone of tube labelled as “repellent zone”. In the tests where the impregnated CO fabrics (both concentrations of the pyrethrum extract) were used, ticks either refused to enter the “repellent zone” or stayed there for less than critical time point of 5 s, despite the host associated stimuli. In addition, same altered behaviour was observed in subsequent evaluations, proving therefore steadiness of the impregnated compound and its repellent activity. Obtained results indicated that impregnation with pyrethrum extract in scCO2 can efficiently impart repellent activity against ticks to CO fabric. However, taking into account that textile goods with such properties are commonly manufactured for garments and technical textiles for outdoor use, it becomes clear that this research requires an extension towards evaluation of washing fastness (garments), rainfall resistance (tents) and effect of humidity on the stability of extracts adsorbed on the fabric surface (application in tropical environment). Therefore, these issues will be elaborated in the following studies. 4. Conclusion Solubility of the commercial pyrethrum extract in scCO2 was determined using the static method at temperatures of 35 and 40 °C and pressures between 8–20 MPa. The solubility of the extract was in the range from 15.09 kg/m3 to 48.69 kg/m3 and was density dependent. Semi-empirical model of del Valle and Aguilera was the most accurate in the solubility data correlation with the AARD% value of 0.46. The SSI at 8 MPa and 40 °C (conditions of the lowest solubility) provided the desired pyrethrum extract quantities of 0.5% and 1% in cotton fabrics after one and two hours of the impregnation, respectively. The presence of pyrethrins on the surface of the cotton fabric was confirmed by FTIR analysis. Fabrics with both examined pyrethrum extract contents (0.5% and 1%) exhibited high repellent activity against ticks. Obtained results indicated high solubility values of the pyrethrum extract in scCO2 and feasibility of SSI in production of textiles with repellent characteristics. Further research concerning the minimum active concentration of the pyrethrum extract on fabrics’ surface as well 71

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