INTRODUCTION

At present, various methods for modifying the surface of textile materials, including using nanoparticles, are widely used to impart specified properties to them. To obtain antibacterial materials with antistatic and heat-reflecting properties, they are modified by metal nanoparticles [1]. Also, the deposition of nanoparticles on the surface of textile materials is used to produce a functional relief on their surface, while the material acquires additional surface properties such as hydrophobicity, enhanced adhesion, refraction, etc. [2].

When depositing nanoparticles on the surface of textile materials, it is important to choose a method for preparing the surface and applying and fixing the nanomodifier. The use of environmentally friendly and resource-efficient approaches in obtaining materials with controlled properties is preferable. When using vacuum-thermal deposition, the advantages of which are adjustable deposition rate and versatility, this method can deposit nanoparticles of pure metals, alloys, dielectrics, and magnetic compositions; the energy of the deposited particles is unregulated and coatings of insufficient purity are prepared [3]. Textile materials prepared by electrochemical metallization are characterized by a rigid neck, and the deposited coating does not always have good adhesion to the substrate [4]. Methods based on the metallization of textile materials from electrolyte solutions are not environmentally friendly, since they imply the use of aggressive and toxic substances [5].

From the economic and technological point of view, the use of low-pressure high-frequency (HF) plasma is promising for modifying textile materials before deposition and for fixing nanoparticles. The research results [6–8] show that the treatment of textile materials with low-pressure HF capacitive discharge plasma makes it possible to change surface properties, improve adhesion and sorption characteristics, and improve physical and mechanical properties of fibers and threads. The change in the surface properties of textile materials is a prerequisite for the further functionalization of their surface by nanoparticles. This is especially true for textile materials based on synthetic fibers, the surface of which is inert and requires activation. In addition, there is a need to obtain nanomodified textile materials with stable properties over time; to this end, it is necessary to solve the problem of the stable fixation of nanoparticles on the surface of a textile material.

Low-pressure HF plasma is also effectively used in the processes of depositing nanoparticles on fibrous materials [9–11]. The preliminary exposure to low-pressure HF plasma provides the preparation of the surface of materials before the subsequent condensation of metallic nanocoating, and the final plasma modification contributes to the increase in the adhesive strength of the deposited coating on the substrate. Despite the presence of a significant amount of research in the field of modifying materials of different natures with nanoparticles using plasma treatment, the activation of nanoparticles in a gas flow with the further effective fixation on the surface of materials has not been studied enough.

EXPERIMENTAL

The use of low-pressure HF plasma in the processes of modification of polypropylene (PP) nonwoven materials with silver nanoparticles to impart antibacterial properties was studied on samples of spunbond material (Plant Elastic Ltd., Kazan); a colloidal aqueous solution of silver nanoparticles AgBion-2 was selected as an antibacterial drug (CJSC Concern Nanoindustry, Moscow). The modification of glass textiles by silicon dioxide nanoparticles prepared by the gas-phase method [12] in low-pressure HF plasma was studied on samples of EZ-200 glass fabric (Plant of Thermal Insulation Materials Ltd, Kopeisk). To modify textile materials, experimental plasma setups of low-pressure high-frequency capacitive (HFC) and induction (HFI) discharges were used [13, 14]. The results of modifying materials with nanoparticles using low-pressure HF plasma were estimated using the values ​​of the capillarity parameters, the wetting angle, the amount of nano-modifier contained in the sample, and the abrasive resistance of the coating. The following analytical equipment was used in the study: Kruss Easy Drop DSA 20E instrument, an Olympus OLS Lext 4100 confocal laser scanning microscope, and an iCAP 6300 DUO ICP spectrometer.

RESULTS AND DISCUSSION

To establish the regularities of the effect of parameters of low-pressure HF plasma on the properties of PP nonwoven materials, the parameters were varied when they were processed: discharge power Wd = 0.4–2.2 kW; processing time τ = 60–600 s; pressure in the working chamber P = 10–30 Pa; plasma-forming gas consumption G = 0.01–0.04 g/s; and the plasma-forming gases were argon, air, argon/air (70/30), and argon/nitrogen (70/30). The values of the wetting angle of PP fibrous materials depending on the modes of plasma modification and the composition of the plasma-forming gas are presented in Table 1.

Table 1. Changes in the wetting angle of the surface of nonwoven PP fabric depending on the composition of the plasma-forming gas and the mode of the plasma modification
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The largest decrease in the wetting angle for the PP nonwoven material is observed when processed in the mode Wd = 1.4 kW; τ = 180 s, Р = 30 Pa; and G = 0.04 g/s, in the mixture of argon/nitrogen gases in the ratio of 70/30. The increase in wettability of the PP material makes it possible to effectively impregnate it with a colloidal solution of silver nanoparticles. Impregnation was carried out using a solution with the concentration of silver nanoparticles of 0.028 g/dm3, solution temperature of 22°С, and impregnation time of 20 min.

For the stable fixing of silver nanoparticles in the surface layer of the nonwoven material, the following HFC plasma treatment mode is proposed: Wd = 1.4 kW, τ = 180 s, Р = 30 Pa, G = 0.04 g/s, and the plasma-forming medium was an argon/propane-butane gas mixture in the ratio of 70/30. The treatment of PP materials modified with silver nanoparticles by low-pressure HFC plasma prevents them from being removed from the surface of fibers during their mandatory preoperation gas sterilization, while the deposition of nanoparticles without plasma treatment removes up to 18% of silver during gas sterilization15].

Repeated plasma treatment leads to the additional fixation of nanoparticles on the surface of the material due to ion bombardment, which contributes to the physical adsorption of silver nanoparticles in the surface layers, as well as to the formation of a surface network due to the presence of propane–butane, which is able to interact in the ionized state with ionic free-radical bombardment in the surface layer of fiber-forming polymers [15].

The processes of the deposition and fixation of SiO2 nanoparticles on glass fibers were studied using low-pressure HFI discharge plasma, the nanoparticle deposition technique described in [16] was used, and the HFI plasma pretreatment of glass fibers was performed in order to eliminate surface defects and increase the adhesion interaction with the deposited material [17]. The preliminary HFI plasma treatment mode was as follows: current at the anode of the generator tube Ia = 2.5 А, installation height of the sample above the plasmatron cut h = 30 mm, τ = 300 s, Р = 60–90 Pa, G = 0.06 g/s, and the plasma-forming medium was argon. The SiO2 nanoparticles in conditions of the HFI plasma were deposited in the following mode: Ia = 1.6 А, h = 30 mm; τ = 60 s, Р  = 55 Pa, G = 0.06 g/s, consumption of SiO2 nanoparticles Gnano = 0.5 g/s, and the plasma-forming medium was argon.

The efficiency of producing a microrelief on the surface of glass fiber with the use of plasma treatment was evaluated by the CLSM method (Fig. 1).

Fig. 1.
figure 1

CLSM images of the surface of a glass-fabric sample: (a) before modification; (b, c) after modification (Ia = 1.6 А, h = 30 mm, τ = 60 s, Р = 55 Pa, G = 0.06 g/s, Gnano = 0.5 g/s, and the plasma-forming medium is argon).

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The effect of modifying glass fabric with SiO2 nanoparticles using low-pressure HFI plasma on wettability is presented in Table 2.

Table 2. Effect of glass-fabric modification with SiO2 nanoparticles using low-pressure HFI plasma on wettability indicators
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It has been established that, when SiO2 nanoparticles are deposited under low-pressure RFI plasma conditions with preliminary plasma glass-fiber processing, a developed functional relief is formed on the surface of modified materials [16]. In addition, the modified glass fiber has high wettability, and the deposited nanoparticles are stably fixed on the surface of materials [17]. The results are of interest for the production of a glass composite with high adhesive strength, as well as insulation materials with controlled wettability.

CONCLUSIONS

The conducted studies make it possible to conclude that the modification of HF plasma of low pressure is a promising method in the processes of depositing and fixing nanoparticles on the surface of chemical fibers and textile materials. The resulting materials can be used to produce disposable medical products with antibacterial properties, as well as to fabricate technical textile materials with adjustable wettability.