**1. Introduction**

Significant progress in the manufacture of composite materials has recently given rise to new opportunities for the use of nonwoven fabrics. The functionalization of composite materials involves the introduction of electrically conductive nanoadditives. It allows acquiring original polymer materials for possible use in smart products. There has been in recent years a growing

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interest in technologies aimed at imparting specific properties to textile products (i.e. gener‐ ating so-called "smart" nonwoven fabrics such as fabrics capable of changing their properties under the influence of external stimuli). Techniques used to produce nanocomposites or select nano and polymeric materials may be of use in the construction of various types of sensors. Smart textiles – also called "active", "interactive" and "adaptive" textiles – can be produced using such solutions.

Smart textiles can be functionalized by incorporating active materials into fibre, or by modi‐ fying the surface of textiles to give them specific characteristics. Active materials can be stimulated by a number of factors such as stressing, temperature, humidity, ultraviolet radiation and chemical substances. Smart textiles react to these stimuli by changing various parameters such as dimension state, change in resistance or in the distribution of stresses [1– 9]. The use of nanotechnology in the functionalization of materials made by classical textile techniques allows certain unique properties, such as sensory properties or electrical conduc‐ tivity, to be achieved. Introducing different types of nanoparticles to fibres can drastically alter the properties of materials [10, 11]. Ongoing work is currently aimed not only at obtaining new polymers, but also at effectively modifying them with nanoadditives and finding new solutions in processing techniques, so as to obtain polymeric materials that can be used in the construction of sensors. Sensors are usually components of a larger system, often defined as devices that receive and respond to a signal or stimulus. Their task is to capture information from the environment or to test an object by recognizing and recording it. Sensors should enable fast, simple and continuous measurements of the value being measured. It is important that the impact of using sensors does not being about changes in the tested objects [12–15].

Innovative solutions of noncontact sensors, material processing and design have an important input in development of smart textiles. Such materials combine a number of features of sensors such as electronic data processing and the ability to send information to other devices (e.g. alarm systems, data loggers, and monitoring devices). This has resulted in a sharp increase in interest in specialized products for medicine, filtration and protective services. Sensors used in textiles such as clothes, carpets, upholstery, furniture, wallpaper and paint have the potential to radically change lifestyles, enabling monitoring and action at a distance [16–21]. Some electroactive polymers may be useful in the production of fibre sensors as a result of their intrinsic dielectric or conductive properties, light weight, flexibility and relatively low price [7–9, 22, 23]. This paper focusses on a new area of research undertaken by the authors, one that deals with transferring properties of electrical conductivity to nonwoven fabrics by incorpo‐ rating carbon nanoparticles into their structure.

This work involves using carbon nanotubes to impart sensory properties. Melt-blown and electrospinning were the methods selected to form fibres. The characteristic properties of carbon nanotubes – such as thermal conductivity, electrical conductivity, high modulus, high strength and resistance to chemicals – make them widely used in nanotechnologies. The electrical properties of carbon nanotubes are typical of two-dimensional structures, and electrical conductivity varies depending on the structure of nanotubes (single or multi-walled) and chirality. The electrical conductivity of nanotubes is also sensitive to the influence of external factors such as electric fields, magnetic fields, mechanical properties, state of the environment (temperature, vapour content of selected chemicals). Mechanical properties are characterized by high mechanical strength, elasticity, susceptibility to deformation as a result of bending, torsion or flexibility (e.g. during stretching the length of nanotubes may increase by up to 40% without changing their structure [24]). The peculiar properties of nanotubes are widely used in many fields of nanotechnology: for example, when creating nanocomposites using nanotubes as reinforcing material and functionalizing composites, when creating nanocontainers to store gases (like hydrogen) [24], when removing dioxins prior to medical waste incineration and from chemical products [24]. Nanotubes play important roles in environmental protection. However, the greatest hope for the peculiar electrical properties of nanotubes (e.g. in microelectronics [25]) lies in their potential to exceed the limits of silicon technology.

The electrical sensory properties of carbon nanotubes were used in this work to functionalize nonwoven fabrics produced using modern techniques. Melt blowing and electrospinning are often used to produce filter materials to protect against toxic molecules. Therefore, the manufacture of nonwoven fabrics that are sensitive to vapours for use in filtration materials represents an innovative approach to receiving signals about the concentration of toxic vapours in the air. A new generation of smart half-masks that protect the respiratory tracts of users can be developed using such fabrics.
