**1. Introduction**

This book chapter tackles a highly interdisciplinary theme: a Life Cycle Assessment (LCA) study of plasma coated textiles for electromagnetic interference (EMI) shielding. Thus, the introduction presents some indicative aspects for all these particular domains.

#### **1.1 EMI shielding textiles**

The textile materials destined for Electromagnetic Interference (EMI) shielding include some additional properties when compared to metallic shields, according to the latest research studies [1–5]:


The additional functionalities offer added value to the textile substrates. Starting from the research phase, the textile shields may be used as promising EM shields in numerous applications, such as civil and military EMI protection, medical devices, or the buildings' EMI shielding. All these applications tackle the attenuation of EMI, needed for the proper functioning of electronic equipment (by electromagnetic compatibility principles), and the protection of living beings against non-ionizing radiation (medicine).

As known from the literature, there is a strong correlation between the electrical conductivity of the textile shield [S/m] and their electromagnetic shielding effectiveness [dB] [6]. Eddy currents induced by the incident EM field generate an opposed EM field, with an attenuating result [7]. Some of the recent advances in manufacturing textile shields with additional properties include integrating various electric conductive raw materials into the fabric structure [1–5].

An eco-efficient method to manufacture a hydrophobic textile substrate with excellent EM shielding properties by carbon nanotubes and graphene dispersion is presented in [1]. Various solutions of manufacturing textile shields by preserving the specific properties of textiles, such as good air permeability, good bending, flexibility, and stability in a hot and wet environment, were achieved by polymerization of Pyrrole and subsequent coating with Nickel [2]. Additional resistance to washing and end-applications of the electric conductive fabric as patch antenna are included in [2]. Carbon nanotubes with nanometer deposition of copper layers were integrated into fabrics for EM shielding [3]. Additional mechanical resistance properties were proved on the achieved fabrics [3]. The special properties of intrinsic conductive polymers (Pyrrole) are presented within the review paper [4]. Another contribution to EM shields was achieved by sintering silver on the fabrics, however, with a significant decrease of EMSE after repeated washing cycles [5]. Hence, textile EM shields combine the EMI shielding properties with the specific advantages of textile fabrics.

#### **1.2 Methods to estimate shielding effectiveness**

The main methods to estimate shielding effectiveness based on material properties are represented by the impedance and circuit methods [6]. Several physical premises apply for each of the methods. Both methods consider an infinite perpendicular plane shield to the incident EM field. While the impedance method is valid for the electromagnetic far field, the circuit method is valid for the near field.

For woven fabrics with inserted metallic yarns in warp and weft direction, the resulting conductive grid structure may be modeled by the impedance method with correction factors [8]. Adaptation of this method for textiles may be found in [9].

*Life Cycle Assessment of Flexible Electromagnetic Shields DOI: http://dx.doi.org/10.5772/intechopen.99772*

Another method for modeling conductive grid structures by balancing EMSE of the grid with EMSE of the sheet, with regard to the electric thin materials, was provided by [10, 11], with specific adjustment for textiles [9, 12]. Further contributions to model EMSE of woven fabrics with metallic yarns were provided by analogy with an RLC circuit [13] and by analogy with small aperture antennas [14].

The main material constants used for modeling EMSE of textiles are electric conductivity and magnetic permeability of the metallic yarns and the composite fabrics, the optical diameter of the yarn/fabric thickness, distance between metallic yarns in the fabric structure. The skin depth of yarns/fabrics has a great significance both in the circuit method and in the impedance method with correction factors [9, 15].

#### **1.3 Magnetron plasma sputtering of textiles**

Textile shields are usually manufactured by two main methods: inserting metallic yarns into the fabric structure and coating with metallic layers [16]. While the insertion of metallic yarns by weaving, knitting, and nonwoven making already represents the classical method, the coating of nanometer scale metallic layers by magnetron plasma represents a modern, promising technique. The main advantage of the plasma coating is the enhancement of EMSE and preservation of flexibility of the fabrics by the nanometer thickness [17].

The copper coating onto the textile fabrics was performed at INFLPR into a dedicated stainless steel spherical vacuum chamber (K.J. Lesker, UK), pumped out by an assembly of afore pump and turbomolecular pump (Pfeiffer, DE), which allowed obtaining of a base pressure down to 3 × 10–5 mbar. A constant argon flow (purity 6.0) of 50 sccm was continuously introduced into the chamber by means of a Bronkhorst mass flow controller, which allowed to establish the processing pressure around 5 × 10−3 mbar. The chamber is provisioned with a rectangular magnetron sputtering gun from K.J. Lesker, accommodating the high purity copper target. The discharge was ignited by a radio frequency generator (13.56 MHz) provisioned with an automatic matching box for adapting the impedance and the deposition time was set to ensure coating thicknesses of 1200 nm on each side of the textile fabric. Enhanced deposition uniformity was achieved by rotating the samples during the deposition process (200 rotations/ min). **Figure 1** presents a sketch of the experimental set-up of the magnetron plasma equipment of INFLPR.

**Figure 1.** *Sketch of the experimental set-up in INFLPR utilized for copper coating of textiles.*
