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■Bio-mathematics, Statistics and Nano-Technologies: Mosquito Control Strategies

15.1

INTRODUCTION

In the second half of the 20th century, cold plasmas were found suitable for surface

modification of temperature-sensitive textile materials [1]. Recently, there has been a trend

in textile engineering toward green finishing processes such as plasma technology [2,3].

Cold plasma can be classified into atmospheric pressure and low-pressure plasma like

plasma enhanced chemical vapor deposition (PECVD) [4,5]. PECVD requires a closed

system with good vacuum condition including appropriate equipment and operation, which

is considered as drawback for commercial applications [1]. Furthermore, the sample size

to be treated is limited to the chamber size and it must be operated off-line in batch mode.

But it provides good control of the gas atmosphere and process parameters being a repro-

ducible technique that results in high-end products with good stability and uniformity in

the surface modification of textiles [6]. Plasma treatment of fabrics shows a great potential

as an environmentally friendly and economical dry finishing technique, as conventional

textile finishing processes require large amounts of chemical agents, water, and energy.

Pretreatments of textiles are carried out to clean fibers from natural or manufacture-related

impurities like oil, grease and volatiles [7]. This is essential to make the fiber receptive to

water, dyes [8], and finishing chemicals [9].

The plasma supported deposition of hydrogenated amorphous carbon (a-C:H) films is

proven to be very beneficial for modifying and improving material properties. Well-known

are mechanical stability, hardness, low friction, chemical inertness, high corrosion resis-

tance, biocompatibility and changed barrier properties that can also be generated on poly-

meric materials [2, 10 - 23]. Also textile properties such as wettability [7, 9], hydropho-

bicity [24 - 26], super hydrophilicity [7, 27], flame-retardant properties and fire-resistance

[28], antimicrobial effects [29, 30], crease resistance, UV protection, or aesthetic proper-

ties are modified to be adapted for special applications e.g. in self-cleaning good progress

was achieved with plasma-treated cotton [27]. Furthermore, Kitahara et al. investigated im-

parting wash-resistant properties to fabrics in combination with a-C:H films to make them

more chemically resistant and mechanically stable [29].

For the plasma treatment it is irrelevant if the textiles are natural or synthetic fibers,

yarns, woven, nonwovens or knitted fabrics, they can all be modified according to their in-

tended functionality. The plasma substrate interactions are caused by the bombardment of

reactive plasma species (ions, electrons, radicals, neutrals and ultraviolet photons) result-

ing in different surface reactions in the outermost layer (~10 nm) [3, 10]: (a) Cleaning the

surface from contaminations, (b) activation by generating chemically reactive sites increas-

ing surface energy and enhancing the affinity for other substances, (c) surface etching by

plasma reactive species followed by desorption, and (d) coating or plasma polymerization

using gases for thin film deposition [31,32]. Depending on the reactive gas or gas mix-

tures used, different functional groups can be formed like amino (-NH2), hydroxyl (-OH),

carbonyl (-C=O), carboxylic (-COOH) etc. The groups formed often have a tendency to

revert to their original state, meaning plasma activation is thermodynamically non-stable

and should be performed just before further treatment [33, 34]. Synthetic fibers often have

a hydrophobic nature due to the absence of polar functional groups limiting their appli-