**6. Factors affecting on the activity of biocides in the fibers**

The activity of biocides depends on many factors, of which the most important include time of contact with the microorganisms, concentration of active substance, type of microorganism, presence of organic and inorganic impurities, temperature, humidity and pH.

The most important factors for affecting biocidal activity are **time** of contact between the active substance and the microorganism cells, and the biocide **concentration** (Brycki, 2003).

The product of the concentration and time of action for specified groups of active substances is a constant value, expressed in terms of Watson's equation:

$$\mathbf{c}\mathfrak{d} \times \mathfrak{k} = \text{const.}\tag{1}$$

where c denotes concentration, t denotes time, and ŋ is a concentration coefficient determined empirically for a given substance.

Example values of the concentration coefficient (ŋ) are 10 for alcohols, 6 for phenols, and 1 for quaternary ammonium salts.

The use of this relationship is important from a practical standpoint – it tells us that given an appropriate concentration of biocide, a biocidal effect will be achieved in a precisely specified time. With a preparation based on alcohol, for example, if it were diluted to half of the concentration, the length of time required to obtain the same effect would increase by 1024 times. In the case of phenol it would increase by 64 times, and for quaternary ammonium salts it would merely double. Because of their properties, alcohols work effectively for a short time, and hence their use is limited to short-lasting disinfection (Brycki, 2003).

With regard to the uses of bioactive fabrics, either a short time of action on microorganisms is required (for example, in the case of protective masks the time should not exceed 8 hours), or the time may be extended to 24–48 hours (filtration and technical materials, etc.).

The effective action of a biocide also depends on the **type of microorganisms**, chiefly the structure of the cell wall and the presence of genetic resistance mechanisms. For this reason, research into the antimicrobial activity of fabrics should include evaluation with respect to different species of microorganisms (Table 7).



SD – standard deviation

280 Woven Fabrics

active against *B.subtilis,* 

active against *S.aureus,* 

active against *B.subtilis,* 

Sousa et al., 2009

Yi et al., 2010

Joshi et al., 2007

*P.aeruginosa*

*K.pneumoniae,* 

*P.vulgaris,*

**Nonvowens Antimicrobial agents Antimicrobial activity Author, year**

Table 6. Nonwovens with natural origin antimicrobial agents (based on the scientific

The activity of biocides depends on many factors, of which the most important include time of contact with the microorganisms, concentration of active substance, type of microorganism,

The most important factors for affecting biocidal activity are **time** of contact between the active substance and the microorganism cells, and the biocide **concentration** (Brycki, 2003). The product of the concentration and time of action for specified groups of active substances

 c<sup>ŋ</sup> ×t = const. (1) where c denotes concentration, t denotes time, and ŋ is a concentration coefficient

Example values of the concentration coefficient (ŋ) are 10 for alcohols, 6 for phenols, and 1

The use of this relationship is important from a practical standpoint – it tells us that given an appropriate concentration of biocide, a biocidal effect will be achieved in a precisely specified time. With a preparation based on alcohol, for example, if it were diluted to half of the concentration, the length of time required to obtain the same effect would increase by 1024 times. In the case of phenol it would increase by 64 times, and for quaternary ammonium salts it would merely double. Because of their properties, alcohols work effectively for a short time, and hence their use is limited to short-lasting disinfection

With regard to the uses of bioactive fabrics, either a short time of action on microorganisms is required (for example, in the case of protective masks the time should not exceed 8 hours),

The effective action of a biocide also depends on the **type of microorganisms**, chiefly the structure of the cell wall and the presence of genetic resistance mechanisms. For this reason, research into the antimicrobial activity of fabrics should include evaluation with respect to

or the time may be extended to 24–48 hours (filtration and technical materials, etc.).

Flavonoids (flavanols, flavonol,

*Azadirachta indica* (contain of:: azadirachtin, nimbin,, nimbidin, salannin, nimbidol, gedunin)

is a constant value, expressed in terms of Watson's equation:

determined empirically for a given substance.

different species of microorganisms (Table 7).

for quaternary ammonium salts.

(Brycki, 2003).

**6. Factors affecting on the activity of biocides in the fibers** 

presence of organic and inorganic impurities, temperature, humidity and pH.

flavone, flavanone, isoflavanone)

Wool, cotton Dye: Citrus grandis Osbeck extract

Cotton Neem seed extract from

Chitosan and viscose

researches)

\*needle-punched nonwoven; polypropylene-silver (in the form of master batches) + acrylic fiber-biocide

Nt: 0 *t N N N* where *N*0—the number of microorganisms on the sample of the textile material for time *<sup>t</sup>*

= 0, *N—*the number of microorganisms on the sample of the textile material for time *t*<sup>n</sup>

Table 7. Microorganisms Survival Index (Nt) for various microorganisms after 6 hours incubation with bioactive nonwoven\* (based on Majchrzycka et al., 2010)

Microorganisms sensitive to the action of biocides are bacteria – Gram-positive cocci and Gram-negative bacilli. The most resistant organisms, with high survival rates, include sporeforming bacteria and moulds (Majchrzycka et al., 2010). This is because the activity of biocides added to fabrics is dependent on the physiological state of the microorganisms: the most sensitive are cells in a phase of vegetative growth, while resistance is shown by endospore of bacteria and the spores of moulds (Gutarowska et al.,2010).

**Organic contaminants** present on the fabric may reduce the biological effect. Proteins are substances that protect microorganisms, sugars and fats may be a source of food and lead to the development of microorganisms, and moreover those compounds may react with the biocides, reducing their effectiveness. Research into antimicrobial activity in the presence of artificial sweat (inorganic compounds) did not reveal any significant effect on the bioactivity of fabrics (Majchrzycka et al., 2010).

Increased **temperature** generally strengthens the antimicrobial activity of chemical agents, due to the increased reactivity of the active substances as well as synergy between the destructive effects of the substance and temperature (Brycki, 2003).

Increased **humidity** strengthens the antimicrobial activity of fabrics containing biologically active substances. The presence of water makes it possible for the biocide to penetrate into the cells of microorganisms in the form of ions, and for these to act effectively. Hence fibres with **hydrophilic** properties containing biocides will be more effective than hydrophobic fibres containing the same active substances (Gutarowska et al., 2010). Comparative studies on the antimicrobial action of hydrophobic PAN fabrics containing quaternary ammonium salts and the same fabrics containing biocide on an inorganic medium – perlite – with hydrophilic properties showed a significant improvement in the biocidal effectiveness of hydrophilic fabrics with added perlite (Table 8). Bioactivity improved with increasing

Microbial Degradation of Woven Fabrics and Protection Against Biodegradation 283

The impact of **pH** on biocidal activity depends on the chemical nature of the compound; it may have both positive and negative effects. In the case of phenol compounds an increase in pH causes a reduction in antimicrobial activity, although such a change causes an increase

Of significant importance for the biological activity of fabrics is the way in which the biocide is introduced into the fabric. The **carriers** for active substances are highly significant. Sample tests with the use of several mineral carriers for silver have shown significant differences in the antimicrobial activity of the resulting fabrics (Gutarowska & Michalski, 2009). In these studies, it was observed the best biocidal effects against test microorganisms (*E.coli, S.aureus, C.albicans, A.niger*) characterized the nonwovens containing silver on TiO2 and BaSO4 carriers (BT nonwovens) and nonwovens with silver on TiO2 and ZnO carriers (TL

in the activity of quaternary ammonium salts (Brycki, 2003).

nonwovens) (Fig.2).

0

WP1/e

B/0 BaSO4 (-) B/e BaSO4 (+) T/0 TiO2 (-)

B/0

B/e

BL/0

incubaction with nonwoven (Gutarowska & Michalski, 2009)

WP1/0 Control without concentrate, (-) WP1/e Control without concentrate, (+)

of static charge (no: -; yes:+)

BL/e

BT/0

Fig. 2. Biocidal activity of nonwoven with biocides (Ag), to bacteria E.coli after 24 hours

Sample code Added concentrate containing 30% Ag/AgCl with a carrier/ Presence

BT/e

**nonwovens**

T/0

T/e

TL/0

TL/e

L/0

L/e

0,5

1

1,5

**biocidal activity after 24 hours**

Legend:

2

2,5

3

3,5

4


concentration of perlite, which changed the properties of the fabric to hydrophilic, and with increasing humidity of the fabric (Table 9).

SD – standard deviation

Table 8. The influence of bioperlite concentration (with alkylammonium microbiocides) in the nonwoven on antimicrobial activity against *E.coli* and *S.aureus* (based on Gutarowska et al., 2010)


\*without the addition of water; SD – standard deviation

Table 9. The influence of the humidity level of a nonwoven with 8% bioperlite on antimicrobial activity against *E.coli* (Gutarowska et al., 2010)

The impact of **pH** on biocidal activity depends on the chemical nature of the compound; it may have both positive and negative effects. In the case of phenol compounds an increase in pH causes a reduction in antimicrobial activity, although such a change causes an increase in the activity of quaternary ammonium salts (Brycki, 2003).

Of significant importance for the biological activity of fabrics is the way in which the biocide is introduced into the fabric. The **carriers** for active substances are highly significant. Sample tests with the use of several mineral carriers for silver have shown significant differences in the antimicrobial activity of the resulting fabrics (Gutarowska & Michalski, 2009). In these studies, it was observed the best biocidal effects against test microorganisms (*E.coli, S.aureus, C.albicans, A.niger*) characterized the nonwovens containing silver on TiO2 and BaSO4 carriers (BT nonwovens) and nonwovens with silver on TiO2 and ZnO carriers (TL nonwovens) (Fig.2).

Fig. 2. Biocidal activity of nonwoven with biocides (Ag), to bacteria E.coli after 24 hours incubaction with nonwoven (Gutarowska & Michalski, 2009)

Legend:

282 Woven Fabrics

concentration of perlite, which changed the properties of the fabric to hydrophilic, and with

Incubation time Reduction

Mean: 1.59×106 SD: 1.53×105

Mean: 2.76×105 SD: 1.49×105

Mean: 0

Mean: 0

Mean: 0

Table 8. The influence of bioperlite concentration (with alkylammonium microbiocides) in the nonwoven on antimicrobial activity against *E.coli* and *S.aureus* (based on Gutarowska et

SD: 0 100

SD: 0 100

SD: 0 100

0 h 6 h

**Number of microorganisms (CFU/sample) Reduction** 

**(%)** Incubation time

SD: 5.60×103 79.66

SD: 6.03×103 80.23

SD: 3.50×103 82.64

SD: 3.68×103 83.14

SD: 1.71×102 99.08

Mean: 4.15×103

Mean: 6.96×103

Mean: 3.54×103

Mean: 3.44×103

Mean: 1.87×102

Mean: 6.07×106 SD: 3.52×106

Mean: 3.72×106 SD: 2.35×106

Mean: 7.23×105 SD: 1.13×105

Mean: 8.67×105 SD: 1.05×105

Mean: 7.05×105 SD: 1.20×105

Mean: 2.04×104 SD: 1.80×104

SD: 3.08×104

SD: 1.78×104

SD: 1.80×104

SD: 1.80×104

Table 9. The influence of the humidity level of a nonwoven with 8% bioperlite on

**Number of bacteria (CFU/sample)** *Escherichia coli Staphylococcus aureus* 

0 h 6 h 0 h 6 h %

Mean: 3.33×106 SD: 2.91×106

Mean: 5.01×106 SD: 3.35×106

Mean: 5.29×106 SD: 4.58×106

Mean: 1.84×107 SD: 3.12×106

Mean: 2.43×106 SD: 1.56×106

Incubation time Reduction

66.0%

92.97

Mean: 1.13×106 SD: 1.02×106

Mean: 2.34×105 SD: 2.05×105

Mean: 0

Mean: 0

Mean: 0

SD: 0 100

SD: 0 100

SD: 0 100

%

73.80

95.45

increasing humidity of the fabric (Table 9).

**Amount of alkylammonium microbiocides in the nonwoven** 

**(%)** 

bioperlite 0

5 % 0.23

10 % 0.46

15 % 0.69

20 % 0.93

SD – standard deviation

**Nonwoven mass humidity level (%)** 

Nonwoven (5%)

Nonwoven (9.5%) Mean: 3.52×104

Nonwoven (43%) Mean: 2.04×104

Nonwoven (213%) Mean: 2.04×104

Nonwoven (1274%) Mean: 2.04×104

\*without the addition of water; SD – standard deviation

antimicrobial activity against *E.coli* (Gutarowska et al., 2010)

**Amount of bioperlite in the nonwoven (%)** 

Control without

Nonwoven bioperlite

Nonwoven bioperlite

Nonwoven bioperlite

Nonwoven bioperlite

al., 2010)

control\*

Sample code Added concentrate containing 30% Ag/AgCl with a carrier/ Presence of static charge (no: -; yes:+) WP1/0 Control without concentrate, (-) WP1/e Control without concentrate, (+) B/0 BaSO4 (-) B/e BaSO4 (+) T/0 TiO2 (-)

Microbial Degradation of Woven Fabrics and Protection Against Biodegradation 285

The need to produce bioactive textiles containing biocides has led to the development of methods for evaluating antimicrobial activity. The final result of such a test is highly dependent on the testing method and the choice of test microorganism. Methods of evaluating antimicrobial properties can be divided into quantitative and qualitative

Evaluation of the antimicrobial activity of textile products by qualitative methods is based on observation of the growth of microorganisms under and around a sample placed on an agar medium with a culture of the microorganisms. The effect of antimicrobial activity is indicated by the variously sized area in which the growth of the microorganisms is

Qualitative methods make it possible to evaluate the biocidal action of textiles both in the form of flat products, namely unwoven, woven and knitted fabrics, and in the form of fibres, threads, etc. The hydrophilic or hydrophobic nature of the textiles also has no effect on the final result. The only criterion for a textile product to be tested by qualitative methods is the diffusion of the active substance into the medium. Products must demonstrate at least

Photo 1. Growth inhibition zone around the *S. aureus;* polypropylene fibers containing 2%

Photo 2. Growth inhibition zone around the *C. albicans* polypropylene fibers containing 2%

**7. Methods for evaluating anti-microbiological activity of nonwovens** 

methods (Dymel et al., 2008; Gutarowska et al., 2009).

suppressed (Photographs 1–3).

minimal diffusion of the active component.

Ingaguard- method according to SN 195 920

Ingaguard- method according to SN 195921


Generally it was observed that appropriate selection of two carriers improves the effectiveness in comparison with nonwovens in which a single carrier was used. Good effect was reflected both by high biocidal activity and by reduced time off effective contact of microorganisms with the nonwoven. High activity was obtained for the majority of nonwovens with electrostatic charge against bacteria (BL/e, BT/e, T/e, L/e) and for all nonwovens with charge against fungi.

Active substances can be added to fabrics in different ways:


In the case of the first method the biocides must be chosen to have suitable properties so that the technological process (high temperature) does not cause inactivation of the compound: many chemical substances display volatility at high temperatures. This method gives a longlasting biological effect, as the biocides are permanently fastened to the fibre matrix. Chemical modification of a polymer by acetylation/phosphorylation makes it possible to obtain fibres with permanent antimicrobial properties. However due to the high costs of the production technology, and frequent change in the strength parameters of fabrics, these methods are rarely used. The most popular method is the application of a biocidal finishing layer. The use of a finish on the surface of the finished product favours high antimicrobial activity, although such a product does not retain its properties for a long time, losing them during successive washing cycles (Szostak-Kot, 2004).

The choice of method of producing a fabric should depend on its intended use. Textiles meant for repeated use (socks, bed linen, aprons, underwear, towels) should be highly wash-resistant; in these case the biocides must be permanently joined to the fibre matrix, in contrast to disposable items (aprons, masks, filters, bandages, dressings, gauzes and hospital foot coverings).

Generally it was observed that appropriate selection of two carriers improves the effectiveness in comparison with nonwovens in which a single carrier was used. Good effect was reflected both by high biocidal activity and by reduced time off effective contact of microorganisms with the nonwoven. High activity was obtained for the majority of nonwovens with electrostatic charge against bacteria (BL/e, BT/e, T/e, L/e) and for all

1. Physical modification – introduction of an active compound into the spinning solution or molten fibre-forming polymer and closure within the fibre (occlusion). The biocidal

2. Chemical modification – chemical reactions on the finished textile product, bonding of the biocide through the formation of chemical bonds, e.g. introduction of metal particles to zeolites added during fibre formation, addition of antibiotics to modified fibres by

3. Finishing – application of a poorly soluble coating, with the use of a polymeric or lowmolecular-weight medium with which the biocide is bonded physically or chemically. 4. Microencapsulation – the introduction into textiles of microcapsules containing volatile

In the case of the first method the biocides must be chosen to have suitable properties so that the technological process (high temperature) does not cause inactivation of the compound: many chemical substances display volatility at high temperatures. This method gives a longlasting biological effect, as the biocides are permanently fastened to the fibre matrix. Chemical modification of a polymer by acetylation/phosphorylation makes it possible to obtain fibres with permanent antimicrobial properties. However due to the high costs of the production technology, and frequent change in the strength parameters of fabrics, these methods are rarely used. The most popular method is the application of a biocidal finishing layer. The use of a finish on the surface of the finished product favours high antimicrobial activity, although such a product does not retain its properties for a long time, losing them

The choice of method of producing a fabric should depend on its intended use. Textiles meant for repeated use (socks, bed linen, aprons, underwear, towels) should be highly wash-resistant; in these case the biocides must be permanently joined to the fibre matrix, in contrast to disposable items (aprons, masks, filters, bandages, dressings, gauzes and

substance then diffuses to its surface, where it acts on the microorganisms.

T/e TiO2 (+) L/0 ZnO (-) L/e ZnO (+)

BT/0 BaSO4 + TiO2 (-) BT/e BaSO4 + TiO2 (+) BL/0 BaSO4 + ZnO (-) BL/e BaSO4 + ZnO (+) TL/0 TiO2 + ZnO (-) TL/e TiO2 + ZnO (+)

nonwovens with charge against fungi.

way of grafted copolymerization.

Active substances can be added to fabrics in different ways:

substances, dyes with antimicrobial action (Nelson, 2002).

during successive washing cycles (Szostak-Kot, 2004).

hospital foot coverings).
