Textile Functionalisation by Printing Fragrant , Antimicrobial and Flame-Retardant Microcapsules

The procedure of applying microcapsules to a cotton fabric using screen printing was investigated. The aim was to explore whether the printing of microcapsules might be a universal approach to functionalise textiles. Fragrant (lavender, rosemary and sage essential oil core), antimicrobial (triclosan core) and fl ame-retardant (triphenyl phosphate core) microcapsules with a melamine-formaldehyde wall were used. The optimal concentration of microcapsules in the printing paste to achieve the desired eff ect was investigated. The mechanical properties of the treated fabrics were analysed before and after the washing. The results showed that diff erent functionalities of fabrics can be achieved using this printing technique. The optimal concentration of microcapsules to produce the desired fragrant or antibacterial textile product was 100 g of suspension (32 g of microcapsules) per kg of fabric. The optimal concentration of microcapsules to produce the desired fi re-retardant material was very high and could not be achieved using the pigment system.

1 Introduction e functionalisation of textiles can be achieved with the use of microcapsules (MCs) [1,2], which can represent a universal procedure for the application of di erent substances to fabrics, thus enabling different types of textile substrates to have special properties.
ese properties increase their utility and market value.Materials with special properties are of great importance in research and commercial use.MCs are a product of the microencapsulation process, which is de ned as "a technology of packaging solids, liquids or gaseous materials in miniature sealed capsules that can release (or not) their contents at controlled rates under the in uence of speci c conditions [3−6]." In this way, the active compounds are
ree di erent types of MCs were used, i.e.MCs with fragrance, with an antimicrobial agent and with a ame retardant.Fragrant MCs imbue the fabric with a scent; antimicrobial agents protect the user from pathogen microorganisms [13,14] and re retardants protect the user from re.Such agents are very important for medical and technical textiles, as well as for textiles in public use [14,15].e crucial characteristics of these fabrics are that they are safe for the producer and the user, show good fastness to washing, work e ciently at the terms of use and do not signi cantly change the original technological properties of the fabric.
e mentioned agents applied to the bres in the form of microcapsules meet all these requirements.In this study, all used MCs had the same melamine formaldehyde wall.In the core, the fragrant MCs contained a mixture of lavender, rosemary and sage essential oil (LRS).
e antimicrobial MCs contained triclosan (TCS) and the re-retardant MCs contained tryphenyl phosphate (TPP).e latter were prepared speci cally for this purpose [16].e use of identical MCs has not been found anywhere in the literature.TCS is a chlorinated bisphenol, as well as synthetic, non-ionic, antimicrobial agent with antibacterial activity (e ective against many types of Gram-positive and Gram-negative bacteria).Additionally, TCS has some antifungal and antiviral properties [17].e mechanism of TCS blocks the active site of the enoyl-acyl carrier protein reductase enzyme (ENR), which is a signi cant enzyme in fatty acid synthesis in bacteria.By blocking the active site, the inhibition of the enzyme and the prevention of fatty acid synthesis, which is necessary for building the cell membrane and for reproduction, are achieved [18,19].
TPP is an e ective re retardant based on phosphorus.It breaks down in the ame to produce chemical species such as P 2 , PO, PO 2 and HPO 2 .ese reactions reduce the hydrogen atom concentration in the vapour phase, thus extinguishing the ame [20].In addition, the intention of our work was to identify a simple and universal procedure for the application of MCs to textiles.Screen printing with a pigment printing system was chosen to achieve this objective.e MCs by mass were synthesised in a partner laboratory.In this study, the optimal MC concentration in the printing paste and, consequently, on the fabric was investigated to achieve a fabric with a lasting aroma, lasting antimicrobial properties and ame-retardant properties.One of the objectives was also to study the changes in the mechanical fabric properties (air permeability, sti ness, mass per unit area and thickness) a er the application of MCs.A cotton fabric was used for the application of MCs. e MC presence on the fabric, as well as distribution, shape and size were analysed using SEM micrographs.e changes in the properties of treated fabrics and the MC fastness to washing were tested using standardised methods of textile research.e presence and fastness of the aroma were investigated using the panel procedure (Lewis) of fragrance evaluation.e e ect of antimicrobial MCs was monitored using microbiological tests and a burial in soil test.e e ect of ame-retardant microcapsules was monitored by analysing their burning and thermal properties (DSC, TGA).

Materials
A bleached and mercerised 100% cotton woven fabric (124 g/m 2 in weight, supplied by Tekstina d. d., Slovenia) was used for the study.Suspensions of MCs 2-8 µm in size with a pressure-sensitive melamine-formaldehyde wall and three di erent cores were prepared in Aero d. d.Celje, Slovenia by in situ polymerisation of melamine-aldehyde prepolymers [7, 21−24].e mass fraction of the cores in all MCs was 75%, and the mass fraction of the walls was 25%.
e e MC suspensions were added to the printing pastes which were composed of a synthetic polyacrylate thickener (Tubivis DRL 300), a polyacrylate binder (Tubifast AS 30), both of which were obtained from CHT, Germany.e pigment Bezaprint (Bezema, Switzerland) was also added.Flat screen printing was performed on a laboratory magnetic printing machine MINI MDF R 390 (Johannes Zimmer AG, Austria).e coverage area of the printing paste on the cotton cloth was approximately 25 × 35 cm.

Printing
Di erent quantities of MC suspensions were added to the printing pastes, resulting in di erent concentrations of active substances on the fabric a er the printing.e mass fraction of the active substance in the MC cores, the concentration of the MC suspension in the printing paste, the amount of the printing paste applied to the fabric, the concentration of the suspension on the fabric and the concentration of MCs on the fabric are presented in Table 3. Washing Some printed (cured) samples were washed for 30 min at 40 °C according to the ISO 105-C01:1989 (E) [25] standard using a soap solution (5 g/L of soap) with pH 7 and a liquor-to-fabric ratio 50 : 1.A er the washing, the samples were air-dried.

SEM observation
Using a scanning electron microscope (Jeol JSM 6060 LV), the uniformity of the deposit, as well as the size and morphological characteristics of di erent MCs on printed fabrics were observed.Moreover, the quantity and condition of MCs that remained on the fabric a er the washing were investigated.e printed samples were coated with gold prior to the observation with a microscope.

Fragrance evaluation
Fragrance evaluation was performed on the samples printed with four di erent quantities of fragrant MCs (0, 100, 150 and 200 g of MCs per kg of printing paste).e method for fragrance evaluation was based on the Lewis procedure [26,27].A portion of fabrics was removed a er 10 wash cycles (ISO 105-C01:1989 (E) standard), air dried for 24 h and tested for the presence of fragrance using a panel of ve judges.e samples were rst hung on a clothesline in a room for 1 hour to stabilise fragrance evaporation.en, the samples were brought to a judge in an evaluation room.A printed fabric was placed on a at, hard board on a table.A judge used their ngernails to scratch an "X" (approximately 3 × 3 cm in size) on the fabric to break some of the capsules and then immediately smelled the swatch.en they recorded "Yes" according to the presence of strong, medium or weak fragrance, or "No" according to the absence of the fragrance.No judge was performing the testing for more than 15 minutes.

Antibacterial activity testing
Antibacterial activity testing was performed on the samples printed with four di erent quantities of TCS MCs (0, 25, 50 and 100 g of MCs per kg of printing paste).e antibacterial activity was estimated for the Gram-negative bacteria Escherichia coli (ATCC 25923) and for the Gram-positive Staphylococcus aureus (25922) according to the standard SIST EN ISO 20645:2005, "Determination of antibacterial activity -Agar di usion plate test [28]." Circular fabric pieces (diameter of 25 ± 5 mm) were placed on two-layer agar plates.e lower layer consisted of a bacterialfree culture medium and the upper layer was inoculated with the selected bacteria.e level of antibacterial activity was assessed by examining the extent of bacterial growth in the contact zone between the agar and the specimen, and the width of the inhibition zone around the specimen.e tests were performed in a certi ed laboratory.

Fungicidal activity
e fungicidal activity testing was performed on the samples that showed the best antibacterial activity (100 g/kg).e activity was estimated for the fungi Aspergillus brasiliensis according to the DIN 53931 standard method [29].e nutrient malt-extract agar (MEA) was prepared to which the fungi was inoculated.e inoculated plates were incubated at 29 °C for 24 h.A erwards, cotton bre samples 5 × 5 cm in size were placed on the medium and were incubated at 29 °C for 7 and 14 days.A er the incubation, the fungicidal activity was determined in terms of mycelia growth on and below the surface of the cottonbres and the sporulation intensity.e degree of fungal growth was ordered in eight grades from 00 to 5, where 00 indicated no growth, 0 indicated fungal growth outside the inhibition zone surrounding the cotton specimen, (0) indicated fungal growth up to the specimen's edge, (1) indicated fungal growth only on and below the specimen's edge, (2) indicated fungal growth on and below less than 25% of the specimen, (3) indicated fungal growth on and below 25-75% of the specimen, (4) indicated fungal growth on and below more than 75% of the specimen and (5) indicated 100% overgrowth of the specimen.e sporulation intensity was assessed using the following symbols: -meant clear, without mycelium; + meant weak, only mycelium; ++ meant noticeable growth, partly with spores; and +++ meant strong overgrowth, extensive spore formation.

Combustion test
Combustion testing was performed on the samples printed with ve di erent quantities of TPP MCs (0, 100, 200, 400 and 600 g of MCs per kg of printing paste).
e combustion performance was studied using the vertical burning test.e vertical burning test was performed in a burning chamber according to the DIN 53906 standard [30].and Flame-Retardant Microcapsules Tekstilec, 2016, 59(4), 278-288 ermal properties of MCs and fabrics treated with TPP MCs -TGA and DSC analysis e samples were examined using a 449c Jupiter Instrument (NETZSCH).e samples were placed on Al 2 O 3 carriers.ey were heated in a protective atmosphere (air) and the measurements were performed from 35-650 °C at the heating rate of 10 K/min.e samples were then cooled at 10 K/min to room temperature.

Fabric properties
e properties of untreated samples and samples printed with di erent types of MCs were examined.
e fabric mass per unit area was determined according to the standard SIST EN 12127:1999 [31], the fabric sti ness was evaluated using the ASTM D-1388-64 method A [32], the fabric thickness was measured according to the standard SIST EN ISO 5084:1999 [33], and the fabric air permeability was determined according to the standard SIST EN ISO 9237:1999 [34].SEM micrographs (Figure 1) show that there are no morphological di erences between the samples printed with di erent MCs.All MCs were round in shape and evenly distributed over the bres.

Results and discussion
ere were no aggregates or ruptured MCs. e micrographs of washed samples reveal that the fastness to washing of all samples was very good.Similar to pigments (pigments and MCs are the same size), MCs were rmly bound to the bres due to the printing system and remained on them a er the laundering.

Fragrance evaluation
e fragrance on the fabric before and a er a selected number of washing cycles was evaluated using a panel of ve judges (Table 5).Before the washing, a strong fragrance was present on all samples with MCs.Even a er 10 washings, the fragrance was judged to remain weakly noticeable (regardless of the quantity of the applied MCs) by the majority of the panel.e fragrance was detected as stronger on the samples containing a higher quantity of capsules.e di erence between lower and higher concentrations remained evident even a er up to 10 washing cycles.

Sample Number of judges per fragrance intensity Strong Medium Weak No
It can be concluded that fragrant MCs work eciently if they are applied to a fabric in the concentration of at least 100 g of suspension (32 g of MC or 6 g of essential oil) per kg of fabric.

Antibacterial effi ciency
e antibacterial activity levels of fabrics printed with di erent quantities of MCs (0, 25, 50 and 100 g/kg) was assessed by examining the extent of bacterial growth in the contact zone between the agar and the specimen, and the width of the inhibition zone around the specimen.e activity of printed and washed samples was estimated for one Gram-negative (E.coli) and one Gram-positive (S. aureus) bacteria.e printed microcapsules were not activated by pressure prior to the testing.e results are shown in Table 6.It can be observed that the unprinted sample (CO) and the sample printed without MCs (CO0) showed no antibacterial action, as expected.ere was no inhibition zone present (Figure 2a).e samples with lower quantities of MCs (TCS50, TCS25) showed satisfactory antibacterial activity only for S. aureus.Excellent antibacterial activity of the samples printed with the highest quantity of TCS MCs (TCS100) was evidenced for both bacteria, although it was better for Staphylococcus aureus, which had a 40-mm-wide inhibition zone.
e inhibition zone remained the same (25 mm for E. coli (Figure 2b) and 40 mm for S. aureus) even a er the washing.It can be concluded that fabrics printed with the highest quantity of TCS MCs (100 g/kg of printing paste) are resistant to E. coli and S. aureus bacteria.e results of the fungal growth evaluation (Table 7) and the photographs (Figure 3) show that all samples are overgrown with fungi.On the sample printed without MCs, rich mycelium development and strong sporulation (black colour) was observed, whereas the sample with MCs exhibited mycelium spread all over the sample but without sporulation.It can be concluded that there is no fungicidal activity on the printed sample.However, due to the di erent medium on this sample, the process of fungal growth was slower compared with the sample without MCs.
e washing of samples did not have a signi cant in uence on the accelerated fungal growth; on some samples, the intensity was reduced or remained the same as before the laundering.TCS is a good antibacterial agent (Staphylococcus aureus, Escherichia coli); however, in the case of the fungi Aspergillus brasiliensis, it did not show satisfactory activity.

Combustion test
Table 8 and Figure 4 represent the results of the in uence of printed MCs on the ammability of the CO samples.e upward burning behaviour shows that most samples glow for a longer period of time than they burn.e addition of TPP MCs did not have a substantial in uence on the burning time of cotton samples.e untreated sample and the samples printed without MCs burned through their whole length, and only a small quantity of residue remained (Figure 4a).e samples printed with higher quantities of MCs (400, 600 g/ kg) also burned through their whole length; however, a signi cant increase in the amount of thenal residue indicates that the printed MCs were able to retard the further degradation process of the char formed during the burning (Figure 4b).None of the samples can be considered as a ameresistant material.e reason for this result is the concentration of applied MCs, which is too low.e highest possible concentration of microcapsules used for the preparation of the printing paste (that still allowed its preparation) was only 600 g/kg.In contrast, we showed in our previous research that the impregnation of a fabric with the MC concentration of 800 g/kg protects the fabric from burning.and Flame-Retardant Microcapsules Tekstilec, 2016, 59(4), 278-288  e TGA curve of the suspension deviates from the dry sample due to the evaporation of water at temperatures below 180 °C.e CO samples lost 60% of their weight at 330 °C.e printed sample started to degrade earlier (at 190 °C) than the raw material.TPP MCs start to degrade at lower temperatures than the surrounding material, and the degradation products, such as P 2 , PO, PO 2 and HPO 2 , in the vapour phase extinguish the ame.Consequently, if there are MCs present on the material, more fabric remains unburned (Figure 4).e DSC curve in Figure 6 con rms that the presence of MCs on the textile material changes its properties.
e printed cotton fabric has lower exothermic peaks that start at lower temperatures than the raw cotton fabric.e MCs decrease the heat released from the cotton fabric.Figure 6 also demonstrates the behaviour of cotton at high temperatures.Natural CO bres gradually degrade in several oxidation reactions, represented by several broad peaks on the DSC curve.It can be concluded that the applied MCs increase the thermo-oxidative stability of cotton; however, they do not prevent the burning.e pigment system does not allow using higher concentrations of MC; therefore, its application is not appropriate to produce re-retardant materials.), TPP400 ( )

Fabric properties
e mechanical properties of fabrics (mass, thickness, sti ness and air permeability) printed with the same quantity of di erent MCs was investigated and compared with the properties of the un nished sample and the sample printed without MCs.e mass per unit area of samples is presented in Figure 7. and Flame-Retardant Microcapsules Tekstilec, 2016, 59(4), 278-288   7 reveals that all printed samples had higher masses than the unprinted fabric.e MCs further increased the mass but not signi cantly.e di erences between the samples printed with di erent MCs were negligible.e sample printed with TPP MCs had the highest mass per unit area.We assume that the reason for this result is a solid core without a solvent, which could not evaporate from some of the MCs that broke during the printing process.After the washing, the mass of all samples increased, which is a consequence of the fabric thickness increase a er the laundering.e fact that the thickness of the printed fabric is similar or even slightly lower than the unprinted fabric is a consequence of the printing process, in which the fabric is compressed.e thickness of all samples printed with di erent MCs was almost the same. is result was expected since all MCs were in the same size range and the deposit of the printing pastes on the fabric was similar in all cases.After the washing, the thickness of all samples increased.is result is an issue of fabric shrinkage and thickening of threads in material.Considering the sti ness of samples (Figure 9), it is evident that according to the expectations, all printed (with and without MCs) samples were more rigid than the un nished sample.It can also be seen that MCs further increased fabric sti ness.ere were no essential di erences between the samples printed with di erent MCs. e sample with TPP MCs was slightly sti er.A er the washing, the stiness of printed samples decreased as the polymer thickener so ened and some MCs were removed.e applied printing paste itself caused a considerable decrease in the permeability, whereas the addition of MCs led to a further decrease.e air permeability of samples printed with di erent MCs was similar.It can be clearly seen that the printing of MCs changes the fabric properties.Even the printing without microcapsules increased the fabric mass per unit area and sti ness, as well as decreased the thickness and air permeability.is result is due to the presence of a thickener and binder in the printing paste, which resulted in an additional sti layer on the fabric.e and Flame-Retardant Microcapsules Tekstilec, 2016, 59(4), 278-288 addition of MCs further increased the changes in fabric properties.

Conclusion
Fragrant, antimicrobial and re-retardant MCs were successfully applied to cotton fabrics using screen printing.e fastness to washing of all MCs was very good.
e fragrant MCs worked best when they were applied to the cotton fabric at the concentration of 100 g suspension per kg of fabric (32 g of MCs or 6 g of oil) and the antibacterial MCs worked best also at the concentration of 100 g suspension per kg of fabric (32 g of MC or 4.8 g of TCS).e latter had no fungicidal activity.In the case of reretardant MCs, the MCs had some in uence on the burning of the cotton sample; however, higher concentrations of MCs applied to the fabric would be needed to substantially inhibit the burning. is result could not be achieved by using the pigment system.e printing of MCs changed the mechanical properties of all samples to some extent.e properties of the samples printed with the same concentration (100 g/kg) of di erent MCs were similar.It was shown in this study that with the use of aminoaldehyde MCs, textiles with di erent functional properties can be achieved.e MCs of this type can be used for the application of a wide range of substances to fabrics since they represent a suitable carrier for di erent water-immiscible compounds.It was also shown that the printing with synthetic swelling thickeners and polymeric binders (pigment system) is appropriate for the application of melamine-formaldehyde microcapsules.
MCs applied this way are able to achieve the desired properties, show good fastness to washing and do not signi cantly change the mechanical properties of the fabric.It can be concluded that the system (model) for the functionalisation of textiles with MCs which can improve the quality, functionality and value of textile products was successfully established.

Table 6 :
Widths of inhibition zones of printed samplesSampleInhibition zone[mm]

Figure 2 :
Figure 2: Activity against E. coli: (a) sample printed without MCs, CO0, with no inhibition zone; and (b) printed and one time washed sample, TCS100-W, with inhibition zone 3.4 Fungicidal activity e results of the fungicidal activity test of samples printed with TCS MCs are shown in Table7.

Figure 4 :
Figure 4: Samples of untreated (a) and printed fabrics with TPP MC (600 g/kg), (b) a er vertical burning test

Figure 7 :
Figure 7: Mass per unit area of untreated sample, sample printed without MCs, sample printed with LRS MCs, sample printed with TCS MCs and sample printed with TPP MCs

Figure
Figure7reveals that all printed samples had higher masses than the unprinted fabric.e MCs further increased the mass but not signi cantly.e di erences between the samples printed with di erent MCs were negligible.e sample printed with TPP MCs had the highest mass per unit area.We assume that the reason for this result is a solid core without a solvent, which could not evaporate from some of the MCs that broke during the printing process.After the washing, the mass of all samples increased, which is a consequence of the fabric thickness increase a er the laundering.

Figure 8 :
Figure 8: ickness of untreated sample, sample printed without MCs, sample printed with LRS MCs, sample printed with TCS MCs and sample printed with TPP MCs Figure 8 shows the thicknesses of samples.e results show that the printing on a fabric without or with MCs does not cause di erences in thickness.efact that the thickness of the printed fabric is similar or even slightly lower than the unprinted

Figure 9 :
Figure 9: Sti ness of untreated sample, sample printed without MCs, sample printed with LRS MCs, sample printed with TCS MCs and sample printed with TPP MCs e air permeability results are presented in Figure 10.As expected, all printed samples show lower permeability than the un nished fabric.eapplied printing paste itself caused a considerable decrease in the permeability, whereas the addition of MCs led to a further decrease.e air permeability of samples printed with di erent MCs was similar.It can be clearly seen that the printing of MCs changes the fabric properties.Even the printing without microcapsules increased the fabric mass per unit area and sti ness, as well as decreased the thickness and air permeability.is result is due to the presence of a thickener and binder in the printing paste, which resulted in an additional sti layer on the fabric.e

Figure 10 :
Figure 10: Air permeability of untreated sample, sample printed without MCs, sample printed with LRS MCs, sample printed with TCS MCs and sample printed with TPP MCs

Table 1
presents the recipes for the printing pastes.Di erent concentrations of MC suspensions in the printing paste were tested.eprinting,drying and curing conditions are presented in Table2.

Table 1 :
Printing pastes recipes * 25−600 (concentrations of individual suspensions of MCs in printing pastes are given as c sp in Table3) ** di erence to 1000

Table 2 :
Printing, drying and curing conditions

Table 3 :
Mass fraction of active substance in core (x a ), concentration of suspension of MCs in printing paste (c sp ), share of printing paste application to fabric (N), concentration of suspension on fabric (c s ) , concentration of MCs on fabric (c m ) and concentration of active substance on fabric (c a ) a er printing

Table 8 :
Results of vertical burning test of printed samples with di erent quantity of applied microcapsules