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Vol.1. No.1. 2009 13
1. Introduction
Microencapsulat ion is one of the latest
technologies used for imparting an array of
unique characteristics to a garment. Particles
filled with active ingredients are applied to
the fabric or garments for long lasting effects.
Microencapsulated particles can be coated on
a textiles' surface or anchored (Chemically or
physically) onto the fi ber. As the wearer moves,
the capsules are activated and they release
the active ingredient in a controlled manner.
The active ingredients in the garment can be
moisturizers, vitamins, therapeutic smells,
essential oils, drugs and others [1,2,3,4,5,6,7,8,9,10]. The
properties of microcapsules (Figure 1), size,
shape, wall material, active substance release
mechanism, have had to be adapted to the
requirements of textile processing methods and
use of final products.
In our current research Rosemary oil
was encapsulated in ethylcellulose (EC)
microcapsules using the phase separation
method [11,12]; the prepared capsules were
analyzed by Scanning Electron Microscopy
(SEM) and Confocal Laser Fluorescence
Microscopy (CLSM). Prepared capsules were
grafted onto cotton textile substrate as mentioned
in literature[11]
; prepared textile materials were
analyzed by Confocal Laser Fluorescence
Microscopy.
2. Experimental
2-1 Materials
Ethylcellulose (EC) was purchased from
Encapsulation of Rosemary Oil in Ethylcellulose Microcapsules
B.Voncina1, O.Kreft2, V.Kokol1, W.T.Chen3
Dept. of Textile Materials and Design, University of Maribor, Maribor, Slovenia1,
Max-Planck-Institute of Colloids and Interfaces, Potsdam-Golm, Germany2
Dept. of Raw Material and Yarn Formations, Taipei, Taiwan, R.O.C.3
Abstract : In textiles, the major interest in microencapsulation is currently in the application of durable fragrances, skin softener,
phase-change materials, antimicrobial agents and drugs delivery systems onto texti le materials. In our research
Rosemary oil was encapsulated in ethylcellulose (EC) microcapsules using a phase separation method; the prepared
capsules were analyzed by Scanning Electron Microscopy (SEM) and Confocal Laser Scanning Microscopy (CLSM).
The Rosemary oil content in the microcapsules was determined by using CLSM. Capsules were grafted onto cotton
textile substrate; the presence of microencapsulated Rosemary oil attached to textile materials was tested by CLSM.
Key words : Microencapsulation, ethylcellulose, confocal laser scanning microscopy, cellulose fi bers.
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Textile and Polymer Journal14
Aldrich, Austria (Viscosity 4 cP, 5% in toluene/
ethanol 80:20, extent of labeling: 48% ethoxyl).
Rosemary oil was provided by Etol, Celje,
Slovenia. 1,2,3,4-Butane tetracarboxylic acid
(BTCA) by Merck, cyanamide (CA) and
fluorescence dye: fluorescein (FITC) from
Aldrich and sodium dodecylsulphate by Fluka
were used. All other chemicals were of analytical
reagent grade.
Pure cotton (Mass = 140 g/m2) was used
after it was first desized, scoured, bleached and
mercerized on continuous production equipment.
It was supplied by MTT, Maribor, Slovenia.
2-2 Test methods and analytical techniques
The microcapsule yield was determined as a
weight percent of the recovered microcapsules
after drying, divided by the initial amount of
ethylcellulose and oil employed.
Diameters and surface morphol ogy of
microcapsules were examined by scanning
electron microscopy (SEM). The samples were
coated with gold for 3.5 min using an Emscope
SC 500 and examined using a Philips XL30
ESEM operating in the secondary electron mode
at 10 KV accelerating voltage. The Quanta has
a tungsten based electron optical column with
a resolution of 3.5 nm and an ion resolution of
10 nm. Measurements were taken in vacuum at
different magnifications. Diameters of capsules
are presented as the mean value ± standard
deviation (SD) of fifty measurements.
For Rosemary oil content in capsules
two methods were used; in first one the oil
in capsules was removed by extraction and
from the differences in capsules mass before
and after extraction the amount of oil was
determine; in the second method the proportion
of empty capsule space was determine by using
CLSM. Confocal images were taken with a
Leica confocal scanning system mounted to a
Leica Aristoplan and equipped with a 100x oil
immersion objective with a numerical aperture
(NA) of 1.4. For visualization, FITC was used to
stain the capsules.
2-3 Preparation of EC microcapsules
and Rosemary essential oil content
determination
EC microcapsules were prepared as reported
in the literature [11]. In order to determine the
Rosemary essential oil content in capsules two
methods were used.
The Rosemary oil content in EC microcapsules
has been determined by pouring them into
cyclohexane and ultrasonicating for 1 min
to extract Rosemary oil from the capsules.
The oil content (ROC) expressed in percent
was determined from the mass differences
of microcapsules containing Rosemary oil
(mECRO) and capsules after oil extraction
(MEC). Five repeated measurements were
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Vol.1. No.1. 2009 15
carried out.
The following equation was used:
mECRO-mEC
ROC= 100% mECRO
EC microcapsules contain around 30% of
Rosemary oil.
In the second method, where Confocal Laser
Scanning Microscopy was used, we placed
one drop of an aqueous capsule suspension
containing essential oil onto a microscope glass
slide and mixed it with a fluorescein solution
(0.1 mg/ml H2O). Capsules without Rosemary
oil were treated likewise and acted as a negative
control. Within a few seconds, the fluorescein
penetrated the capsules wall and the overa ll
fluorescence intensity within the boundary of
one capsule was determined by CLSM (Figure 2).
The flourescence intensity of an identical region
outside the capsule was used for calibration
and set to 100 percent (Figure 2). Ten repeated
measurements were carried out. By comparison
of the fluorescence intensity of the capsule area
with fluorescence intensity of the same blank
area it is possible to estimate the proportion of
empty capsule space. The average empty space
in prepared capsules was 40%.
2-4 Grafting of EC microcapsules on textile
substrate using BTCA
EC microcapsules were linked onto cotton via
grafting with 1,2,3,4-butanetetracarboxylic acid
(BTCA) as described in literature[6,11]
. Empty
and with Rosemary oil loaded microcapsules
grafted on textile materials were analysed by
using CLSM.
3. Results and discussions
3-1 Analysis of ethylcellulose microcapsules
From the SEM shown in Figure 1 it was
observed that EC microcapsules had a regular
spherical shape. Microcapsules in the 10-90µm
size range were obtained.
Figure.1. SEM image of EC microcapsules containingrosemary oil (1000× magnification).
The size and degree of sphericity of
the microcapsules depend on the stirring
speed employed in the encapsulation. Table
1 presents the inf luence of the s t i r r ing
speed on microcapsule diameter and on
microencapsulation yield. Reducing the stirring
speed increases the size of microcapsules. The
yield of microencapsulation was measured by
comparing the total weight of the microcapsules
with the combined weight of the polymer and
oil. Good results in terms of recovery, shape
and size distribution were obtained in the case
of blank microcapsules (Table 1). The presence
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Textile and Polymer Journal16
Table1. Influence of the stirring speed on yield of microencapsulation and diameter of microcapsule.
OilStirrer speed,
rpm
Yield,
%
Diameter± SDa,
µm
Rosemary oil
350 68 72±8
500 58 43±13
750 67 42±5.6
1000 50 20±5.1
Blank microcapsules 350 75 78±15
aeach value represents the mean± standard deviation (SD) of fifty measurements
3-2 Rosemary oil content determination
The Rosemary oil content (ROC) of 30%
was determined from the mass differences of
microcapsules containing Rosemary oil and
capsules after oil extraction by using ultrasound.
By using CLSM (The second method mentioned
in paragraph 2.3), the representative CLSM
images of empty EC microcapsules and ECmicrocapsules containing Rosemary oil were
studied. Figure 2 presents microcapsules without
Rosemary oil "embedded" in fluorescent dye.
By comparison of the fluorescence intensity of
the capsule area with fluorescence intensity of
the same blank area it is possible to estimate
the proportion of empty capsule space. The
average empty space in prepared capsules was
determined to be 40%. Figure 3 a presents CLSM
images of microcapsules containing essential
oil "embedded" in fluorescence dye and empty
microcapsule "embedded" in fluorescence dye
as Figure 3. In the case when microcapsules
contain hydrophobic Rosemary essential oil
(Figure 3a) the penetration of the hydrophilic
fluorescence dye into capsule's porous systems is
hindered, while in the case of empty capsules the
hydrophilic fluorescent dye can penetrate into
capsules easily.
of oil causes deficiencies of the microcapsule
recovery. In order to facilitate the encapsulation
of oil, this should have a density comparable to
that of the aqueous external phase and complete
immiscibility with the external phase. The
density of Rosemary oil is 0.91 g/ml which could
explain the slight decrease in yield of Rosemary
oil microencapsulation.
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Vol.1. No.1. 2009 17
Figure.2. Microcapsules without Rosemary oil
"embedded" in fluorescent dye.
Figure.3. Microcapsule containing essential oil
"embedded" in fluorescence dye (a) and empty
microcapsule "embedded" in fluorescence dye (b).
3-3 Microcapsules on textile substrate
Prepared microcapsules containing Rosemary
oil and microcapsules without Rosemary oil were
covalently bound to hydroxyl groups of cellulose
by using BTCA. Grafting of microcapsules onto
textile materials occurred at 110°C for 2 min
thus some of the essential oil might evaporated
through the microcapsule walls. When textile
material grafted with empty microcapsules was
embedded in fluorescence dye solution, the dye
penetration into microcapsules was indicated
by the capsules colouring green (Figure 4a), on
the other hand, fluorescence dye penetration
into microcapsules was hindered when textile
materials was grafted with microcapsules
containing Rosemary oil. This can be indicated
by black microcapsules on image b in Figure 4.
We can conclude that heating of microcapsules
containing Rosemary oil at 110°C for 2 min
during the grafting process does not have a
significant influence on the Rosemary oil content
of microencapsulated textile material.
a)
b)
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Textile and Polymer Journal18
Figure.4. Microcapsules without Rosemary oil on
textile materials "embedded" in fluorescence dye, a)and microcapsules containing Rosemary oil on textile
materials "embedded" in fluorescence dye, b).
4. Conclusion
This work described the preparation of
EC microcapsules containing Rosemary oil
by th e ph ase separ at ion me tho d. The size
range of EC microcapsules depends on the
stirring speed employed during encapsulation.
Reducing the stirring speed increased the size
of microcapsules. The Rosemary oil content in
microcapsules was determined by extraction of
oil in cyclohexane by ultrasound and CLSM. We
observed that the oil content is about 30% and
that the empty space in capsule is around 40%.
We can conclude that results obtained from both
methods are comparable; EC microcapsules
have in average 40% of empty space which
are is fully occupied by Rosemary oil. Further,
microcapsules were grafted onto cotton textile
substrate and the presence of Rosemary oil in
microcapsules bonded onto textile materials was
tested by CLSM. We observed that after grafting
of microcapsules on textile materials at elevated
temperature the Rosemary oil is still present in
microcapsules. This indicates that grafting of
EC microcapsules containing Rosemary oil onto
textile materials at 110°C for 2 min by using
BTCA is appropriate method to prepare textile
materials for cosmetic application.
Acknowledgement
We are grateful to European project MTKD-
CT-2005-029540 POLYSURF, for its financial
support.
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Vol.1. No.1. 2009 19
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