Upload
others
View
1
Download
0
Embed Size (px)
Citation preview
World Journal of Textile Engineering and Technology, 2015, 1, 1-22 1
E-ISSN: 0000-0000/15 © 2015 Synchro Publisher
Current Status and Future Outlook Pertaining to Encapsulation of Organic Pigments: Review Article
O.A. Hakeim*, A.A. Arafa and L.A.W. Abdou
Textile Research Division, National Research Centre, Dokki, Cairo, Egypt
Abstract: Organic pigments have a wide range of commercial applications in coatings, printing and paint industries. Encapsulating pigments with various polymers is a promising approach for improving the quality of the pigment
dispersion. This article gives a summary of the most commonly and new processes along with techniques for encapsulation of organic pigments. It must be noted that a successful encapsulation technique should not impair the original color appearance of pigments, but enhance their dispersion. The review describes a wide variety of polymeric
materials or functional nanomaterials can be used for encapsulation to create nanoscale organic pigments with completely new properties. Many techniques have been reviewed for encapsulating organic pigments such as emulsion or miniemulsion polymerization, phase separation, layer-by layer assembly, sol-gel, and free radical precipitation
polymerization. Additionally, some living materials such as macro-RAFT copolymer and polymerizable dispersant were also reported for pigment encapsulation. The effect of polymer encapsulation on electrophoretic property of organic pigments has been also reviewed.
Keywords: Pigments, Encapsulation, Miniemulsion, Layer by layer and UV-curable resins.
1. INTRODUCTION
Organic pigments have been extensively used in
coating, ink and plastic industries or even in color filters
[1] for electronics and communication apparatus since
they have many advantages such as photosensitivity,
color strength, excellent transparence and etc. Pigment
coatings for textiles in dyeing and printing have many
advantages [2], such as a simple and short product
process, little wastewater, and a low production cost.
However, traditional pigment coatings cannot satisfy
the demand of textile industry for their large particles,
poor stability and color performance that greatly limit
the organic pigment application in textiles [3].
Pigment and polymer latex are the most important
ingredients in water-based paint and ink formulations
[4]. During film formation, latex particles coalesce to
form a polymer film covering the substrate surface while
the presence of pigment particles in the film provides
the final coating with color and influences other appear-
ance properties, such as opacity and gloss [5]. With
such an important role, pigments are typically manufac-
tured with a primary particle size that is designed to
deliver optimum effects in the paint film [4]. However,
due to their surface properties and small size, usually
sub-micrometer, one of the most challenging tasks for
the paint technologist is to disperse pigments to their
primary particle size and to maintain the quality of that
dispersion throughout the manufacturing, storage, and
*Address correspondence to this author at the Textile Research
Division, National Research Centre, Dokki, Cairo, Egypt; Tel: +202-33371499; E-mail: [email protected]
most importantly, through the film formation process to
the final coating [6].
A general problem with latex paints is that pigment
agglomeration occurs during the film formation process,
forming pigment aggregates. The pigment particles are
easy to aggregate to form larger particles due to the
van der waals attractive forces, which represent a big
disadvantage of pigments compared with dyes [6, 7].
Pigment agglomeration thus significantly reduces the
pigment efficiency, resulting in a lower quality product
at higher cost. Moreover; the appearance of aggre-
gates on the film surface reduces surface smoothness
and leads to lower gloss [5]. Thus, the organic pig-
ments must be modified before using .The coating of
organic pigments by polymers may be of great benefit
to improve their processing. [8]. Polymeric dispersants
during the last years have proven good properties in
stabilizing pigments in coating system [9, 10]. In recent
years, more and more copolymers have been synthe-
sized and applied in pigment dispersions.
Recently, researchers reported ultimate solutions to
avoid pigment agglomeration by encapsulating the pri-
mary pigment particles with a layer of binder polymer,
creating polymer shells that ensure that the pigment
particles remain separated during film formation. For
this approach to be effective, the process needs to be
very efficient, ensuring that all pigment particles are
coated and avoiding such problems as pigment agglo-
meration during the encapsulation process [5]. In the
last 10 years a large number of successful encapsula-
tions have been reported, it will be dealt with in this
review.
2 World Journal of Textile Engineering and Technology, 2015, Vol. 1 Hakeim et al.
2. DEFINITION: PIGMENTS–DYES
Colorants are classified as either pigments or dyes.
Pigments are inorganic or organic, colored, white or
black materials, which are practically insoluble in the
medium in which they are incorporated. Dyes, unlike
pigments, do dissolve during their application and in
the process lose their crystal or particulate structure. It
is thus by physical characteristics rather than chemical
composition that pigments are differentiated from dyes
[11, 12]. In many cases, the general chemical structure
of dyes and pigments is the same. Partial solubility of
the pigment is a function of application medium and
processing conditions. Under certain circumstances, it
may even be advantageous to have a pigment dissolved
to some degree in its binder system, in order to
improve certain application properties such as tinctorial
strength and rheological behavior. The performance of
a colorant in its role as a commercial pigment is there-
fore defined by its interaction with the application med-
ium under the conditions that govern its application [12].
3. ORGANIC–INORGANIC PIGMENTS
In some application areas, inorganic pigments can be
used frequently in combination with organic pigments.
Most inorganic pigments exhibit excellent hiding power.
Their rheology is usually an advantage, being superior
to that of most organic pigments under comparable
conditions. However, many inorganic pigments have
much less strength than organic pigments and, the
spectral range that is accessible by inorganic pigments
alone is very limited. Many hues cannot be produced in
this manner by inorganic pigments. Besides, the poor
tinctorial strength and lack of brilliance restricts the use
of inorganic pigments in printing inks. There are areas
of application, however, where it is hardly, at all,
possible to replace the inorganic species by an organic
pigment. The ceramics industry, for example, requires
extreme heat stability, which precludes the use of
organic compounds. Thus, the organic and inorganic
classes of pigments are generally considered comple-
mentary rather than competitive [12].
The application of organic pigments dates to
antiquity. They were used not only for dyeing textiles
but also, due to their ability to adsorb on mineral based
substrate such as chalk and china clay, were used for
solvent resistant coatings for decorative purposes.
4. CLASSIFICATION OF ORGANIC PIGMENTS
Publications have over the course of the years
proposed several classification systems for organic
pigments. Basically, it seems appropriate to adopt a
classification system by grouping pigments either by
chemical constitution, or by coloristic properties. Strict
separation of the two classification systems is not very
practical, because the categories tend to overlap; so it
is useful to list pigments according to chemical
constitution. A rough distinction can be made between
azo and nonazo pigments; the latter are also known as
polycyclic pigments. The commercially important group
of azo pigments can be further classified according to
structural characteristics, as by the number of azo
groups, by the type of diazo or coupling component. On
the other hand, polycyclic pigments may be identified
by the number and the type of rings that constitute the
aromatic structure [12].
5. ENCAPSULATION OF ORGANIC PIGMENTS BY MINIEMULSION POLYMERIZATION
5.1. Miniemulsion Technique
For the preparation of nanoparticles from radically
polymerized monomers, the emulsion polymerization is
often applied. As the process of emulsion polymeriza-
tion is limited because of diffusion processes, the
generation of complex structures is often difficult or
even impossible. An elegant way to circumvent these
problems is the miniemulsion process [13]. Miniemul-
sion polymerization was found to be particularly
attractive to obtain polymeric nanoparticles, which
cannot be achieved by current procedures [14, 15].
Miniemulsions consist of a liquid/liquid dispersion of a
monomer phase in water with diameters in the range of
approximately 50–500nm. The size of the monomer
droplets is usually controlled by shearing the system in
the presence of a surfactant and an hydrophobe
(costabilizer), whose role is to stabilize the emulsion
against diffusion degradation (Ostwald ripening).
Contrary to conventional emulsion polymerization, the
monomer droplets are sufficiently small and numerous
so that the polymerization predominantly occurs by
radical entry into the preexisting miniemulsion droplets
without formation of new particles. Miniemulsion
polymerization is therefore particularly attractive for the
encapsulation reaction of any compound that can be
satisfactorily suspended into the monomer phase [16,
17] as schematically represented in Figure 1.
5.2. Organic Pigments and Carbon-Based Materials
Direct dispersions of carbon black or organic
pigments in the monomer (e.g. styrene) are possible;
however, a limited pigment content of about 10wt% in
the monomer phase can be used for further processing
Current Status and Future Outlook Pertaining World Journal of Textile Engineering and Technology, 2015, Vol. 1 3
due to a drastic increase of the viscosity of the organic
phase, making it difficult to disperse this phase in
aqueous media [18,19]. A great improvement with
respect to the amount, which can be encapsulated, is
offered by the so-called co-sonication process. Instead
of directly dispersing the pigment in the monomer, in
the first step of the process, a dispersion of the
respective pigment in water is generated using a
surfactant [20]. This dispersion is then mixed with a
monomer miniemulsion stabilized with the appropriate
surfactant. A fusion/fission process triggered by ultra-
sonication leads to an encapsulation of the hydropho-
bic or hydrophobized pigment into the monomer drop-
lets. [16]. Subsequent polymerization of the monomer
allows the formation of hybrid nanoparticles. Initially
developed for carbon black [16], this technique was
also successfully applied for other organic pigments
(Figure 2) [20]. Using the cosonication process, the
ratio pigment to polymer can be varied in a wide range
and allowed the formation of hybrid particles with up to
80wt% of pigment. The successful encapsulation could
be shown by TEM and, in the case of using carbon
black, with nitrogen sorption measurements. [16]. The
pigment itself cannot take over osmotic droplet stabili-
zation without the hydrophope as the number of aggre-
gates is too low to be able to create a significant osmo-
tic pressure. Besides, the ultrahydrophobic compo-
nents serve as mediator between the pigment surface
and the monomer or the resulting polymer.
5.3. Encapsulation of Organic Pigment into UV-Curable Resins via a Miniemulsion Technique
The preliminary investigations on encapsulation of
nano-scale Pigment Red 122 into a UV-curable system
containing polyester acrylate (oligomer) and 1,6-hexa-
nedioldiacrylate (monomer) using the mini-emulsion
technique have been reported by Hakeim et al. [21].
TGA, SEM and ultracentrifuge sedimentation results
showed that CI Pigment Red 122 is successfully encap-
sulated into polyester acrylate/HDDA resins (Figure 3).
The particles of encapsulated pigment exhibit spherical
shape heterogeneously distributed with an average
size close to 100nm (Figure 4). The oligomer (polyester
acrylate) in the presence of organic pigment could
stabilize the mini-emulsion droplets without introducing
any other hydrophobes (co-stabilizer) in the formula-
tion. The most stable emulsions, as shown by the long-
est shelf-life results, were those obtained in the absence
Figure 1: Schematic representation of the encapsulation reaction of organic pigments through miniemulsion polymerization [19].
Figure 2: Encapsulate of materials by the cosonication process: (a) carbon black in PS; (b) nanotubes in PS; (c) azo-pigment in PS [13].
4 World Journal of Textile Engineering and Technology, 2015, Vol. 1 Hakeim et al.
of known hydrophobe. Polyester acrylate oligomers
may be used as a costabilizer as long as they meet the
criteria of hydrophobe that being essentially insoluble in
water, but soluble in the monomer mixture, and are
innocuous in the final product. Conventional hydroph-
obes such as hexadecane goes through the polymeri-
sation reaction unchanged [19,20] as a residue of the
organic compound. Therefore, it is preferably removed,
requiring an additional step, which is costly and difficult.
Besides, the acrylate oligomers based on polyester
acrylate in the presence of water-soluble initiator stabi-
lizes the mini-emulsion droplets and ink formulation
with time. This trial offers a great benefit of industrial
importance in application of pigmented UV-curable inks
for textiles and, could find numerous applications in
surface coating. Using the encapsulated pigment in
UV-curable inkjet printing on textiles is a much simpler
and cheaper and environment friendly method. The
printed fabrics had soft handle and very good fastness
properties [22, 23]. The US Environmental Protection
Agency views UV-curable inks as a green technology
that it deems preferable to conventional solvent-based
ink systems [24].
6. ENCAPSULATED ORGANIC PIGMENT DISPER- SION BY LIQUID PHASE SEPARATION TECHNIQUE
This preparation method is on the basis of the liquid
droplet coalescence method followed by phase separa-
tion belonging in the physicochemical method category
[25].
Figure 4: Statistics graph of particle size distribution for encapsulated CI Pigment Red 122 [21].
Namely, the oil droplets dissolving a shell material
are forced to collide and coalesce with the core oil
Figure 3: SEM micrographs: (a) Nano-scale CI Pigment Red 122 dispersion that used SDS as dispersant; (b) mini-emulsion droplets of HDDA/ polyester acrylate encapsulated CI Pigment Red 122; (c) UV curable film of HDDA/polyester acrylate
encapsulated CI Pigment Red 122 [21].
Current Status and Future Outlook Pertaining World Journal of Textile Engineering and Technology, 2015, Vol. 1 5
droplets in the continuous water phase. Here, the core
oil droplet phase is a poor solvent for the shell material
but a good solvent for the oil droplet phase dissolving
the shell material. When the oil droplets dissolving the
shell material are forced to collide and coalesce with
the core oil droplets, the shell material has to be
separated in the newly formed oil droplets by phase
separation (Figure 5), because the core oil phase is a
poor solvent for the shell material [26].
If interfacial energy between the continuous phase
and the shell material is lower than that between the
continuous phase and the newly formed oil phase, the
shell material separated in the newly formed oil
droplets has to transfer to the outer region of the newly
formed oil droplet and form the microcapsule shell [26].
Microencapsulation of organic pigment, can improve
the applicable properties of pigments by modifying sur-
face properties. It includes solvent evaporation, spray
drying, liquid phase separation, and suspension cross-
linking and monomer polymerization. Copper phthalocy-
anine (CuPc) was microencapsulated by liquid phase
separation in an organic solvent using a polystyrene
(PS) wall [27]. In this method the wall material was
dissolved in solvent (A); (2) CuPc powder was well
dispersed into the above solution; and (3) solvent (B),
called a coacervation agent, which dissolves solvent
(A) to partially desolvate the wall material but does not
dissolve the wall material, is added to the dispersion
(Figure 6).
The wettability, flowability and dispersibility level for
the microcapsule was improved significantly, compared
to untreated pigment. The molecular weight of wall
material, PS was found to be influential and required
optimization. The higher molecular weight of PS has an
adverse effect on the dispersing level of CuPc. The
longer polymer chains may adsorb two or more
pigment particles and connect them together, leading
to flocculation (Figure 7). Based on these data, the
amount of PS should be carefully controlled; otherwise
a reduction in tinctorial strength may occur.
Figure 6: Schematic representation of microencapsulation mechanisms by coacervation [26].
Microcapsules containing a PS wall were analyzed
by scanning electronic microscopy (SEM, Figure 8).
When PS/CuPc was 5%, a few microcapsules were
observed, but the particle distribution was not uniform
and many small particles existed. When PS/CuPc was
20%, all particles were nearly microcapsules and
particle distribution was uniform.
Ongoing research along this line, Xu and his
workers fabricated colloidal nanoparticles consisting of
oxidized carbon black (CB) encapsulated by poly(vinyl
pyrrolindone) (PVP) by a simple phase separation
method [28]. PVP and CB particles were first dispersed
in water, then acetone, served as a nonsolvent of PVP,
and was added to induce precipitation of the PVP to
Figure 5: Microencapsulation mechanism with liquid droplet coalescence method followed by phase separation [25].
6 World Journal of Textile Engineering and Technology, 2015, Vol. 1 Hakeim et al.
absorb onto the CB particle surface. Finally, initiator
was added to make the particles shell-crosslinked
(Figure 9). TEM indicated a core-shell structure for the
composite (Figure 10).
Excessive amount of acetone can cause the precipi-
tation of CB/PVP nanoparticles before crosslinking re-
action while inadequate amount also cannot sufficiently
precipitate the PVP to induce encapsulation layer on
the surface of CB particles [28].
The crosslinking of PVP shell with loading adequate
amount of initiator provides an effective way to prepare
stable CB nanoparticles in aqueous media (Figure 10).
Copolymers of styrene and maleic acid (PSMA)
were synthesized by free radical polymerization and
used as encapsulating agent for pigment red 122 by
sedimentation, milling and phase separation method
[29]. The pigment dispersion prepared by phase
separation method had higher stability, smaller particle
size, and narrower particle size distribution than those
prepared by milling method with dispersant using molar
content of maleic acid was at 0.43. The results of
contact angle confirmed that the pigment was
successfully encapsulated by phase separation method
and showed that encapsulated pigment can be wetted
by water more easily than those without modification
(Figure 11).
Figure 7: A possible model for bridging flocculation caused by very long PS chain [27].
Figure 8: The SEM of PS microencapsulated CuPc. A: PS/CuPc=5%; B: PS/CuPc=20% [27].
Figure 9: Schematic diagram for the fabrication process of CB/PVP nanoparticles via the phase separation method [28].
Current Status and Future Outlook Pertaining World Journal of Textile Engineering and Technology, 2015, Vol. 1 7
Further hydrolyzing of encapsulated C.I.P.R122
(Figure 12) lead to fine and small uniformly dispersion
in aqueous media than without hydrolyzing. This
attributed to the negative charges on pigment surface,
which hinder the pigment particles to combine together.
Based on the aforementioned results a schematic
representation was given for the illustration of the
whole encapsulation process divided into four steps
(Figure 13).
With the same manner, Fu et al. [30] investigated
the encapsulation of CuPc with a copolymer PSMA via
Figure 13: Schematic of encapsulation course by phase separation method [29].
Figure 10: TEM image of CB/PVP nanoparticles obtained by adding 2ml of acetone, with and without crosslinking reaction [28].
Figure 11: Wettability of pigment powder; (a) starting C.I.P.R122; (b) encapsulation C.I.P.R122 by milling method; (c)
encapsulation C.I.P.R122 by phase separation method [29].
Figure 12: TEM photo of pigment in different stage, (a) encapsulated C.I.P.R122 (enlarge about 40,000 times); (b) hydrolyzing
of encapsulated C.I.P.R122 (enlarge about 70,000 times) [29].
8 World Journal of Textile Engineering and Technology, 2015, Vol. 1 Hakeim et al.
a phase-separation technique. Here too, the particles in
the PSMA-encapsulated pigment dispersion were dis-
tributed in aqueous media more uniformly than those of
the PSMA-dispersed pigment in the dispersion (Figure
14).
The apparent viscosity of the PSMA encapsulated
CuPc dispersion was lower than that of the PSMA-
dispersed pigment dispersion. In addition, max of the
PSMA-encapsulated pigment dispersion was lower
than that of the PSMA-dispersed pigment dispersion
[30], and this indicated that the color of the former was
purer than that of the latter (Figure 15).
Figure 15: Absorbency of the PSMA-encapsulated pigment dispersion and PSMA-dispersed pigment dispersion [30].
The effects of process conditions on properties of
pigment red 122 encapsulated by PSMA have been
also evaluated [31]. Hydrolyzing of encapsulated pig-
ment red 122 using optimum amount of sodium hydrox-
ide is accompanied by small particle size, highest and
superior performance of dispersion stability compared
with the other additives, ammonia and triethanolamine.
The effect of sodium hydroxide concentration can be
indicated by the relationship between the amount of
sodium hydroxide and Zeta potentials (Figure 16). The
encapsulation process by PSMA dispersion was
optimized by hydrolysis in 15 minutes at 45ºC; with the
molar amount of sodium hydroxide being about 0.60–
0.68 [31]. The morphology image of pigment red 122
encapsulated by PSMA and particle size distribution
(Figures 17,18) indicated that the dispersing property
was significantly improved after poly (styrene-maleic
acid) encapsulation of the pigment surface under the
set of conditions.
Figure 16: The effect of the amount of sodium hydroxide on Zeta potentials of pigment particle: hydrolysis temperature 45ºC; hydrolysis time 30 minutes; stirring rate 10000r/min [31].
Fu and Wang [32] investigated the rheological pro-
perties of Azo pigment yellow 14 (P.Y.14) encapsulated
Figure 14: Scanning electron microscopy images of the particles in (a) the PSMA-encapsulated pigment dispersion and (b) the PSMA-dispersed pigment dispersion [30].
Current Status and Future Outlook Pertaining World Journal of Textile Engineering and Technology, 2015, Vol. 1 9
into copolymer of styrene and maleic acid (PSMA) via
phase separation technique followed by preparation of
composite dispersions. The results revealed that all the
dispersions show shear-thinning behavior at molar
content of maleic acid (FM) in PSMA about 0.38 and
Figure 17: TEM photo of composite particle in the dispersion: MNaOH% 0.64; hydrolysis temperature 45ºC, stirring rate 10000r/min [31].
Figure 18: Particle size distribution of composite dispersion: M NaOH% 0.64; hydrolysis temperature 45ºC, stirring rate 10000r/min [31].
0.68. The composite dispersion was closer to Newton-
ian fluid when FM was about 0.53 than that of 0.38 and
0.68 [32] (Figure 19). At a small amount of PSMA, the
particles could not completely be encapsulated by
PSMA, where the pigment can be easily combined via
van der walls forces, thus resulted in large apparent
viscosity (na). Additional, when PSMA amount was high
enough, the PSMA that was not encapsulated onto the
pigment dissolved into water, which would greatly in-
crease na [32].
Figure 19: Effect of FM on rheological properties of PSMA-encapsulated pigment dispersion, PSMA structure: the amount of initiators to monomers: 1.8 wt%, RC=P%, 12%; pigment content: 10% [32].
Fu et al. [33] reviewed the ink formulations and
color performance of encapsulated pigment yellow 74
(PY74) prepared by the phase-separation technique
and by the milling method using copolymer PSMA. The
encapsulation of pigment onto PSMA layer increases
the wettability and hindered the PY74 to combine with
each other; this led to a small particle size and a
narrow particle size distribution compared to surface –
modified PY74 dispersion (Figure 20).
The nozzle-clogging rate of the ink made from the
PSMA-encapsulated PY74 dispersion was lower than
Figure 20: Particle size distributions of the dispersions [33].
10 World Journal of Textile Engineering and Technology, 2015, Vol. 1 Hakeim et al.
that of the surface-modified PY74 dispersion. These
poor stability and printing performance [33] might have
been due to the larger particle size and the easier
clogging the nozzle of the printhead (Figure 21). The
color strength, rubbing fastness, and washing fastness
of the fabrics were better when they were printed with
the PSMA-encapsulated PY74 ink.
Figure 21: Printing performances of the pigment ink [33].
7. SURFACE CHARGE MODIFICATION USING
LAYER-BY-LAYER DEPOSITION FOR ORGANIC PIGMENT ENCAPSULATION
Layer-by-layer deposition is a simple and versatile
method to construct multiple layer thin films on the
surface of a substrate [34]. Electrostatic interactions
facilitate the adsorption of a polyelectrolyte on the
surface, consequently imparting its charge to the
substrate. This cycle can be repeated many times to
increase film thickness with the final charge on the
substrate surface being decided by the charge of the
outermost adsorbed polyelectrolyte.
Layer-by-layer deposition has been successfully used
to form polymer thin films on a number of substrates
such as silica nanoparticles [34], polymer latex and
carbon nanotubes [35-37]. Yuan and his worker [38]
investigated the nano silica-encapsulation of organic
pigment Yellow 109 by depositing multilayer polyelect-
rolyte films. Two kinds of polyelectrolytes, poly-(diallyl-
dimethylammonium chloride) (PDADMAC) and poly-
(sodium 4-styrenesulfonate) (PSS), adsorbed onto the
surfaces of the organic pigment and then coated by
colloidal nano-SiO2. The mechanism of coating of
colloidal nano-SiO2 particles onto the surfaces of the
organic pigment can be schematically described as
shown in Figure 22. The first layer of nano-silica
assembly increased the particle size of the organic
pigment, causing a relatively rough surface and a broad
pore size distribution, but the second and the third
layers of nano-silica assembly preferred to fill the pores
caused by the first layer of silica, causing a relatively
smooth surface, slight increases in shell thickness and
a narrow pore size distribution [38] (Figure 23).
This study proved that the encapsulated nano-SiO2
pigment acquire the UV scattering property [38], after
the second and the third layers of nano-SiO2 assembly,
in turn enhanced the weather durability and dispersion
ability for the organic pigment in waterborne systems.
Benzidine yellow G was applied as organic pigments
since this pigment has good color strength, good trans-
parency, and low cost and is widely used in various
types of printing inks while the poor light fastness and
weatherability limit its applications in coatings, rubbers
and plastics [39]. The properties of the organic pigment,
Benzidine yellow G particles encapsulated with nano-
silica particles via multi-step layer-by-layer self-assemb-
ly technique was further investigated by Yuan et al.
Figure 22: Mechanism for preparation of organic pigment particles coated with colloidal silica particles [38].
Current Status and Future Outlook Pertaining World Journal of Textile Engineering and Technology, 2015, Vol. 1 11
[40]. The encapsulation of nano-silica onto the pigment
surfaces improved the dispersibility of organic pigment
in water-borne system (Figure 24). Besides that, the
nano-silica coating could depress the decomposition
rate of organic pigment. Additionally, the acid and alkali
resistance performances of the encapsulated organic
pigment were enhanced.
Figure 23: SEM images of uncoated organic pigment (a), PE6-SiO2-coated organic pigment (b), PE6-2SiO2-coated organic pigment (c), and PE6-3SiO2- coated organic pigment (d) [38].
Figure 24: benzidine yellow G (b); PE6e2SiO2-20 nm coated benzidine yellow G (c); PE6e3SiO2-20 nm coated benzidine yellow G (d); PE6e3SiO2-10 nm coated benzidine yellow G (e); PE6e3SiO2-5 nm coated benzidine yellow G (f) [39].
12 World Journal of Textile Engineering and Technology, 2015, Vol. 1 Hakeim et al.
Ageing test revealed that encapsulated pigment
could shield 254 nm UV ray remarkably, which was
consistent with the nano-silica particle itself [39].
The layer-by-layer deposition method was also
explored by Nguyen et al. [5] to modify the surface
charge of Paliotol Yellow pigment for its eventual
encapsulation with polymer. Cationic polyeletrolyte poly
(allylamine hydrochloride) (PAH) was first adsorbed
onto the negatively charged surface of the pigment.
After PAH adsorption, the pigment was dispersed in a
negatively charged macro-RAFT copolymers solution,
resulting in adsorption of the macro-RAFT copolymers
via electrostatic interactions. The adsorbed living
copolymers by emulsion polymerization successfully
encapsulate the pigment particles (Figure 25).
Figure 25: Polymer encapsulated Paliotol yellow pigment [5].
8. ENCAPSULATION OF ORGANIC PIGMENT PART- ICLES VIA SOL-GEL PROCESS
The sol–gel method seems to be more conventional
for application of nano silica on textile materials, due to
easy processing and acceptable treatment conditions
[41]. In this method, hydrolysis and condensation
reactions of the precursor material, tetraethoxysilane
(TEOS) are carried out to form a nano-colloidal
solution, and a network of nanoparticles will be formed
on the substrate through the gradual evaporation of the
solvent as shown in the reaction shown below:
Si (OC2H5)4 +H2O Si (OH) 4 + 4C2H5OH (1)
2Si (OH) 4 2 (Si O Si) + H2O (2)
A simple approach to encapsulate the organic
pigment, Yellow 109 (2GLTE) particles with silica shell
via sol-gel process using tetraethylorthosilicate (TEOS)
as the precursor was investigated [42]. The surfaces of
the organic pigment were first orderly modified by
poly(sodium 4-styrenesulfonate) (PSS) and poly(diallyl-
dimethylammonium chloride) (PDADMAC) to endow
enough affinity of organic pigment with silica, and give
positively charged surfaces of particles, then coated by
silica via sol-gel process of TEOS. The polyvinyl-
pyrrolidone (PVP) adsorbed on the surfaces of organic
pigment could not offer enough affinity for organic
pigment to silica (Figure 26b). Comparing with the
original organic pigment (Figure 26a), the relatively
Figure 26: TEM images of original organic pigment (a) and uncharged organic pigment particles modified by PVP (b), positively
charged organic pigment coated with silica (c), positively charge organic pigment coated with silica in the presence of PVP (d) [42].
Current Status and Future Outlook Pertaining World Journal of Textile Engineering and Technology, 2015, Vol. 1 13
much darker surfaces of the organic pigment particles
indicated that silica was successfully coated on the
surfaces of the organic pigment particles. However, it
seemed that the silica coated the organic pigment
particles was very inhomogeneous. The high amount of
silica coating corresponded to thicker silica coating,
indicated that the thickness of silica coating could be
easily modulated with various TEOS loading (Figure
27).
Figure 27: Variation of silica content coated organic pigment with different TEOS loading [42].
Yuan et al. [43] further investigated the organic pig-
ment coating with titania to improve the weatherability
and dispersion ability in waterborne system via sol-gel
process, then coated by titania via sol-gel process from
titanium n-butoxide (TBOT) (Figure 28).
It is interesting to mention that, the two polyelectro-
lyte layers adsorption could guarantee the titania
coating on the surfaces of the organic pigment particles
efficiently [43], probably because more polyelectrolyte
layers resulted in more hydration on the surfaces of
pigment particles. The water and TBOT content
strongly influences the morphology of the titania-coated
organic pigment particles (Figure 29). At higher water
level, more titania particles formed on the surfaces of
the organic pigment particles due to the faster hydro-
lysis and condensation of TBOT. Coating of titania
could considerably improve the UV shielding property
and thermal stability of organic pigment. It was claimed
that this method was more efficient than the organic
pigment particles coated with colloidal nanosilica via
layer-by-layer assembly.
Organic pigments have been successfully used as
photosensitizers for TiO2 [44]. Thus, without special pre-
cautions, organic pigments might fade quite significant-
ly with time if used in conjunction with a photo catalyst
[45].
Figure 28: TEM images of original organic pigment (a) titania-coated organic pigment with two polyelectrolyte layers (b); four polyelectrolyte layers (c) [43].
Figure 29: TEM images of the Titania coating organic pigment with different content water: (a) 3.8 mol/L (b) 4.5 mol/L); (c) 6.0 mol/L [44].
14 World Journal of Textile Engineering and Technology, 2015, Vol. 1 Hakeim et al.
Recently Fabjan and his workers [44] succeeded in
protection of organic pigments, (ß copper phthalocy-
anine) against photocatalysis by encapsulation process
via sol-gel process. The aim of their approach is to
prepare a thin transparent layer (inorganic shell)
around each individual pigment particle. The thin
protective layer should not only be resistant against the
reactive species released during photocatalysis but
also extremely compact (non-porous) to prevent
penetration of such species through it.
The obtained silica shells served as an efficient
protection against the highly reactive products of photo-
catalysis (Figure 30). The thickness of silica shells
depend mainly on the temperature and pH of prepara-
tion (Figure 31). The degree of protection depends not
only on the thickness of silica shells but also on their
porosity. The thin and compact silica shell around
individual pigment particles may be a good trial for
protection of organic pigment that found in the vicinity
of photocatalytically active paint additives. Thicker and
smaller mesoporosit silica shells showed a better
protection. It is essential that porosity of the protective
shell around the pigment be minimized.
9. ENCAPSULATION OF ORGANIC PIGMENT USING A POLYMERIZABLE DISPERSANT VIA EMULSION POLYMERIZATION
The dispersants play the role in building voluminous
shells and intensifying charges on the pigment surface
that help resist flocculation and coagulation of pigments
in media [46-48]. Nowadays, many structured polymeric
dispersants have been developed for pigment disper-
sions [49-51]. These polymeric materials can also be
employed to encapsulate pigments by techniques such
an emulsion or mini-emulsion polymerisation [19, 20,
21, and 52], phase separation [53, 54], in situ polymeri-
zation [55, 56], layer-by-layer assembly [40], sol-gel
[42], and free-radical precipitation polymerisation [57].
Few researches are investigated the polymerizable
dispersant, which contained allyl groups in emulsion
Figure 30: Evaluation of the efficiency of pigment protection against photocatalysis by fast irradiation method. The protection efficiency is expressed as the total colour change (DE) of TiO2-pigment mixture. This colour change is monitored as a function of time for the unprotected (UP) and differently encapsulated pigment particles (EP). Two UV light intensities were used: a 60 and b 180 W m-2 [44].
Current Status and Future Outlook Pertaining World Journal of Textile Engineering and Technology, 2015, Vol. 1 15
polymerization for encapsulation the pigment. Nowa-
days, some pigments that are encapsulated by poly-
merizable dispersant were also developed [58, 59].
A novel polymer-encapsulated C.I. Pigment blue
15:3 dispersion by a polymerizable dispersant has been
developed [58]. The encapsulation process involves
three steps: predispersing C.I. Pigment blue 15:3 using
allyloxy nonyl-phenoxypropanol-polyoxyethyleneethe-
rammonium sulfonate (ANPS, Figure 32) as dispersant
and emulsifer, emulsifying with the addition of comon-
omers, and polymerizing comonomer and ANPS.
(CH2)8
O
H2C O
OH
O C2H4 CH2 SO3NH4
n
Figure 32: Chemical structures of ANPS [62].
The similarity of the hydrophobic benzene ring of
styrene to the aromatic structure of pigment promotes
the attractive forces between pigment and styrene, thus
reduces the desorption of commoners and ANPS from
pigment surface, facilitating to form smaller particles
and larger amount of copolymer content. The thickness
of core–shell encapsulation layer can be adjusted
according to the mass ratio of monomer to pigment
(Figure 33). The encapsulated pigment dispersion had
improved wettability and enhanced stabilities to centri-
fugal force, temperature, pH value and electrolytes.
Encapsulation of phthalocyanine blue pigment with
a polymerizable dispersant via emulsion polymerization
was also studied by Fu et al. [60]. Small particles was
obtained when the mass ratio of ANPS to phthalocy-
anine blue pigment, styrene (St) to phthalocyanine blue
pigment, and ammonium persulfate (APS) to St was
Figure 31: TEM micrographs of a Sample encapsulated pigment at 70ºC -pH10-one shell, b Sample encapsulated pigment- at 70ºC -pH8-one shell and c Sample encapsulated pigment- at 70ºC -pH10 with two number of shell [44].
Figure 33: TEM imagines of (a) original C.I. Pigment blue 15:3, (b) polymer encapsulated pigment dispersion with a mass ratio of styrene to pigment of 0.1, and (c) polymer- encapsulated pigment dispersion with a mass ratio of styrene to pigment of 0.2 [60].
16 World Journal of Textile Engineering and Technology, 2015, Vol. 1 Hakeim et al.
about 0.2, 0.2, and 0.01, respectively. The emulsion–
polymerization process for encapsulation of phthalocy-
anine blue pigment with a polymerizable dispersant
includes four steps was illustrated in Figure 34.
The polymer-encapsulated phthalocyanine blue
pigment dispersion had an enhanced stability com-
pared with the conventional phthalocyanine blue pig-
ment dispersion.
Fu et al. [61] further investigated the encapsulation
of phthalocyanine blue pigment with a polymerizable
dispersant for inkjet printing inks. The analyses proved
the polymer encapsulation layer onto phthalocyanine
blue pigment surface and had a narrow particle size
distribution. XRD indicated that the crystal structure of
phthalocyanine blue pigment was not changed during
the encapsulation process. The wettability, dispersion
stability to temperature and centrifugal forces were
improved after polymer encapsulation. Its rheological
behavior was close to Newtonian fluid. This method
provided a novel and practical solution for preparing
the encapsulated phthalocyanine blue pigment disper-
sion for formulation of inkjet printing ink.
10. PIGMENT ENCAPSULATION USING MACRO-RAFT COPOLYMERS
Recent advancements in the use of Reversible
Addition Fragmentation chain Transfer (RAFT), tech-
nology have demonstrated that nanoparticles can be
successfully encapsulated using macro-RAFT copoly-
mers [5, 62]. The method is based on the adsorption of
macro-RAFT copolymers on the particle surface
followed by the growth of each individual RAFT copoly-
mer during polymerization as was illustrated in Figure
35.
Figure 34: Emulsion polymerization process for encapsulation of phthalocyanine blue pigment [59].
Figure 35: Schematic diagram for RAFT technology [5].
Current Status and Future Outlook Pertaining World Journal of Textile Engineering and Technology, 2015, Vol. 1 17
For particles with a hydrophilic positively charged
surface such as titanium dioxide pigment [5] and
Gibbsite nanoclay [62], the dispersed particles carry a
net negative charge that helps to stabilize them in
water. However, there is a large range of particle types
such as silica nanoparticles [34], nanoclays [63] and
pigments, which carry a net negative charge, the
dispersion and encapsulation of such particles in water
requires the macro-RAFT copolymers to have a
positive charge on the polymer backbone, inquiring the
design and synthesis of a whole new range of macro-
RAFT copolymers.
The encapsulation of both hydrophilic inorganic,
zirconia and alumina coated titanium dioxide and
hydrophobic organic, phthalocyanine blue pigments
with poly (methyl methacrylateco- butyl acrylate) using
living amphipathic random macro-RAFT copolymers
has been reported [5]. Encapsulated organic pigments
by thick polymer shells were formed that had core-shell
morphology (Figure 36).
The encapsulated particles by this trend were stabi-
lized in the aqueous phase by an anchored hydrophilic
layer of negatively charged carboxyl groups on the
surface. The method was found to be incredibly effi-
cient in that 100% of the pigment particles were
encapsulated and almost all of the polymer growth was
within the encapsulating polymer shells. This is first
attributed to the use of macro-RAFT copolymers as
stabilizers that do not self-assemble in the aqueous
phase and/or do not form centers for secondary particle
nucleation, leading to the formation of a uniform coat-
ing over the entire particle surface. This encapsulation
approach is simple and can be readily scaled up for
industrial production.
11. ENCAPSULATED ORGANIC PIGMENTS VIA FREE-RADICAL PRECIPITATION POLYMERIZATION
Nanoscale azo pigment yellow 13 (PY13) was
encapsulated by PSMA with a free-radical precipitation
polymerization [57]. The four step schematic diagram
for the encapsulation course by free-radical precipita-
tion polymerization was shown in Figure 37. The
results revealed that, the molar ratios of the feeding of
maleic acid, styrene, initiator and pigment have an im-
pact on particle size and the stability of the PY13/
PSMA dispersions.
Figure 36: TEM images of poly (methyl methacrylate-co-butyl acrylate) encapsulated phthalocyanine particles: (A) poly (methyl methacrylate-co-butyl acrylate) encapsulated phthalo-
cyanine blue latex particles and (B) an even coating over a particle with large aspect ratio. Macro-RAFT RAFT was used as a dispersant. Emulsion polymerization was carried out at 70 °C using MMA/BA (7:3 by weight) monomer mixture and V-501 initiator [5].
The morphological structure indicated that the
particle size of encapsulated pigment (Figure 38b) was
uniformly distributed and was a little larger than that of
PSMA-dispersed PY13 (Figure 38a) in the dispersion
[57].
Figure 37: Schematic diagram of the encapsulation course by free-radical precipitation polymerization [57].
18 World Journal of Textile Engineering and Technology, 2015, Vol. 1 Hakeim et al.
The particle size of the encapsulated pigment
mainly distributed in the range 50–700 nm and was
smaller than that of PSMA-dispersed PY13 dispersion.
12. ENCAPSULATION OF ORGANIC PIGMENTS FOR ELECTROPHORETIC COLOR DISPLAY
Electrophoretic displays (EPDs) have attracted a
great deal of interest because of their merits of good
brightness and contrast, wide viewing angles, and low
power consumption [64-68]. Organic pigments due to
their brilliant colors, great brightness, low-specific
gravity and easiness of being charged, are suitable to
use for EPDs. The research progress on using pigment
particles as electrophoretic particles have shown that
the pigment particles in the microcapsules used for
EPDs can move reversibly at a constant velocity in a
DC electric field.
The effect of polymer encapsulation on electro-
phoretic properties of organic pigment nanoparticles in
low dielectric medium was investigated [68]. The blue
organic pigments were encapsulated with poly (methyl
methacrylate) via two-step dispersion polymerization of
methyl methacrylate in presence of organic pigments.
Vinyl imidazole was adopted as a functional co-
monomer to enhance the electrophoretic properties of
the pigments. The results indicated that the polymer
coated organic pigments possess an average net
charge of plus 12mV on their surface, while the
uncoated organic pigments exhibit an average charge
of minus 1mV on their surface. The surface charge of
P(MMA-co-vinyl imidazole) coated organic pigments
changed from negative to positive upon coating with
organic pigments, pertaining to the comonomer, vinyl
imidazole, affected the charge of particle. The charge
control agent (CCA), OLOA 1200 improves the only
minus charge of the nanoparticles and more effective
to the colored particles than to the white particles when
the two particle systems were investigated for their
electrophoretic properties. The electrophoretic response
was observed to be much better than the neat organic
pigment [69]. Nanoscale red organic pigment was
encapsulated with poly (acrylamide-co-methylmetha-
crylate) (PAAm-co-MMA) using in-situ dispersion
polymerization to enhance the electrophoretic move-
ment [70]. The results clearly demonstrated that the
irregular shape of organic pigment nanoparticle was
still maintained through the coating process (Figure
39). Zeta potential and mobility value indicated that
Figure 39: SEM image of (a) unencapsulated pigment and (b) Poly (AAm-MMA) encapsualted organic pigment [70].
Figure 38: Transmission electron micrographs of the (a) encapsulated pigment dispersion and (b) PY13/PSMA dispersion [57].
Current Status and Future Outlook Pertaining World Journal of Textile Engineering and Technology, 2015, Vol. 1 19
polymer encapsulated organic pigment had average
net charge of plus 6mV on their surface, while the
uncoated red pigment has no specific value, demon-
strating that the introduced acrylamide functional group
helps to enhance the plus charge on their surface. The
electrophoretic movement of the electrophoretic parti-
cles can be detected by observing color transition when
the product particles were dispersed with the white
pigment particles (Figure 40). The color difference for
polymer coated pigment red was observed to be more
distinct than for raw pigment red in the presence of
charge transfer agent. It showed also that the polymer
encapsulation enhance the electrophoretic mobility of
organic pigment.
Diarylide yellow pigments/modified SiO2 core/shell
hybrid composite particles were fabricated via a newly
developed two-step procedure. The surface of diarylide
yellow pigments was coated with SiO2 by the hydrolysis
of Na2SiO3. The obtained particles were then modified
with in situ generated 3-aminopropylsilanetriol or
succinic acid to form composite particles containing
amino or carboxyl groups.
The results showed that the obtained composite not
only have organic pigments’ brilliant color and inorganic
pigments’ good solvent resistance, but also have a
core-shell structure with smooth surface morphology
and a high chargeability, which can be applied in EPDs
triumphantly [71].
13. SUMMARY AND OUTLOOK
It is shown that the encapsulation of organic pig-
ments can be used to create numerous hybrid nano-
particles have a large number of many different
materials and compounds in a wide variety of different
(functional) polymeric shells using different techniques.
The most commonly and new processes and tech-
niques for encapsulation of organic pigments are
reviewed in the article. A compatibilization step is often
required between the organic pigments and monomer/
polymer shell so that the pigment is easily to be
incorporated in the shell prior to polymerization. Special
intention is paid to the encapsulation of pigment using
miniemulsion polymerization, the most appropriate
particularly attractive method to obtain polymeric nano-
particles which would ideally offer the nanocapsules
with the stated high requirements compared with the
other techniques. Besides, encapsulated organic pig-
ment with a copolymer via a phase-separation tech-
nique was found to be distributed in aqueous media,
more uniformly than those milled and dispersed pig-
ments. The thickness of silica shell played a deter-
mined role in the properties of encapsulated pigment,
irrespective of the method of encapsulation. The encap-
sulation of pigment using macro-RAFT copolymers
have shown to be incredibly efficient in that 100% of
the pigment particles can be encapsulated within the
polymer shell. We are convinced that many more
functional encapsulated organic pigments for a wide
field of applications, inks, paints and electrophoretic
displays can still be created in the future.
REFERENCES
[1] Gregory P. High-technology applications of organic colorants. New York: Plenum; 1991. http://dx.doi.org/10.1007/978-1-4615-3822-6
[2] Fang KJ, Wang CX, Zhang X, Xu Y. Dyeing of cationised cotton using nanoscale pigment dispersions. Colorat
Technol. 2005; 121: 325-329. http://dx.doi.org/10.1111/j.1478-4408.2005.tb00377.x
[3] Fu S, Xu CH, He C. Effects of process conditions on properties of nanoscale organic pigment encapsulated by
poly(styrene-maleic acid) dispersion. J Disper Sci Technol. 2010; 31: 617-621. http://dx.doi.org/10.1080/01932691003682389
Figure 40: Prototype device performance using EGMEA-PMMA coated TiO2 particles and organic pigment particles: (a) polymer coated, (b) uncoated pigment without charge transfer agent, (c) polymer coated, and (d) uncoated pigment with charge transfer agent [70].
20 World Journal of Textile Engineering and Technology, 2015, Vol. 1 Hakeim et al.
[4] Urban D, Distler D. Introduction, in polymer dispersions and
their industrial applications, Wiley-VCH verlag GmbH & Co. KGaA, Weinheim, FRG, 2003.
[5] Nguyen D, Zondanos HS, Farrugia JM, Serelis AK, Such CH, Hawkett BS. Pigment Encapsulation by emulsion polymerization using Macro-RAFT copolymers. Langmuir
2008; 24: 2140-2150. http://dx.doi.org/10.1021/la7027466
[6] Tiarks F. Conference on coatings science and technology. Proceedings. 28thl Athens, Greece. 2002; July 1-5, 293.
[7] Tiarks F, Frechen T, Kirsch S, Leuninger J, Melan M, Pfau A, et al. Effects on the pigment distribution in paint formulations.
Macromol Symp. 2002; 187: 739-751. http://dx.doi.org/10.1002/1521-3900(200209)187:1<739::AID-MASY739>3.0.CO;2-M
[8] Hoy KL, Glancy CW, Lewis JMO. Micro-composite systems
and processes for making same. Eur Pat Appl. 1989; 392: 065.
[9] Fujitani T. Stability of pigment and resin dispersions in waterborne paint. Prog Org Coat. 1996; 29: 97-105. http://dx.doi.org/10.1016/S0300-9440(96)00661-3
[10] Khan AU, Briscoe BJ, Luckham PF. Interations of binders
with dispersant stabilized alumina suspension. Colloid Surf A 2000; 161: 243-257. http://dx.doi.org/10.1016/S0927-7757(99)00374-X
[11] DIN 55 943: Farbmittel, Begriffe. ISO 4618-1-1984 (TC 35): Paints and varnishes-Vocabulary, Part 1: General terms.
[12] Herbst W, Hunger K. Industrial organic pigments. Third Edition. 2004; Wiley-VCH Verlag GmbH & Co. KGaA,
Weinheim. http://dx.doi.org/10.1002/3527602429
[13] Landfester K, Weiss CK. Encapsulation by miniemulsion polymerization. Adv Polym Sci. 2010; 229: 1-49. http://dx.doi.org/10.1007/12_2009_43
[14] Landfester K. Polyreactions in miniemulsions. Macromol
Rapid Commun. 2001; 22: 896-936. http://dx.doi.org/10.1002/1521-3927(20010801)22:12<896:: AID-MARC896>3.0.CO;2-R
[15] Soula R, Saillard B, Spitz R, Claverie J, Llauro MF, Monnet
C. Catalytic copolymerization of ethylene and polar and nonpolar -olefins in emulsion. Macromolecules 2002; 35: 1513-1523. http://dx.doi.org/10.1021/ma011366e
[16] Tiarks F, Landfester K, Antonietti M. Encapsulation of carbon
black by miniemulsion polymerization. Macromol Chem Phys. 2001; 202: 51-60. http://dx.doi.org/10.1002/1521-3935(20010101)202:1<51:: AID-MACP51>3.0.CO;2-J
[17] Erdem B, Sudo ED, Dimonie VL, El-Aasser M. Encapsulation of inorganic particles via miniemulsion polymerization. I. dispersion of titanium dioxide particles In organic media
using OLOA370 as stabilizer. J Polym Sci Polym Chem. 2000; 38: 4419-4430. http://dx.doi.org/10.1002/1099-0518(20001215)38:24<4419:: AID-POLA110>3.0.CO;2-X
[18] Bechthold N, Tiarks F, Willert M, Landfester K, Antonietti M.
Miniemulsion polymerization: application and new materials. Macromol Symp. 2000; 151: 549-555. http://dx.doi.org/10.1002/1521-3900(200002)151:1<549::AID-MASY549>3.0.CO;2-D
[19] Lelu S, Novat C, Graillat C, Guyot A, Bourgeat-Lami E. Encapsulation of an organic phthalocyanine blue pigment into polystyrene latex particles using a miniemulsion
polymerization process. Polym Int. 2003; 52: 542-547. http://dx.doi.org/10.1002/pi.1029
[20] Steiert N, Landfester K. Encapsulation of organic pigment particles via miniemulsion polymerization. Macromol Mater Eng. 2007; 292: 1111-1125. http://dx.doi.org/10.1002/mame.200700138
[21] Hakeim OA, Fan QG, Kim YK. Encapsulation of pigment red
122 into UV-curable resins via a mini-emulsion technique. Pigment Resin Technol. 2010; 39: 3-8. http://dx.doi.org/10.1108/03699421011009537
[22] Hakeim OA, Arafa AA, Zahran MK, Abdou LAW. UV-curable encapsulation of surface—modified organic pigments for
inkjet printing of textiles. Colloid Surf A 2014; 447: 172-182. http://dx.doi.org/10.1016/j.colsurfa.2014.01.075
[23] Hakeim OA, Diab HA, Adams J. Preparation and characterization of UV curable-encapsulated phthalocyanine
blue pigment. Prog Org Coat. 2015; 84: 70-78. http://dx.doi.org/10.1016/j.porgcoat.2015.02.007
[24] Cahill VJ. Radtech Report, July/August 2001; 20.
[25] Takahashi M, Taguchi Y, Tanaka M. Microencapsulation of hydrophilic solid powder as fire retardant agent with epoxy resin by droplet coalescence method. J Appl Polym Sci.
2008; 110: 1671-1676. http://dx.doi.org/10.1002/app.28211
[26] Yokoyama Y, Fuchigami K, TaguchiY, Tanaka M. Preparation of microcapsules with liquid droplet coalescence method followed by phase separation. J Encap Adsorp Sci.
2013; 3: 93-97. http://dx.doi.org/10.4236/jeas.2013.33011
[27] Tianyong Z, Xuening F, Jian S, Chunlong Z. Properties of copper phthalocyanine microencapsulated in polystyrene by
phase separation. Dyes Pigment. 1999; 44: 1-7. http://dx.doi.org/10.1016/S0143-7208(99)00047-9
[28] Xu W, Chen H, Li H, Wang M. Fabrication of carbon black/crosslinked poly (Vinyl Pyrrolidone) core-shell nanoparticles stable in water. Colloid Surf A 2005; 266: 68-
72. http://dx.doi.org/10.1016/j.colsurfa.2005.05.072
[29] Fu SH, Fang K. Properties of waterborne nanoscale pigment red 122 dispersion prepared by phase separation method. J App Polym Sci. 2008; 108: 3968-3972. http://dx.doi.org/10.1002/app.27955
[30] Fu S, Ding L, Xu C, Wang C. Properties of copper phthalocyanine blue encapsulated with a copolymer of styrene and maleic acid. J Appl Polym Sci. 2010; 117: 211-
215. http://dx.doi.org/10.1002/app.31960
[31] Fu SH, Xu CH, He C. Effects of process conditions on properties of nanoscale organic pigment encapsulated by poly (styrene-maleic acid) dispersion. J Dispersion Sci
Technol. 2010; 31: 617-621. http://dx.doi.org/10.1080/01932691003682389
[32] Fu SH, Wang C. Rheological properties of nansocale poly(styrene-maleic acid) encapsulated organic pigment
dispersion by phase separation technique. J Disper Sci Technol. 2010; 31: 1474-1478. http://dx.doi.org/10.1080/01932690903269693
[33] Fu SH, Du C, Zhang K, Wang C. Colloidal properties of
copolymer-encapsulated and surface-modified pigment dispersion and its application in inkjet printing inks. J Appl Polym Sci. 2011; 119: 371-376. http://dx.doi.org/10.1002/app.32635
[34] Caruso F. Nanoengineering of particle surfaces. Adv Mater.
2001; 13: 11-22. http://dx.doi.org/10.1002/1521-4095(200101)13:1<11::AID-ADMA11>3.0.CO;2-N
[35] Zykwinska A, Radji-Taleb S, Cuenot S. Layer-by-layer
functionalization of carbon nanotubes with synthetic and natural polyelectrolytes. Langmuir 2010; 26: 2779-2784. http://dx.doi.org/10.1021/la902818h
[36] Wang XD, Yang WL, Tang Y, Wang YJ, Fu SK, Gao Z.
Fabrication of hollow zeolite spheres. Chem Commun. 2000; 2161-2162. http://dx.doi.org/10.1039/b006539k
Current Status and Future Outlook Pertaining World Journal of Textile Engineering and Technology, 2015, Vol. 1 21
[37] Zhang YB, Qian XF, Xi HA, Yin J, Zhu ZK. Preparation of
polystyrene core-mesoporous silica nanoparticles shell composite. Mater Lett. 2004; 58: 222-225. http://dx.doi.org/10.1016/S0167-577X(03)00449-X
[38] Yuan J, Zhou S, You B, Wu L. Organic pigment particles coated with colloidal nano-silica particles via layer-by-layer
assembly. Chem Mater. 2005; 17: 3587-3594. http://dx.doi.org/10.1021/cm048000b
[39] Christie RM, Standring PN. Colour and constitution relation- ships in organic pigments part 2: Disazoacetoacetanilides.
Dyes Pigments 1989; 11: 109-121. http://dx.doi.org/10.1016/0143-7208(89)85031-4
[40] Yuan J, Xing W, Gu G, Wu L. The properties of organic pigment encapsulated with nano-silica via layer-by-layer assembly technique. Dyes Pigments 2008; 76: 463-469. http://dx.doi.org/10.1016/j.dyepig.2006.10.002
[41] El-Gabry LK, Allam OG, Hakeim OA. Surface functionaliza- tion of viscose and polyester fabrics toward antibacterial and coloration properties. Carbohyd Polym. 2013; 92: 353-359. http://dx.doi.org/10.1016/j.carbpol.2012.08.108
[42] Yuan J, Zhou S, Gu G. Encapsulation of organic pigment
particles with silica via sol-gel process. J Sol-Gel Sci Technol. 2005; 36: 265-274. http://dx.doi.org/10.1007/s10971-005-4063-5
[43] Yuan J, Zhou S, Wu L, You B. Organic pigment particles
coated with Titania via sol-gel process. J Phys Chem B 2006; 110: 388-394. http://dx.doi.org/10.1021/jp053938t
[44] Fabjan ES, kapin AS, kapin L, Zkrlep P, ivec P, Ceh M, et al. Protection of organic pigments against photocatalysis
by encapsulation. J Sol-Gel Sci Technol. 2012; 62: 65-74. http://dx.doi.org/10.1007/s10971-012-2684-z
[45] Zhao L, Lei Z, Li X, Li S, Xu J, Peng B, et al. A novel approach of preparation and patterning of organic fluorescent nanomaterials. Chem Phys Lett. 2006; 420: 480-483. http://dx.doi.org/10.1016/j.cplett.2006.01.023
[46] Croll S. DLVO theory applied to Tio2 pigments and other materials in latex paint. Prog Org Coat. 2002; 44: 131-146. http://dx.doi.org/10.1016/S0300-9440(01)00261-2
[47] Chen YM, Hsu RS, Lin HC, Chang SJ, Chen SC, Lin J. Synthesis of acrylic copolymers consisting of multiple amine
pendants for dispersing pigment. J Colloid Interf Sci. 2009; 334: 42-49. http://dx.doi.org/10.1016/j.jcis.2009.03.069
[48] Faouzi N, Naceur A, Chevalier Y. Selection of dispersants for
the dispersion of C.I. pigment violet 23 in organic medium. Dyes Pigments 2007; 74: 133-140. http://dx.doi.org/10.1016/j.dyepig.2006.01.047
[49] Spinelli HJ. Polymeric dispersants in ink jet technology. Adv Mater. 1998; 10: 1215-1218.
http://dx.doi.org/10.1002/(SICI)1521-4095(199810)10:15< 1215::AID-ADMA1215>3.0.CO;2-0
[50] Auschra C, Eckstein E, Muhlebach A, Zink MO, Rime F. Design of new pigment dispersants by controlled radical
polymerization. Prog Org Coat. 2002; 45: 83-93. http://dx.doi.org/10.1016/S0300-9440(02)00048-6
[51] Zhou Y, Yu D, Xi P, Chen SL. Influence of styrene-maleic anhydride copolymers on the stability of quinacridone red pigment suspensions. J Disper Sci Technol. 2003; 24: 731-
737. http://dx.doi.org/10.1081/DIS-120023821
[52] Reuter E, Silber S, Psiorz C. The use of new blockcopoly- meric dispersing agents for waterborne paints - theoretical
and practical aspects. Prog Org Coat, 1999; 37: 161-167. http://dx.doi.org/10.1016/S0300-9440(99)00072-7
[53] Zhang TY, Fei XN, Song J, Zhou CL. Properties of copper phthalocyanine microencapsulated in polystyrene by phase separation. Dyes Pigments 1999; 44: 1-7. http://dx.doi.org/10.1016/S0143-7208(99)00047-9
[54] Fu SH, Fang KJ. Preparation of copolymers and its
application in encapsulated pigment red 122. J Appl Polym Sci. 2007; 105: 317-321.
http://dx.doi.org/10.1002/app.26001
[55] Tasdelen MA, Kreutzer J, Yagci Y. In situ synthesis of
polymer/clay nanocomposites by living and controlled/living polymerization. Macromol Chem Phys. 2010; 211: 279-285.
http://dx.doi.org/10.1002/macp.200900590
[56] Vodnik VV, Bozanic DK, Dzunuzovic E. Thermal and optical
properties of silver-poly(methylmethacrylate) nanocompo- sites prepared by in-situ radical polymerization. Eur Polym J. 2010; 46:137-144.
http://dx.doi.org/10.1016/j.eurpolymj.2009.10.022
[57] Fu SH, Xu C. Preparation of nanoscale azo pigment yellow 13/ poly (styrenemaleic acid) composite dispersions via free-radical precipitation polymerization. J Appl Polym Sci. 2010;
115: 1929-1934.
http://dx.doi.org/10.1002/app.31171
[58] Taniguchi T, Takeuchi N, Kobaru S, Nakahira T. Preparation of highly monodisperse fluorescent polymer particles by
miniemulsion polymerization of styrene with a polymerizable surfactant. J Colloid Interf Sci. 2008; 327: 58.
http://dx.doi.org/10.1016/j.jcis.2008.08.003
[59] Fu SH, Xu C, Duc C, Tiana A, Zhang M. Encapsulation of
C.I. pigment blue 15:3 using a polymerizable dispersant via emulsion polymerization. Colloid Surf A 2011; 384: 68-74.
http://dx.doi.org/10.1016/j.colsurfa.2011.03.009
[60] Fu SH, Xu C, Duc C, Zhang M, Tian A, Zhang X. Preparation and properties of polymer-encapsulated phthalocyanine blue
pigment via emulsion polymerization. Prog Org Coat. 2012; 73: 149-154.
http://dx.doi.org/10.1016/j.porgcoat.2011.10.006
[61] Fu SH, Zhang K, Zhhang M, Tian L. Encapsulated
phthalocyanine blue pigment with polymerisable dispersant for inkjet printing inks. Pigm Resin Technol. 2012; 41: 3-8.
http://dx.doi.org/10.1108/03699421211192226
[62] Ali SI, Heuts JPA, Hawkett BS, van Herk AM. Polymer
encapsulated gibbsite nanoparticles: efficient preparation of anisotropic composite latex particles by RAFT-based starved feed emulsion polymerization. Langmuir 2009; 25: 10523-
10533.
http://dx.doi.org/10.1021/la9012697
[63] Kiliaris P, Papaspyrides CD, Polymer/layered silicate (clay) nanocomposites: An overview of flame retardancy. Prog
Polym Sci. 2010; 35: 902-958.
http://dx.doi.org/10.1016/j.progpolymsci.2010.03.001
[64] Comiskey B, Albert JD, Yoshizawa H, Jacobson J. An electrophoretic ink for all-printed reflective electronic
displays. Nature 1998; 394: 253-255.
http://dx.doi.org/10.1038/28349
[65] Chen Y, Au J, Kazlas P, Ritenour AH, McCreary GM. Electronic paper: Flexible active-matrix electronic ink display.
Nature 2003; 423: 136.
http://dx.doi.org/10.1038/423136a
[66] Werts MPL, Badila M, Brochon C, Hebraud A, Hadziioannou G. Titanium dioxide polymer core-shell particles dispersions
as electronic inks for electrophoretic displays. Chem Mater. 2008; 20: 1292-1298.
http://dx.doi.org/10.1021/cm071197y
[67] Yin PP, Wu G, Dai RY, Qin WL, Wang M, Chen HZ. Fine
encapsulation of dual-particle electronic ink by incorporating block copolymer for electrophoretic display application. J Colloid Interf Sci. 2012; 388: 67-73.
http://dx.doi.org/10.1016/j.jcis.2012.08.039
[68] Le Y, Xu H, Li D, Chen J. Ultrafine copper phthalocyanine complex and its molecular structure in solvents. J Molec Struct Theochem. 2010; 954: 2-6.
http://dx.doi.org/10.1016/j.theochem.2009.12.016
22 World Journal of Textile Engineering and Technology, 2015, Vol. 1 Hakeim et al.
[69] Kim YH, Park BJ, Choi HJ, Effect of polymer encapsulation
on electrophoretic property of organic pigment. Mol Cryst Liq Cryst. 2008; 492: 257-261. http://dx.doi.org/10.1080/15421400802330499
[70] Lee MA, Kim YH, Park BJ, Choi HJ. Synthesis and electrophoretic properties of poly(acrylamide-co-
methylmethacrylate) coated organic pigments. Mol Cryst Liq Cryst. 2009; 499: 305-310. http://dx.doi.org/10.1080/15421400802619669
[71] Wen Z, Feng Y, Li X, Li X, Bai Y, Tang Q, et al. Fabrication
Of diarylide yellow pigments/modified Sio2 coreeshell hybrid composite particles for electrophoretic displays. Curr Appl Phys. 2012; 12: 259-265. http://dx.doi.org/10.1016/j.cap.2011.06.015
Received on 01-09-2015 Accepted on 15-09-2015 Published on 05-10-2015
© 2015 Hakeim et al.; Licensee Synchro Publisher. This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/), which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.