2.14 Microencapsulation
41
2.14 Microencapsulation
Fragrance compounds and essential oils are volatile substances. The most difficult
task in preparing a fragrance-finished textile is how to prolong the fragrant effect
in the finished textile product [212]. Microencapsulation is an effective and popular
technique to solve this problem [213, 214]. Microencapsulation is the process of
producing small capsules by encasing tiny particles of one material within another
material. The dimension of the resulting capsules ranges from less than one micron
to several hundred microns. Microcapsules are very tiny particles containing core
material surrounded by a shell [215]. The shapes of microcapsules can be spherical,
asymmetrical or variably shaped with droplets of core material embedded throughout
the microcapsule. The material encapsulated is called the core or nucleus, while
the encapsulating material is referred to as the shell or wall. Various types of core
materials such as dyes, drugs, fragrances and biological shells can be coated by the
shells of various materials such as wax, fat and polymers.
By selecting appropriate materials for core and shell, microcapsules with a variety
of functions can be prepared. Solids, liquids and gases may be microencapsulated.
Microencapsulation allows liquid and gases to be processed similar to solids, and
in addition, hazardous materials can be easily and safely processed [216]. For the
successful application of PCM by microencapsulation, the following parameters need
to be considered [134].
• Particle size;
• Uniformity of particle size;
• Particle size distribution;
• Stability to mechanical actions such as shear, abrasion and pressure;
• Stability to chemicals and
• Core-to-shell ratio (the proportion of the core with respect to the whole should be
as high as possible, and the thickness of the shell should be sufficient to maintain
capsule stability).
Microcapsules can be encased with core materials for any specific period of time
and can be released gradually. The release of the core material can be achieved by
breaking the capsule walls or when the external conditions cause the capsule walls to
rupture, melt or dissolve. For the effectiveness of the PCM, it is necessary to encapsulate them in a physically and chemically stable shell. PCM were first incorporated
into textile materials by microencapsulation technology in 1987 [217]. The application of PCM in different areas by microencapsulation has been studied by several
researchers [218–221]. Various companies such as BASF [222] and Microtek [190]
have modified and developed new PCM which can be applied by microencapsulation.
The paraffin waxes as PCM for textiles cannot be directly into incorporated textile
substrates because of their low melting points. Therefore, paraffin waxes need to be
microencapsulated by a suitable polymer. Colvin and Mulligan [223] from Triangle
Research and Development Corporation (TRDC) were the first to prove that paraffin
PCM can be successfully microencapsulated and suspended in water. In addition to
41
2.14 Microencapsulation
Fragrance compounds and essential oils are volatile substances. The most difficult
task in preparing a fragrance-finished textile is how to prolong the fragrant effect
in the finished textile product [212]. Microencapsulation is an effective and popular
technique to solve this problem [213, 214]. Microencapsulation is the process of
producing small capsules by encasing tiny particles of one material within another
material. The dimension of the resulting capsules ranges from less than one micron
to several hundred microns. Microcapsules are very tiny particles containing core
material surrounded by a shell [215]. The shapes of microcapsules can be spherical,
asymmetrical or variably shaped with droplets of core material embedded throughout
the microcapsule. The material encapsulated is called the core or nucleus, while
the encapsulating material is referred to as the shell or wall. Various types of core
materials such as dyes, drugs, fragrances and biological shells can be coated by the
shells of various materials such as wax, fat and polymers.
By selecting appropriate materials for core and shell, microcapsules with a variety
of functions can be prepared. Solids, liquids and gases may be microencapsulated.
Microencapsulation allows liquid and gases to be processed similar to solids, and
in addition, hazardous materials can be easily and safely processed [216]. For the
successful application of PCM by microencapsulation, the following parameters need
to be considered [134].
• Particle size;
• Uniformity of particle size;
• Particle size distribution;
• Stability to mechanical actions such as shear, abrasion and pressure;
• Stability to chemicals and
• Core-to-shell ratio (the proportion of the core with respect to the whole should be
as high as possible, and the thickness of the shell should be sufficient to maintain
capsule stability).
Microcapsules can be encased with core materials for any specific period of time
and can be released gradually. The release of the core material can be achieved by
breaking the capsule walls or when the external conditions cause the capsule walls to
rupture, melt or dissolve. For the effectiveness of the PCM, it is necessary to encapsulate them in a physically and chemically stable shell. PCM were first incorporated
into textile materials by microencapsulation technology in 1987 [217]. The application of PCM in different areas by microencapsulation has been studied by several
researchers [218–221]. Various companies such as BASF [222] and Microtek [190]
have modified and developed new PCM which can be applied by microencapsulation.
The paraffin waxes as PCM for textiles cannot be directly into incorporated textile
substrates because of their low melting points. Therefore, paraffin waxes need to be
microencapsulated by a suitable polymer. Colvin and Mulligan [223] from Triangle
Research and Development Corporation (TRDC) were the first to prove that paraffin
PCM can be successfully microencapsulated and suspended in water. In addition to