Microcapsule Technology

Use Microencapsulation Technology Change Life

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Microencapsulation Material Examples

Art-and-Crafts

UV-Dosimetry

Educational-Materials

Eyewear

Fashion-and-Accessories

Health-and-Safety-Equipment

Medical-Devices

Nail-Art

Novelty-Items

Promotional-Items

Protective-Gear

Security-Printing

Microcapsule Pigment Materials

Thermochromic Powder

Photochromic Powder

Anti-Counterfeiting Powder

Frangrance Pigment Powder

Color-changing materials and fragrance powders has certain deficiencies in performance. For example, they have poor chemical stability. Under strong acid or strong base conditions, they are easy to lose color-changing properties. They also have poor thermal. Their work temperature are below 200°C. Thus, the above deficiencies limit their application. With the advancement of microencapsulation technology, microencapsulation techniques prove to be sound in its properties. For example, they can be used in color-changing materials and fragrance powders to improve the materials’ storage stability, functionality and work performance. Currently, the microencapsulation of color-changing materials and fragrance powders is a hot topic. It is important and of significance to develop the market of color-changing materials and fragrance powders by integrating with microcapsule technology.

The definition of microcapsule

A microcapsule is a miniature container. It is developed by encapsulating liquids, solids, gas using a film-forming material. The particle size of microcapsules is around 1 to 1000 μm. The film-forming material is the shell material of the microcapsule. The liquids, solids, gas which is enclosed is the core material of the microcapsule. The technique used to encapsulate core material substances is referred to microencapsulation technology. The production process of microcapsules is called microencapsulation. We should select appropriate shell materials based on the inherent properties of the substance being encapsulated during the microencapsulation of core material substances. We usually use high molecular weight substances to produce microcapsule shell materials.

Microcapsule Functionality

Microcapsules have multiple functions. In order to preserve its original chemical properties and original physical properties, the microcapsules can, through enclosing core material with shell materials, block the way for core material to contact with exterior environment.

1. Improve the Stability of Core Materials

In order to maintain the core material’s inherent characteristics, shield the internal core material from environmental influences that could alter its physical and chemical nature, we can use microencapsulation technology to encapsulate gaseous, liquid, and solid substances into powder-like solid materials. This process can enable the stable properties of film-forming shell material. For instance, paraffin wax, during its phase transition between liquid and solid states, absorbs and releases substantial heat. However, it is difficult to apply its sound phase change characteristics in actual use, because its physical state is unstable.

2. Control and release

Under specific environmental conditions, microcapsule will form to be shell material. During this process, it will expand, contract, rupture and degrade. The flow rate of the diffusing core material decreases, limiting the release of the core material when the shell material contracts. The core material escapes the confinement of the microcapsule and diffuses into the surrounding environment when the shell material expands, ruptures, or degrades. Therefore, we can change environmental conditions to control the release of the core material in a microcapsule system.

The preparation method for microcapsule

1. Traditional preparation method for microcapsule

This method is based on phase separation of the condensed phase. The phase separation method is to disperse the core material in a continuous phase containing the shell material. Then, we can change the physicochemical conditions of the dispersion system. By doing this, we can reduce the solubility of the shell material in the continuous phase. The microcapsules is then formed when the remaining shell material in the dispersion system encapsules the core material. This method is mostly used for the microencapsulation of water-soluble or hydrophilic substances. The ratio of the core material to the shell material in the microcapsules can be adjusted over in a wider range by using this method.

2. Preparation Methods Based on Polymerization Techniques

Interfacial Polymerization Method

Interfacial polymerization method is explained as follows. Polymer monomer A integrates with the core material to form an oil phase (or aqueous phase). Then the monomer A and the core material are dispersed into an aqueous phase (or oil phase). This process generates extremely small oil droplets (or water droplets). When adding monomer B, soluble in the aqueous phase (or oil phase), to the aqueous phase (or oil phase) and then stirring the entire system, a polymerization reaction occurs at the interface between the aqueous and oil phases. As a result, a film of the shell polymer material is formed on the surface of the core material. The core material is encapsulated within this film and then forms a microcapsule. The interfacial polymerization method is suitable for industrial-scale production. The materials are easy to control. The production system doesn’t need high requirements for raw material purity. The reaction time is short. The production condition is mild and the production process is simple. Among them, the important factor to impact microcapsules is the dispersion ability of the core material in the dispersion system. The stabilizers, dispersants, type and amount of emulsifiers, and along with the effectiveness of mechanical stirring, generate great impact on the wall thickness of microcapsules and particle size distribution. To achieve uniform microcapsules, a stable dispersion system should be maintained.

In-situ polymerization

This method is different from interfacial polymerization. The capsule shell of interfacial polymerization is formed by the polymerization of two monomers with different solubilities. One solubility is located inside and the other outside. Here is the in-situ polymerization for encapsulation. We can add the core material to the continuous phase containing the monomer A of the wall-forming polymer. Then we can add an initiator to the continuous phase. While stirring the entire system, this process can trigger polymerization. As a result, the wall polymer is incompatible with the continuous phase. Hence, they deposit on the surface of the core material, encapsulating it to form a microcapsule system. This method is cost-effective with good sealing. It allows control over the thickness of the wall and the core content, and it is simple to operate.

Microemulsion polymerization

In microemulsion polymerization aimed at producing nanocapsules, a series of components including an emulsifier, a co-emulsifier, and specific monomers for the core and wall materials that are unmixable with the continuous phase are blended. Mechanical mixing ensures the dispersion of these monomers into micelle formations. Subsequently, the addition of an initiator catalyzes the polymerization of the wall material monomer within the micelle environment, concurrently effectuating the encapsulation of the core material within the developing polymeric barrier. The critical aspect of preparing nanocapsules using this method is the degree of dispersion of the core material and the polymerizable monomer.

3. New Microcapsule Preparation Technologies

Interfacial Solvent Exchange Technology

This technology is based on spray technology. It disperses a liquid into fine droplets. Then it uses the interfacial transfer behavior between two miscible liquids to form a microcapsule system where the shell material encapsulates the core material.

Double Emulsion Evaporation Technique

The microcapsule system formed by double emulsion solvent evaporation is a reservoir system. The shell polymer forms the outer shell. The core material is concentrated in the inner layer. It can get effective controlled release when the core material dissolves out through the micro-pores of the shell material’s microsphere.

Self-assembly Technology

The microcapsule system can be produced by using self-assembly technology. The core material and shell material form a layered encapsulation microcapsule system through non-covalent interactions such as electrostatic forces, van der Waals forces, hydrogen bonds, under the conditions that the core material and shell material are placed in an environment without influenced by external circumstances.

Supercritical Fluid Technology

Supercritical fluid technology differs from conventional microcapsule preparation methods. Supercritical fluid technology leverages the differing solubilities of solutes and solvents in supercritical fluids and unique physical properties of the fluids, to produce microcapsules. Due to its high mass transfer properties, high diffusivity, high solvent power, low viscosity, supercritical carbon dioxide is often used as the supercritical fluid.

We first place the core material into a fluidized bed and fluidizing it with carbon dioxide. We can use supercritical carbon dioxide as both the solvent for the shell material and the carrier fluid for the core material. The shell material is first dissolved in supercritical carbon dioxide in an extraction vessel. The resulting supercritical fluid is then atomized, expanded, and crystallized through nozzles in the fluidized bed, causing the shell material to deposit on the surface of the core material, forming an encapsulation. At this time, no aggregation of particles occurs.

Applications of Microencapsulated Organic Reversible Thermochromic Materials

Microencapsulated organic reversible thermochromic materials are now extensively used in printing, textile, daily life, food, industrial sectors. Because microcapsules can reduce toxicity and volatility, as well as improve material stability.

Industrial Applications

Microencapsulated thermochromic materials can produced into temperature sensors for temperature detection in the industrial sector. For instance, a battery voltage test strip can be made using microencapsulated organic thermochromic materials. During the energy conversion process in batteries, as the temperature of the test strip rises, its color changes, allowing for a rough estimation of the battery voltage level.

Thermochromic devices embedded in tires, made from microencapsulated thermochromic materials, can monitor tire temperature. When the operating temperature of a tire exceeds the recommended usage temperature, the device will display a warning color.

Food Industry

Microencapsulated thermochromic materials can be used to produce temperature-indicative labels that are attached to the packaging of frozen food items. This process can contribute positively to the maintenance of frozen food quality, as it enables food storage staff to visually judge if the freezing temperature is within the normal range.

Daily Life Applications

In the plastics industry, microencapsulated organic reversible thermochromic materials can be produced into thermochromic powders for use. They can be used to make drinking cups, enabling users to visually ascertain whether the water temperature is appropriate for consumption by monitoring the cup’s color change. Baby bottles or spoons can be produced by using this material. With tools made by this material, parents can determine if the milk or food is at a suitable temperature for their child by observing the color change of the bottle or spoon. If this kind of material is used in daily life, people’s life experience and quality can be greatly enhanced.

Textile Industry

In the textile industry, the application of thermochromic materials mainly involves color-changing fibers and color-changing dyes. Organic thermochromic powders are primarily used as color-changing dyes for textiles. Microencapsulation technology has qualitatively advanced the application of organic thermochromic dyes in textiles after undergoing microencapsulation, the thermochromic powders significantly improve the dye’s rub fastness and wash fastness.

Organic reversible thermochromic powders used for garment dyeing can enhance the smart perception of clothing. For instance, it can build a connection among psychological emotions, color changes, and environmental temperatures by establishing a relationship between pattern temperature variations and human psychological changes. Another example, in the seasons of spring, summer, autumn, and winter, people can feel changes in the ambient and body temperatures if thermochromic pastes are applied to clothing patterns.

Publishing and Printing Industry

The organic reversible thermochromic powders can be extensively used in printing, mainly in temperature indication and thermochromism. It can be added into ink to create thermochromic ink. Therefore, its application is very mature in the field of printing. Using thermochromic ink for printing promotional posters can generate impressive advertising effects. Thermochromic ink can also be used for printing cartoon patterns on children’s toys, where the magical color-changing effect creates an extraordinary gaming experience for children. Printing decorative patterns with thermochromic ink on drinking cups allows consumers to judge the water temperature inside the cup based on the color change of the pattern, determining if it is suitable for drinking. Organic reversible thermochromic inks can generate good results in extensive areas. It can be used in various fields as the testing is straightforward, accurate, swift, and convenient. For example, it can be used in anti-counterfeiting packaging printing, lottery ticket printing, and ID card printing and for products. The feature of anti-counterfeiting packaging printing is exemplified by its ability to quickly identify the authenticity of a product by heating without damaging the outer packaging. Thermochromic printing holds significant competitive advantages with its ease of identification, relatively low printing costs, close resemblance to standard printing techniques, rich colors.