**Introduction to microencapsulation**

The term microencapsulation comes from the Greek "mikros," which means small, and from the Latin "en" and "capsula," which mean respectively in and a small box. This technology refers to the formation of polymer particles with diameters ranging from nanometers to millimeters, containing an active substance regardless of its physical state, i.e., in solid, liquid, or gaseous form, and which may have several types of morphologies. Over the past two decades, microencapsulation has been a growing field with applications in many technological disciplines. However, the principle of encapsulation is not new; biochemistry is one of the great founding principles of life, and the presence of a membrane allows the containment of essential molecules in cells. Nature is full of examples of encapsulation, from the macro- to the nanoscale, to protect material from the surrounding environment, such as a seed in a coat, a bird's egg, or a cell in a membrane. Thus, the development of microencapsulation processes is similar to an imitation of nature, to design innovative systems to immobilize, structure, or release the active ingredient. Since encapsulation has applications in various industrial fields, many definitions depend on the needs in a specific field. The most general definition probably corresponds to the trapping of a compound or system in a dispersed material for its immobilization, protection, transfer control, structuring, and functionalization.

The development of the field of microencapsulation is closely linked to the progress of many advanced technologies to produce an innovative component for a specific application or industrial field, and thus to create a new application or market for products. One of the benefits of microencapsulation is that it combines various technologies from other unrelated industrial fields, which are combined to develop a new product. Also, in recent decades, the development of microencapsulation technology has also been accompanied by the reduction of particle size to the manometric scale, which is used in some advanced markets.

The first mechanical microencapsulation technologies were developed at the end of the nineteenth century, and more particularly from spray coating and drying. It was only in the 1930s that the first attempts at phase coacervation microencapsulation were made by Bungenburg de Jong and Kass. A few years later, B. Green, a research chemist at the National Cash Register Company in Dayton, became interested in this technology and studied how the concept of microencapsulation could have a potential application in document copying. From the concept of phase coacervation developed by Bungenburg de Jong and Kass, he prepared the first gelatin-based microcapsules. The development of this technology from the laboratory to industrial scale took several years, and it was not until 1951 that NCR introduced the first carbonless copy paper. Green filed a patent for microencapsulation on June 30, 1953.

At the end of the 1950s, microencapsulation was gradually introduced in the pharmaceutical and chemical sectors. Since then, microencapsulation processes and technologies have been continuously improved, modified, and adapted for various purposes and/or uses. Thus, the development of new methods and the expansion

**II**

**Chapter 7 111**

Lag, Constant and Decay Release Characteristic of St-PVOH Encapsulated Urea as a Function of Coating Thickness Using

*by Chigozie Francolins Uzoh and Stone Raphael Odera*

Different Empirical Models

of the range of new polymer materials adapted to the different trapping techniques have made it possible to create new products and applications according to customer supply and demand or sometimes as a result of merged projects. The development of microencapsulation technology has been characterized in recent decades by rapid growth in patent applications and scientific articles, reflecting the interest of industrial and academic research in this subject. Thus, this technology has a host of potential applications in a wide range of industrial sectors, i.e., cosmetics, pharmaceutical and medical, electronic, waste treatment, printing, food, agriculture, biotechnology, chemical, textile, etc.

In the coming years, the size of the global microencapsulation market is expected to reach \$19.34 billion by 2025, with a compound annual growth rate of 13.6%. This increase is mainly driven by the food and beverage industry, where the demand for microencapsulated flavors, probiotic bacteria, and immobilized cells or enzymes will increase further. The microencapsulation markets are mainly dependent on geographical regions. In North America, for example, this technology has mainly been introduced in the pharmaceutical, food, and personal care industries, while the textile industry could also play a more critical role in the future. In Western Europe, the second largest regional market in 2017, the market is overgrowing regarding the availability of raw materials, coating technologies, and fields of application, and more specifically in the pharmaceutical and cosmetics industries. The Asia-Pacific market is expected to be one of the main growth areas, driven in particular by the rapid growth of the pharmaceutical and food industries and the growth of the detergent market.
