Active agents microencapsulation

Price, R., Gaber, B. and Lvov, Y. (2001) In-vitro release characteristics of tetracycline, khellin and nicotinamide adenine dinudeotide from halloysite a cylindrical mineral for delivery of biologically active agents. Journal of Microencapsulation, 18, 713—723. 

Microencapsulation can be used to provide a temporary barrier between a chemical species and its surrounding environment see also Section 14.3). This permits controlled (slow) release of the active agents following application. Depending on the product and the situation, an active ingredient such as a pesticide may need to be released slowly at low concentration, or slowly at high concentrations. Such controlled release can both reduce the number of crop applications that are required and also help prevent over use and subsequent run-off. The barrier can be provided by a polymer film, in the case of suspensions [867], or a liquid membrane, in the case of single or multiple emulsions [865], Microemulsions have also been used [234,865],... 

Active agent deposition in a film covering a surface (e.g., leaves, seeds) Air-suspended solid microparticles or droplets of active agents as such or in solution Microencapsulated active agents, paint-in lacquers or resin strips for indoor use... 

Several reviews on microencapsulation processes are available [1-5]. In this section, those methods that are novel and related to the microencapsulation of liquid active agents are discussed. 

Microencapsulation by a polycondensation process, which may be either normal dispersion polycondensation or interfacial polycondensation, is especially attractive for liquid active agents. The important advantage of this method is that in most cases very high active agent loadings can be obtained. These methods are well reviewed by Arshady [6], and are discussed in detail elsewhere in this book. 

For microencapsulation by miniemulsion polymerization, oil can be a monomer and the hydrophobe can be a hquid active agent in the above-mentioned miniemulsion system. The monomer and oil are chosen in such a way that these two components are misdble before the polymerization process. As soon as polymerization takes place, phase separation occurs and at the end of polymerization microcapsules containing active agent are obtained. 

In another report, Scher discussed pesticide microcapsules and reported that these capsules could be used to reduce mammalian toxicity, to extend activity, to reduce phytotoxicity, to protect pesticides from rapid environmental degradation, and to reduce pesticide levels in the environment [68]. Thus, many advantages are obtainable with microcapsular pesticide formulations. In an overview, Gimeno has discussed the definition of the criteria to select an active agent for microencapsulation, together with the techniques used in commercial microencapsulated formulations [69]. 

This chapter wdl outline a variety of active agents used in microencapsulation for textile-based systems. The importance of controlled release and microencapsulation will be addressed as well. Methods of embedding microcapsules into textile structures and the parameters of interest will be further elaborated upon. In addition, the chapter will give an overview of the controlled release of different microencapsulated active agents from textiles. These topics are necessary to understand the challenges that researchers face in developing textile structures with embedded microcapsules for controlled release. 

Controlled release of microencapsulated active agents from textile structure... 

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