Physical Methods for Preparing Microcapsules

Goodwin, John T.; Somerville, G

doi:10.1007/978-1-4684-0739-6_13

Cited by 6 publications

(1 citation statement)

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“…The shell is then hardened by chemical crosslinkings, cooling, or solvent evaporation. Different types of extrusion nozzles have been developed in order to optimize the process [103].…”

Section: 93mentioning

confidence: 99%

Functional Coatings and Microencapsulation: A General Perspective

Ghosh¹

2006

Functional Coatings

159

130

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Today, many objects that we come across in our daily lives, including the house in which we live and the materials we use (e.g., toothbrushes, pots and pans, refrigerators, televisions, computers, cars, furniture) all come under the "umbrella" of coated materials. Likewise, fields such as military applications -for example, vehicles, artilleries and invisible radars -and aerospace products such as aircraft, satellites and solar panels all involve the widespread use of coated materials. Clearly, the importance of coatings has increased hugely during the modern era of technology.Coating is defined as a material (usually a liquid) which is applied onto a surface and appears as either a continuous or discontinuous film after drying. However, the process of application and the resultant dry film is also regarded as coating [1]. Drying of the liquid coating is mostly carried out by evaporative means or curing (cross-linking) by oxidative, thermal or ultraviolet light and other available methods. Paint can be defined as a dispersion that consists of binder(s), volatile components, pigments and additives (catalyst, driers, f low modifiers) [2]. The binder (polymer or resin) is the component that forms the continuous film, adheres to the substrate, and holds the pigments and fillers in the solid film. The volatile component is the solvent that is used for adjusting the viscosity of the formulation for easy application. Depending on their compositions, paints can be divided into three groups: solvent-borne, water-borne and solvent-free (100% solid). Solvent-borne paints consist of resin, additives and pigments that are dissolved or dispersed in organic solvents. Similarly, in water-borne paints the ingredients are dispersed in water. In solvent-free compositions, the paints do not contain any solvent or water and the ingredients are dispersed directly in the resin.The properties of coating films are determined by the types of binders, pigments and miscellaneous additives used in the formulation. Moreover, types of substrates, substrate pretreatments, application methods and conditions of film formation

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“…The shell is then hardened by chemical crosslinkings, cooling, or solvent evaporation. Different types of extrusion nozzles have been developed in order to optimize the process [103].…”

Section: 93mentioning

confidence: 99%

Functional Coatings and Microencapsulation: A General Perspective

Ghosh¹

2006

Functional Coatings

159

130

View full text Add to dashboard Cite

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Controlled Release Technology, Agricultural

Wilkins

2004

Kirk-Othmer Encyclopedia of Chemical Technology

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Controlled release formulations (CRFs) are intended to improve the delivery of pesticides and related biologically active substances. The consequent improvement in efficiency reduces losses in use and has many benefits, such as reduction in exposure to both workers and the environment, particularly in minimizing leaching and evaporation. This article introduces the advantages of CRFs and provides a theoretical rationale for their use based on pseudo‐first‐order loss kinetics, which are typical for pesticide dissipation in the environment. Thus, the greater the loss rate, especially for pesticides of short duration, the greater the potential for improvement in delivery to the target pest. As a consequence of this principle, reduced levels of pesticide delivered efficiently can be as efficacious as higher amounts of conventional formulations. The types of CRFs are introduced and are classified as physical, chemical, or biological. The kinetics of release from CRFs is central to their successful use, and the mathematical basics of this are described. The mechanisms of release vary according to the type of formulation, and these are covered for physical and chemical types. Common release characteristics include first order, diffusion (square root of time) based, and zero order (constant). Release kinetics are usually measured under controlled laboratory conditions, but field determination are preferable. Design of properties of CRFs then follow. The main groups of the physical‐type formulations, such as reservoirs with release‐rate controlling membranes and without membrane and the monolith or matrix structures, are those based on microencapsulated liquid cores in sprayable concentrate formulations, and polymeric matrix methods that are often fabricated as granules. The polymers used and the approaches employed for designing these types of CRFs are introduced with emphasis on encapsulation methods, such as phase separation and interfacial polymerization. In addition, other formulation types are included, such as laminates, coated granules, microparticles, matrix granules (swellable and nonswellable), matrix devices for animal and public health protection, plastic films, and mulches. The article closes with the recent biological approach to formulation based on living or dead genetically modified microorganisms containing proteinaceous toxins.

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Controlled Release Formulations of Pesticides

Wilkins

2002

Encyclopedia of Agrochemicals

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Controlled release formulations (CRFs) are intended to improve the delivery of pesticides and related biologically active substances. The consequent improvement in efficiency reduces losses in use and has many benefits, such as reduction in exposure to both workers and the environment, particularly in minimizing leaching and evaporation. This chapter introduces the advantages of CRFs and provides a theoretical rationale for their use based on pseudo–first‐order loss kinetics, which are typical for pesticide dissipation in the environment. Thus, the greater the loss rate, especially for pesticides of short duration, the greater the potential for improvement in delivery to the target pest. As a consequence of this principle, reduced levels of pesticide delivered efficiently can be as efficacious as higher amounts of conventional formulations. The types of CRFs are introduced and are classified as physical, chemical, or biological. The kinetics of release from CRFs is central to their successful use, and the mathematical basics of this are described. The mechanisms of release vary according to the type of formulation, and these are covered for physical and chemical types. Common release characteristics include first order, diffusion (square root of time) based, and zero order (constant). Release kinetics are usually measured under controlled laboratory conditions, but field determination are preferable. Design and properties of CRFs then follow. The main groups of the physical‐type formulations, such as reservoirs with release‐rate controlling membranes and without membrane and the monolith or matrix structures, are those based on microencapsulated liquid cores in sprayable concentrate formulations, and polymeric matrix methods that are often fabricated as granules. The polymers used and the approaches employed for designing these types of CRFs are introduced with emphasis on encapsulation methods, such as phase separation and interfacial polymerization. In addition, other formulation types are included, such as laminates, coated granules, microparticles, matrix granules (swellable and nonswellable), matrix devices for animal and public health protection, plastic films, and mulches. The article closes with the recent biological approach to formulation based on living or dead genetically modified micro‐organisms containing proteinaceous toxins.

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Physical Methods for Preparing Microcapsules

Cited by 6 publications

References 0 publications

Functional Coatings and Microencapsulation: A General Perspective

Functional Coatings and Microencapsulation: A General Perspective

Controlled Release Technology, Agricultural

Controlled Release Formulations of Pesticides

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