Encapsulation of chemical catalyst and structural epoxy in microcapsules generated via microcapillary devices
Abstract
Protection and controlled release of chemicals through encapsulation have been extensively used in daily applications such as drug delivery, food processing, enzyme stabilization, and chemical storage. A significant need for further development in this area is to reduce the capsule size and to obtain more predictable performance by narrowing the capsule geometry distribution. For the past decade, microfluidics have been rapidly developed to become a popular technique for the generation of monodisperse single/double/multiple emulsion drops in the micrometer to millimeter size range. With this technique, polymeric microcapsules with a narrow size distribution can be fabricated by adding different polymer blends into the dispersed phase. Microencapsulation of reactive chemicals would provide solutions to modern industry's demands to improve formula shelf life, reaction efficiency, targeted release and predictability of properties. In this project, we've successfully developed different systems for encapsulation of coating catalyst and structural epoxy with microfluidics. The particles and capsules generated in this project have a diameter ranging from 15 &mgr;m to 280 &mgr;m with a coefficient of variation (CV) less than 3%. A water-soluble catalyst, 1,4-diazabicyclo[2.2.2]octane (DABCO), was successfully encapsulated in pressure-sensitive capsules composed of UV-crosslinkable acrylate (trimethylolpropane trimethacrylate). These capsules are monodisperse, and have a failure strength that can be adjusted across 2-3 orders of magnitude by changing capsule size, shell thickness, or microstructure. Based on pH measurement of DABCO released from broken capsules, the percent yield of the encapsulation process can be over 90%. In addition, a water-immiscible bisphenol A epichlorohydrin epoxy, EPON 825, was also efficiently encapsulated in acrylamide hydrogel capsules with 93 wt% in the final product. The released epoxy was proven to be functional and was able to react with its hardener without the need of agitation. Other capsules that are chemically soluble, heat-sensitive, or bio-compatible have also been developed. Efforts to improve production rate and better understand the shell formation mechanisms will also be discussed.
Degree
Ph.D.
Advisors
Martinez, Purdue University.
Subject Area
Engineering|Materials science
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