Capsules are currently of high interest in many applications where protection of ingredients is needed or a specific effect by controlled release is desired. Typical compounds for encapsulation include flavors, fragrances, enzymes, bacteria, biocides, catalysts, drugs, monomers, nutrients, colors etc.
Polymer particles are used as fillers and additives to bulk materials and coatings for obtaining new or improved properties. Some examples are increased strength, color, traceability, impact resistance etc.
Surface modification of polymer particles and capsules can be performed to obtain tailored properties, like increased stability in certain surroundings (interaction towards biological components, stability in blood), compatibility with bulk materials or end products, specific binding to certain molecules, or to tailor-make surfaces to specific applications.
SINTEF possesses advanced characterization equipment for particles and capsules. Characterization of size, size distribution and surface charge / zeta potential is performed. The equipment includes a laboratory for characterization of porous polymer particles and other materials as regards density, pore volume and pore size distribution (by mercury porosimetry). SINTEF also has a world class infrastructure where molecular weight and composition of polymers can be determined, and release of active ingredients from capsules can be investigated in complex media.
Examples on relevant applications for polymer particles:
- Magnetic particles for medical applications (isolation and purification of DNA/RNA, proteins, cells, bacteria etc)
- Fluorescent nanoparticles for use in diagnostic assays
- Particles for water purification by removal of endocrine disruptors
- Particles for environmental clean-up of radioactive pollution
- Polymer particles for use in chromatography
- Metal plated polymer particles for use in conductive glue
- Hybrid particles for binders in paints
- Additives for polymers and paints
- Polymer particles as friction-reducing additives water- and oilbased mud
- Swellable polymer particles for blocking of water in formations during oil production
Examples on relevant applications for polymer capsules:
- Nanoparticles and nanocapsules for targeted diagnostic and medication within nanomedicine
- Encapsulation of perfume for personal care products
- Encapsulation of Dead Sea minerals and vitamins for use in dermatological products
- Encapsulation of biocides for antifouling paint
- Preparation of self-healing materials by use of capsules containing monomers etc for use in textiles, coatings and electrical insulation materials
- Capsules for medication of oil wells for increased oil recovery
- Encapsulation of corrosion inhibitors in coatings for offshore applications, wind energy etc.
Methods
Particles and capsules can be prepared with sizes from nano to several hundred micrometers, with narrow (monodisperse) and broad size distributions. A broad variety of polymers can be used, from acrylates and styrenes to condensation polymers like polyurea, as well as silica and biopolymers like chitosan. Porous and compact particles with various additives can be prepared.
Techniques available at SINTEF are:
- Emulsion polymerization
- Miniemulsion polymerization
- Minisuspension polymerization
- Dispersion polymerization
- Suspension polymerization
- Membrane emulsification
- Sol-gel preparation
- Nano spray drying
- Encapsulation by interfacial polymerization
