Encapsulation of aluminium hydroxide fillers with poly-methyl-methacrylate.
A process was developed for the microencapsulation of inorganic filler particles with poly-methyl-methacrylate, to increase the interaction between the hydrophilic filler particles and a polymer matrix. The filler utilised was aluminium hydroxide with an average diameter of 1.9 microm and a specific surface area of 5 m2/g. The process comprised a surface modification, in which a monolayer of isopropoxy titanium isostearate was chemically bound to the surface to render it hydrophobic and to ensure a chemical bond between the filler and the organic phase. Then, an encapsulation reaction was carried out by means of an emulsion-like polymerization process at monomer starved conditions. The modified particles were stabilized in water with sodium-dodecyl-sulphate. A redox system consisting of cumene-hydroperoxide in combination with sodium-formaldehyde-sulphoxylate and iron(II) salt was applied for the initiation of the polymerization. Besides surface polymer, free polymer particles were also formed. The parameters which varied were the filler concentration, the concentration of the initiator components and the surfactant concentration. At optimum conditions, approximately 50% of the added monomer polymerized at the modified filler surface, thus forming encapsulated filler particles. SEM together with TGA analysis indicated that a smooth polymer layer had been formed on the filler surface. At high filler loading, however, coagulation occurred.
Geurts
F L
FL
Laboratory of Polymer Chemistry and Technology, Eindhoven University of Technology, The Netherlands.
van Herk
A M
AM
German
A L
AL
D000536:Aluminum Hydroxide; D002214:Capsules; D004339:Drug Compounding / Q000379:methods*; D004492:Edetic Acid; D007501:Iron; D008855:Microscopy, Electron, Scanning; D010316:Particle Size; D019904:Polymethyl Methacrylate; D012967:Sodium Dodecyl Sulfate; D013499:Surface Properties; D013501:Surface-Active Agents
D002214:Capsules; D013501:Surface-Active Agents; D012967:Sodium Dodecyl Sulfate; D000536:Aluminum Hydroxide; D019904:Polymethyl Methacrylate; D004492:Edetic Acid; D007501:Iron