Abstract
In this paper, polyaryl polymethylene isocyanates (PAPI) were used as an innovative alternative material to prepare isocyanate microcapsules. PAPI could be used as core materials, which would react with small molecules containing active hydrogen (1,4-butanediol, ethylene glycol, 1,2-diaminoethane etc.). The reaction products of PAPI and active hydrogen would form a shell by interfacial polymerization reaction in an oil-in-water emulsion. Smooth spherical microcapsules of 70 ~ 180 μm in diameter were produced by controlling agitation rate (600 ~ 1200 rpm). High yields (~80%) of a free-flowing powder of PAPI/polyurethane and polyurea capsules were produced with a high isocyanate groups (–NCO) content of 23 wt % as determined by titration analysis. Structural analysis and quality assessments of each batch of microcapsules were performed by using thermogravimetric analysis, Fourier transform infrared spectroscopy and scanning electron microscopy. Preliminary results indicated the microcapsules were stable with only about 20% loss of –NCO detected after one month storage under ambient conditions. This work showed the great potential of novel microencapsulation technique in development of protection of –NCO and in aspects of micro- and nano-structure construction materials.
Highlights
The fundamental properties of isocyanates (R–NCO) were discovered during the years 1885–1900.the practical uses of these compounds were not realized until about forty years later [1,2].Since isocyanates included in non-formaldehyde class performs well in terms of bonding property, water resistance, aging-resistant performance and fine manufacturability, it has been widely used in the field of coatings and adhesive [3,4,5,6,7,8,9,10]
Structural analysis and quality assessments of each batch of microcapsules were performed by using thermogravimetric analysis, Fourier transform infrared spectroscopy and scanning electron microscopy
The prepared isocyanate microcapsules were polyaryl polymethylene isocyanates (PAPI) as core materials and the reaction products, of which PAPI reacted with small molecules containing active hydrogen (1,4-butanediol, ethylene glycol, 1,2-diaminoethane etc.) as shell by via interfacial polymerization reaction in an oil-in-water emulsion
Summary
The fundamental properties of isocyanates (R–NCO) were discovered during the years 1885–1900. Microcapsules are micro containers (well-defined reaction environments) containing an active liquid or solid ingredient inside as well-defined reaction environments, to protect the material inside from environmental influences [31,32,33] They were used in various fields just like nanomaterials [34], including agricultural [35], pharmaceuticals [36,37], cosmetic [38], and textile industries [39,40]. The prepared isocyanate microcapsules were polyaryl polymethylene isocyanates (PAPI) as core materials and the reaction products, of which PAPI reacted with small molecules containing active hydrogen (1,4-butanediol, ethylene glycol, 1,2-diaminoethane etc.) as shell by via interfacial polymerization reaction in an oil-in-water emulsion. The change of –NCO in the process of preparation and storage environment were concerned in order to provide reference for its application in future
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