Reduction of formaldehyde emission from plywood using composite resin composed of resorcinol–formaldehyde and urea-modified scallop shell nanoparticles

摘要

More than 200,000 tons of scallop shells are disposed annually 1 alone in Japan. Nanoparticles derived from scallop shells have the potential to adsorb gaseous formaldehyde; therefore such discarded shells have now been tested as additive filler in plywood adhesive by mixing high specific surface area, urea-modified shell nanoparticles with a resorcinol?formaldehyde resin; with this procedure it was found that the emission of formaldehyde from the resulting plywood could be substantially reduced. The urea-modified scallop shell nanoparticles were prepared by two different methods: (i) by a dry method in which the shells were treated with planetary ball-grinding under ambient conditions ? a completely dried powder was obtained after addition of the surface-modifying urea solution; (ii) by a moist method by treating dry-ground shell particles in a wet grinding process with the urea solution, followed by the use of centrifugation to obtain a paste. The specific surface area of the nanoparticles obtained by both treatments was 42 ± 3 m213 /g. Measurement of the subsequent formaldehyde emission showed that the addition of the modified scallop shell nanoparticles substantially reduced the formaldehyde emission from plywood; the reduction depends from the specific mass uptake of urea on the nanoparticles which especially was the case when resins containing nanoparticles processed by the moist method were used.