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

More than 200,000 tons of scallop shells are disposed annually 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: (1) a dry method where the shells were treated by planetary ball-grinding under ambient conditions—a completely dried powder was obtained after addition of the surface-modifying urea solution; (2) a moist method by treating dry ground shell particles in a wet grinding process with the urea solution, followed by centrifugation to obtain a paste. The specific surface area of the nanoparticles obtained by both treatments was 42 ± 3 m 2 /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 of the specific mass uptake of urea depends on the nanoparticles which especially was the case when resins containing nanoparticles processed by the moist method were used.