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Effects of polyurethane (PU) coating thicknesses (0.15, 0.30, 0.45, and 0.60 mm) on sound absorption coefficients of four wood species were investigated using the standing wave ratio method with an input sound vibration frequency range set between 125 and 4000 Hz. Wood species of four specific gravity (SG) levels were Korean spruce, European spruce, Sitka spruce, and Picea brachytyla . Experimental results indicated that PU coating can significantly increase sound absorption coefficients of higher SG species such as Sitka spruce and Picea brachytyla in all tested frequency levels, but this significant increase was not observed in lower SG species such as Korean and European spruces when tested in the frequency range from 800 to 2000 Hz. Effects of coating thickness on sound absorption coefficients of four evaluated species were found to interact with wood SG values and input sound vibration frequency ranges. Specifically, coating 0.30-mm-thick PU on Korean and European spruces tends to result in significantly lower sound absorption coefficients among the ones coated with four evaluated thicknesses when tested at the frequency less than 800 Hz, but PU coating thickness resulting in lower sound absorption coefficients on Sitka spruce and Picea brachytyla was 0.15 mm. Sitka spruce and Picea brachytyla coated with 0.30- and 0.6-mm-thick PU had lower sound absorption coefficients when tested at the frequency ranging from 1000 to 2000 Hz. When tested at the frequency greater than 2500 Hz, sound absorption coefficients of four coated species increased as coating thickness increased from 0.30 to 0.60 mm with an increment of 0.15 mm, but these four species coated with three thicker PU had significantly lower sound absorption coefficients than the ones coated with 0.15-mm-thick PU. The uncoated higher SG species tended to have lower sound absorption coefficients than uncoated lower SG ones when tested in the frequency ranging from 500 to 4000 Hz, but the differences were not found when tested under the frequency less than 400 Hz. Coating four species with different thicknesses of PU could alter their SG effects on their sound absorption coefficients.

High dispersibility of carbon black (CB) is a great significance to its interfacial compatibility with organic or inorganic materials. We reported a type of alkyl-carbon black (aCB) nanoparticles with hydrophobic and lipophilic properties which were modified by Octadecyl isocyanate. The water contact angle of aCB was changed from 34.3°/38.9° to 102°, which exhibited excellent dispersion ability in organic solutions. Covalent modification of aCB was confirmed by the increase of particle size from 474 nm to 499 nm and the loss of organic groups at temperatures from 30 °C to 800 °C. After reaction between CB and Octadecyl isocyanate, the characteristic band of isocyanate ( N C O) disappeared and formed new amide groups or carbamate, the decrease of O 1 s and C 1 s and the increase of N 1 s confirmed the alkyl chain grafted to the surface of CB. aCB showed an organic-inorganic hybrid and multi-layer substance with disordered and high crystallization capacity.