A STUDY OF STRENGTH, HARDNESS AND DEFORMATION OF ACETYLATED SCANDINAVIAN SOFTWOODS

In this work, properties such as bending strength (expressed as modulu s of rupture and modulus of elasticity), hardness, and deformation und er cyclic relative humidity have been studied for acetylated Scandinav ian pine and spruce. The acetylation was performed with a limited amou nt of liquid acetic anhydride without addition of catalyst or organic cosolvent. The weight gain due to acetylation was 19.1% for the pine s amples. Two kinds of spruce samples were acetylated to 18.2% (narrow a nnual rings) and 23.3% (broad annual rings), respectively. The results indicated that only small changes in strength were obtained. For pine , modulus of rupture decreased with about 6%, and increased with about 7% for spruce. The modulus of elasticity also decreased for pine but increased for spruce. For practical applications, these properties can be considered unaltered. Acetylated pine wood showed increased Brinel l hardness. Acetylated spruce wood did not tend to deform as much as u nmodified wood when exposed to moisture cycled between 40 and 90% rela tive humidity.