Studies on Epoxy Resin Adhesives for Wood

[Author abstract]Effect of resin-hardner systems on the curing behavior, bonding properties and durability of epoxy resin wood adhesives were studied. The results obtained were summerized as follows. Curing behavior of epoxy adhesives during bonding could be estimated by infrared analysis. Bonding velocity, degree of cure and bond strength of epoxy adhesives were influenced remarkably by the kind and quantity of hardner added to the resins, and bond strength of the adhesive was proportional to the degree of cure of resin. Physical properties and durability of cured adhesive films were very sensitive to heat or hot water treatment, and these properties of epoxy adhesives were also affected by the combination of resin-hardner systems. Plate bending fatigue test were carried out for specimen bonded with epoxy resins contained various amount of flexibilizer. The endurance limit of epoxy resin (EP-0) was approximately constant without regard to glue-line thickness. But on the contrary, endurance limit of epoxy resins mixed with flexibilizer (EP-20, EP-40, and EP-60) were very changeable and decrease with increasing glue-line thickness. The ratio of the endurance limit to the static strength was about 0.30 for EP-0, 0.27 for EP-20, 0.21 for EP-40 and 0.12～0.21 for EP-60. [著者抄録]木材接着剤としてのエポキシ樹脂の性質についての基礎的知見を得る目的で,種々の樹脂組成でつくられた接着剤についての接着挙動,物性,及び耐久性についての実験を行ない,大要次の結果を得た.(1)接着過程にあるエポキシ接着剤の硬化挙動を赤外分光分析法を利用して評価することができた。接着速さ,樹脂硬化率,及び接着強度等は樹脂に添加される硬化剤の種類と量によって影響されるが,接着強度は樹脂の硬化率と比例的関係にあることがわかった.(2)接着剤の皮膜物性および接着耐久性におよぼす接着剤組成の影響について検討した結果,これらの諸性質は,熱と水に敏感なことがわかった.(3)フレキシビライザー含有量の異なる種々の接着剤で調整された試験片を用いて曲げ疲労試験を行なった結果,フレキシビライザーを添加しないエポキシ樹脂(EP-0)を用いた接着系での疲労耐久限度は接着層の厚さに関係なく一定であるのに対し,フレキシビライザーを添加した接着系(EP-20,EP-40,EP-60)では耐久限度は接着層厚さが大きい程低下した.静的強度に対する疲労耐久限度の比は,EP-0では0.30, EP-20では0.27. EP-40では0.21,EP-60では0.12～0.21であった