黒鉛微粒子-フェノール樹脂複合材の導電性評価と発熱合板への応用

摘要

北海道の合板工業は地域経済に大きな影響力を有するが，近年の低価格で輸入される合板に押され苦境に立たされている。この状況を打破するためには，優れた機能を備えた付加価値の高い合板を製造することが必要である。合板自体を発熱させることができれば，暖房兼内装材としての利用の可能性がある。%Functional plywood can produce constant heat by applying a voltage to the conductive bonding layer between wood sheets. Herein functional plywood was prepared by filling various microsized graphite particles (3.3-52.5 μm in diameter) and nanosized carbon black (CB ; 29 nm) into a phenolic resin. To investigate the electrical conductivity, the resulting composite resin was coated onto a commercial glass slide. The effects of particle size, mass fraction of the conductive fillers (graphite and CB), and the weight ratio of graphite to the fillers (φ = graphite/ (graphite + CB)) on the conductive properties of the composite resin, particularly the specific resistance and its variation coefficient, were estimated. A composite resin, which included at least 30 mass % of filler, yielded a relatively low variation coefficient for the specific resistance. Additionally, the composition of the resin had superior conductivity when the weight ratio was 55-66 mass % and the graphite particles were 22.9 μm or less in diameter.rnThe above experiment indicated heating plywood was produced. Consequently, its surface temperature was measured. With respect to particle size, the standard deviation in the surface temperature of the plywood corresponded to that of the conductive properties on the glass slide. Hence, the method proposed herein using a glass slide is suitable for conductive characterization to determine the appropriate conditions to prepare heating plywood.