Netsu Sokutei, 35 (2), p. 87, (2008)



Acoustic Analysis of Boundary Layers within Polymeric Composite Materials Containing Inorganic Small Particles

微粒子分散高分子複合材料の高分子マトリクスと微粒子間に存在する境界層の圧縮率は溶媒和モデルに基づく二状態モデルを適用することで決定できる。本解説ではその境界層の弾性特性評価法について説明するとともに,音響的材料評価法についての手段と特徴についても紹介する。今回使用した材料はカーボンブラック配合スチレンブタジエンゴム(SBR/CB)と炭酸カルシウム配合塩化ビニル(PVC/CC)複合材料の2種類であり,それぞれに適した弾性波速度測定装置を使用して試料の弾性率を決定した。音響画像と表面波速度は超音波顕微鏡を使用して測定した。PVC/CCとSBR/CB複合材料の境界層の量は,それぞれ音響画像とTG曲線から決定した。それぞれの粒子の部分比容は粒子の比容と同じ値であった。CC粒子とCB粒子の部分比断熱圧縮率は,それぞれ1.4±0.7×10?10 Pa?1と?0.5±0.5×10?10 Pa?1である。これらの値から,PVC/CC にはPVCよりも柔らかい境界層があり,SBR/CBにはSBRよりも硬い境界層があることが示唆された。
Compressibility of boundary layers in polymer composites can be evaluated acoustically by applying a two states model based on a solvation model. In this tutorial paper, we introduced the method to characterize the elastic properties of the boundary layer, as well as features of acoustic characterizations for materials. Polyvinylchloride (PVC) and styrene-butadiene rubber (SBR) were used as polymer matrices. Calcium carbonate (CC) and carbon black (CB) were used as fillers and these were dispersed in the matrices. Velocities of elastic waves propagating in the PVC/CC and SBR/CB composites were measured by using two bulk wave velocity measurement systems. Acoustic images and surface wave velocities of the composites were measured with an acoustic microscope. Amount of boundary layers for the PVC/CC and SBR/CB composites were determined from the acoustic image and from the thermal gravimetric curve, respectively. The partial specific volume of those particles was almost same as the specific volume in each particle. Values of the partial specific adiabatic compressibility of the CC and CB were 1.4±0.7×10?10 Pa?1 and ?0.5±0.5×10?10 Pa?1. These values suggested that the boundary layer in the PVC/CC composite was softer than the matrix and that in the SBR/CB composite was harder than the matrix.