Volume change and gas transport at uniaxial deformation of filled natural rubber

Abstract

The volume dilatation of differently filled specimens of natural rubber has been measured using a deformation dilatometer. If the matrix detaches from the filler particles, hollow spaces form. The volume dilatation caused by this effect can be measured and calculated if the material is submerged in a liquid medium. The measured volume dilatation reflects the interaction between filler and matrix. If we take a measurement in a gas, only the volume dilatation of the matrix is recorded, but not that of the visible hollow spaces, because gas can diffuse from the measurement chamber into the sample. Stress-induced crystallization occurs with all samples. Its course due to deformation has been examined using a deformation calorimeter. Here an influence of the interaction between filler and matrix has been found. Filler particles which do not adhere closely to the matrix enhance the diminution of locally high tensions and deformations and thus hinder the stress-induced crystallization. The volume contraction caused by stress-induced crystallization can be recorded clearly only if one uses a liquid as the measurement medium. Due to gas exchange between the sample and its environment and the different gas solubilities in the amorphous and crystalline material no stress-induced crystallization can be detected. At the same time, a possibility opens up of determining gas solubilities in crystalline material.[/p]