Transparent acryl–clay nanohybrid films with low thermal expansion coefficient

The aim of this study was to prepare transparent nanohybrid films with low coefficient of thermal expansion (low CTE), which consist of acryl resin and nanosized clay. The hybrid films with different clay contents were prepared by UV curing of tricyclodecane dimethanol diacrylate (TCDDMDA) including nanosized clay. All obtained films were transparent similar to pure poly(TCDDMDA). In addition, the film containing 40 wt.% of clay showed a low CTE of 10 ppm/K in 150–200 °C, which is similar to that of inorganic materials such as glass. The significant property improvement is related to shape effect and orientation of clay in polymer matrix. Wide-angle X-ray diffraction measurement was carried out to investigate orientation of nanosized clay in polymer matrix. From this measurement, it was confirmed that the clay platelets were oriented parallel with film surface with increasing clay content, and orientation coefficient of the clay in polymer matrix reached to f = 0.65 for the hybrid film containing 40 wt.% of clay. Though, in comparison with the matrix, the flexibility of the hybrid film evaluated by the wind roll test with steel bar was lowered by increase of clay content, the hybrid film containing 40 wt.% of clay could be rewound with steel bar 10 mm across, and its flexibility was retained.