Evaluation of Filler Distribution in TiO2 Filled LDPE Injection Moldings by Acoustic Velocity Measurement

In order to understand distribution of TiO2 in LDPE molded by injection molding, acoustic velocity measurement was performed. As acoustic velocity is a function of elastic modulus and density of an object, it is expected to express the filler content that affects both elastic modulus and density. The specimen fabricated has step-like shape, and the thickness varies 1, 2, 3, 4mm in one molding. It was found that the acoustic velocities on a step were very scattered. The meaning of acoustic velocity was considered and it is confirmed that it is greatly affected by filler content. Therefore the scatter of acoustic velocity meant the heterogeneous distribution of TiO2 in LDPE. The filler contents showed large scatter around the steps, and filler contents were slightly changed from the gate to the end of flow in injection molding. It could be understood by acoustic velocity measurements that the distribution of filler content can be improved by adding surface treatment agent.