Investigation of anomalous surface properties of polyethylene melt using the spinning drop method, and the error analysis of the spinning drop tensiometer

Polyethylene is a widely used product commercially. However, our knowledge is incomplete about the properties of polyethylene (PE) at temperatures above its melting point, where solid crystals disappear. Studies by several authors in the last decade have seen anomalous behavior of the high temperature polymer melt which suggests the possibility of structural order on a long-range level. In this thesis, the interfacial tension of PE melt against silicone oil will be reported in the same temperature range that anomalous phase transitions have been observed in the bulk HDPE (between 200 and 230°C). Phase transitions in the interfacial tension of the HDPE were found. The densities of HDPE in the temperature range of 160 to 250°C were also measured and small phase transitions were observed between 200 and 230°C. A spinning drop tensiometer acquired from SDT Ltd. was used for the interfacial tension measurements. A detailed investigation of the precision of the spinning drop apparatus and the errors associated with the system will be given. Preliminary data with water/air and silicone oil/air are described. It was found that the apparent interfacial tension values varied with rotation rate of the samples. Possible causes of this anomaly are discussed in detail. Different experiments were conducted to examine this observation.