Direct Observation of Morphology and Growth Rate of Extended Chain Single Crystals of Polyethylene

Extended chain single crystals (ECSC) of polyethylene growing from liquid under isobaric and isothermal condition were directly observed by microscope in a high pressure apparatus at 3 kbar. ECSC grew as rhombic plate-like crystal several µm thick. The longer diagonal was parallel to the a-axis of hexagonal lattice, the side surfaces were indexed {110} plane, and it seemed that the ECSC was a nearly “perfect crystal”. The growth rate of its longer diagonal G l obeyed an experimental formula, G l =A·exp (-B/Δ T), where A=3.4×103 nm/sec and B=12.6 K, which confirms that the growth rate determining process is a secondary nucleation process.