Formation of α Form Nylon 12 under High Pressure

Abstract

The formation conditions of α form Nylon 12 under high pressure from the melt and from the quenched state were investigated by means of high-pressure differential thermal analysis and wide-angle X-ray diffraction. The α form was formed by crystallization from the melt above 200 MPa, and the γ form disappeared in the sample obtained above 500 MPa. The quenched state was transformed into the α form at lower temperature than the melting point of the α form under high pressure, whereas the γ form was hardly transformed at all. The thermal behavior of the α form at atmospheric pressure was also studied. Two endotherms due to the meltings of the α and γ forms and one exotherm due to the α to γ form transformation were observed. This transformation occurred without melting of the α form at a slow heating rate and was regarded as a monotropic transition.