Melting of Binary Mixtures of Nylon 6 and Nylon 66. A Study by Pressure–Volume–Temperature Measurements

Abstract

Pressure-volume-temperature (PVT) measurements on binary mixtures of nylon 6 and nylon 66 were performed for melt-spun monofilament samples. During heating in the isobaric modes (form 20 to 180 MPa), two definite volume changes corresponding to the melting of nylon 6 and nylon 66 in mixtures were observed in the composition range where nylon 6 is the major part. From observed volume change at the melting, the heat of fusion ΔHm was estimated using the Clausius–Clapeyron equation. Thus, the amounts of coexisting two crystalline phases of both nylon components at a given composition can be estimated. A series of estimated ΔHm is self-consistent and reasonable. However, ΔHm, obtained from the estimated values at finite pressures by extrapolating as P→0, are 33 and 28 (cal g−1) for nylon 6 and nylon 66, and smaller than the literature data of 45 (cal g−1). The cause for this difference is discussed.