Melting of binary mixtures of nylon 6 and nylon 66. A study by pressure-volume-temperature measurements

Pressure-volume-temperature (PVT) measurements on binary mixtures of nylon 6 and nylon 66 were performed for melt-spun monofilament samples. During he ating in the isobaric modes (form 20 to 180 MPa), two definite volume chang es corresponding to the melting of nylon 6 and nylon 66 in mixtures were ob served in the composition range where nylon 6 is the major part. From obser ved volume change at the melting, the heat of fusion Delta H-m was estimate d using the Clausius-Clapeyron equation. Thus, the amounts coexisting two c rystalline phases of bath nylon components at a given composition can be es timated. A series of estimated Delta H-m is self-consistent and reasonable. However, Delta H-m, 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 far this difference is discussed.