Crystallization in Polyamide 6/Polysulfone Blends: Effect of Polysulfone Particle Size

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Abstract
By reactive blending of polyamide 6 (PA) with polysulfone (PSU) using a gram-scale mixer (Mini-Max Molder), we prepared a series of PA/PSU (80/20 wt.ratio) with various diameters of PSU particles: 90 nm by using phthalic anhydride-terminated PSU (PSU−PhAH), 0.2 μm by carboxylic acid-grafted PSU (PSU−COOH), and 1.0 μm by nonreactive PSU (nf-PSU). Isothermal crystallization was carried out at 200 °C. Light scattering studies showed that spherulites in the blends can grow to more than 10 μm in diameter, as in the case of neat PA. It suggests that crystal growth in the radial direction can be achieved by circumventing the PSU obstacles; i.e., it does not matter how big or small they are in the range of 90 nm to 1 μm. The smaller the PSU particles, the slower was the overall rate of crystallization. The slower rate may be caused by the higher population of brush PA chains attached to PSU particles as block or graft chains, since the brushes may be hard to organize into crystal lamellae, compared with free chains. The blends showed rather broad wide-angle X-ray diffraction profiles. The smaller the PSU particles, the broader was the profile. The scattering from the particles themselves should appear only at extremely low angles (-1, suggesting the evolution of interlamellar spacing of 8.7 nm. However, the scattering profile was much broader than that of neat PA. It implies a less ordered lamellar stacking in the blend.

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