Preparation of Polyamide-6 Submicrometer-Sized Spheres by In Situ Polymerization.

Polyamide-6 (PA6) submicron-sized spheres are prepared by two steps: (1) anionic ring-opening polymerization of ε-caprolactam in the presence of poly(ethylene glycol)-block-poly-(propylene glycol)-block-poly(ethylene glycol)(PEG-b-PPG-b-PEG) and (2) separation of PA6 spheres by dissolving PEG-b-PPG-b-PEG from the prepared blends. The PA6 microspheres obtained are regular spherical, with diameter ranging from 200 nm to 2 µm and narrow size distribution, as confirmed by scanning electron microscopy. By comparison with PA6/PS and PA6/PEG systems, it is denominated that the PEG blocks in PEG-b-PPG-b-PEG can effectively reduce the surface tension of PA6 droplets and further decrease the diameter of the PA6 microspheres. The PPG block in PEG-b-PPG-b-PEG can prevent the PA6 droplets coalescing with each other, and isolated spherical particles can be obtained finally. The phase inversion of the PA6/PEG-b-PPG-b-PEG blends occurs at very low PEG-b-PPG-b-PEG content; the PEG-b-PPG-b-PEG phase can be removed by water easily. The whole experiment can be finished in a short time (approximately in half an hour) without using any organic solvents; it is an efficient strategy for the preparation of submicron-sized PA6 microspheres.

Non-isothermal crystallization kinetics of graphene/PA10T composites.

Crystallization kinetics is the key factor in controlling the polymer crystallization process and affecting crystallinity and crystalline morphology, which determine the polymer's main properties. In this work, the non-isothermal crystallization kinetics of graphene/PA10T composites are investigated by the Jeziorny method and Mo method, and the crystallization activation energy is calculated by the Kissinger method. It is found that the addition of an appropriate amount of graphene to PA10T can significantly promote the crystallization of PA10T and accelerate its crystallization rate. The Jeziorny equation does not have a linear relationship across the whole crystallization range, while the Mo equation does a good linear fitting. In addition, the crystallization activation energy decreases when the graphene content is below 1 wt.%. TGA results indicate that the addition of graphene improves the thermal stability of PA10T.

Rheological and Crystallization Properties of ABS/PA6-Compatibilized Blends via In Situ Reactive Extrusion.

ABS/PA6-compatibilized blends were prepared by in situ reactive extrusion method. The main objective was to evaluate the influences of the morphology and blend composition on the rheological and nonisothermal crystallization properties. The morphology of submicron-sized ABS droplets evenly dispersed in PA6 led to dilatant fluid behavior and a transition from elastic to viscous behavior in the low-frequency region. The crystallization results indicated that reactive blends had elevated crystallization temperatures and crystallization rates, which were due to the heterogeneous nucleation of the submicron-sized ABS particles. In addition, it was observed that the theory by Mo suitably described the nonisothermal crystallization process. The activation energy slightly decreased for ABS contents of 5 and 15 wt % and then increased for a content of 25 wt %, indicating that the ABS promoted the crystallization of the blends at appropriate contents.