Confined crystallization phenomena in immiscible polymer blends with dispersed micro-and nanometer sized PA6 droplets part 4: polymorphous structure and (meta)-stability of PA6 crystals formed in different temperature regions

The genesis and stability of different PA6 crystalline polymorphs, dispersed as micro- and submicrometer sized droplets inside an amorphous polymer matrix, are discussed over a very broad temperature range. Different PA6 droplet sizes lead to different PA6 crystallization events in a 100 °C wide temperature window that extends down to 85 °C. Static WAXD and DSC experiments on micrometer sized PA6 droplets indicate the formation of a stable γ-crystal phase in the region between 175 and 130 °C. Sub-micrometer sized PA6 droplets only crystallize at 85 °C in the β-phase. Upon heating above the PA6 glass transition, these crystals progressively increase their perfection and ultimately transform into the α-phase around 170 °C.