Research article

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The study scrutinizes the coincidental formation and stabilization of bio-based polyamide (PA) nanofibers within biodegradable polylactide (PLA) in a single stage. The results reveal that the formation of nanofibril-matrix morphology is dominated by viscosity and elasticity ratios of the dispersed component to the matrix. It is shown that there are upper and lower bounds for the ratios providing efficient in situ fibrils formation. For PLA/PA, critical values of viscosity and elasticity ratios are in the range of 0.3–2.8 and 2.0–15.0, respectively. As these parameters decrease, thinner and longer PA nanofibers form, and ultimately a network of nanofibrils develops. Below the lower boundary, formed very thin, less than 250 nm, nano - fibrils become unstable, and their flow is accompanied by breaking-up into sub-nanodroplets. Above the upper boundary, the viscosity of the polymer matrix is insufficient to arrange droplets to fibers transitions, and the presence of a compatibilizer can only lead to a partial formation of a fibrillar structure. The shear-induced crystallization is proposed for the stabilization of PA nanofibers immediately under applying a high shear rate without subsequent cooling. A higher effect (more significant increase in the crystallization temperature of PA and a narrower temperature range in which the crystallization process occurs) is achieved in the case of PA with a higher viscosity.