The Formation of a Highly Oriented Structure and Improvement of Properties in PP/PA6 Polymer Blends during Extrusion-Stretching

Abstract

During the “slit die extrusion-hot stretching” process, highly oriented polyamide 6 (PA6) dispersed phase was produced and retained in the polypropylene (PP) matrix directly. By adjusting the stretching forces, the PA6 spherical phase evolved into the ellipsoid, rod-like microfibril with a decreasing average diameter; then, the PA6 microfibrils broke. Moreover, the effects of the PA6 phases formed in the process of the microfibrillation on PP’s crystallization behaviors were studied systematically. As the stretching forces increased, the crystallization ability and orientation degree of PP crystals improved significantly. Differential scanning calorimetry and polarizing optical microscopy confirmed the formation of PP spherulite, fan-shaped lamellae and a transcrystalline layer under the induction of the PA6 phases with different morphology. In the PP/PA6 microfibrilar composites (MFCs), PP crystals showed smaller average size, more crystals and stronger interface adhesion due to more excellent heterogeneous nucleation ability of the PA6 microfibrils, which made contributions to the improvement of the melt elasticity responses and oxygen barrier properties of the PP/PA6 polymer blends.

The Entangled Conductive Structure of CB/PA6/PP MFCs and Their Electromechanical Properties

“…In our previous study [ 25 ], the PA6 polymer fibrils were in situ generated in the PP matrix through an in situ fibrillation technique. These in situ generated fibrils had the characteristics of high aspect ratios and great dispersion [ 26 , 27 ].…”

Preparation of stiffer ternary blends of polypropylene/polyamide 6/biodegradable polymers with improved interfacial adhesion

“…Even being incompatible with PP, PA6 has been used to address the PPs deficiencies, expanding its applications. [6][7][8][9] Multicomponent polymeric mixtures are usually prepared by melt mixing of two or more miscible or immiscible polymers. The blending of polymer is a powerful route for obtaining new materials combining existing desired properties in specific neat polymers, adapting them to satisfy a wide range of uses.…”

“…Some grafted polymers with maleic anhydride are found as compatibilizers for PP/PA6 blend. 6,8,23 Thermoplastic polyurethane (TPU) was used as an additive for modifying the toughness of PA6/PLA blends. 24 PA6/PLA/TPU ternary blends were prepared by melt blending, and the effects of blend compositions on the morphology, thermal, and mechanical properties of blends were investigated.…”

“…They observed through scanning electron microscopy (SEM) a better interfacial adhesion due to potential condensation reactions of PA6 terminal groups with the carboxylic end groups of PLA, as well as carboxyl groups of PA6 can react with the OH groups of PLA. Some grafted polymers with maleic anhydride are found as compatibilizers for PP/PA6 blend 6,8,23 . Thermoplastic polyurethane (TPU) was used as an additive for modifying the toughness of PA6/PLA blends 24 .…”

“…Still, it has some limitations such as low‐impact resistance at low temperatures, swelling in hydrocarbon solvents, and relatively low‐gas barrier property. Even being incompatible with PP, PA6 has been used to address the PPs deficiencies, expanding its applications 6–9 …”