Phase Control of Polyamide 6 via Extension‐Dominated Polymer Blend Reactive Extrusion

Improving dispersive mixing in compatibilized polystyrene/polyamide-6 blends via extension-dominated reactive single-screw extrusion

Extensional mixing elements (EMEs) that impose extension-dominated flow via stationary single-plane or double-plane hyperbolic converging-diverging channels were previously designed for twin-screw and single-screw extruders (TSE and SSE, respectively). In a recently published work by the authors, reactive extrusion was performed on PS/PA6 polymer blends TSE using EMEs and a crystalline phase transition of the minor phase in these droplets was observed as the size of droplet decreases from micron to submicron. Herein, we expand upon this work to SSE and study: a) The ability of the EMEs to improve dispersive mixing in the same blends; b) Assess the possibility of achieving the same crystalline phase transition in SSEs. The final blends were characterized by DSC, rheologically and morphologically via SEM, and the results show that while EME-based SSE leads to much improved mixing, better than non-EME TSE, the reduction in size of the PA6 disperse phase is not enough to induce the phase transition observed in EME-based TSE.

Morphology optimization of poly(ethylene terephthalate)/polyamide blends compatibilized via extension-dominated twin-screw extrusion

Poly(ethylene terephthalate) (PET) and polyamide (PA) are immiscible polymers, which requires the use of compatibilizers to stabilize the morphology and achieve acceptable property levels. Therefore, controlling the degree of dispersion, especially the size of the disperse PA droplets in the PET matrix is of paramount importance. This study aims to improve the mixing, i.e., minimize PA droplet size, in immiscible and compatibilized PET/PA and PET/Nylon-MXD6 (MXD6) blends by resorting to extension-dominated mixing in twin-screw extrusion (TSE). MXD6 is an aromatic polyamide similar in polarity to PET, so it is expected that it will blend more effectively than is the case with aliphatic nylon-6 and PET. Two screw configurations are used, a benchmark shear-dominated screw with kneading blocks (KBs) in an aggressive configuration, and an extension-dominated screw configuration with static mixers with hyperbolic C–D channels, recently developed by our group, in place of the KBs. The results show that the use of extensional mixing elements (EMEs) in place of KBs results in a significant decrease of both average and maximum droplet size for all blends, and up to more than one order of magnitude between the most extreme cases of the KB-processed immiscible blend and EME-processed compatibilized blends.

Properties of Styrene-Maleic Anhydride Copolymer Compatibilized Polyamide 66/Poly (Phenylene Ether) Blends: Effect of Blend Ratio and Compatibilizer Content

Two different blend ratios of polyamide 66 (PA66) and poly (2,6-dimethyl-1,4-phenylene ether) (PPE) (60/40 and 40/60 w/w) were produced via melt mixing. A styrene-maleic anhydride copolymer (SMA) was utilized at various contents from 2.5-15 wt% to compatibilize the immiscible blend system. The influence of SMA content and blend ratio was investigated based on (thermo-) mechanical and morphological properties of the PA66/PPE blends. Correlations between the interaction of SMA with the blend partners were established. For 60/40 blends, a droplet-sea morphology was visualized by transmission electron microscopy, wherein no major changes were seen upon SMA addition. In the case of 40/60 blends, strong coalescence was found in the binary blend. Up to 5 wt% SMA, the coalescence was inhibited by the interfacial activity of SMA, whereas 10 wt% SMA initiated a disperse-to-co-continuous transition, which was completed at 15 wt% SMA. An enhancement of tensile properties was achieved for all blends possessing SMA, where the maximum concentration of 15 wt% resulted in the highest elongation at break and tensile strength values. The relative improvement of the tensile properties was higher with the PPE-rich blend (40/60) which was attributed to a partial emulsification of the PPE phases forming a bimodal PPE domain size distribution with nano-droplets in the range of 60-160 nm.