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

Abstract

Control of the crystalline phase transition of polymers is critical to improve mechanical properties and to achieve good levels of thermal properties in polymer engineering. Current methods control the transition process by using thermal methods that is, annealing above the glass transition temperature (T g ) to get the targeting crystalline phase. It requires precise control of the temperature and process time and is limited to a small scale. In contrast, a novel processing-based method developed in our group by combining the use of reactive processing technique and extensional mixing elements (EME) allows different sizes of minor phase droplets in immiscible polymer blends to be achieved by controlling the degree of aggressiveness of the EME. The use of EME can confine polyamide crystalline structure into the γ-phase from the α-phase. The reactive processing benefits in stabilizing these droplets and in freezing the corresponding crystalline morphologies in droplets. Crystalline phase transition of the minor phase in these droplets is therefore observed as the size of droplet decreases from micro to submicron. Furthermore, phase transition can be precisely controlled by tuning additives and EME blocks. FIG. 7. Curves of the first cooling cycle of DSC measurements for various pellet-shaped samples with a cooling rate of 10 C/min.

Effects of the blending time on the properties and non‐isothermal crystallization behavior of PA6/EVOH blends

“…[ 10 ] Incompatible polymer blends have poor mechanical and physical properties and the enhancement of compatibility is key. [ 11–13 ] Compatible polymer blends with strong adhesion between phases, the performance is better than a single polymer. [ 14 ]…”

Extension‐dominated improved dispersive mixing in single‐screw extrusion. Part 2: Comparative analysis with twin‐screw extruder

“…EMEs have also been proven to generate phase changes when reactive extrusions were conducted on polyamide-6 dispersed in the polystyrene with styrene-maleic anhydride used as the compatibilizer. 65 In Part 1 of this work, 58 EMEs were adapted to SSE and were computationally and experimentally validated. Important findings included the fact that the addition of the EME to the pin screw did not bring about a significant penalty in the throughput and greatly enhanced the dispersive mixing in all the tested polymer blends and composite systems.…”

“…The optimized designs have also been tested experimentally for blend and nanocomposite systems and were found to yield higher dispersive mixing. EMEs have also been proven to generate phase changes when reactive extrusions were conducted on polyamide‐6 dispersed in the polystyrene with styrene‐maleic anhydride used as the compatibilizer 65 …”

Comparative computational analysis of dispersive mixing in extension‐dominated mixers for single‐screw extruders

“…[20] The number of channels in the EME design were optimized to lower the pressure drop without limiting the dispersive mixing capability. Carson et al, [18] Chen et al, [19,21] and Danda et al, [20] validated the EME dispersive mixing efficiency experimentally, for two types of systems: (a) Immiscible polymer blends, that is, fluid-fluid systems, and (b) Nanocomposites, that is, fluid/solid systems. The EME has been shown to being effective in dispersing droplets up to very high viscosity ratios in the case of blends, and yielding significant smaller aggregates in the case of polymer nanocomposites than even the most aggressive KB-based geometries.…”