Crystallization in Polyamide 6/Polysulfone Blends: Effect of Polysulfone Particle Size

Area of Science:

• Polymer Science
• Materials Science
• Crystallization Kinetics

Background:

• Polyamide 6 (PA) and polysulfone (PSU) are common engineering thermoplastics.
• Understanding the influence of filler morphology on polymer crystallization is crucial for material design.

Purpose of the Study:

• To investigate the effect of polysulfone (PSU) particle size on the crystallization behavior of polyamide 6 (PA) during reactive blending.
• To analyze the impact of reactive blending on the crystal perfection and lamellar structure of PA/PSU blends.

Main Methods:

• Reactive blending of PA/PSU (80/20 wt.ratio) using various PSU particle sizes (90 nm, 0.2 µm, 1.0 µm) via a Mini-Max Molder.
• Isothermal crystallization at 200°C.
• Characterization using light scattering, wide-angle X-ray diffraction (WAXS), and small-angle X-ray scattering (SAXS).

Main Results:

• Spherulite growth in PA/PSU blends exceeded 10 µm, indicating radial crystal growth around PSU particles regardless of size.
• Overall crystallization rate decreased with smaller PSU particle sizes, attributed to increased brush PA chains hindering lamellar organization.
• WAXS profiles broadened with decreasing PSU particle size, suggesting reduced PA crystal perfection, potentially due to brush chains in reactive systems.
• SAXS revealed interlamellar spacing of 8.7 nm but broader scattering profiles compared to neat PA, indicating less ordered lamellar stacking.

Conclusions:

• Polysulfone particle size does not impede spherulite growth in PA/PSU blends, but smaller particles significantly slow crystallization kinetics.
• Reactive blending, especially with smaller PSU particles, leads to reduced PA crystal perfection and less ordered lamellar stacking.
• The formation and increased population of brush chains in reactive systems are key factors influencing crystallization behavior and crystal perfection in PA/PSU blends.