Controlling Processing, Morphology, and Mechanical Performance in Blends of Polylactide and Thermotropic Polyesters

Area of Science:

• Materials Science
• Polymer Science
• Composite Materials

Background:

• Thermotropic liquid crystalline polymers (LCPs) offer promising mechanical properties and recyclability for reinforced composites.
• A lack of design rules for LCP-reinforced thermoplastic composites hinders their development due to complex component interactions.

Purpose of the Study:

• Investigate processing parameters influencing morphological development and mechanical performance of poly(l-lactide)/LCP composites.
• Determine the impact of blend composition and processing conditions on composite mechanical response.

Main Methods:

• Rheology
• Wide-angle X-ray Diffraction (WAXD)
• Mechanical analysis
• Microscopy
• Processing via injection molding and melt drawing

Main Results:

• Matrix viscosity and viscosity ratio control LCP droplet deformation and breakup during extrusion.
• Rapid cooling-induced viscosity ratio increase prevents LCP phase orientation during injection molding.
• Melt drawing effectively stabilizes elongated LCP droplets, enabling fibril formation irrespective of viscosity ratio.

Conclusions:

• Viscoelastic properties, particularly the temperature-dependent viscosity ratio, are crucial for LCP composite morphology and performance.
• Guidelines for designing LCP polymers and composites are provided based on processing insights.