Development of High Temperature Resistant Stereocomplex PLA for Injection Moulding

Area of Science:

• Polymer Science
• Materials Engineering
• Crystallization Science

Background:

• Stereocomplex poly(L-lactide)/poly(D-lactide) (sc-PLA) offers superior thermal and mechanical properties compared to homopolymers.
• Efficient production of sc-PLA via compounding and injection molding is crucial for industrial adoption.
• Nucleating agents (NA) can significantly influence the crystallization behavior and final properties of sc-PLA.

Purpose of the Study:

• To investigate the production of sc-PLA formulations using selective nucleating agents.
• To analyze the effect of nucleating agents on the crystallization behavior of PLLA/PDLA blends.
• To evaluate the thermo-mechanical properties and potential applications of the developed sc-PLA.

Main Methods:

• Compounding of poly(L-lactide)/poly(D-lactide) (PLLA/PDLA) with nucleating agents (NA) using a twin-screw extruder.
• Differential Scanning Calorimetry (DSC) to study crystallization behavior under varying cooling rates.
• Wide-Angle X-ray Diffraction (WAXD) to confirm stereocomplex crystal formation.
• Thermo-mechanical testing, including Young's modulus, yield stress, elongation, and heat deflection temperature (HDT-B).

Main Results:

• Selective nucleating agents, particularly NA-21 (aluminium complex of a phosphoric ester), were identified and compounded.
• Complete stereocomplex (sc) crystal formation was achieved even at high cooling rates (up to 70 K/min) with NA-21.
• The sc-PLA formulations exhibited a Young's modulus of ~3 GPa, yield stress of 30-40 MPa, elongation of 1%, and HDT-B up to 180 °C.

Conclusions:

• The study successfully demonstrated the production of sc-PLA with enhanced thermal stability using specific nucleating agents.
• The developed sc-PLA materials possess properties suitable for high-temperature applications.
• Processing sc-PLA via compounding and injection molding opens new application avenues for polylactic acid-based materials.