Covalent Adaptable Network of Semicrystalline Polyolefin Blend with Triple-Shape Memory Effect

Area of Science:

• Materials Science
• Polymer Chemistry
• Chemical Engineering

Background:

• Thermoplastic polyolefin blends offer versatility but often lack robust mechanical properties and long-term stability.
• Covalent adaptable networks (CANs) provide dynamic crosslinking for enhanced material properties and recyclability.
• Shape memory polymers (SMPs) enable materials to recover their original shape upon stimulation, offering advanced functionalities.

Purpose of the Study:

• To fabricate a novel covalent adaptable network (CAN) from semicrystalline polyolefin blends.
• To investigate the triple-shape memory effects and chemical crosslinking within the polyolefin blend.
• To evaluate the mechanical properties, thermal behavior, and reprocessability of the developed CAN.

Main Methods:

• Reactive melt blending of maleated polypropylene (mPP) and maleated polyolefin elastomer (mPOE) with a tetrafunctional thiol (PETMP) and TBD.
• Characterization using Fourier-transform infrared spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), and torque variation monitoring.
• Mechanical testing including tensile strength and elongation at break measurements.
• Solubility tests and repeated melt processing to assess recyclability and reprocessability.

Main Results:

• Successful fabrication of a chemically crosslinked CAN from mPP/mPOE blends via thiol-ene click chemistry.
• Confirmation of crosslinking through FTIR, torque changes, solubility tests, and DMA.
• DSC analysis showed two distinct melting transitions, indicating preserved crystallinity of both polyolefin components.
• Enhanced tensile strength and elongation at break compared to the simple blend.
• Maintained mechanical properties after repeated melt processing, demonstrating excellent reprocessability.

Conclusions:

• The developed CAN exhibits promising triple-shape memory effects and enhanced mechanical performance.
• The crosslinked polyolefin blend demonstrates good recyclability and reprocessability, transforming thermoplastic blends into high-performance materials.
• This study highlights the potential of CANs for creating value-added, sustainable polyolefin-based materials.