A chemical bonding adhesive for PEEK based on aromatic ring interactions

Area of Science:

• Biomaterials Science
• Polymer Chemistry
• Adhesive Dentistry

Background:

• Polyetheretherketone (PEEK) is a high-performance thermoplastic known for its excellent chemical resistance and mechanical properties, making it suitable for dental and medical applications.
• However, its inert surface and semicrystalline nature present significant challenges for achieving reliable adhesive bonding.
• Current methods often require aggressive surface treatments that can compromise the material's integrity.

Purpose of the Study:

• To develop a novel two-part adhesive system for bonding to polyetheretherketone (PEEK).
• To achieve strong adhesion by targeting PEEK's phenylene backbone units through noncovalent π-π interactions and ensuring chain-level compatibility.
• To evaluate the adhesive's performance without requiring aggressive chemical pretreatments.

Main Methods:

• Candidate solvents and monomers were screened for miscibility with PEEK using differential scanning calorimetry (DSC).
• A two-part adhesive formulation was designed using 1-vinylimidazole and glycidyl methacrylate, along with other methacrylate monomers and a photoinitiator system.
• Interfacial chemistry was analyzed using Fourier transform infrared spectroscopy (FTIR), and micro-shear bond strength was tested on grit-blasted PEEK at 24 hours and 2 weeks.

Main Results:

• Differential scanning calorimetry (DSC) indicated chain-level compatibility between the adhesive components and PEEK.
• Fourier transform infrared spectroscopy (FTIR) confirmed chemical interactions, showing decreased PEEK phenylene/ether bands and increased epoxy ring-opening product bands.
• The optimized adhesive formulation achieved a micro-shear bond strength of 19.3 ± 3.4 MPa at 2 weeks, significantly outperforming a commercial control adhesive.

Conclusions:

• The developed two-part adhesive successfully bonds to PEEK by leveraging π-π interactions and achieving chain-level compatibility.
• This non-aggressive bonding strategy offers a promising clinical approach for PEEK in adhesive dentistry.
• The findings suggest potential applications for this adhesive system on other aromatic engineering polymers after further validation.