Mercury-free catalysis and bio-based isocyanates for polyurethane thermosets

Overview

This technology provides a sustainable alternative to conventional polyurethane thermosetting resins, which are widely used for optoelectronic encapsulation but historically rely on toxic mercury-based catalysts and fossil-derived isocyanate precursors. Researchers have developed an eco-friendly formulation that replaces these hazardous components with a mixed bismuth-zinc catalyst system and bio-based isocyanate feedstocks. By utilizing a Design of Experiments (DoE) multivariate approach, the researchers optimized the formulation to maintain high performance in critical parameters such as optical transparency, thermal stability, and mechanical properties, ensuring the resulting materials meet rigorous industrial standards for electronics.

Technical specifications

• Catalyst System: Replaces traditional toxic mercury-based catalysts with a tailored, low-toxicity organobismuth and organozinc catalyst mixture.
• Bio-based Content: Achieves up to 65% w/w content of circular and bio-based components through the use of renewable isocyanates.
• Optical Properties: Delivers high transmittance (approaching 90% at 555 nm), meeting requirements for optoelectronic encapsulation.
• Stability: Optimized gel time (78 minutes), glass transition temperature (35.7 °C), and long-term stability comparable to commercial fossil-based references.
• Formulation Enhancement: Incorporates a 1% w/w long-chain fatty acid as a reactivity modulator to eliminate trapped bubbles, ensuring optical purity.
• Process Compatibility: Solvent-free, ready-to-market formulation designed to integrate seamlessly into existing polyurethane production workflows.

Technology readiness level

The technology is at TRL 4-5. The formulation has been successfully validated in laboratory settings using multivariate chemometric optimization and demonstrates performance parity with commercial industrial resins, with readiness for scaling and industrial pilot testing.