Preparation of isocyanate microcapsules as a high-performance adhesive for PLA/WF

Abstract

The application of liquid isocyanate in composite material is limited because of its high activity and toxicity. In this work, microcapsules were employed to preserve the activity of isocyanates. The liquid isocyanates were also solidified which allowed them to be easily added to the Polylactic acid/wood flour (PLA/WF) to enhance the properties by controlling the release of isocyanate. The stable isocyanate microcapsules (IM) were synthesized by minimalist complex coacervation without extra crosslinker. The properties of IM and composites were studied by chemical titration, Fourier Transform Infrared (FTIR) spectroscopy, Particulate Size Analysis (PSA), Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), etc. The results showed that the prepared IM were approximately 200 μm in diameter, the active content was around 25% and the core accounted for 80% of the total weight. When the amount of IM added was 2.5%, the tensile strength, Young's strength and bending strength of the composite increased by 23.2%, 46.4% and 22.0% respectively compared with pure PLA. The impact strength increased by 52.3% compared with the composite without isocyanate microcapsules. Furthermore, IM improve the stability of isocyanate, suggesting the promising application of IM in various building materials.