In situ encapsulation technique for fabrication of self‐healing thermosetting polyurethane with tungsten (VI) chloride

Abstract

Polymeric composites as materials with special engineering structure and favorable properties are widely used in different industries. The concept of self‐healing in polymers, inspired by biological systems, has been introduced in recent years. Growing applications of thermosetting polyurethanes have also resulted in their extensive use in engineering applications. There are various methods for self‐healing mechanisms, one of which involves microcapsules containing healing agents. Given that the most past research on encapsulation‐based methods carried out for self‐healing epoxy resins, the present work aims to develop the in situ technique and examine the healing efficiency for thermosetting polyurethanes due to their wide variety of applications. To do so, urea–formaldehyde microcapsules, 73 μm in average diameter containing dicylopentadiene as the healing agent, phenylacetylene as the coactivator, and nonylphenol as the dissolution agent were synthesized using in situ polymerization technique. Tungsten (VI) chloride catalyst was used for the implementation of ring‐opening metathesis polymerization. The sizes of microcapsules were measured using optical microscopes, and surface morphology and shell‐wall thickness of microcapsules were examined using FESEM. The healing efficiency was calculated using samples with tapered double‐cantilever beam (TDCB) geometry. Moreover, the impact of adding microcapsules as well as catalyst on mechanical properties of polyurethane resin was studied.

Self‐healing polyurethane based on a substance supplement and dynamic chemistry: Repair mechanisms and applications

“…The most common healing principle is ring‐opening metathesis polymerization (ROMP), where healing agents achieve the desired polymerization reaction at the active center of the catalyst, and the most widespread is the ROMP of dicyclopentadiene on Grubbs type catalysts 32 . Amini‐Nejad et al 33 synthesized a urea‐formaldehyde microcapsules with an average particle size of 75 μm by in‐situ polymerization. After embedding in a thermosetting PU, the healing agent of dicyclopentadiene could be released under external impact.…”

“…(a) The action mechanism showing the ring‐opening metathesis polymerization 33 (reproduced with permission). (b) Self‐healing of the polyurethane matrix after embedding double microcapsules 34 (reproduced with permission).…”