Biobased Carbon Fiber Composites with Enhanced Flame Retardancy: A Cradle-to-Cradle Approach
Parisa Zamani, Omid Zabihi, Mojtaba Ahmadi, Roya Mahmoodi, Thathsarani Kannangara, Paul Joseph, Minoo Naebe
Abstract
With circular economy gaining increased importance in carbon fiber reinforced polymers (CFRPs) in the recent years, development of recyclable thermosetting polymers is a promising approach to avoid further waste generation in both polymers and carbon fibers. In this work, we synthesized a multifunctional Schiff base monomer based on reaction of vanillin as a renewable and biosource aromatic material with a phosphonitrilic chloride trimer as a phosphorus-/nitrogen-rich compound. The resultant monomer having six aldehyde reactive sites can be cured using a diamine to form a highly crosslinked Schiff base polymer. The CFRP was fabricated using this Schiff base polymer (Schiff base CFRP), and its tensile, flexural, and dynamic mechanical properties were obtained and compared with those of a conventional epoxy resin reinforced with carbon fibers. The Schiff base CFRP showed high tensile and flexural strengths of 461 and 455 MPa, respectively, with a high glass transition temperature (Tg) of 129 °C. A mechanically failed Schiff base CFRP also demonstrates excellent repairability performance after carrying out the repairing process twice, retaining ∼70 and ∼58% of its original flexural strength. Surface clean carbon fibers were also reclaimed from Schiff base CFRP by a chemical recycling process under very mild conditions at room temperature without deteriorating mechanical properties of the reclaimed carbon fibers. Because this Schiff base CFRP highly contains phosphorus/nitrogen rings in its structure, outstanding fire retardancy was achieved, showing V0 rating in the UL94 test.