PVA/carbon dots composite vitrimer film with enhanced mechanical properties, reprocessability and flame retardancy

Employing carbon dots as the crosslinking agent for polyvinyl alcohol (PVA) allows the formation of multiple interactions between carbon dots and PVA. • The fragmented PVA/BP-CDs0.3 vitrimer film can be reprocessed via hot pressing at 150 °C for 2 h to regenerate an intact film. • The phosphorus species present on the surface of carbon dots simultaneously imparts good flame-retardant properties to the composite PVA vitrimer film with a 27.7% LOI and VTM-0 rating. • Compared with pure PVA, the tensile strength of the PVA/BP-CDs0.3 composite vitrimer film is increased by approximately 122%, while its Young's modulus is enhanced by about 35%. The design of crosslinked network is important for polyvinyl alcohol (PVA) to overcome the disadvantages in weak mechanical strength and water resistance. Herein, the strategy of using carbon dots as PVA crosslinking agent was proposed. The carbon dots made of phenylboric acid and phosphoric acid could generate the combination effect of nano-enforcement and dynamic exchangeable network in PVA because of the multiple interactions between PVA and carbon dots. In addition, the existence of phosphorus element on the carbon dots could be expected to synchronously endow the composited PVA film with flame retardancy. The experimental results showed that compared to pure PVA, the tensile strength of PVA/BP-CDs0.3 significantly increased from 63.89 MPa to 142.03 MPa, and the Young's modulus increased from 1.56 GPa to 2.10 GPa, respectively. The limiting oxygen index (LOI) and vertical burning rating of PVA/BP-CDs0.3 were also improved to be 27.7% and a VTM-0 grade. Furthermore, it retained a mechanical strength of 16.05 MPa after being immersed in water for 15 days, indicating an excellent water resistance. It was worth noting that the shredded PVA/BP-CDs0.3 film could be reprocessed under hot-pressing with the condition of 150 °C and 2 h, forming a complete film. This work is helpful to provide new insights for the development of functional and recyclable PVA composite vitrimer film. Download: Download high-res image (138KB) Download: Download full-size image