Lightweight and Ultrastrong Polymer Foams with Unusually Superior Flame Retardancy

5 years ago

Lightweight and Ultrastrong Polymer Foams with Unusually Superior Flame Retardancy

Hui Li, Karel Goossens, Chungui Cheng, Jianxin Geng, Yong Huang, Peng Liu, Linhong Xiao, Linli Xu, Christopher W. Bielawski, Pan Jia

High-performance flame-retardant materials are urgently needed to address outstanding issues that pertain to safety. Traditional flame retardants are toxic to the environment and/or lack the physical properties required for use in many contemporary applications. Here, we show that isocyanate-based polyimide (PI) foam, a flammable material, can exhibit unusually superior flame retardancy as well as other excellent properties, such as being lightweight and displaying high mechanical strength, by incorporating red phosphorus (RP)-hybridized graphene. The covalent bonds formed between the graphene platelets and the PI matrix provide the resultant PI foam with a specific Young’s modulus (83 kNm kg^–1) that is comparable to or even higher than those displayed by state-of-the-art foams, including silica aerogels, polystyrene foams, and polyurethane foams. In addition, even a low content of the RP-hybridized graphene (2.2 wt %) results in an exceptionally higher limiting oxygen index (39.4) than those of traditional flame-retardant polymer-based materials (typically 20–30). The resultant PI foam also exhibits thermal insulation properties that are similar to that of air. Moreover, the RP-hybridized graphene is prepared using a one-step ball milling process in 100% yield, and does not require solvent or produce waste. The preparation of the flame-retardant PI foams can be scaled as the starting materials are commercially available and the techniques employed are industrially compatible.

Publisher URL: http://dx.doi.org/10.1021/acsami.7b06282

DOI: 10.1021/acsami.7b06282