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Flexible sensing electronics have received extensive attention for their potential applications in wearable human health monitoring and care systems. Given that the normal physiological activities of the human body are primarily based on a relatively constant body temperature, real-time monitoring of body surface temperature using temperature sensors is one of the most intuitive and effective methods to understand physical conditions. With its outstanding electrical, mechanical, and thermal properties, graphene emerges as a promising candidate for the development of flexible and wearable temperature sensors. In this review, the recent progress of graphene-based wearable temperature sensors is summarized, including material preparation, working principle, performance index, classification, and related applications. Finally, the challenges and future research emphasis in this field are put forward. This review provides important guidance for designing novel and intelligent wearable temperature-sensing systems.

A polyphosphonate (PDPA) flame retardant that contains phenyl phosphonic dichloride and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide groups, has been synthesized. The flame retardant was introduced into epoxy resins (EP) and cured by 4,4’-diamino diphenylmethane. The vertical burning, limited-oxygen index and cone calorimeter tests reveal that the PDPA can enhance the flame-retardant properties of the EP significantly. With only a 4 wt% PDPA loading, the EP composites achieved a limited-oxygen index value of 33.4% and a V-0 rating in the vertical burning test, and the peak heat release rate and total heat release were decreased by 40.9% and 24.6%, respectively. The thermal properties and gas pyrolysis products of the EP composites were evaluated by thermogravimetric analysis and thermogravimetric analysis-Fourier transform infrared spectroscopy, and the morphology and structure of residual char were characterized by scanning electron microscopy, Flourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. To explain the combined effects of the condensed and gas phases, modes of the flame-retardant action are proposed.

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