Fig. 5. Mechanical and comprehensive performance.

a Tensile stress, strain, and b toughness. c Compression resilience. d–f SEM images for the tensile fracture of pure FPUF, PUFF/K-formate, FPUF/K-malate, respectively. g Comparison of K-formate filled FPUF with other recently reported flame-retardant FPUF samples in terms of filler loading, fire safety performance, tensile stress variation, tensile strain variation, and environmental protection^54–60. All error bars represent a particular confidence interval.