Epoxy resin flame retarded and toughed via flexible siloxane chain containing phosphaphenanthrene

• Published in: Polymer degradation and stability 2020-02, Vol.172, p.109055, Article 109055
• Main Authors: Bao, Qiuru, Wang, Biwu, Liu, Yuan, Wang, Qi, Yang, Zhongqiang
• Format: Article
• Language: English
• Subjects: Chains; Cone calorimeters; Differential scanning calorimetry; Epoxy resin; Epoxy resins; Flame retardancy; Flame retardants; Flammability; Gravimetric analysis; Impact strength; Macromolecules; Phosphaphenanthrene; Siloxanes; Stability analysis; Temperature; Tensile strength; Thermal degradation; Thermal stability; Toughening; Toughness
• ISSN: 0141-3910; 1873-2321
• DOI: 10.1016/j.polymdegradstab.2019.109055

In order to improve the flammability, and meanwhile increase the toughness of epoxy resin (EP), a flexible siloxane chain containing phosphaphenanthrene structure (KHDOPO) was chemically grafted onto epoxy resin macromolecules. Because of the polar phosphaphenanthrene group and the flexible siloxane chain interacting with the matrix, this modified epoxy resin (KHDOPO-EP) exhibited satisfactory flame retardancy and thermal stability. The thermal degradation and fire behaviors of KHDOPO-EP were systematically evaluated by thermo-gravimetric analysis (TGA), limiting oxygen index (LOI), vertical burning (UL-94) and cone calorimeter (CC) tests. The results showed that KHDOPO-EP achieved V-0 rating in UL-94, with the LOI value of 33.1%. Furthermore, the introduced flexible siloxane chain effectively maintained the toughness of the flame retardant EP, whose tensile strength and impact strength were as high as 71.7 MPa and 15.56 kJ/m2 respectively, much higher than those of neat EP, showing the characteristics of simultaneous toughening and strengthening. As an efficient flame retardant and flexibilizer, KHDOPO-EP possesses promising prospect in modification field of EP material. This work synthesized a flexible siloxane chain containing phosphaphenanthrene structure (KHDOPO), which was chemically grafted onto epoxy resin macromolecules. Due to the synergistic effect of P and Si, the modified epoxy resin (KHDOPO-EP) exhibited satisfactory flame retardancy and thermal stability, as well as excellent mechanical properties. [Display omitted] •The liquid flame retardant was beneficial to improve the homogenous dispersion.•KHDOPO-EP exhibited good flame retardancy due to the flame retardant effect of P and Si.•KHDOPO showed the characteristics of simultaneous toughening and strengthening.