A phenethyl‐bridged DOPO derivative (DiDOPO) is combined with polytetrafluoroethylene (PTFE) in thermoplastic polyurethane (TPU). The flame retardancy and thermal stability of TPU/PTFE/DiDOPO composites with different weight percentages of DiDOPO are investigated by using limiting oxygen index (LOI), UL‐94 test, cone calorimetry test (CCT), scanning electronic microscopy (SEM), energy‐dispersive spectrometry, and thermogravimetric analysis (TGA). With the incorporation of 8 wt% DiDOPO, the LOI value of TPU/PTFE/DiDOPO composites increases to 34.0% from 25.4% of TPU, and the V‐0 rating level is achieved. The CCT results indicate that the peak heat release rate and total heat release of TPU/PTFE/DiDOPO composites decrease due to the addition of DiDOPO and PTFE. The thermal decomposition process of TPU is changed due to the present of DiDOPO and PTFE. Based on this, the Flynn–Wall–Ozawa method for the determination of characteristic degradation kinetics parameters is evaluated. SEM results and residues from TGA curves show that the addition of DiDOPO promotes the increase in the char layer and a crosslinked char coating exists after burning. The flame‐retardant mechanism is flame inhibition. Overall, these findings indicate that the combination of DiDOPO with PTFE in TPU is an effective way in developing high‐performance resins with attractive flame retardancy. POLYM. ENG. SCI., 59:1593–1602 2019. © 2019 Society of Plastics Engineers

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In this work, a novel fiber treatment method is introduced in the preparation of epoxy soybean oil (ESO) toughened jute fiber/polypropylene (PP) matrix composites. The jute fibers are pre‐treated by r‐valerolactone (GVL), and the ESO/jute fiber/PP composites are fabricated by melt blending. The microstructure of the treated fiber, the mechanical properties, thermal stability, and crystallization behaviors of the composites are investigated and discussed in detail. The results show that the surface of GVL treated fiber becomes rough and the aspect ratio increases. It is found by scanning electron microscopy (SEM) that the interface between the fiber and matrix debones seriously without the addition of ESO. With increasing the content of ESO, the toughness and thermal stability of the composites are gradually improved. The tensile strength of the composites containing 5% ESO reaches 42.2 MPa. In addition, the impact strength and elongation at break are higher than pure PP and PP/jute composites. Moreover, GVL treated fibers can improve the thermal stability of PP/jute fiber composites. In addition, the crystallinity of PP in the PP composites increases first and then decreases, while the crystallization temperature of the composites decreases. At the same time, the complex viscosity of the composites also increases.

In this work, the effect of thermo-oxidative aging on organic montmorillonite/intumescent flame retardant/long glass fiber–reinforced polypropylene composites was investigated for different exposure times at 140°C. Limiting oxygen index, Underwriters Laboratories-94 tests, cone calorimeter test, and thermogravimetric analysis were used to evaluate the flammability and thermal stability. The results of limiting oxygen index values, Underwriters Laboratories 94 test, and cone calorimeter test show that aging performs negative effect on the flame retardancy of organic montmorillonite/intumescent flame retardant/long glass fiber–reinforced polypropylene composites. Thermal oxidation aging markedly changes the decomposition process of organic montmorillonite/intumescent flame retardant/long glass fiber–reinforced polypropylene composites. The scanning electronic microscopy images of the external surface of composites indicate that many ground particles and micro-scale cracks are scattered in the surfaces of the composites after aging. The sharp micro-scale cracks and crazing formed on the surface promote the heat and oxygen to penetrate into the bulk of polypropylene matrix. According to the mechanical test results, the thermal oxidation aging reduces the tensile, flexural, and notched impact strengths of organic montmorillonite/intumescent flame retardant/long glass fiber–reinforced polypropylene composites.

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