Rigid polyurethane foam (RPUF) composites filled with expandable graphite (EG), hollow glass microspheres (HGM), and glass fibers (GF) have been synthesized and characterized by limiting oxygen index, radiation ignition, compressing and torsion testing, and scanning electron microscopy. The results indicate HGM and GF benefit to the mechanical properties, while EG is good for flame retardancy. Proper ingredient of additive can lead to good flame retardancy and mechanical properties of the RPUF. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40253.

In this article, a flame retardant microcapsule ammonium polyphosphate microencapsulated by polyurea (POAPP) was successfully synthesized by interfacial polymerization method using ammonium polyphosphate (APP) as core and polyurea as shell. The microencapsulation is observed by scanning electron microscopy and characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis and hydroscopicity test, which prove the success in synthesizing microencapsulation. When the POAPP is added into rigid polyurethane foam (RPUF), the flame retardant and mechanical properties are investigated using cone calorimeter, limited oxygen index test, and compressive strength test. The PHRR of RPUF‐POAPP20 decreased from 336.52 kW/m2 (Ref. RPUF) to 203.84 kW/m2 and the THR of RPUF‐POAPP20 was only 7.6 MJ/m2, which is 33.9% lower than that of Ref. RPUF. Furthermore, the limiting oxygen index of RPUF‐POAPP20 reaches 24.8%, which increased by 36.3% compared to Ref. RPUF. Whereas the maximum compressive strength of RPUF‐POAPP5 was 7.46 MPa, which is higher than that of RPUF‐APP5.

Nowadays, reducing the fire hazard and improving the mechanical strength of rigid polyurethane foams (RPUFs) at the same time are important research direction in the fields of safety materials. Expandable graphite (EG) is an effective flame retardant for RPUF, but would destroy the compatibility of the matrix. In this article, EG is capsuled by melamine cyanurate (MCA) and then microencapsulated expandable graphite (MCEG) is obtained, which is added into RPUF. The mechanical properties of composites were evaluated by compressive strength test, torsion strength test and shear stress test. The fire characteristics including smoke and heat production of RPUF composites were studied using cone calorimeter test. And the thermal decomposition and flammable properties were further evaluated using thermogravimetric analysis and limiting oxygen index. The results show that the mechanical properties of RPUF containing MCEG are similar with RPUF and better than RPUF containing EG. Furthermore, MCA cover would impede expanding of EG, which weakens the protective and insulation effects of expanding layer. Therefore, the composites containing MCEG decompose faster and produce more smoke than the composites containing EG. However, MCA and EG have the synergistic enhancing effect on the flame retardant property of composite. POLYM. COMPOS., 40:E1006–E1014, 2019. © 2018 Society of Plastics Engineers

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Ammonium polyphosphate (APP) is an effective phosphorus‐containing flame retardant. But APP also has excellent hygroscopic capacity and decreases the mechanical property of composite. The aim of the study was to microencapsulate APP with polymethyl methacrylate (PMMA) to prepare microencapsulated ammonium polyphosphate (PMAPP) in order to eliminate the harmful effects caused by the mechanical property of composite. The microcapsules are characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), and hydroscopicity test and observed by scanning electron microscopy (SEM). Fire hazard of rigid polyurethane foam (RPUF) is evaluated using a cone calorimeter and limited oxygen index test. The mechanical property of RPUF is studied by compressive strength test. The results show that APP has been microencapsulated by PMMA successfully and the shell does not decrease the beneficial effect of APP on fire hazard of RPUF. Furthermore, the shell also reduces the damage of APP on the mechanical property of composite. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48307.

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In order to reduce the fire risk of rigid polyurethane foams (RPUF), three kinds of zeolitic imidazolate frameworks (ZIFs) were prepared. The results of Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM and X-ray diffraction (XRD) showed that ZIFs were successfully prepared. The combustion test results showed that the heat and smoke production of the composite containing ZIFs was obviously reduced. In particular, the peak heat release rate (PHRR) of ZIF-8/RPUF decreased from 740.85 kW/m2 (Ref. RPUF) to 489.56 kW/m2, while the PHRR of ZIF-7/RPUF and ZIF-11/RPUF is 598.39 and 583.36 kW/m2, respectively. The addition of ZIFs improved the thermostability of the composite. The T50% of ZIF-8/RPUF, ZIF-7/RPUF and ZIF-11/RPUF increased to 364, 382 and 380 °C, respectively. The maximum light absorption of ZIF-7/RPUF and ZIF-11/RPUF was about 88%, which is higher than that of ZIF-8/RPUF (75%). The results of Raman spectroscopy showed that the ID/IG value of Ref. RPUF is 2.96, while the ID/IG value of ZIFs/RPUF reduces to less than 2.80. The main mechanism of ZIFs for reducing the fire risk of RPUF was the catalysis and incarbonization of ZIFs during combustion based on the results of thermogravimetric analysis and Raman spectroscopy of char residue.

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