In this work, 12-tungestocobaltic acid based organic–inorganic hybrid material, [Bmim]₆CoW₁₂O₄₀ (CoW) was synthesized and applied as a synergist in polypropylene (PP)/intumescent flame retardant (IFR) composites. The flame retardant properties were investigated by the limiting oxygen index (LOI), UL-94 vertical burning test, thermal gravimetric analyzer (TGA), cone calorimeter and scanning electron microscopy (SEM) etc. The results showed that the PP composites with 16 wt% IFR and 1 wt% CoW achieves the UL-94 V-0 rating and gets a LOI value 28.0. However, only add no less than 25 wt% single IFR, can the PP composites obtain the UL-94 V-0 rating, which suggests that CoW has good synergistic effects on flame retardancy of PP/IFR composites. In addition, the SEM and cone calorimeter tests indicated the CoW improves the quality of char layer. The rate of char formation has been enhanced also because of the existence of CoW. It is the combination of a better char quality and a high rate of char formation promoted by CoW that results in the excellent flame retardancy of PP/IFR composites. Copyright © 2016 John Wiley & Sons, Ltd.

In this paper, thermoplastic phenol formaldehyde (PF) grafted cyclic neopentyl phosphate (PFCP) was synthesized by using PF and 2,2-dimethyl-1,3-propanediol phosphoryl chloride. It was characterized by Fourier transform infrared spectroscopy (FTIR), 1H and 31P nuclear magnetic resonance (NMR). Compared to PF, PFCP shows improved thermal and thermoxidative stability and allows itself to be used in polyamide 6 (PA6). A micro-intumescent flame retardant system was constructed by using cyclic neopentyl phosphate as acid source, PF as charring agent and PA6 whose decomposition products work as blowing agent. The results showed that PA6/PFCP composite is classified the UL-94 V-0 rating and get a LOI value of 35.5% at 25% loading of PFCP. SEM results showed that the outside of char residues is continuous and dense, but the inside is micro-intumescent and porous. XPS analysis of char revealed that most of phosphorus remained in the char layer. All the results suggest that the mode of flame retardant's action for PA6/PFCP composites is shifted from melting away to charring protection with the content of PFCP increasing. The coherent char generated by the decomposition of PFCP contributes most to flame retardancy of PA6. Copyright © 2016 John Wiley & Sons, Ltd.

Aluminum hypophosphite (AHP) was introduced into polylactide/intumescent flame retardant (PLA/IFR) systems by melt blending. The flame retardant and thermal properties of the PLA composites were investigated. The results suggest that a synergistic effect exists between IFR and AHP on the char formation and anti-dripping behavior of PLA composites. The PLA/IFR composites containing 10 wt% IFR can pass the UL-94 V-0 rating but the test is accompanied by heavy melt dripping. For the PLA/AHP a UL-94 V-2 rating is obtained for the same loading of IFR. However, the composites containing 7 wt% IFR and 3 wt% AHP pass the UL-94 V-0 rating with modified dripping behavior. Moreover, the char from combustion of PLA/IFR is flexible but of poor quality. That for PLA/AHP is brittle with many cracks. In contrast, that for PLA/IFR/AHP is strong and compact. Thus it can resist the erosion due to heat and gas formation and protect the inside of the matrix. In addition, AHP causes the crosslinking among APP, which promotes the char formation and prevents the melt dripping. This is the main reason for the good flame retardant properties of PLA composites. Copyright © 2015 John Wiley & Sons, Ltd.

Three kinds of organic intercalation agent containing flame retardant groups, melamine (MA), triphenylphonium (TPP) chloride, and tetradecyl trihexyl phosphonium (TTP) bromide were intercalated into montmorillonite (MMT) via cation exchange reactions. These modified MMTs are combined with intumescent systems and compounded with PP. The flame retardant and thermal properties of the PP composites are studied. The organic intercalation agents in the layers of MMT play important roles in the char formation and flame retardant properties of PP composites. MA shows a better performance in limiting oxygen index (LOI) value and TPP helps to increase UL-94 properties, whereas TTP maintains or deteriorates the flame retardancy of polypropylene/intumescent flame retardant (IFR) composites. The LOI and UL-94 properties increase firstly and then decrease as the content of MMT increases. The MA acts as a blowing agent and emits an inert gas to provide migration impetus, which results in a better intumescent structured and stronger char to endure heat erosion. Although TPP and TTP emit combustible gas that burn, especially for TTP as it has a more flammable aliphatic chain. The synergistic effect between MA-MMT and IFR is better than that for TPP-MMT and TTP-MMT. Copyright © 2014 John Wiley & Sons, Ltd.

A novel phosphorus-containing poly (ethylene terephthalate) (PET) copolyester/nano-SiO₂ composite (PET-co-DDP/SiO₂) was synthesized by in situ polycondensation of terephthalic acid (TPA), ethylene glycol (EG), [(6-oxide-6H-dibenz[c,e] [1,2]oxaphosphorin-6-yl)-methyl]-butanedioic acid (DDP), and nano-SiO₂. The morphology of PET nanocomposites was observed by using transmission electron microscope and scanning electron microscope. It was found that the SiO₂ nanoparticles were dispersed uniformly at nanoscale in the copolyesters with content 2 wt %. The thermal degradation behavior of PET nanocomposites was investigated by thermogravimetric analysis performed with air and nitrogen ambience. The activation energies of thermal degradation were determined using Kissinger and Flynn–Wall–Ozawa methods, respectively. The results obtained from Kissinger method showed that the activation energy was increased with the introduction of SiO₂. Moreover, the activation energy is decreased for PET-co-DDP system in nitrogen and air. The results also indicated that the SiO₂ and DDP had synergic effect on the early decomposition and the late charring in air. Furthermore, in the PET-co-DDP/SiO₂ system, the activation energy increased when the DDP component increased. However, the opposite results were obtained when the Flynn–Wall–Ozawa method was used. That was because the Doyle approximation stands correct as the conversion degree is from 5% to 20%. The effects of SiO₂ and DDP on the PET thermal degradation were lower in nitrogen than in air. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

A hyperbranched polyamine was prepared using an A₂ + B₃ approach. It acted as a hyperbranched charring and foaming agent (HCFA) in combination with ammonium polyphosphate (APP) to form a new intumescent flame retardant (IFR) system for polyamide 6 (PA6). Effect of HCFA on flame retardant and thermal degradation properties of IFR-PA6 was investigated by limiting oxygen index (LOI), UL-94 vertical burning, cone calorimeter, and thermogravimetric analysis (TGA) tests. The IFR system presented the most effective flame retardancy in PA6 when the weight ratio of APP to HCFA was 2:1. The LOI value of IFR-PA6 could reach 36.5 with V-0 rating when the IFR loading was 30 wt%. Even if the loading decreased to 25 wt%, IFR-PA6 could still maintain V-0 rating with an LOI value of 31. TGA curves indicated that APP would interact with both PA6 and HCFA in PA6/APP/HCFA composite under heating. The interaction between APP and HCFA improved the char formation ability of IFR system and then much more char was formed for PA6/APP/HCFA composite than for PA6/APP. Therefore, better flame retardancy was achieved. Moreover, the structure and morphology of char residue were studied by Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The results indicated that compact and foaming char layer containing P-O-C structure was formed for PA6/APP/HCFA system during combustion. Copyright © 2010 John Wiley & Sons, Ltd.

Melamine-modified montmorillonite (MA-MMT) was prepared via cation exchange. The intercalation behavior was investigated by Fourier transform infrared spectrometer (FT-IR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The results showed that the d-spacing value increased from 1.25 nm for Na-montmorillonite (Na⁺MMT) to 1.53 nm for MA-MMT. Different kinds of montmorillonite combined with melamine pyrophosphate (MPP) were used to prepare flame-retardant polyamide 6 (FR-PA6). Flame retardance of FR-PA6 samples was investigated by limiting oxygen index (LOI), UL-94 vertical burning method, and cone calorimeter test. Morphology and component of char residues for FR-PA6 were investigated by scanning electron microscope (SEM) and XPS. It was found that MA-MMT/MPP system contributed both excellent flame retardance and anti-dripping ability for PA6. MA-MMT particles can fill flaws of char residues and strengthen the char layer, leading to form more intumescent char layer. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers