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A nanorod-structured strontium hydroxystannate [SrSn(OH)6] flame retardant was synthesized via a facile coprecipitation method and employed in epoxy resin (EP). Based on X-ray diffraction analysis, scanning electron microscopy, and transmission electron microscopy, the as-synthesized SrSn(OH)6 nanorods exhibited high crystallinity and uniform size distribution. The flame retardancy and smoke suppression properties of EP/SrSn(OH)6 composites were investigated by limiting oxygen index and cone calorimetry tests. The results showed that incorporation of SrSn(OH)6 led to a dramatic reduction of the fire hazards of EP, including a 21.9% maximum decrease in the peak heat release rate, a 33.3% reduction in the toxic CO yield, and a 133.3% increase in the char residue. In particular, this is the first attempt to evaluate the flame retardancy properties of SrSn(OH)6 nanorods in EP. The improved flame retardancy properties of the SrSn(OH)6 nanorods is attributed to their catalytic carbonization effect. [ABSTRACT FROM AUTHOR]

Abstract: In this work, a reactive polymeric intumescent flame retardant (PDSPB) was synthesized and applied to ABS resin. The flame retarded materials were prepared by direct melt blending of ABS and PDSPB (ABS/PDSPB), as well as melt cross-linking of PDSPB to ABS (ABS-c-PDSPB). The cross-linking reaction was characterized by fourier transform infrared spectrometry (FTIR) and gel content measurement. The thermal stability, flame retardancy, carbonization chemistry and dynamic mechanical properties were investigated by TGA, dynamic FTIR, SEM, CONE calorimetry and dynamic mechanical analysis (DMA). The results showed that the addition of PDSPB can effectively reduce the flammability properties including peak heat release rate (PHRR), total heat release (THR) and average mass loss rate (AMLR). An improvement of the limited oxygen index value was also observed. Especially, the cross-linking of PDSPB can improve the ignition time and reduce THR during combustion. Moreover, ABS-c-PDSPB displayed a more obvious intumescent char layer and char weight than that of ABS/PDSPB blends. Furthermore, cross-linking of PDSPB enhanced the thermal stability and considerably delayed the thermal oxidation degradation of ABS. The dynamic mechanical properties were improved and the plasticization effect was reduced by cross-linking of PDSPB. [Copyright &y& Elsevier]

Recent advances in flame retardant polymers have centered on the flame retardancy of nano-fillers contained polymer nanocomposites. Among which, organo-clay (OMMT), layered double hydroxides (LDHs), polyhedral oligomeric silsesquioxane (POSS), and carbon nanotubes (CNTs) have been reported and proved to be effective flame retardants for variable polymers. In this paper, a systematical study was executed on flame retarded polypropylene (PP) composites containing intumescent flame retardant (IFR) and the most popular nano-fillers. Dispersion of the nano-fillers was characterized by using transmission electron microscopy (TEM), the results revealed that all nano-fillers dispersed homogeneously in PP matrix. The effects of nano-fillers on thermal stability and flammable of PP were investigated by thermogravimetry (TG) and cone calorimetry tests, respectively. The results indicated that different nano-fillers played different roles in thermal and flammability properties of composites. PP composites with OMMT gave the best reductions in heat release rate (PHRR) and endowed PP with relatively better flame retardancy. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: A melt blending method was used to prepare ABS/clay and ABS-g-MAH/clay nanocomposites. Cone calorimeter and advanced rheological extension system (ARES©) were employed to measure flammability and dynamic rheological properties. The main aim is to establish a relationship between the clay network structure and flammability properties of polymer nanocomposites. From the results of dynamic rheological measurements, it was found that the clay network structure was formed in ABS-g-MAH/clay nanocomposites, which strongly affected the flammability properties of the nanocomposites. The clay network improves the melt viscosity and results in restraint on the mobility of the polymer chains during combustion, which leads to significant improvement of flame retardancy for the nanocomposites. [Copyright &y& Elsevier]

Abstract: A novel phosphorous–nitrogen structure containing intumescent flame retardant, poly(4,4-diaminodiphenyl methane spirocyclic pentaerythritol bisphosphonate) (PDSPB) was synthesized and characterized. Thermal stability and flammability properties of ABS/PDSPB composites were investigated by thermogravimetric analysis (TGA) and cone calorimeter test, respectively. The results showed that the addition of PDSPB enhanced the thermal stability and flame retardancy of ABS significantly. The weight of residues improved greatly with the addition of PDSPB. FTIR and SEM investigations revealed that the residual chars contain polyphosphoric or phosphoric acid, which plays an important role in the process of carbonization. The intumescent chars formed from PDSPB and ABS/PDSPB composites were intact, multicellular and strong. It is confirmed that the char structure was a critical factor for flame retardancy of ABS resin. [Copyright &y& Elsevier]

Abstract: ABS-g-MAH (maleic anhydride) with different grafting degree, ABS/OMT (organo montmorillonite) and ABS-g-MAH/OMT nanocomposites were prepared via melt blending. The grafting reaction, phase morphology, clay dispersion, thermal properties, dynamic mechanical properties and flammability properties were investigated. FTIR spectra results indicate that maleic anhydride was successfully grafted onto butadiene chains of the ABS backbone in the molten state using dicumyl peroxide as the initiator and styrene as the comonomer and the relative grafting degree increased with increasing loading of MAH. TEM images show the size of the dispersed rubber domains of ABS-g-MAH increased and the dispersion is more uniform than that of neat ABS resin. XRD and TEM results show that intercalated/exfoliated structure formed in ABS-g-MAH/OMT nanocomposites and the rubber phase intercalated into clay layers distributed in both SAN phase and rubber phase. TGA results reveal the intercalated/exfoliated structure of ABS-g-MAH/OMT nanocomposites has better barrier properties and thermal stability than intercalated ones of ABS/OMT nanocomposites. The T g of ABS-g-MAH/OMT nanocomposites was also higher than that of neat ABS/OMT nanocomposites. The results of cone measurements show that ABS-g-MAH/OMT nanocomposites exhibit significantly reduced flammability when compared to ABS/OMT nanocomposites even at the same clay content. The chars of ABS-g-MAH/OMT nanocomposites were tighter, denser, more integrated and fewer surface microcracks than ABS/OMT residues. [Copyright &y& Elsevier]

High global warming potential (GWP) refrigerants for refrigeration and heat pump systems or organic Rankine cycle systems are being phased out because of their impact on climate change, such as R134a, R410A and R404A. So it is urgent to find the refrigerants with excellent environmental protection performance. Firstly, nearly 40 alternative refrigerants, including pure refrigerants and mixed refrigerants, are classified according to their environmental and safety characteristics. Secondly, the performance parameters of some typical alternatives, such as refrigerating capacity, COP, safety and environmental protection, are comprehensively compared. It can be concluded that R513a and R466A have good comprehensive performance as alternative refrigerants of R134a and R410A respectively, while those alternatives to R404A have both advantages and disadvantages. The application and technical characteristics of R32, some typical HFOs, natural refrigerants and mixtures are summarized and analyzed. In addition, our group has carried out experimental and theoretical research on the flammability of low GWP and flammable refrigerants such as R1234yf, R161, R290, R600a and R1150, and found that hydrocarbons are more difficult to be inhibited than halogenated hydrocarbons. Finally, a new research idea on the risk of refrigerant explosion is put forward, which can cover the refrigerant leakage, combustion and risk aversion. [ABSTRACT FROM AUTHOR]

• The flammability limits of R134a, R1234ze(E) and R13I1 mixed with R32 were tested. • The suppression effect of R134a, R1234ze(E) and R13I1 to R32 was researched. • The chemical inhibition mechanism of the three flame-retards was analyzed. R-32 (difluoromethane) has got much attention as an alternative for R-22 (chlorodifluoromethane) or R-410A with excellent thermodynamic property. However, R-32 is flammable, and also has been listed in the Kigali Amendment for relatively high global warming potential (GWP). To make up for the shortcomings, it is necessary to research the reduction of the flammability and GWP of R-32 by developing the mixtures of R-32. In this paper, the flammability characteristics of R-32 mixed with R-134a (1,1,1,2-tetrafluoroethane), R-1234ze(E) (trans-1,3,3,3-tetrafluoroprop-1-ene) and R-13I1 (trifluoroiodomethane) were experimentally studied. The flammability limits of the three mixtures were measured in a 12 L spherical glass flask according to ASHRAE method, and the flame-retarding effect of the three retardants was researched. The test results showed that the flame inhibition effect of R-13I1 was better than that of R-134a and R-1234ze(E). The inhibition effect of R-1234ze(E) was the worst, which would not completely suppress the flammability of R-32. The minimum inerting concentrations of R-134a and R-13I1 on R-32 were about 28.6% and 13.8%, respectively. Besides, the chemical inhibition mechanism of the three flame-retards was analyzed. The results will provide a comprehensive understanding of R-32 and its mixtures in combustibility hazard, flame retardant mechanism and environmental protection. [Display omitted] [ABSTRACT FROM AUTHOR]