Flame‐retardant and thermal degradation mechanism of low‐density polyethylene modified with aluminum hypophosphite and microencapsulated red phosphorus

Aluminum hypophosphite (AHP), a novel flame retardant, was used to improve the flame retardancy of low‐density polyethylene (LDPE) with microencapsulated red phosphorus (MRP). The synergistic effect between MRP and AHP was investigated by the limiting oxygen index (LOI), vertical burning test (UL‐94), and thermogravimetric analysis. When the contents of MRP and AHP were 10 and 30 phr, the LOI of LDPE/10MRP/30AHP composite was 25.5%, and it passed the UL‐94 V‐0 rating (the number before “MRP” and “AHP” is the loading of MRP and AHP, In LDPE/10MRP/30AHP, the content of the LDPE, MRP and AHP is 100phr, 10phr and 30phr, where phr refers to parts per hundreds of resin). The results of cone calorimetry testing show that the heat release rate of the composites was significantly reduced, and the strength of the char layer improved when the loading of AHP increased. The thermal stability of the LDPE/10MRP/30AHP composite was enhanced. The structure of the char was investigated by Fourier transform infrared spectrometry and scanning electron microscopy/energy‐dispersive spectrometry. The results indicate that AHP promoted the formation of stable char. This research provided a good way to prepare flame‐retardant materials with a halogen‐free flame retardant and contributed to environmental protection. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43225.     

Combustion characteristics and synergistic effects of red phosphorus masterbatch with expandable graphite in the flame retardant HDPE/EVA composites

In this work, the flammability behaviors and synergistic effects of red phosphorus masterbatch (RPM) with expandable graphite (EG) in flame‐retardant high‐density polyethylene/ethylene vinyl‐acetate copolymer (HDPE/EVA) composites have been investigated by limiting oxygen index (LOI), UL‐94 test, cone calorimeter test (CCT), thermogravimetric analysis (TGA), Fourier‐transform infrared (FTIR) and scanning electron microscopy (SEM). The data obtained from LOI, UL‐94 test and CCT showed that suitable amount of RPM had synergistic effects with EG in the HDPE/EVA/EG/RPM composites. The addition of RPM greatly increased the LOI values by 3.4%, obtained UL‐94 V‐0 rating, decreased the heat release rates and total heat release, and prolongated the ignition time when 6.7 phr RPM substituted for EG in the HDPE/EVA/EG/RPM composites. The data from TGA and FTIR spectra also indicated the synergistic effects of RPM with EG considerably enhanced the thermal degradation temperatures. The morphological observations after UL‐94, CCT, and SEM images presented positive evidences that the synergistic effects took place for RPM with EG, and the flame‐retardant mechanism has been changed in flame‐retardant HDPE/EVA/EG/RPM composites. The formation of stable and compact charred residues promoted by RPM acted as effective heat barriers and thermal insulations, which improved the flame‐retardant performances and prevented the underlying polymer materials from burning. POLYM. ENG. SCI., 55:2884–2892, 2015. © 2015 Society of Plastics Engineers     

MRP/MH/EG协同阻燃HDPE的性能研究

以微胶囊化红磷(MRP)、氢氧化镁(MH)及可膨胀石墨(EG)为阻燃剂,采用熔融挤出法制备了多组高密度聚乙烯(PE-HD)阻燃复合材料。采用氧指数测试、垂直燃烧测试、红外光谱分析、激光拉曼光谱分析、热重-差热分析、扫描电子显微镜分析及拉伸性能测试等方法对复合材料的阻燃性能、热稳定性、力学性能和断面的微观形貌进行了研究,并探讨了阻燃机理。结果表明,单独使用EG时阻燃效果差,但将EG与MRP、MH复配使用能有效改善材料的阻燃性能;当PE-HD/MH /MRP /EG = 100/35/15/5(质量份,下同)时,复合材料的氧指数为28.5 %,垂直燃烧达到UL 94 V-0级,而阻燃剂的加入对材料拉伸性能的影响并不是很大;SEM分析表明, EG与PE-HD基材有很好的相容性,而MRP或MH与PE-HD基材的相容性较差。     

Low‐temperature synthesis of Mg(OH)2 nanoparticles from MgO as halogen‐free flame retardant for polypropylene

Mg(OH)₂ (MH) nanoparticles were synthesized by hydration of the light‐burned MgO at low temperature (70°C). Effects of additives, such as magnesium nitrate and magnesium acetate, on the size, morphology and agglomeration of MH particles were investigated. MH nanoparticles have platelet‐like structure and approximately 20–40 nm in thicknesses. The supersaturation degree plays an important role in magnesia hydration and is defined. When magnesium acetate was used as the additive, the hydroxyl ion can be homogeneously introduced into the solution. The size and morphology of MH nanoparticles are more homogeneous. Modified by titanate coupling agent, MH nanoparticles were used as the flame retardant for polypropylene (PP). The combustibility, mechanical properties and thermal behaviors of the PP/MH composites were characterized. The mechanical properties of PP/MH composites are not seriously deteriorated with increasing MH content. When the amount of MH fraction reached 65, the limiting oxygen index (LOI) value and UL 94 testing result of MH65 are 33.8 and V‐0 grading, respectively. The onset temperature (T_10%) and the maximum thermal decomposition temperature (T_max) of MH65 separately increased by approximately 100°C and 77°C than those of neat PP. Copyright © 2012 John Wiley & Sons, Ltd.     

Synergistic effects of expandable graphite with magnesium hydroxide on the flame retardancy and thermal properties of polypropylene

In this study, the flammability characterization and synergistic effects of different particle size of expandable graphite (EG) with modified magnesium hydroxide (MH) in flame‐retardant polypropylene (PP) composites were studied by limiting oxygen index (LOI), UL‐94 test, thermogravimetric analysis (TGA), and fourier transform infrared (FTIR) spectroscopy. The results showed that the particle size of EG had a great effect on the flammability of the PP/MH/EG composites. The EG2 with smaller particle size could apparently increase the LOI value and improved the UL‐94 flammability properties rating of the PP composites. The data obtained from the TGA and FTIR curves indicated that the thermo‐oxidative stability of PP/MH/EG composites increased with decreasing particle size of EG. And the smaller the particle size of EG, the higher the residues of the composite. POLYM. ENG. SCI., 47:1756–1760, 2007. © 2007 Society of Plastics Engineers     

Flame retardation and thermal degradation of flame‐retarded polypropylene composites containing melamine phosphate and pentaerythritol phosphate

The flame retardation of polypropylene (PP) composites containing melamine phosphate (MP) and pentaerythritol phosphate (PEPA) was characterized by limiting oxygen index (LOI) and UL 94. The morphology of the char obtained from the combustion of the composites was studied by scanning electron microscopy (SEM). The thermal degradation of the composites was investigated using thermogravimetric (TG) analysis and real‐time Fourier transform infrared (RTFTIR) spectroscopy. It has been found that the PP composites containing only MP do not show good flame retardancy even at 40% additive level. Compared with the PP/MP binary composites, all the LOI values of the PP/MP/PEPA ternary composites at the same additive loading increase, and UL 94 ratings of the ternary composites at suitable MP/PEPA ratios are raised to V‐0 from no rating (PP/MP). The TG and RTFTIR studies indicate that the interaction occurs among MP, PEPA and PP. Copyright © 2008 John Wiley & Sons, Ltd.     

An easy‐to‐obtain silicone‐containing flame retardant and its effects on the combustion of polycarbonate

A novel silicone‐containing flame retardant (HSOBA) synthesized from hydrogen‐containing silicone oil and Bisphenol A via a simple approach has been incorporated into polycarbonate (PC) matrix to study its effects on the flame retardancy. The flame retardancy of PC/HSOBA composites is investigated by limiting oxygen index (LOI), vertical burning tests (UL‐94), and cone calorimeter measurement. The LOI value of the composites is 31.7 and the UL‐94 rating reaches V‐0, when the content of HSOBA is 3 wt %. Cone calorimeter data confirm that the HSOBA acts as an effective additive functioning both as flame retardants and as smoke suppressant. Evolution of the thermal behaviors of the composites tested by TGA, the morphological structures, and the constituent of char residue after LOI tests characterized by scanning electronic microscopy‐energy‐dispersive X‐ray analysis were used to explain the possible flame‐retardant mode. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Flammability and thermal degradation of intumescent flame‐retardant polypropylene composites

The flammability of polypropylene (PP) composites containing intumescent flame‐retardant additives, i.e., melamine pyrophosphate (MPP) and 1‐oxo‐4‐hydroxymethyl‐2,6,7‐trioxa‐1‐phosphabicyclo[2.2.2]octane (PEPA) was characterized by limiting oxygen index (LOI), UL 94 test, and cone calorimeter. In addition, the thermal degradation of the composites was studied using thermogravimetric analysis (TG) and real‐time Fourier transform infrared (RTFTIR). It has been found that the PP composite only containing MPP (or PEPA) does not show good flame retardancy even at 30% additive level. Compared with the PP/MPP binary composite, the LOI values of the PP/MPP/PEPA ternary composites at the same additive loading are all increased, and UL 94 rating of the ternary composite (PP3) studied is raised to V‐0 rating from no rating (PP/MPP). The cone calorimeter results show that the heat release rate of some ternary composites decreases in comparison with the binary composite. It is noted from the TG data that initial decomposition temperatures of ternary composites are lower than that of the binary composites. The RTFTIR study indicates that the PP/MPP/PEPA composites have higher thermal oxidative stability than the pure PP. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Synthesis of a magnesium/aluminum/iron layered double hydroxide and its flammability characteristics in halogen‐free,flame‐retardant ethylene/vinyl acetate copolymer composites

Mg–Al–Fe ternary hydrotalcites were synthesized by a coprecipitation method and characterized with powder X‐ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The flame‐retardant effects of Mg/Al–CO₃ layered double hydroxides (LDHs) and Mg/Al/Fe–CO₃ LDHs in an ethylene/vinyl acetate copolymer (EVA) were studied with the limited oxygen index (LOI), the UL‐94 test, and the cone calorimeter test (CCT), and the thermal degradation behavior of the composites was examined by thermogravimetric analysis. The results showed that the LOI values of the EVA/(Mg/Al/Fe–CO₃ LDH) composites were basically higher than those of the EVA/(Mg/Al–CO₃ LDH) composites at the same additive level. In the UL‐94 test, there was no rating for the EVA/(Mg/Al–CO₃ LDH) composite at the 50% additive level, and a dripping phenomenon occurred. However, the EVA/(Mg/Al/Fe–CO₃ LDH) composites at the same loading level of LDHs containing a suitable amount of Fe³⁺ ion reached the V‐0 rating, the dripping phenomenon disappearing. The CCTs indicated that the heat release rate (HRR) of the EVA composites with Mg/Al/Fe–CO₃ LDHs containing a suitable amount of Fe³⁺ decreased greatly in comparison with that of the composites with Mg/Al–CO₃ LDHs. The introduction of a given amount of Fe³⁺ ion into Mg/Al–CO₃ LDHs resulted in an increase in the LOI, a decrease in the HRR, and the achievement of the UL‐94 V‐0 rating. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Influence of polyamide 6 as a charring agent on the flame retardancy,thermal, and mechanical properties of polypropylene composites

In this work, polyamide 6 (PA6) as a charring agent has been used in combination with thermoplastic polyurethane (TPU)‐microencapsulated ammonium polyphosphate (MTAPP) forming intumescent flame retardants (IFRs) which applies in polypropylene (PP). The effects of the IFRs on the flame retardancy, morphology of char layers, water resistance, thermal properties and mechanical properties of flame‐retardant PP composites are investigated by limiting oxygen index (LOI), UL‐94 test, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and mechanical properties test. The results show that the PP/MTAPP/PA6 composites exhibit much better flame‐retardant performances than the PP/MTAPP composites. The higher LOI values and UL‐94 V‐2 of the PP/MTAPP composites with suitable amount of PA6 are obtained, which is attributed to the thick and compact char layer structure evidenced by SEM. The results from TGA and DSC demonstrate that the introduction of PA6 into PP/MTAPP composites has a great effect on the thermal stability and crystallization behaviors of the composites. Furthermore, the mechanical properties of PP/MTAPP/PA6 composites are also improved greatly due to the presence of PA6 as a charring agent. POLYM. ENG. SCI., 55:1355–1360, 2015. © 2015 Society of Plastics Engineers     

The effect of morphology on the flame‐retardant behaviors of melamine cyanurate in PA6 composites

Three types of melamine cyanurate (MCA) with micrometer‐size sphere‐like, micrometer‐scale rod‐like, and nanometer‐scale flake‐like morphologies were synthesized by changing the chemical circumstances of the reactions. The microcosmic morphologies of MCA were characterized via scanning electron microscopy and X‐ray diffraction. After the MCAs with different morphologies were incorporated into polyamide 6 (PA6), the flame‐retardant properties of the MCA/PA6 composites were investigated using the limited oxygen index (LOI), UL94, and cone calorimeter tests. The MCA/PA6 composites with nanometer‐scale flake‐like MCA obtained an LOI value of 29.5% and a UL94 V‐0 rating, which were higher than those with micrometer‐size sphere‐like and rod‐like MCAs. However, the different morphologies did not affect the heat release rate, total smoke release, average carbon monoxide yield, and average carbon dioxide yield based on the cone calorimeter. The flame‐retardant mechanism of MCAs with different morphologies was investigated via thermal gravimetric analysis (TGA) and TGA‐Fourier transform infrared spectra. The results show that the different morphologies of MCA resulted in different dispersed evenness of MCA. Further, the nanometer‐scale flake‐like morphology of MCA brought more interactions of hydrogen bond between MCA and PA6, which resulted in the delay of MCA decomposition and the enhancement of MCA flame‐retardant effect. The nanometer‐scale flake‐like MCA had a better performance compared with the other samples because of the delaying and even release of flame‐retardant effect by the decomposition of evenly dispersed MCA. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40558.     

Flame‐retardant polycarbonate/acrylonitrile‐butadiene‐styrene based on red phosphorus encapsulated by polysiloxane: Flame retardance,thermal stability,and water resistance

Red phosphorus encapsulated by polysiloxane (MRP) was prepared, and the chemical structure and morphology of MRP were characterized by FTIR and TEM, respectively. A series of flame retardant polycarbonate/acrylonitrile‐butadiene‐styrene containing MRP (PC/ABS/MRP) were prepared via melt‐blending. The flame retardance of PC/ABS/MRP was investigated by limiting oxygen index (LOI) and UL‐94 test. It was shown that the LOI value was increased to 27.7 and UL‐94 achieved a V‐0 rating at a 15 wt % loading of MRP. Cone calorimetric results showed that the peak of heat release rate (PHRR) of PC/ABS/15% MRP decreased from 452.7 to 198.0 kW/m², and the total heat release decreased from 92.9 to 60.7 MJ/m² compared with virgin PC/ABS. Thermal stability analysis showed that the char yield of the PC/ABS/15% MRP increased from 0 to 16.1 wt % under air atmosphere, and from 15.2 to 27.4 wt % under nitrogen atmosphere compared to virgin PC/ABS, respectively. The sample PC/ABS/15% MRP also showed excellent water resistance of flame retardance in 70°C water for 168 h. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synergistic effect of metal oxides on the flame retardancy and thermal degradation of novel intumescent flame‐retardant thermoplastic polyurethanes

The synergistic effects of some metal oxides on novel intumescent flame retardant (IFR)–thermoplastic polyurethane (TPU) composites were evaluated by limiting oxygen index (LOI), vertical burning test (UL‐94), thermogravimetric analysis (TGA), cone calorimetry, and scanning electron microscopy. The experimental data indicated that the metal oxides enhanced the LOI value and restricted the dropping of the composites. The IFR–TPU composites passed the UL‐94 V‐0 rating test (1.6 mm) in the presence of magnesium oxide (MgO) and ferric oxide (Fe₂O₃) at 35 wt % IFR loading, whereas only the MgO‐containing IFR–TPU composite reached a UL‐94 V‐0 rating at 30 wt % IFR loading. The TGA results show that the metal oxides had different effects on the process of thermal degradation of the IFR–TPU compositions. MgO easily reacted with polyphosphoric acid generated by the decomposition of ammonium polyphosphate (APP) to produce magnesium phosphate. MgO and Fe₂O₃ showed low flammability and smoke emission due to peak heat release rate, peak smoke production rate, total heat release, and total smoke production (TSP). However, zinc oxide brought an increase in the smoke production rate and TSP values. Among the metal oxides, MgO provided an impressive promotion on the LOI value. The alkaline metal oxide MgO more easily reacted with APP in IFRs. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Flame retardant performance of a carbon source containing DOPO derivative in PET and epoxy

The combination of gas‐phase and condensed‐phase action will contribute to high quality flame retardant. A novel 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO)‐based flame retardant (DOPO‐DOPC), which contains carbon source was synthesized in favor of conducting the effect of gas‐phase as well as promoting the char formation in condensed‐phase. The chemical structure of DOPO‐DOPC was characterized by nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR). DOPO–DOPC was used as an additive in poly(ethylene terephthalate) (PET) and epoxy resin (EP). The flame retardancy of PET/DOPO‐DOPC and EP/DOPO‐DOPC composites were studied by limiting oxygen index (LOI) and UL‐94 test. The results showed that the incorporation of DOPO–DOPC into PET or EP could obviously improve their flame retardancy. The LOI values of modified PET or EP, which contained 10 wt % DOPO‐DOPC reached 42.8 and 31.7%, respectively. The thermogravimetric analysis (TGA) results revealed that DOPO–DOPC enhanced the formation of char residues. The Laser Raman spectroscopy (LRS) was used to investigate the carbon structure of thermal oxidation residues. Because of the combination of the gas phase flame retardant effect of DOPO moiety and the promoting formation of char residues in condensed phase, the PET and EP composites exhibited significant improvement toward flame retardancy. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44639.     

Synergistic flame retardant effects of ammonium polyphosphate in ethylene‐vinyl acetate/layered double hydroxides composites

Mg–Al–Fe ternary layered double hydroxides (LDH) were synthesized based on bayer red mud by calcination‐rehydration method, and characterized using X‐ray diffraction and thermogravimetric analysis (TGA). The synergistic flame retardant effects of ammonium polyphosphate (APP) with LDH in ethylene‐vinyl acetate (EVA) composites were studied using limiting oxygen index (LOI), UL 94 test, cone calorimeter test (CCT), and smoke density test (SDT). The thermal degradation behavior of EVA/LDH/APP composites was examined by thermal gravimetric analysis‐fourier transform infrared spectrometry (TG‐FTIR). The results showed that LOI values decreased by incorporation of APP together with LDH; and, a suitable amount of APP in EVA/LDH composites can apparently improve UL 94 rating. The CCT results indicated that heat release rate (HRR) of the EVA/LDH/APP composites with APP decreased in comparison with that of the EVA/LDH composites. The SDT results showed that APP was helpful to suppress smoke. The TG‐FTIR data showed that the composites with APP had a higher thermal stability than the EVA/LDH composites at high temperature. POLYM. ENG. SCI., 54:766–776, 2014. © 2013 Society of Plastics Engineers     

The flame retardant effect of aluminum phosphinate in combination with zinc borate,borophosphate, and nanoclay in polyamide‐6

The effect of zinc borate (ZnB), borophosphate (BPO₄), and organoclay were studied to improve the flame retardancy of polyamide‐6 composites containing organic phosphinates. The flame retardancy of polyamide‐6 composites was investigated using limiting oxygen index (LOI), Underwriters Laboratories (UL‐94) standard, thermogravimetric analysis, Fourier transform infrared spectroscopy, and mass loss calorimeter. The addition of 15 wt% aluminum phosphinate (AlPi) increased the LOI value from 22.5 to 29.5, and V0 rating was obtained from UL‐94 test. The addition of organoclay, ZnB, and borophosphate does not change the predominant gas phase mechanism of AlPi during LOI and UL‐94 tests. The addition of organoclay increased the condensed phase mechanism of AlPi physically by the protective effect of layered silicate, whereas the addition of ZnB increased the condensed phase mechanism of AlPi chemically by the formation of boron aluminum phosphate species deducted from mass loss calorimeter studies. Copyright © 2012 John Wiley & Sons, Ltd.     

Influence of the pentaerythritol phosphate melamine salt content on the combustion and thermal decomposition process of intumescent flame‐retardant ethylene–vinyl acetate copolymer composites

Pentaerythritol phosphate melamine salt (PPMS) as a single‐molecule intumescent fire retardant was synthesized and characterized. The influence of the PPMS content on the combustion and thermal decomposition processes of intumescent‐flame‐retardant (IFR) ethylene–vinyl acetate copolymer (EVA) composites was studied by limiting oxygen index (LOI) measurement, UL 94 rating testing, cone calorimetry, thermogravimetric analysis, and scanning electron microscopy. The LOI and UL 94 rating results illustrate that PPMS used in EVA improved the flame retardancy of the EVA composites. The cone calorimetry test results show that the addition of PPMS significantly decreased the heat‐release rate, total heat release, and smoke‐production rate and enhanced the residual char fire performance of the EVA composites. The IFR–EVA3 composite showed the lowest heat‐release and smoke‐production rates and the highest char residue; this means that the IFR–EVA3 composite had the best flame retardancy. The thermogravimetry results show that the IFR–EVA composites had more residual char than pure EVA; the char residue yield increased with increasing PPMS content. The analysis results for the char residue structures also illustrated that the addition of PPMS into the EVA resin helped to enhance the fire properties of the char layer and improve the flame retardancy of the EVA composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42148.     

The effect of red phosphorus on the fire properties of intumescent pine wood flour – LDPE composites

Red phosphorus (RP) was used to improve the fire performance of wood flour – low density polyethylene (LDPE) composites containing ammonium polyphosphate (APP). The fire performance of LDPE‐based composites was investigated by using limiting oxygen index (LOI), UL‐94 standard, thermogravimetric analysis, and cone calorimeter. The addition of 30 wt% APP increased the LOI value from 17.5 to 24.2 and still burned to clamp (BC) in UL‐94 test. The RP showed beneficial effect when combinedly used with APP. The maximum beneficial effect was seen at ratio of 5:1 (APP : RP) with the highest LOI value of 27.2 and UL‐94 rating of V0. RP showed its beneficial effect via increasing the gas phase action of the flame retardant system. Copyright © 2015 John Wiley & Sons, Ltd.     

Effect of OMMTs on flame retardancy and thermal stability of poly(ethylene‐co‐vinyl acetate)/LDPE/magnesium hydroxide composites

The aim of this study was to prepare poly (ethylene‐co‐vinyl acetate) (EVA)/ low density polyethylene (LDPE)/magnesium hydroxide (MH) composites applicable in cable industry with required flame retardancy. For this reason, two types of organo‐modified montmorillonites (OMMT) with different surface polarites (Cloisite 15A and Cloisite 30B) at various concentrations, and also combination of these two OMMTs with overall loadings of 2 wt % and 5 wt % were used. The samples were compounded using a twin screw extruder with total (MH + OMMT) feeding of 55 wt % and 60 wt %. Limiting oxygen index (LOI) of the samples containing 2 wt % of OMMTs increased about 16% and dripping was suppressed according to vertical burning test (UL‐94V). Thermogravimetric results of EVA/LDPE/MH samples containing OMMT showed that the beginning of second step degradation was shifted about 50°C to higher temperatures. The composite tensile strength results showed enhancement by incorporating some amount of nanoclays with EVA/LDPE/MH composites. Scanning electron microscopy images confirmed that MH particles had better wetting by EVA matrix in presence of nanoclays. Oxidative induction time of the EVA/LDPE/MH/OMMT nanocomposites was 140 min, which was more than that of the samples without OMMT (20 min). Employing the equal weight ratios of the two OMMTs demonstrated a synergistic effect on flame retardancy of the samples according to the both tests results (LOI, UL‐94V). X‐ray diffraction analysis of the samples confirmed the intercalation/semiexfoliation structure of nanosilicate layers in the bulk of EVA/LDPE matrix. This led to longer elongation at break and thermal stability of Cloisite 15A based nanocomposites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40452.     

Microencapsulation of ammonium polyphosphate: Preparation,characterization, and its flame retardance in polypropylene

Microencapsulated ammonium polyphosphate (MCAPP) with a melamine–formaldehyde (MF) resin coating layer was prepared by in situ polymerization. MCAPP was characterized by Fourier transform infrared, X‐ray photoelectron spectroscopy, and so on. The results show that the microencapsulation with MF resin leads to a decrease in the particles' size and water absorption. The flame retardant action and mechanism of MCAPP and ammonium polyphosphate (APP) in polypropylene are studied using limiting oxygen index (LOI) and UL 94 test, and their thermal stability is evaluated by thermogravimetric analysis. The LOI value of the PP/MCAPP composite at 30 wt% loading is 30.5%, whereas the corresponding value of the PP/APP composite is only 20%. Moreover, the LOI values of the PP/MCAPP/PER composites are higher than the ones of the PP/APP/PER composites. In the UL 94 test, the PP/MCAPP/PER composites with suitable ratios of MCAPP to PER can reach the V‐0 rating, and the best rating of the PP/APP/PER composites is V‐1. V‐1. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers