Cone Calorimeter Test Test Research Articles

Tannic acid as cross-linker and flame retardant for preparation of flame-retardant polyurethane elastomers

Bio-based tannic acid (TA) has been first applied as a reactive flame retardant for the preparation of polyurethane elastomers (PUEs). The flame retardant properties of PUEs are evaluated by limiting oxygen index (LOI), cone calorimeter test (CCT), thermogravimetric analysis (TGA), scanning electron microscope (SEM) and Raman tests, which confirm the flame retardant of TA for PUE owing to its polyphenol and cross-linked aromatic structure. When 5 wt% of TA is involved, the LOI value of the sample (PUE4) increases to 40%. According to CCT, TGA, SEM and Raman tests, the introduction of TA can reduce the heat release of PUE and greatly promote the generation of carbon residue during combustion. The flame retardant mechanism of PUEs is also investigated by TGA-FTIR test, indicating that TA inhibits the generation of combustible gas during combustion. Compared with PUE1, the elongation at break of TA-modified PUEs decreases obviously due to the presence of benzene ring structure (474.5–632.7%), but their tensile strength increases significantly owing to the hydroxyl groups and cross-linked structure of TA (14.8–31.1 MPa).

Preparation of bisDOPO-NH2-POSS flame retardant and its application to plywood using modified urea-formaldehyde resin

ABSTRACT A new type of polyhedral oligomeric silsesquioxanes bisDOPO-NH2-POSS flame retardant consisting of one polyhedral oligomeric silsesquioxane (POSS), two units of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and reactive –NH2 groups, was synthesized and characterized by FTIR, 1H NMR, and 31P NMR. It was applied to modified conventional environmentally friendly E0 grade urea formaldehyde (UF) resin to prepare flame-retardant plywood. Two other POSS structure flame retardants were used for comparison. The results showed that the addition of bisDOPO-NH2-POSS flame retardant to E0 UF resin improved bonding strength while lowering formaldehyde emission owing to the increase in cross-linking of the UF molecule chain in condensation. TGA curves showed that bisDOPO-NH2-POSS-E0 UF exhibited the highest thermal stability. The flammability characteristics of the plywood were evaluated by a cone calorimeter test (CCT), and the results indicated that the heat release and smoke production of flame-retardant plywood were lower than those of the control E0-UF plywood. Moreover, compared to E0-UF plywood, the char residue remaining after the CCT test of the flame-retardant plywood with POSS structure increased. In particular, bisDOPO-NH2-POSS-E0-plywood had a continual compact outer carbon layer, which was conducive to effectively forming a physical barrier to hinder the penetration of oxygen and heat and exhibiting the outstanding synergistic effect of phosphorous, silicon and nitrogen.

Research on Flame Retardant Formaldehyde-Free Plywood Glued by Aqueous Polymer Isocyanate Adhesive

Due to pronounced mechanical performance and being environmental friendly, aqueous polymer isocyanate adhesive (API) has been widely applied in the production of formaldehyde-free wood products. In this study, flame retardant formaldehyde-free plywood was prepared by incorporation of flame retardants into the API adhesive. Partially phosphorylated poly (vinyl alcohol) (PPVA) which was prepared by reacting poly (vinyl alcohol) with phosphoric acid was used to replace PVA in API formula. In addition, Mg-Al layered double hydroxides (LDH) was chosen as additive flame retardant, replacing traditional filler CaCO3 in API adhesive formula. And then, the flame retardant API adhesive with main agent (PPVA replacing PVA70wt.%, SBR emulsion 30wt.%), curing agent 10wt.% (accounts for of the main agent), and 20wt.% LDHs (accounts of the main agent) was used to prepare flame retardant plywood. The effect of application of PPVA and Mg-Al LDH on bonding strength of plywood was investigated. The flammability characteristics of the plywood were determined by cone calorimeter test (CCT). The results revealed that compared with the plywood prepared with API adhesive, the use of PPVA and LDH enhanced the flame retardancy of plywood without negatively affecting bonding strength. The CCT tests indicated that the heat release and smoke production flame retardant API plywood were lower than those of the ordinary API glued plywood. Promising developments for flame retardant API adhesive were expected in future applications of flame retardant formaldehyde-free plywood.

Superior fire safety performances of chelates copper(II) salicylaldehyde complexes with intumescent flame retardant TPU

To improve the flame retardant of thermoplastic polyurethane elastomer (TPU) is a very important issue in fire hazard fields. In this article, the structure of copper (II) chelate salicylaldehyde (CuSA) was characterized by X‐ray diffraction (XRD), Fourier transform infrared (FTIR), and scanning electron microscopy (SEM). The influence of CuSA on the fire safety performances of TPU/APP composites was intensively investigated using cone calorimeter test (CCT), smoke density test (SDT), micro‐scale combustion calorimetry (MCC), thermogravimetric‐Fourier transform infrared spectrum (TG‐FTIR), and other testing methods. The CCT test results showed that the peak heat release rate (pHRR) value of CuSA2 sample was 128.1 kW/m2, which was much lower than that of TPU‐APP sample with the pHRR value of 161.9 kW/m2. The SDT test results showed that the luminous flux of CuSA4 is much higher than that of TPU‐APP sample. Therefore, an appropriate amount of CuSA had obvious improvement of fire safety performances in TPU composites. This work provides a new idea for the design and manufacture of fire safety materials.

Smoke suppression of [Glu]H2PW12O40 in thermoplastic polyurethane elastomer

As is known there is a large amount of smoke released from the combustion process of thermoplastic polyurethane elastomer (TPU). To reduce the fire risk of TPU is one of the research contents in the fire safety fields. In this paper, [Glu]H2PW12O40 was used as smoke suppressant in TPU, and the smoke suppression effect of [Glu]H2PW12O40 was intensively investigated using nuclear magnetic resonance, scanning electron microscope, cone calorimeter test (CCT), smoke density test (SDT), and thermogravimetric analysis/infrared spectrometry, respectively. In the CCT test, the peak value of smoke production rate (SPR) of TPU-3 with 0.5 mass% of [Glu]H2PW12O40 was 0.036 m2 s−1, reduced by 75% compared with the peak SPR value of TPU-0 without [Glu]H2PW12O40 (0.145 m2 s−1). [Glu]H2PW12O40 could decrease the total smoke release (TSR) from 1560 to 694 m2 m−2. And [Glu]H2PW12O40 could decrease the smoke factor from 1838 to 538 W m−2. The SDT results showed that the luminous flux value of TPU-3 with 0.5 mass% of [Glu]H2PW12O40 decreased by 30% compared with pure TPU at the end of the test without flame. The photographs from the CCT test showed that [Glu]H2PW12O40 could promote char residue formation. TG test also revealed that [Glu]H2PW12O40 could improve the thermal stability at high temperature. At the end of thermal decomposition, the mass of TPU-3 with 0.5 mass% of [Glu]H2PW12O40 increased 6.3% compared with the mass of TPU-0 without [Glu]H2PW12O40. Based on the above result, it could be concluded that [Glu]H2PW12O40 can suppress smoke generation by promoting char generation. In addition, [Glu]H2PW12O40 has a good prospect in smoke suppression of TPU.

Synergistic effects between a triazine-based charring agent and aluminum phosphinate on the intumescent flame retardance of thermoplastic polyether ester

The triazine-based charring agent (CFA) with perfect charring ability was synthesized and characterized. The synergistic effects between CFA and aluminum phosphinate (AlPi) on flame retardancy, thermal degradation, and flammability properties of thermoplastic polyester-ether elastomer (TPEE) were investigated by limiting oxygen index (LOI), vertical burning test (UL-94), cone calorimeter test (CCT), thermogravimetric analysis (TGA), laser Raman spectroscopy (LSR) and scanning electron microscopy (SEM). The results from UL-94 test showed that, by compounding 14 wt% AlPi and 4 wt% CFA with TPEE, the LOI value reached 28.5% and the UL-94 rating reached V-0 (1.6 mm). TGA results indicated that there is good synergistic charring ability between CFA and AlPi, especially the increased residues at high temperature (T > 700 °C). The CCT test results showed that CFA could change the combustion behavior of TPEE and effectively accelerate the formation of expanded carbon layers. The residues after combustion were measured by LRS and SEM, demonstrating that CFA can promote the formation of dense and stable carbon layers during the combustion, which could inhibit the melt dropping and improve the fire retardancy of TPEE composites. Thus, CFA was a promising synergistic agent in halogen-free flame retardant TPEE.

Influence of ammonium polyphosphate on flame-retardant behavior and smoke suppression property of EVA/magnesium hydroxide composites

ABSTRACTTo overcome the flammability and smoke generation of EVA, samples with different mass fraction of magnesium hydroxide (MH) and ammonium polyphosphate (APP), have been prepared by internal mixer and cured by compression molded. The fire characteristics including smoke and heat production of EVA composites were studied by cone calorimeter test (CCT), limiting oxygen index test, UL-94 test, scanning electron microscopy, and thermogravimetric (TG) analysis, respectively. For the sample EVA5 loading 10.0 mass% APP and 40.0 mass% MH, the LOI value can be increased to the value of 31.1 and reach V-0 level. The CCT test showed that APP and MH could significantly improve the fire safety of EVA. Remarkably, the peak of heat release rate, the peak of smoke production rate, and total smoke release for EVA5 were decreased by 75.4%, 88.1% and 70.8% compared with pure EVA, respectively. TG test showed that APP promoted the char formation in the degradation process of EVA; as a result, the residual carbon was increased. The results indicated that APP combined with MH could facilitate the formation of the rigid intumescent char and obviously enhance the flame retardancy, smoke suppression and thermal stability of the EVA matrix.

A recycled environmental friendly flame retardant by modifying para-aramid fiber with phosphorus acid for thermoplastic polyurethane elastomer

The application of fibers is more and more extensive, and the pollution caused by abandoned fibers is getting more serious, which has aroused wide attention. So it is necessary to find a way to solve the problem. In this paper, the para-aramid fiber (AF) was recycled and modified by phosphoric acid, and then was applied as environmental friendly flame retardant for thermoplastic polyurethane elastomer (TPU). The flame retardant properties of TPU were tested using cone calorimeter test (CCT) and thermogravimetric/Fourier transform infrared spectroscopy (TG-IR). The CCT test showed that AF-P had better flame retardant effect on TPU than pure AF. Remarkably, the pHRR value for the sample with 1.00wt% content of AF-P was decreased by 48.1%; AF-P had improved the char forming progress and the residual mass was 30.6%, which was much more than pure TPU. TG test showed that AF-P could improve the thermal stability of TPU at high temperature. The TG-IR test revealed that AF-P had reduced the release of CO2 at the beginning. Based on the above results, it will make a great influence on the study of reuse of fibers and environmental friendly flame retardant of polymer.

The synergistic effect of hollow glass microsphere in intumescent flame-retardant epoxy resin

A series of flame-retardant epoxy resin (EP) composites, with different mass ratio of intumescent flame-retardant (IFR) and hollow glass microspheres (HGM), have been prepared. The synergistic flame-retardant effects of HGM between IFR in EP blends have been examined through several conventional methods, such as limiting oxygen index (LOI) test, UL-94 test, cone calorimeter test (CCT), scanning electron microscopy (SEM), and thermogravimetric analysis (TG), respectively. The LOI and UL-94 results show that when 2.0 mass% IFR is replaced by HGM, the LOI value can be increased to the maximum value of 34.7 among all samples. The data obtained from the CCT test indicate the peak value of heat release rate of EP/IFR/HGM sample with 2.0 mass% HGM reduced to 177.6 from 851.1 kW m−2 (pure EP). The digital photographs and SEM of char residues after CCT give positive evidence of the synergistic flame-retardant effects between HGM and IFR. Firstly, HGM could promote the formation of dense and compact charred layers. Secondly, it could prevent the charred layers from cracking. The TG results reveal that EP/IFR/HGM samples show higher thermal stability at high temperature than EP/IFR sample.

Fire safety improvement of para-aramid fiber in thermoplastic polyurethane elastomer

This article mainly studied fire safety effects of para-aramid fiber (AF) in thermoplastic polyurethane (TPU). The TPU/AF composites were prepared by molten blending method, and then the fire safety effects of all TPU composites were tested using cone calorimeter test (CCT), microscale combustion colorimeter test (MCC), smoke density test (SDT), and thermogravimetric/fourier transform infrared spectroscopy (TG-IR). The CCT test showed that AF could improve the fire safety of TPU. Remarkably, the peak value of heat release rate (pHRR) and the peak value of smoke production rate (pSPR) for the sample with 1.0wt% content of AF were decreased by 52.0% and 40.5% compared with pure TPU, respectively. The MCC test showed that the HRR value of AF-2 decreased by 27.6% compared with pure TPU. TG test showed that AF promoted the char formation in the degradation process of TPU; as a result the residual carbon was increased. The TG-IR test revealed that AF had increased the thermal stability of TPU at the beginning and reduced the release of CO2 with the decomposition going on. Through the analysis of the results of this experiment, it will make a great influence on the study of the para-aramid fiber in the aspect of fire safety of polymer.

Synergistic effects of 4A zeolite on the flame‐retardant properties and thermal stability of an efficient halogen‐free flame‐retardant EVA composite

The synergistic effects of 4A zeolite (4A) on the thermal degradation, flame retardancy, and char formation of an efficient halogen‐free flame‐retardant ethylene‐vinyl acetate copolymer composite (EVA/IFR) were investigated by limited oxygen index (LOI), vertical burning test (UL‐94), cone calorimeter test (CCT), digital photography, scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), laser Raman spectroscopy (LRS) and thermogravimetric analytical (TGA) methods. It was found that a small amount of 4A clearly improved the LOI value of the EVA/IFR composite and reinforced the fire retardant performance with a great reduction in the combustion parameters of the EVA/IFR system from the CCT test. The entire composites passed the UL‐94 V‐0 rating test. The TGA and integral procedure decomposition temperature (IDPT) results showed that 4A enhanced the thermal stability of the EVA/IFR system and increased the char residue content effectively. The morphological structures observed by digital and SEM imaging revealed that 4A could promote EVA/IFR to form a more continuous and compact intumescent char layer. The LRS and EDS results demonstrated that by introduction of 4A into the EVA/IFR system, a more graphite structure was formed with increase phosphorus content in the char residue. POLYM. ENG. SCI., 56:380–387, 2016. © 2016 Society of Plastics Engineers

Influence of zinc borate on the flame retardancy and thermal stability of intumescent flame retardant polypropylene composites

The influence of zinc borate (ZB) on the flame retardancy and thermal stability of intumescent flame retardant polypropylene composites (PP/IFR) containing ammonium polyphosphate (APP) and charring-foaming agent (CNCA-DA) were characterized by limiting oxygen index (LOI), UL-94 measurement, cone calorimeter test (CCT), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and thermogravimetry analysis (TGA). The results revealed that a small amount of ZB could effectively improve the LOI value, UL rating of the PP/IFR systems, and reduce the combustion performance of PP/IFR systems from CCT test, including heat release rate (HRR), total heat release (THR), smoke production rate (SPR) and total smoke production (TSP). The catalytic effectivity (CAT-EFF) results showed that when 1% ZB was added to PP/IFR, it had the highest CAT-EFF, and could enhance the LOI value from 27.1 to 30.7. The morphological structures observed by digital photos and SEM indicated that ZB could promote to remain more P and O, and B could participate the connecting reaction to form the more continuous and more compact intumescent char layer on the char surface to hinder heat diffusion and oxygen transmission effectively. The TGA data revealed that ZB could change the degradation behavior of the IFR and PP/IFR, improve the thermal stability of the PP/IFR systems at high temperature and increase the char residue.

Synergistic effect of allophane with intumescent flame retardants on thermal behavior and fire retardancy of polypropylene

The effects of allophane (ALL) as a synergistic agent on the flame retardancy and thermal stability of intumescent flame-retardant (IFR) polypropylene composites were studied by limiting oxygen index (LOI), UL-94 test, cone calorimeter test (CONE) and thermogravimetric analysis. The incorporation of ALL led to enhanced thermal stability, LOI value and UL-94 ratings. CONE tests indicated that heat release rate, peak rate of heat release, smoke production rate, total smoke production and mass loss values of PP/IFR/ALL sample were much lower than those of PP/IFR and pure PP samples. Fourier transform infrared spectrometry result proved the presence of silicoaluminophosphate which can act as a catalytic agent to enhance the oxidative dehydration crosslinking charring process. Scanning electron microscopy and Raman spectra observation demonstrated that ALL could promote forming homogenous and compact char layer. The mechanical properties of PP composites were also improved by the loading of ALL.

Highly-effective Flame Retardancy of Poly(lactide) Composite Achieved Through Incorporation of Amorphous Nickel Phosphate Microparticle

In this study, amorphous nickel phosphate (NiPO) was prepared through urea-assisted hydrothermal process. The composition of NiPO was investigated via X-ray photoelectron spectrum (XPS). And the structure of NiPO was characterized by Fourier transform infrared spectrometer (FTIR) and X-ray diffraction measurement (XRD).Then poly(lactide) (PLA) was melt blended with the resulting NiPO to prepare flame retardant PLA composites. The flame retardant property of PLA composites was probed using limiting oxygen index test (LOI), UL-94 vertical burning test (UL-94), cone calorimeter test (CCT). And the thermal combustion property was analyzed through pyrolysis combustion flow calorimeter test (PCFC). In the meantime, the thermal stability of NiPO microparticles and PLA composites was analyzed through thermogravimetric analyzer (TGA) and integrated procedural degradation temperature (IPDT). In the meantime, the melting and crystallization property of PLA composites was investigated through DSC analysis. Results showed that NiHPO3 was the main component of NiPO. PLA composite with only 2 wt.% NiPO powder exhibited excellent flame retardancy (LOI = 27.5% and UL-94 V-0 rating). In the CCT and PCFC test, it showed that HRR of PLA composites was higher in the early stage of combustion and lower in the late stage of combustion than that of pure PLA. Moreover, a slightly increased CO production rate (COP) and obviously decreased total smoke production (TSP) were found in PLA composites containing 2 wt.% NiPO in CCT. In the DTG curve, the similar weight derivation trend to HRR in CCT and PCFC test was also observed. Additionally, the intrinsic thermal stability was enhanced significantly by 19°C with 2 wt.% NiPO into PLA composites. DSC results showed that NiPO could also improve the crystallization property of PLA composites.

Synergistic flame retardant effects between hollow glass microspheres and magnesium hydroxide in ethylene-vinyl acetate composites

Abstract A series of flame retardant ethylene-vinyl acetate (EVA) composites, with different content of magnesium hydroxide (MH) and hollow glass microspheres (HGM), have been prepared. The synergistic flame retardant effects of HGM with MH in EVA/MH blends have been studied by limiting oxygen index (LOI), UL-94 tests, cone calorimeter test (CCT), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM), respectively. The LOI and UL-94 results show that when 2.00 wt% magnesium hydroxide (MH) is substituted with HGM, the LOI value can be raised to the maximum value of 42.1 among all samples. The data obtained from the CCT test indicate the heat release rate (HRR) of EVA/MH/HGM sample with 1.00 wt% HGM reduced by 37% when compared with EVA/MH sample without HGM. The digital photo graphs and scanning electron microscope (SEM) of char residues after CCT give positive evidence that the synergistic flame retardant effects between HGM and MH can be described that HGM mixed with MH can decrease the melt viscosity of EVA/MH/HGM, and promote the homogeneous dispersion of MH. HGM also can promote the formation of compact charred layers and prevent the charred layers from cracking, which effectively protects the underlying materials from burning. The TGA results reveal that EVA/MH/HGM samples show higher thermal stability at high temperature than EVA/MH sample.

Flame retardancy and thermal degradation behaviors of polypropylene composites with novel intumescent flame retardant and manganese dioxide

The flame retardancy and thermal degradation behavior of polypropylene composites containing ammonium polyphosphate (APP), novel charring agent (CNCA-DA) and manganese dioxide (MnO2) were characterized by limiting oxygen index (LOI), UL-94 measurement, cone calorimeter test (CCT), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and energy dispersive spectrometry (EDS). It was found that a small amount of MnO2 could dramatically increase the LOI value, UL rating of the PP/IFR systems, and reduce the combustion parameters of PP/IFR system from CCT test, including peak heat release rate (p-HRR), total heat release (THR), and smoke production rate (SPR). The catalytic effectivity (CAT-EFF) results showed that when 1wt% MnO2 was added, it had the highest CAT-EFF, and could promote the LOI value of the composites from 27.1 to 30.7. The TGA data revealed that MnO2 could change the degradation behavior of the IFR and PP/IFR, improve the thermal stability of the PP/IFR systems at high temperature and increase the char residue. The morphological structures observed by digital photos and SEM indicated that MnO2 could effectively help to form more continuous and compact intumescent char layer on the outer surface to protect the underlying materials from burning. The EDS results illustrated that the existence of MnO2 could promote to remain more P and O in the char layer.

Synergistic effects of 4A zeolite on the flame retardant properties and thermal stability of a novel halogen‐free PP/IFR composite

The synergistic effects of 4A zeolite (4A) on the thermal degradation, flame retardancy and char formation of a novel halogen‐free intumescent flame retardant polypropylene composites (PP/IFR) were investigated by the means of limiting oxygen index (LOI), vertical burning test (UL‐94), digital photos, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), cone calorimeter test (CCT), laser Raman spectroscopy (LRS) and X‐ray photoelectron spectroscopy (XPS). It was found that a small amount of 4A could dramatically enhance the LOI value of the PP/IFR systems and the materials could pass the UL‐94 V‐0 rating test. Also, it could enhance the fire retardant performance with a great reduction in combustion parameters of PP/IFR system from CCT test. The morphological structures observed by digital and SEM photos revealed that 4A could promote PP/IFR to form more continuous and compact intumescent char layer. The LRS measurement, XPS and TGA analysis demonstrated that the compactness and strength of the outer char surface of the PP/IFR/4A system was enhanced, and more graphite structure was formed to remain more char residue and increase the crosslinking degree. Copyright © 2013 John Wiley & Sons, Ltd.

The synergistic effects of boroxo siloxanes with magnesium hydroxide in halogen-free flame retardant EVA/MH blends

The synergistic effects of boroxo siloxanes (BSil) with magnesium hydroxide in halogen-free flame retardant EVA/MH blends have been studied by cone calorimeter test (CCT), Fourier transfer infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), transmission electron microscopy (TEM), scanning electron microscopy (SEM), mechanical properties measurements, limiting oxygen index (LOI), UL-94 and torque tests. The LOI and UL-94 data show that when 3 wt% boroxo siloxane substituted for the magnesium hydroxide (MH) can increase 8% LOI values of the EVA/MH blends and keep the V-0 rating. The data obtained from the CCT tests indicate the heat release rates (HRR) reduced by about 23% for the EVA/MH sample with 3 wt% BSil when compared with the EVA/MH sample without BSil. The experimental observations from the torque, FTIR, TEM and SEM give positive evidence that the synergistic effects mechanism of BSil with MH can be described to: (i) BSil react with MH and increases the melt viscosity; (ii) BSil promote the homogeneous dispersion of MH; (iii) BSil promote the formation of compact charred layers and prevent the charred layers from cracking, which effectively protects the underlying polymer from burning. The TGA and dynamic FTIR spectral reveal that EVA/MH/BSil samples show slower thermal degradation rate and higher thermal degradation temperature than the EVA/MH sample. The mechanical tests show that the mechanical properties of EVA/MH/BSil blends are markedly improved by suitable amount of BSil.

Synergistic effect of zinc hydroxystannate with intumescent flame-retardants on fire retardancy and thermal behavior of polypropylene

The flammability and thermal degradation properties of polypropylene (PP) composites containing zinc hydroxystannate (ZHS) and intumescent flame retardant additives (IFR), i.e. ammonium polyphosphate (APP) and pentaerythritol (PER) were characterized respectively by limiting oxygen index (LOI), UL-94 measurements, Cone calorimeter test (CCT) and Thermogravimetry analysis (TGA) in this work. A synergistic effect in flame retardancy was observed when ZHS was used in combination with APP and PER. The experimental data indicated that ZHS enhanced the LOI value, UL-94 ratings and restricted the dripping of the composites. The PP/IFR composites passed the UL-94 V-0 rating test in the presence of 1 wt% ZHS. The CCT tests indicated that the heat release rate (HRR), peak rate of heat release (PHRR) and mass loss rate (MLR) values of the PP/IFR/ZHS samples were much lower than those of the PP/IFR and pure PP samples. The TGA results showed that ZHS could accelerate the char formation of IFR, therefore, greatly increase the thermal stability of PP composites. The Fourier transformed infrared spectra (FTIR) revealed that the flame retardant mechanism of ZHS could be ascribed to its catalysis degradation of the PP resin, which promoted the formation of charred layers with the P–O–P and P–O–C complexes in the condensed phase. SEM observation further indicated that ZHS could promote forming stable and compact intumescent char layer and effectively protect the underlying polymer from burning.

Synergistic effects of layered double hydroxide with phosphorus-nitrogen intumescent flame retardant in PP/EPDM/IFR/LDH nanocomposites

Synergistic effects of layered double hydroxide (LDH) with intumescent flame retardanct (IFR) of phosphorus-nitrogen (NP) compound in the polypropylene/ethylene-propylene-diene/IFR/LDH (PP/EPDM/IFR/LDH) nanocomposites and related properties were studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), limiting oxygen index (LOI), UL-94 test, cone calorimeter test (CCT) and thermo-gravimetric analysis (TGA). The XRD and TEM results show that the intercalated and/or exfoliated nanocomposites can be obtained by direct melt-intercalation of PP/EPDM into modified LDH and that LDH can promote the IFR additive NP to disperse more homogeneously in the polymer matrix. The SEM results provide positive evidence that more compact charred layers can be obtained from the PP/EPDM/NP/LDH sample than those from the PP/EPDM/LDH and PP/EPDM/NP samples during burning. The LOI and UL-94 rating tests show that the synergetic effects of LDH with NP can effectively increase the flame retardant properties of the PP/EPDM/NP/LDH samples. The data from the CCT and TGA tests indicate that the PP/EPDM/NP/LDH samples apparently decrease the HRR and MLR values and thus enhance the flame retardant properties and have better thermal stability than the PP/EPDM/LDH and PP/EPDM/NP samples.