Influence of silicon dioxide addition and processing methods on structure, thermal stability and flame retardancy of EVA/NR blend nanocomposite foams

Rubber nanocomposite foams based on 60/40 ethylene vinyl acetate (EVA)/natural rubber (NR) were melt-mixed with flame retardant silicon dioxide (SiO2) (20 parts per hundred rubber, phr), and foamed by compression molding process. In this study, the effect of mixing phenomena of SiO2 through two different compounding techniques such as direct mixing (DM) and phase selective mixing (PSM) methods on structure, thermal stability, combustility and flame retardancy of EVA/NR blend nanocomposite foams were investigated. DM method is a melt mixing of EVA, NR, layered silicate and SiO2, followed by foaming. PSM is a new method based on pre-mixing EVA with SiO2, then melt mixing of EVA/SiO2 masterbatch with NR and layered silicate, and finally foaming. Based on TEM technique, it was found that the SiO2 was exclusively located in dispersed NR phase for the sample prepared by DM method, and the SiO2 was preferably dispersed in continuous EVA matrix when PSM method was employed. However, the different mixing methods did not significantly alter their cellular structures. The thermal stability and char residue content of foamed samples with SiO2 increased obviously when compared with those of corresponding foams without SiO2. The results based on limiting oxygen index (LOI) test and oxygen bomb calorimetry indicated that the foams combined with SiO2 had better combustion resistance and flame retardancy due to barrier effect of thermally stable silicon-based char layer. Further, the SiO2 filled foamed system obtained from the PSM method showed a higher degree of improvement in thermal stability, combustion resistance and flame retardancy than that of DM method because the homogeneous dispersion of SiO2 in EVA matrix rather than the selective dispersion in NR phase. This resulted in the continuity of flame retardant EVA/SiO2 phase in the 60/40 EVA/NR nanocomposite foams, which exerted more efficient fire barrier of the silicon-based char layer.

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Enhancing cellular structure, mechanical properties, thermal stability and flame retardation of EVA/NR blend nanocomposite foams by silicon dioxide-based flame retardant

Progress in Rubber Plastics and Recycling Technology ◽

10.1177/14777606211042028 ◽

2021 ◽

pp. 147776062110420

Author(s):

Alif Walong ◽

Bencha Thongnuanchan ◽

Nattapon Uthaipan ◽

Tadamoto Sakai ◽

Natinee Lopattananon

Keyword(s):

Electron Microscopy ◽

Thermal Stability ◽

Silicon Dioxide ◽

Flame Retardant ◽

Flame Retardancy ◽

Cellular Structure ◽

Gas Chromatography Mass Spectrometry ◽

Pyrolysis Gas ◽

Nanocomposite Foams ◽

Blend Nanocomposites

Flame retardant rubber foams of ethylene vinyl acetate (EVA)/natural rubber (NR)/layered silicate blends filled with silicon dioxide (SiO2) were prepared by using azodicarbonamide (ADC) as a blowing agent. Specifically, SiO2 was added in EVA/NR blend nanocomposites to produce good flame retardant foams. The properties of EVA/NR blend nanocomposite foams with different SiO2 loading (0, 20, 30, 40 parts per hundred rubber, phr) were investigated through transmission electron microscopy (TEM), scanning electron microscopy (SEM), rheological property test, mechanical property measurement, flammability tests, thermogravimetry analysis (TGA) and pyrolysis-gas chromatography-mass spectrometry (Pyrolysis-GC-MS). Compared with the simple EVA/NR blend nanocomposite, the added SiO2 increased the blend compatibility between EVA and NR phases and melt strength/viscosity of the EVA/NR blend nanocomposites, thus promoting cellular structure of the EVA/NR nanocomposite foams. Increasing SiO2 loading resulted in higher cell density, smaller cell size, and lower volume of void. These improvements caused higher strength and elastomeric recovery. The LOI test results showed that flame retardancy of the EVA/NR blend nanocomposite foams increased at higher SiO2 loading as a result of formation of insulation silicon dioxide-based char. TGA and pyrolysis-GC-MS analyses also validated the finding that the silicon dioxide-based char in the foamed samples containing higher SiO2 loading was more effective on improving thermal stability, which was responsible for lower material combustibility and better flame retardancy. Based on our finding, it was concluded that a good flame retardant EVA/NR blend nanocomposite foam with the best improvement in strength and elastomeric recovery was achieved when combined with 40 phr SiO2.

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Synergism between flame retardant and modified layered silicate on thermal stability and fire behaviour of polyurethane nanocomposite foams

Polymer Degradation and Stability ◽

10.1016/j.polymdegradstab.2008.08.005 ◽

2008 ◽

Vol 93 (12) ◽

pp. 2166-2171 ◽

Cited By ~ 97

Author(s):

M. Modesti ◽

A. Lorenzetti ◽

S. Besco ◽

D. Hrelja ◽

S. Semenzato ◽

...

Keyword(s):

Thermal Stability ◽

Flame Retardant ◽

Layered Silicate ◽

Fire Behaviour ◽

Nanocomposite Foams

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Effects of Tung Oil-Based Polyols on the Thermal Stability, Flame Retardancy, and Mechanical Properties of Rigid Polyurethane Foam

Polymers ◽

10.3390/polym11010045 ◽

2018 ◽

Vol 11 (1) ◽

pp. 45 ◽

Cited By ~ 10

Author(s):

Wei Zhou ◽

Caiying Bo ◽

Puyou Jia ◽

Yonghong Zhou ◽

Meng Zhang

Keyword(s):

Thermal Stability ◽

Polyurethane Foam ◽

Flame Retardancy ◽

Covalent Bond ◽

Rigid Polyurethane Foam ◽

Limiting Oxygen Index ◽

Sem Micrographs ◽

Tung Oil ◽

Char Layer ◽

Ring Opening Reaction

A phosphorus-containing tung oil-based polyol (PTOP) and a silicon-containing tung oil-based polyol (PTOSi) were each efficiently prepared by attaching 9,10-dihydro-9-oxa-10-phosphaphenanthrene (DOPO) and dihydroxydiphenylsilane (DPSD) directly, respectively, to the epoxidized monoglyceride of tung oil (EGTO) through a ring-opening reaction. The two new polyols were used in the formation of rigid polyurethane foam (RPUF), which displayed great thermal stability and excellent flame retardancy performance. The limiting oxygen index (LOI) value of RPUF containing 80 wt % PTOP and 80 wt % PTOSi was 24.0% and 23.4%, respectively. Fourier transfer infrared (FTIR), Nuclear Magnetic Resonance (NMR) and thermogravimetric (TG) analysis revealed that DOPO and DPSD are linked to EGTO by a covalent bond. Interestingly, PTOP and PTOSi had opposite effects on Tg and the compressive strength of RPUF, where, with the appropriate loading, the compressive strengths were 0.82 MPa and 0.25 MPa, respectively. At a higher loading of PTOP and PTOSi, the thermal conductivity of RPUF increased while the RPUF density decreased. The scanning electron microscope (SEM) micrographs showed that the size and closed areas of the RPUF cells were regular. SEM micrographs of the char after combustion showed that the char layer was compact and dense. The enhanced flame retardancy of RPUF resulted from the barrier effect of the char layer, which was covered with incombustible substance.

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Preparation of lignin–silica hybrids and its application in intumescent flame-retardant poly(lactic acid) system

High Performance Polymers ◽

10.1177/0954008312451476 ◽

2012 ◽

Vol 24 (8) ◽

pp. 738-746 ◽

Cited By ~ 41

Author(s):

Rui Zhang ◽

Xifu Xiao ◽

Qilong Tai ◽

Hua Huang ◽

Jian Yang ◽

...

Keyword(s):

Thermal Stability ◽

Lactic Acid ◽

Flame Retardant ◽

Flame Retardancy ◽

Photoelectron Spectroscopy ◽

Intumescent Flame Retardant ◽

Poly Lactic Acid ◽

Limiting Oxygen Index ◽

Silica Hybrids ◽

Thermal Stability Of

Lignin–silica hybrids (LSHs) were prepared by sol–gel method and characterized by Fourier transform infrared (FT-IR) spectra, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). LSH and ammonium polyphosphate (APP) were added into poly(lactic acid) (PLA) as a novel intumescent flame-retardant (IFR) system to improve the flame retardancy of PLA. The flame-retardant effect of APP and LSH in PLA was studied using limiting oxygen index (LOI), vertical burning (UL-94) tests and cone calorimeter. The thermal stability of PLA/APP/LSH composites was evaluated by thermogravimetric analysis (TGA). Additionally, the morphology and components of char residues of the IFR-PLA composites were investigated by SEM and XPS. With the addition of APP/LSH to PLA system, the morphology of the char residue has obviously changed. Compared with PLA/APP and PLA/APP/lignin, a continuous and dense intumescent charring layer with more phosphor in PLA composites is formed, which exhibits better flame retardancy. All the results show that the combination of APP and LSH can improve the flame-retardant property and increase the thermal stability of PLA composites greatly.

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PREPARATION OF IRON- REDUCED GRAPHENE OXIDE/ EPOXY RESIN COMPOSITE AND ITS FLAME RETARDANCY AND THERMAL STABILITY

DYNA INGENIERIA E INDUSTRIA ◽

10.6036/10327 ◽

2022 ◽

Vol 97 (1) ◽

pp. 98-103

Author(s):

XIAN WANG ◽

JINLONG ZHUO ◽

TIANQING XING ◽

Xingran Wang

Keyword(s):

Thermal Stability ◽

Graphene Oxide ◽

Flame Retardant ◽

Epoxy Resin ◽

Iron Powder ◽

Flame Retardancy ◽

Limiting Oxygen Index ◽

Cone Calorimeter Test ◽

Industrial Manufacture ◽

Ul 94

In order to reduce flammability, smoke release and enhance thermal stability of epoxy resin (EP), iron powder is mixed with graphene oxide/ epoxy resin (GO/EP) composite by mechanical blending. The combustion performance of composite material is investigated through limiting oxygen index (LOI), Underwriters Laboratory (UL)-94 test, and cone calorimeter test (CCT). Thermogravimetric-Fourier transform infrared spectroscopy (TG-FTIR) and scanning electron microscope (SEM) are also used to explore the mechanism of flame retardancy and smoke suppression. Results show that, with the addition of 0.5% mass fraction of GO and the corresponding iron powder combination (EP3 sample), the LOI value can achieve 32.5% while reaching the UL-94 V0 rating. Compare with EP0, the peaks of heat release rate, smoke production rate, and smoke factor values of EP3 are decreased by 42%, 60%, and 50%, respectively. The char and TG-FTIR data of EP3 reveal that it has a more compact structure, good thermal stability, and produce fewer toxic gases and smoke. Reduction of GO could inhibit the degradation of EP, and iron catalyzes the formation of carbonaceous char on the surface. Thus, the thermal stability and flame retardancy of EP are improved significantly. This study provides a suitable way to prepare graphene/EP composites that contain iron catalyst and can be extended to the industrial manufacture of flame retardant polymer composites. Keywords: iron powder; epoxy resin; graphene oxide; flame retardant; thermal stability

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Flame Retardant Waterborne Polyurethanes: Synthesis, Characterization, and Evaluation of Different Properties

Biointerface Research in Applied Chemistry ◽

10.33263/briac123.31983214 ◽

2021 ◽

Vol 12 (3) ◽

pp. 3198-3214

Keyword(s):

Thermal Stability ◽

Flame Retardant ◽

Flame Retardancy ◽

Oxygen Index ◽

Polymeric Chain ◽

Resonance Spectroscopy ◽

Mixing Process ◽

Polyester Polyol ◽

Limiting Oxygen Index ◽

Waterborne Polyurethanes

A series of flame retardant waterborne polyurethanes (WBPUs) with varying NCO:OH mole ratio, i.e., isocyanate:hydroxyl groups, was synthesized using phosphorus-based polyester polyol and isophorone diisocyanate (IPDI). The phosphorus moiety was kept in the polymeric chain, which improves flame retardancy of the WBPU films. The prepolymer mixing process was adopted for the synthesis route of WBPU systems. The presence of structural-functional groups was confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. The thermal stability and percentage char yield were observed by TGA analysis. As a consequence of the existence of phosphorous moiety, these WBPUs also exhibit flame retardancy, which was examined by limiting oxygen index (LOI) and UL-94 test. All the samples show an increment in thermal stability with an increase in NCO:OH ratio. Maximum flame retardancy was obtained in FWP5 and FWP6 systems with LOI value of 32%.

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Flame Retardancy and Mechanism of Novel Phosphorus-Silicon Flame Retardant Based on Polysilsesquioxane

Polymers ◽

10.3390/polym11081304 ◽

2019 ◽

Vol 11 (8) ◽

pp. 1304 ◽

Cited By ~ 3

Author(s):

Shengjie Zhu ◽

Weiguang Gong ◽

Ji Luo ◽

Xin Meng ◽

Zhong Xin ◽

...

Keyword(s):

Heat Release ◽

Flame Retardant ◽

Gas Phase ◽

Condensed Phase ◽

Flame Retardancy ◽

Carbon Layer ◽

Poly Lactic Acid ◽

Limiting Oxygen Index ◽

Synergistic Flame Retardant ◽

Silicon Based

A novel phosphorus-silicon flame retardant (P5PSQ) was prepared by bonding phosphate to silicon-based polysilsesquioxane (PSQ) and used as flame retardant of poly (lactic acid) (PLA). The results show that PLA with 10 wt % P5PSQ has a limiting oxygen index (LOI) 24.1%, the peak heat release rate (PHRR) and total heat release (THR) of PLA decrease 21.8% and 25.2% compared to neat PLA in cone calorimetric test, indicating that P5PSQ shows better flame retardancy in comparison to PSQ. Furthermore, the study for the morphology and composition of carbon residue after the combustion of PLA and the gas release of PLA during combustion illustrate that P5PSQ has flame retardancy in condensed phase and gas phase simultaneously. In condensed phase, phosphorus from phosphate promotes the formation of more stable and better carbon layer containing Si and P, which inhibits the transfer of heat and oxygen in the combustion. In gas phase, the phosphate in P5PSQ emits phosphorus-containing compound that can restrain the release of C–O containing products, which may have effective flame retardancy for PLA in gas phase to a certain extent. In one word, P5PSQ is denoted as a good phosphorus-silicon synergistic flame-retardant.

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Intumescent flame retardant coating for polyamide 6,6 (PA 6,6) fabrics containing carbon nanotubes: Synergistic effect of filler on thermal stability and flame retardancy

Textile Research Journal ◽

10.1177/0040517518783355 ◽

2018 ◽

Vol 89 (10) ◽

pp. 2031-2040 ◽

Cited By ~ 4

Author(s):

Fanglong Zhu ◽

QQ Feng ◽

YF Xu ◽

JF Hu

Keyword(s):

Carbon Nanotubes ◽

Thermal Stability ◽

Heat Release ◽

Flame Retardant ◽

Heat Release Rate ◽

Flame Retardancy ◽

Release Rate ◽

Intumescent Flame Retardant ◽

Flame Resistance ◽

Limiting Oxygen Index

Flame retardant mixtures of multi-walled carbon nanotubes (MWCNTs) and intumescent flame retardant (IFR) coatings were applied to polyamide 6,6 (PA 6,6) fabrics to explore whether MWCNTs acted as a good synergist on the thermal stability and flame resistance of the IFR system. The influence of MWCNTs on the flame retardant properties and thermal degradation of the PA 6,6 fabrics were investigated by limiting oxygen index (LOI), vertical burning test (VBT), thermogravimetric analyzer (TGA), scanning electron microscopy (SEM) and cone calorimeter test (CCT). The peak heat release rate and total heat release of the IFR-PA 6,6 fabric with three kinds of wt% MWCNTs were lower than those of the only traditional IFR-PA 6,6 fabric (reduced by 74.2–76.4% and 74.3–76.5%, respectively). As compared to the traditional IFR coating, it was found that no enhancements for thermal stability and flame retardancy in terms of the ability to retard ignition were achieved for the MWCNT/IFR coating. These results demonstrated that the introduction of MWCNTs into an IFR coating can improve the flame retardancy of PA 6,6 fabric in terms of the heat release rate from CCT analysis, but it failed other burning measurements, such as LOI and VBT.

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Intumescent Flame Retardant Mechanism of Lignosulfonate as a Char Forming Agent in Rigid Polyurethane Foam

Polymers ◽

10.3390/polym13101585 ◽

2021 ◽

Vol 13 (10) ◽

pp. 1585

Author(s):

Weimiao Lu ◽

Jiewang Ye ◽

Lianghai Zhu ◽

Zhenfu Jin ◽

Yuji Matsumoto

Keyword(s):

Thermal Stability ◽

Flame Retardant ◽

Flame Retardancy ◽

Flame Retardants ◽

Hydroxyl Groups ◽

Condensed Phases ◽

Limiting Oxygen Index ◽

Cone Calorimeter Test ◽

Intumescent Flame Retardants ◽

Flame Retardancy Mechanism

Intumescent flame retardants (IFR) have been widely used to improve flame retardancy of rigid polyurethane (RPU) foams and the most commonly used char forming agent is pentaerythritol (PER). Lignosulfonate (LS) is a natural macromolecule with substantial aromatic structures and abundant hydroxyl groups, and carbon content higher than PER. The flame retardancy and its mechanism of LS as char forming agent instead of PER in IFR formulation were investigated by scanning electron microscopy, thermogravimetric analysis, limiting oxygen index testing and cone calorimeter test. The results showed LS as a char forming agent did not increase the density of RPU/LS foams. LOI value and char residue of RPU/LS foam were higher than RPU/PER and the mass loss of RPU/LS foam decreased 18%, suggesting enhanced thermal stability. CCT results showed LS as a char forming agent in IFR formulation effectively enhanced the flame retardancy of RPU foams with respect to PER. The flame retardancy mechanism showed RPU/LS foam presented a continuous and relatively compact char layer, acting as the effect of the flame retardant and heat insulation between gaseous and condensed phases. The efficiency of different LS ratio in IFR formulation as char forming agent was different, and the best flame retardancy and thermal stability was obtained at RPU/LS1.

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