Preparation of borate–modified expandable graphite and its flame retardancy on acrylonitrile‐butadiene‐styrene resin

A borate‐modified expandable graphite (written as MEG) was prepared through one step intercalating reaction of natural graphite, using KMnO₄ as oxidant, H₂SO₄ and sodium tetraborate as intercalator and assistant intercalator, respectively. The dilatability, structure, element contents, thermal stability, and flame retardancy on acrylonitrile‐butadiene‐styrene (ABS) were investigated. Compared with the normal expandable graphite (written as EG, which was prepared with only H₂SO₄ as intercalator), the results show that MEG exhibits higher expandable property, thermal stability and flame retardancy on ABS. The EDS, FT‐IR, and XRD results reveal that borate has been inserted into graphite layers. With the addition of MEG or EG at a 30 wt%, LOI of 70ABS/30MEG composite improved to 27.9%, 2.2% higher than that of 70ABS/30EG. Moreover, the synergistic effect between MEG and traditional intumescent flame retardant (IFR, consists of ammonium polyphosphate (APP), pentaerythritol (PER), and melamine (MEL) with a mass ratio of 7.5:4.5:3.0) improves the LOI of 70ABS/15MEG/15IFR composite to 32.6%, and the UL‐94 level reaches V‐0. This synergistic efficiency is attributed to the formation of continuous and compact residual char. Addition of MEG together with IFR changes the ABS pyrolysis behavior, and there is not only physical synergy, but also chemical reaction. POLYM. COMPOS., 37:2673–2683, 2016. © 2015 Society of Plastics Engineers     

Application of a novel halogen‐free intumescent flame retardant for acrylonitrile‐butadiene‐styrene

A novel intumescent flame retardant (IFR), containing ammonium polyphosphate (APP) and poly(tetramethylene terephthalamide) (PA4T), was prepared to flame‐retard acrylonitrile‐butadiene‐styrene (ABS). The flame retardation of the IFR/ABS composite was characterized by limiting oxygen index (LOI) and UL‐94 test. Thermogravimetric analysis (TGA) and TGA coupled with Fourier transform infrared spectroscopy (TG‐FTIR) were carried out to study the thermal degradation behavior of the composite and look for the mechanism of the flame‐retarded action. The morphology of the char obtained after combustion of the composite was studied by scanning electron microscopy (SEM). It has been found the intumescent flame retardant showed good flame retardancy, with the LOI value of the PA4T/APP/ABS (7.5/22.5/70) system increasing from 18.5 to 30% and passing UL‐94 V‐1 rating. Meanwhile, the TGA and TG‐FTIR work indicated that PA4T could be effective as a carbonization agent and there was some reaction between PA4T and APP, leading to some crosslinked and high temperature stable material formed, which probably effectively promoted the flame retardancy of ABS. Moreover, it was revealed that uniform and compact intumescent char layer was formed after combustion of the intumescent flame‐retarded ABS composite. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Flame retardancy and water resistance of novel intumescent flame‐retardant oil‐filled styrene–ethylene–butadiene–styrene block copolymer/polypropylene composites

A novel halogen‐free flame‐retardant composite consisting of an intumescent flame retardant (IFR), oil‐filled styrene–ethylene–butadiene–styrene block copolymer (O‐SEBS), and polypropylene (PP) was studied. On the basis of UL‐94 ratings and limiting oxygen index (LOI) data, the IFRs consisted of a charring–foaming agent, ammonium polyphosphate, and SiO₂ showed very effective flame retardancy and good water resistance in the IFR O‐SEBS/PP composite. When the loading of IFR was only 28 wt %, the IFR–O‐SEBS/PP composite could still attain a UL‐94 V‐0 (1.6 mm) rating, and its LOI value remained at 29.8% after a water treatment at 70°C for 168 h. Thermogravimetric analysis data indicated that the IFR effectively enhanced the temperature of the main thermal degradation peak of the IFR–O‐SEBS/PP composites because of the formation of abundant char residue. The flammability parameters of the composites obtained from cone calorimetry testing demonstrated that water treatment almost did not affect the flammability behavior of the composite. The morphological structures of the char residue and fractured surfaces of the composites were not affected by the water treatment. This was attributed to a small quantity of IFR extracted from the composite. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39575.     

Synergistic effect of ammonium polyphosphate and expandable graphite on flame‐retardant properties of acrylonitrile‐butadiene‐styrene

A new intumescent flame‐retardant (IFR) system consisting of expandable graphite (EG) and ammonium polyphosphate (APP) was applied in acrylonitrile–butadiene–styrene (ABS) resin. A synergistic effect between EG and APP on the flame retardancy of ABS was observed. Fixing the total loading of flame retardant at 15 wt %, the limited oxygen index (LOI) could reach 31 vol % at a weight ratio of 3 : 1 for EG and APP. While LOI values of EG‐ and APP‐filled ABS were only 26.0 and 21.5 vol % at the same loading, respectively. The UL‐94 vertical burning test suggested that samples with different ratios of EG and APP could all pass V‐0 rating while the samples containing EG and APP alone only passed V‐1 rating. Thermogravimetric analysis indicated that the addition of EG and APP (3 : 1 by weight) to ABS led to an increase in the amount of high‐temperature residue by 11.8 wt %, and a decrease of mass loss rate by 0.7%/°C compared with pure ABS. Scanning electronic microscopy revealed a homogeneous compact intumescent char layer of ABS/EG/APP samples. Based on our experiment and combined with others' previous studies, the synergistic mechanism is inferred. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

阻燃ABS的热稳定性研究

建立了评价阻燃丙烯腈–丁二烯–苯乙烯塑料(ABS)材料热稳定性的不同方法,从阻燃剂及添加剂的分解机理进行分析,发现Mg O对四溴双酚A具有很好的热稳定作用,硬脂酸镁/有机锡热稳定剂组合很好地抑制氯化聚乙烯(PE-C)的热降解,开发了一种具有较好热稳定性的阻燃ABS热稳定体系,具有很好的市场应用前景。     

Synergistic effect of a novel charring agent with ammonium polyphosphate on flame retardancy and thermal degradation of acrylonitrile‐butadiene‐styrene copolymer

A novel charring agent poly(1,3‐propylene terephthalamide) (PPTA) was synthesized and characterized by Fourier transform infrared spectroscopy and ¹H nuclear magnetic resonance. This novel charring agent combined with ammonium polyphosphate (APP) was adopted as an intumescent flame retardant (IFR) to impart flame retardance and dripping resistance to acrylonitrile‐butadiene‐styrene copolymer (ABS). Flammability and thermal behaviors of the treated ABS were investigated by limiting oxygen index, vertical burning test and thermogravimetric analysis. The results showed that the IFR with the novel charring agent had both excellent flame retardant and anti‐dripping abilities for ABS. The thermogravimetric analysis curves indicated that there was a synergistic effect between PPTA and APP, which greatly promoted the char formation of IFR‐ABS composites. Meanwhile, the thermal degradation mechanism of PPTA and APP/PPTA was characterized using thermogravimetric analysis/infrared spectrometry. The results demonstrated that APP changed the thermal degradation behavior of PPTA and reacted with PPTA to form a crosslinked structure. Additionally, the structure and morphology of char residues were studied by Fourier transform infrared spectroscopy and scanning electron microscopy. Copyright © 2011 Society of Chemical Industry     

Synergistic effect of organo‐montmorillonite on intumescent flame retardant ethylene‐octene copolymer

Nanocomposite of thermoplastic elastomer ethylene‐octene copolymer/maleated ethylene‐octene (POE/POE‐g‐MAH) with organo‐montmorillonite (OMMT, 11 wt %) as masterbatch have been obtained by melt blending and it has been characterized by transmission electron microscopy (TEM). Flame retardant POE/POE‐g‐MAH/OMMT/ammonium polyphosphate‐pentaerythritol (APP‐PER) (an intumescent flame retardant with 75 wt % ammonium polyphosphate and 25 wt % pentaerythritol) composites were prepared by using melting processing to study their structures, flame‐retardancy, thermal, and mechanical properties. TEM showed exfoliated structures throughout POE/POE‐g‐MAH/OMMT masterbatch and POE/POE‐g‐MAH/OMMT/APP‐PER nanocomposites. Synergistic effect was observed between OMMT and APP‐PER resulting in significant improvements on thermal stability, flame‐retardancy and mechanical properties in the POE/POE‐g‐MAH/OMMT/APP‐PER nanocomposites. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Flame‐retardant properties of acrylonitrile–butadiene–styrene/wood flour composites filled with expandable graphite and ammonium polyphosphate

Expandable graphite (EG) and ammonium polyphosphate (APP) were used to improve the flame retardancy of acrylonitrile–butadiene–styrene based wood–plastic composites (WPCs). A synergistic effect between EG and APP on the flame retardancy of the WPCs was proposed. The results show that the highest limited oxygen index (LOI) of 34.2% and a V‐0 rating were achieved when the ratio of EG to APP 12.5:7.5; this comprised 20 wt % of the total amount. However, LOI values of the samples with EG and APP alone were only 30.5 and 24.5%, respectively. Thermogravimetric analysis indicated that the flame retardants improved the amount of residue. The EG and EG/APP additives greatly decreased the peak heat release rate and suppressed smoke according to cone calorimetry testing. The scanning electron microscopy analysis indicated that the surface of the wormlike char was covered with a granular substance, which may have been the viscous phosphoric acid or poly(phosphoric acid) decomposed from APP. The flame‐retardant additives worsened the mechanical properties of the WPCs. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40281.     

Fire retardancy effect of phosphorus‐modified halloysite on polyamide‐11 nanocomposites

Halloysite nanotubes (HNTs) were successfully incorporated as flame retardants in polyamide‐11 (PA11) after their modification with methyl phosphonic acid. Fourier transform infrared spectroscopy, thermal gravimetric analysis (TGA) and pyrolysis–gas chromatography–mass spectrometry were used to evidence the functionalization of the clay. Raw and modified HNTs were then incorporated by melt mixing in PA11 at 20 wt%. Compositions containing both ammonium polyphosphate (APP) and HNTs were also prepared. TGA and pyrolysis combustion flow calorimeter exhibited enhancement in thermal stability upon incorporation of both raw and modified halloysite nanotubes while APP causes degradation at lower temperature. Cone calorimeter data showed that modified halloysite acts by forming an insulating barrier during the combustion, which limits heat and mass transfers. Moreover, elemental analysis of sample residues after cone test evidenced that a part of the phosphorus of the modified halloysite was transferred to the gaseous phase. These results suggest the full potential of halloysite as fire retardant agent for polyamides. POLYM. ENG. SCI., 59:526–534, 2019. © 2018 Society of Plastics Engineers     

Flame retardancy and mechanical properties of polyamide 6 with melamine polyphosphate and ionic liquid surfactant‐treated montmorillonite

The mechanical properties and inflammability of polyamide 6 (PA6) nanocomposites incorporated with Montmorillonite organoclay (MMT) modified with thermal stable ionic liquid surfactants were investigated. The compatibility between ionic liquid‐treated MMT and PA6 matrix was improved and the intercalation morphology was achieved, which resulted in the increaseof tensile modulus. However, the addition of organo‐MMTs alone did not improve the inflammability of the PA6 nanocomposite, because of strong melt‐dripping behavior of PA6 matrix. Addition of auxiliary melamine polyphosphate (MPP) intumescent flame retardant to the nanocomposite prevented the melt dripping and enhanced inflammability performance. The enhanced inflammability of PA6/organoclay/MPP nanocomposites was attributed to the synergistic effect between imidazolium or phosphonium organo‐MMTs and intumescent flame retardant MPP. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40648.     

Flame-retardant properties of phenol–formaldehyde-type resins and triphenyl phosphate in styrene–acrylonitrile copolymers

The thermal and flame-retardant properties of phenol–formaldehyde-type resins (crosslinked and noncrosslinked) in mixtures with triphenyl phosphate and styrene–acrylonitrile resins were evaluated. The mixtures show a synergistic effect between triphenyl phosphate and novolacs. Those containing phenol–formaldehyde novolac resins are found to be most flame retardant. There does not seem to be a relationship between the oxygen index (OI) and UL 94 tests. Scanning electron microscopy analysis show a surface structure with cavities and stratification, very similar to that of intumescent additives. Evidence was found indicating that this flame-retardant system works in both the gas and condensed phase. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1067–1076, 1998     

Functionalizing carbon nanotubes by grafting cyclotriphosphazene derivative to improve both mechanical strength and flame retardancy

An intumescent flame‐retardant, hex(4‐carboxylphenoxy) cyclotriphosphazene (HCPCP) was synthesized and covalently grafted on to the surface of multiwalled carbon nanotubes (MWNTs) to obtain MWNT‐HCPCP. MWNT/epoxy resin (EP) and MWNT‐HCPCP/ EP nanocomposites were prepared via thermal curing. Transmission electron microscopy results showed that a core–shell structure with MWNTs as the hard core and HCPCP as the soft shell were formed after HCPCP (10 wt%) were attached to the MWNTs. The results of flammability tests showed an increased limited oxygen index value for MWNT‐HCPCP/EP nanocomposites. The mechanical properties including tensile strength and elongation were both dramatically improved due to the better dispersion of MWNT‐HCPCP in the EP matrix. The grafting of HCPCP can improve both the dispersion of nanotubes in polymer matrix and flame retardancy of the nanocomposites. POLYM. COMPOS., 35:2187–2193, 2014. © 2014 Society of Plastics Engineers     

Resonance tracking atomic force acoustic microscopy quantitative modulus mapping of carbon nanotubes‐reinforced acrylonitrile–butadiene–styrene polymer

This work presents a resonance tracking atomic force acoustic microscopy (RT‐AFAM) quantitative modulus mapping of carbon nanotubes‐reinforced acrylonitrile–butadiene–styrene polymer. RT‐AFAM average local modulus values registered were in good agreement with those measured by nanoindentation test. RT‐AFAM mapping modulus, nanoindentation, and transmission electron microscopy imaging showed that carbon nanotubes reinforcement of acrylonitrile–butadiene–styrene polymer matrix gives an elastic modulus enhancement of approximately 18.3% compared with the polymer matrix alone and showed that this technique provides high spatial resolution and helps to characterize the elastic properties of reinforced thermoplastic polymers and new compound materials at nanoscale. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40628.     

Intumescent flame retardants for polymers. I. The poly(acrylonitrile)–ammonium polyphosphate–hexabromocyclododecane system

The influence of ammonium polyphosphate (APP) and hexabromocyclododecane (HBCD) as flame retardant (FR) on poly(acrylonitrile) (PAN) has been examined. The APP–HBCD system behaves as an intumescent flame retardant (IFR) formulation, APP being the char-forming agent and HBCD the blowing agent. A negligible gas-phase mode of action was ascertained for HBCD with this substrate. A synergism between the two FR agents was observed, corresponding to about 50% increased efficacy with respect to the separate effects of the two components. Thermogravimetry (TG), oxygen index (OI), nitrous oxide index (NOI) experiments and phosphorous residue measurements were performed to substantiate the conclusion that a conclusion that a condensed phase mechanism of action accounts for all the facts observed.     

Effect of a nanoclay/triphenyl phosphate hybrid system on the fire retardancy of polycarbonate/acrylonitrile–butadiene–styrene blend

The effect of a hybrid system of nanoclay and triphenyl phosphate (TPP) on the fire retardancy of a polycarbonate (PC)/acrylonitrile–butadiene–styrene (ABS) blend was examined in this study. The nanoclay in the polymers decreased the peak heat release rates (PHRRs) with no significant effect on the ease of ignition and times to extinguishment. Improvements in the flame retardancy were observed only when nanoparticles were used with conventional flame‐retardant (FR) additives. Thermogravimetric analysis (TGA), cone calorimetry, and limited oxygen index (LOI)/UL 94 (Underwriters Laboratory) testing were used to investigate the thermal degradation, fire behavior, and flammability of the materials. The results show that when we used a combination of TPP and nanoclay as an FR system, degradation of the polymer blends was reduced as the TGA curves shifted to higher temperatures. PHRR in cone calorimetry testing decreased from 1032 kW/m² for the PC/ABS blend to 300 kW/m² for the PC/ABS/(12% TPP–2% nanoclay) sample, and the LOI increased from 23 to 35%, respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Catalytically synergistic effects of novel LaMnO3 composite metal oxide in intumescent flame‐retardant polypropylene system

The newly prepared LaMnO₃ was introduced as a novel perovskite composite metal oxide catalyst for the first time to improve the flame retardancy of flame‐retarded (FR) polypropylene with intumescent flame‐retardant (IFR) system consisting of ammonium polyphosphate (APP), pentaerythritol (PER), and melamine (MA). The synergistic effects of LaMnO₃ catalyst on the performance of IFR PP composites as well as the corresponding catalytically synergistic FR mechanism were investigated. The experimental results show that the incorporated LaMnO₃ catalyst plays an excellently catalytic and synergistic part in improvement of the flame retardancy of FR PP system. Compared with FR system without LaMnO₃, the incorporation of only 0.5 wt% LaMnO₃ into PP FR system could obviously improve the UL‐94 level from failure to V‐0 rating and decrease the micro‐scale calorimetry parameters peak heat release rate and heat release capacity. The remarkable improvement in flammability can be ascribed to the catalytic carbonization effect of LaMnO₃ on the intumescent flame retardant PP system. The incorporation of appropriate amount of LaMnO₃, on one hand, could improve the thermal stability of FR PP material, and on the other hand, could also act as nuclei to induce formation of the continuous, compact and smooth condensed phase intumescent charred layer with radialized spherulite‐like structure. As a result, the char yield and also the quality of the formed condensed phase charred layers are correspondingly enhanced remarkably, which is beneficial to improvement of the FR properties. POLYM. COMPOS., 35:2390–2400, 2014. © 2014 Society of Plastics Engineers     

Preparation of microencapsulated aluminum hypophosphite and flame retardancy and mechanical properties of flame‐retardant ABS composites

Microencapsulated aluminum hypophosphite (MFAHP) with a shell of melamine–formaldehyde resin (MF) was prepared via in situ condensation polymerization. The presence of MFAHP increased the water resistance of flame‐retarded (FR) acrylonitrile–butadiene–styrene (ABS) composites after hot water treatment. The mechanical properties indicate that the tensile strength and flexural strength of the FR ABS/MFAHP composites is enhanced with the incorporation of MFAHP. Cone calorimeter test results demonstrated that the peak heat release rate, total heat release, and total smoke release values of the ABS/MFAHP composites were significantly decreased. Digital photos and scanning electron microscopy images of the residues of ABS/25 wt % MFAHP₂ composites exhibited compact char layer structures, with many cobweb‐like nanoparticle arrangements formed on the surface by the burning process. The investigation of flame‐retardant mechanisms of ABS/MFAHP composites using infrared spectroscopy and energy‐dispersive X‐ray spectroscopy indicated that both the formation of char residue in the condensed phase and the release of inert gases by the MF shell in the gas phase led to the formation of compact and stable char layers containing carbon/pyrophosphate and aluminum polyphosphate, consequently leading to the good flame‐retardant performance of MFAHP. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45008.     

Microencapsulated melamine phosphate via the sol–gel method and its application in halogen‐free and intumescent flame‐retarding acrylonitrile‐butadiene‐styrene copolymer

In this paper, a facile method is introduced to modify melamine phosphate (MP) via the sol–gel process. The aim was simultaneously to increase the water resistance of MP and improve the dispersion and compatibility of MP in acrylonitrile‐butadiene‐styrene copolymer (ABS). In addition, the incorporation of SiO₂ particles into the MP/dipentaerythritol (DPER) system can further ameliorate the char‐forming ability and enhance the flame retardant properties of polymer composites. The chemical structure and surface morphology of SiO₂@MP were confirmed and observed by Fourier transform infrared (FTIR) spectroscopy, SEM and TEM, respectively. The results demonstrate that ABS/SiO₂@MP/DPER (3/1) at a loading of 30 phr reaches 31.2% limiting oxygen index and achieves a UL‐94 V‐0 rating. Moreover, FTIR spectra indicate that the main char‐forming process of the SiO₂@MP/DPER system occurs at 365–420 °C. A potential condensed flame retardant mechanism of SiO₂@MP and DPER in ABS composites is proposed via the systematic analysis of char residue after combustion by FTIR spectroscopy, SEM and X‐ray photoelectron spectroscopy. © 2015 Society of Chemical Industry     

The effects of intumescent flame retardant including ammonium polyphosphate/pentaerythritol and fly ash fillers on the physicomechanical properties of rigid polyurethane foams

In this study, rigid polyurethane foams that contain up to 5.0 wt % fly ash (FA) being a by‐product of thermal power stations and being cheap source were successfully produced using a polyurethane injection machine. The effects of FA content on the thermal conductivity, compressive strength, and flammability were investigated. The morphology of the cell was observed under a special microscope. The incorporation of FA in rigid polyurethane foams may dramatically decrease production costs and reduce environmental pollution. In addition, the effects of intumescent flame retardant composed of ammonium polyphosphate and pentaerythritol were examined in pure rigid polyurethane foams and FA‐rigid polyurethane foams. It was found that 5.0 and 7.5 wt % intumescent flame retardant loadings enhanced the thermal stability and improved the flammability resistance of the foams. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Development of halogen‐free flame‐retardant thermoplastic elastomer polymer blend

Ethylene‐propylene diene rubber (EPDM) and isotactic polypropylene (iPP) blends have widest industrial applications that require a degree of flame retardancy. Halogen‐free intumescent technology based on phosphorous salt is a significantly advanced approach to make the polymer flame‐retardant. Both ammonium polyphosphate and ethylenediamine phosphate are important intumescent compounds. Their combination with carbonific and spumific agents were studied in binary blends of EPDM/PP. The polymer system was vulcanized online during melt mixing. Intumescent flame‐retardant polymer systems exhibit good flame‐retardancy with optimum comparable physiomechanical, electrical, and fluid resistance properties, including lower smoke emission, which is essential to protect people because the visibility remains unaffected in the event of fire. Pronounced charring and intumescent effect appear to enhance the flame‐retardancy of the polymers. Possible expected intumescent mechanism is proposed based on the nonpyrolysis mechanism for the flame‐retarded polymer and the intumescent components. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 407–415, 2004