Flammability,thermal stability,and mechanical properties of ethylene-propylene-diene monomer/polypropylene composites filled with intumescent flame retardant and inorganic synergists

Three kinds of inorganic particles, zinc borate (ZB), organic montmorillonite (OMMT), and expanded graphite (EG) as synergistic flame retardants, are incorporated into ethylene-propylene-diene monomer/polypropylene (EPDM/PP) composites filled with intumescent flame retardants (IFR). The effect of three synergistic flame retardants on the combustion, thermal stability, and mechanical properties of the EPDM/PP/IFR composites are investigated by limiting oxygen index (LOI), UL-94 test, cone calorimeter test (CCT), thermogravimetric analysis (TGA), scanning electron microscopy, mechanical property testing, and dynamic mechanical analysis (DMA). The results from LOI, UL-94, and CCT show that the synergistic effect of IFR with ZB and EG is better than IFR with OMMT in the flame retardant EPDM/PP/IFR composites. The TGA results indicate that the thermal stability and char residues of the composites is improved with the addition of inorganic particles, which is attributed to the formation of dense char layers to isolate heat flow. DMA results including storage modulus (G'), loss modulus (G"), and loss factor (tan δ) suggest that the composites with inorganic particles exhibit more rubber-filler interaction, which limits the movement of the rubber chains.     

Flame-retardant properties and synergistic effect of ammonium polyphosphate/aluminum hydroxide/mica/silicone rubber composites

The flammability behaviors of ammonium polyphosphate/aluminum hydroxide/mica/silicone rubber (APP/Al[OH]₃/mica/SiR) ceramifying composites containing APP, Al[OH]₃, and mica are investigated by cone calorimeter test. The thermal degradation and the synergistic effect of APP/Al(OH)₃/mica/SiR composites are investigated by thermal gravimetric analysis, X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. APP/Al(OH)₃/mica/SiR composites with 25 wt% of APP, 20 wt% of Al(OH)₃, 25 wt% of mica, and 30 wt% SiR presents a much lower total heat release, the value of peak heat release rate (PHRR), the maximum average heat release rate, the longest time to ignition, and time to the PHRR (t_PHRR), compared with the flame-retardant properties from composites with filler of APP and mica or APP and Al(OH)₃ alone. The results indicate that there is an excellent synergism in APP, Al(OH)₃, and mica, which endows APP/Al(OH)₃/mica/SiR composites with both good flame retardancy and fire prevention. The study on the synergism effect between fire prevention and flame retardancy of APP/Al(OH)₃/mica/SiR composites indicates that compounds containing P-O-Al are formed due to the reaction between APP and Al(OH)₃ during combustion in the early stage and a coherent, dense, and sealed structure is formed due to the reaction in mica, phosphates, and the thermal decomposition products of SiR during combustion in the later stage.     

聚磷酸铵的合成及其在聚丙烯阻燃中的应用

聚丙烯具有易燃性,限制其进一步应用。以磷酸二氢铵、五氧化二磷、尿素为原料合成聚磷酸铵,然后将其应用于聚丙烯中考察其阻燃性。在氨气压力为0.5 MPa、温度295℃下反应1.5 h,停止加热,降温至150℃,得到聚磷酸铵。红外光谱和X-衍射线表明合成聚磷酸铵是I型和II型混合型。当聚丙烯复合材料中膨胀型阻燃剂质量分数为30%,极限氧指数达30.8%,通过UL-94测试。结果表明,应用聚磷酸铵为原料的阻燃剂具有较好的阻燃性能。     

Optimization of intumescent flame retardant system based on ammonium polyphosphate,double pentaerythritol,and zinc borate for thermoplastic polyurethane composite

The widespread industrial applications of thermoplastic polyurethane (TPU) are partially limited by its flammability. The design of high-performance intumescent flame retardants (IFR) is of great significance for enhancing flame retardant (FR) performance of TPU. In this work, an IFR system consisting of ammonium polyphosphate (APP), double pentaerythritol (DPER), and zinc borate (ZB) is proposed. The optimized experimental parameters with 15 wt.% additive amount of FR, APP-DPER weight ratio of 2.28:1 and 15.56 wt.% ZB content are regulated based on Box–Behnken design-response surface methodology (BBD-RSM) to obtain TPU/FR composite with superior limiting oxygen index value of 30.2%. Noticeably, the design efficiency of TPU/FR composite is significantly improved by utilizing BBD-RSM. Results of vertical burning test show that the optimized TPU/FR composite passes UL 94 V-0 rating and peak heat release rate is dramatically reduced from 1355.88 (neat TPU) to 201.01 KW/m² through cone calorimeter test. In addition, scanning electron microscopy accompanied with Raman spectroscopy are conducted to characterize the morphology and composition of residual char for further exploring the FR mechanism of IFR system in TPU. The as-prepared TPU/FR composite has provided new potential application in engineering fields.     

Flame retardant and mechanical properties of epoxy composites with ammonium polyphosphate and hyperbranched silicon-containing polymers

The epoxy resin was mixed with ammonium polyphosphate (APP) and hyperbranched silicon-containing polymers (HBP-B2). The cured composites were investigated by thermogravimetric analysis, Underwriters Laboratory standard for the flammability properties under vertical burning (UL-94V), and limited oxygen index (LOI) test methods. The LOI of 43.5 and could be obtained at the weight ratio of 70:25:5 for the epoxy resin:APP:HBP-B2, Sample A25B5, and the LOI was higher than that of the composite with 30 wt % APP only, Sample A30B0, of which the LOI was 34.5. It suggested that the HBP-B2 could cooperate with the epoxy/APP composite to form a more effective protection layer during combustion, which resulted in a higher second-stage thermal degradation temperature. During the UL-94V test, the flame was extinguished immediately once the burner was removed. Furthermore, the tensile and impact strength of the epoxy/APP composite could also be improved by using HBP-B2 compound as the toughening agent. The composite containing 20% of APP and 10% of HBP-B2, Sample A20B10, still had excellent flame retardant properties with a V-0 rating. Moreover, the tensile strength and impact strength of that composite got 19 and 25% increases compared with the Sample A30B0, which contained 30% of APP only. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48857.     

The flame retardancy and mechanical properties of jute/polypropylene composites enhanced by ammonium polyphosphate/polypropylene powder

Surface flame retarded jute/polypropylene composites (J/P/A) were prepared via a modified strategy: the mixture of PP and APP powder was spread over the surface of jute/PP nonwoven felts, and then transformed into the flame retarded layer by the hot pressing process. The flame retardancy and thermal properties of composites were analyzed by limit oxygen index (LOI), horizontal burning rate (HBR), thermogravimetric analyses (TGA), and differential scanning calorimetry (DSC). We demonstrated that the flame retardancy and mechanical properties of composites was significantly improved compared with those obtained by presoaking the nonwoven fiber felts in flame retardant (FR) solvent before hot pressing. The mechanism of thermal degradation of jute fiber and flame‐retardant mechanism of composites were analyzed by Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), and scanning electron microscope (SEM). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43889.     

Simultaneously enhanced fracture toughness and flame‐retardant property of poly(l‐lactic acid) via reactive blending with ammonium polyphosphate and in situ formed polyurethane

The preparation of poly(l ‐lactic acid) (PLLA) with high mechanical and ideal flame‐retardant properties is a great challenge. Herein, a simultaneous toughness and flame‐retardant PLLA composite was successfully fabricated by using a one‐step process which introduces 4,4′‐methylenediphenyl diisocyanate and ammonium polyphosphate (APP) into PLLA/poly(ε‐caprolactone) blends. SEM, Fourier transform infrared spectroscopy and TGA were adopted to confirm that APP participated in the in situ reaction during the melt process. The impact strength was increased to 13.5 kJ m^?2 from 1.0 kJ m^?2 for L8P2A5 composite, indicating the toughening effect of reactive blending. The cone calorimeter test, limiting oxygen index and vertical burning test results indicate that the flame‐retardant properties of the composites are enhanced with increasing APP content. This work provides a method to prepare PLLA with high mechanical properties and enhanced flame retardancy. © 2020 Society of Chemical Industry     

Influence of ammonium polyphosphate modified with 3‐(methylacryloxyl) propyltrimethoxy silane on mechanical and thermal properties of wood flour–polypropylene composites

In this article, the influence of ammonium polyphosphate (APP) and ammonium polyphosphate modified with 3‐(Methylacryloxyl) propyltrimethoxy silane (M‐APP) on mechanical properties, flame retardancy, and thermal degradation of wood flour–polypropylene composites (WF/PP composites) have been investigated. Polypropylene grafted with m‐isopropenyl‐α,α‐dimethylbenzyl‐isocyanate (m‐TMI‐g‐PP) was used to improve the adhesion of WF/PP composites. APP and M‐APP were used as flame retardants. The experimental results demonstrated that addition of M‐APP obviously enhanced mechanical properties of WF/PP composites. According to cone calorimetry results, M‐APP is also an effective flame retardant for WF/PP composites, compared to that of APP. It was also found that M‐APP decreased the 1% weight loss temperature and increased char residue. The thermal degradation of wood flour based upon the first peak temperature of wood decreased from 329.3 to 322.9°C and the thermal degradation of PP based upon the second peak temperature of PP improve from 518.0 to 519.6°C, when M‐APP was added to the WF/PP composites. From SEM results the char layer of the 25% M‐APP systems is much more intumescent than that of the 25% APP systems, indicating that 3‐(Methylacryloxyl) propyltrimethoxy silane can improve the char‐forming ability of WF/PP composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synergistic Effect of the Charring Agent on the Thermal and Flame Retardant Properties of Polyethylene

Summary: A new charring agent (CA), a derivative of triazines, was synthesized. The flame retardancy and thermal behavior of a new intumescent flame‐retardant (IFR) system for PE (PE‐IFR) were investigated by limited oxygen index (LOI), UL‐94 test, thermogravimetric analysis (TGA), and FTIR spectroscopy. The TG curves shows that the amount of residue of IFR‐PE system are largely increased compared to those of PE at temperatures ranging from 350 to 700 °C. The new PE‐IFR system can apparently reduce the amount of decomposing products at higher temperatures and promotes the formation of carbonaceous charred layers. It showed a distinct synergistic flame retardant effect (SE) between nitrogen and phosphorus. The flame retardant PE composition was optimized to achieve a LOI value of 31.2 and UL‐94 V‐0 performance with the synthesized charring agent, ammonium polyphosphate (APP).

TG curves of PE, APP, CA, and different PE/CA/APP systems.     

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     

Influence of modified ammonium polyphosphate on the fire behavior and mechanical properties of polyformaldehyde

In this work, three kinds of APP, coated with melamine (MF-APP), silane (GW-APP), epoxy (MC-APP) were employed to compound with novolac resin (Novolac) and melamine (ME), aimed to study the effect of the modified APP on the flame-retardant performance, mechanical properties, and thermal stability of polyformaldehyde (POM). The results showed that composites with modified APP exhibited better flame retardant and mechanical performance than that with unmodified APP. In contrast, GW-APP had the best synergistic effect with Novolac and ME, and POM/GW-APP composites reached UL-94 V-0 rating and its limit oxygen index (LOI) value was up to 34.0%. The morphology of the carbon layer showed that the silane coating material can promote the charring process in condensed phase better than epoxy and melamine coating materials in flame retardant POM system, leading to the formation of integrated char layers with more quantity and higher quality, which effectively delayed the mass and heat transfer during combustion.     

Mechanical,thermal and combustion properties of intumescent flame retardant biodegradable poly (lactic acid) composites

ABSTRACT

Despite extraordinary mechanical properties and excellent biodegradability, poly (lactic acid) (PLA) still suffers from a highly inherent flammability, restricting its applications in the electric and automobile fields. Although a wide range of flame retardants have been developed to reduce the flammability, they normally compromise the mechanical strength of PLA. In this study, a series of composites based on PLA, have been prepared by melt-blending with intumescent flame retardants (IFRs). The morphology, thermal stability and burning behaviour of the composites were investigated using a scanning electron microscope–energy dispersive spectrometer (SEM–EDS), thermogravimetric analysis (TGA), the limiting oxygen index (LOI), vertical burning (UL-94) and the cone calorimeter test (CCT). The LOI value reached 38.5% and UL-94 could pass V-0 for the PLA/IFR composite containing only 12 wt-% IFR. The dispersion of IFR in PLA was observed using SEM–EDS. A significant improvement in fire retardant performance was observed for the PLA/IFR composite from the CCT (reducing the heat release rate and the total heat release). More importantly, compared to pure PLA, the addition of IFR did not seriously deteriorate the mechanical properties of the material.     

Morphology,thermal, and mechanical properties of flame‐retardant silicone rubber/montmorillonite nanocomposites

Flame‐retardant methyl vinyl silicone rubber (MVMQ)/montmorillonite nanocomposites were prepared by solution intercalation method, using magnesium hydroxide (MH) and red phosphorus (RP) as synergistic flame‐retardant additives, and aero silica (SiO₂) as synergistic reinforcement filler. The morphologies of the flame‐retardant MVMQ/montmorillonite nanocomposites were characterized by environmental scanning electron microscopy (ESEM), and the interlayer spacings were determined by small‐angle X‐ray scattering (SAXS). In addition to mechanical measurements and limited oxygen index (LOI) test, thermal properties were tested by thermogravimetric analysis (TGA). The decomposition temperature of the nanocomposite that contained 1 wt % montmorillonite can be higher (129°C) than that of MVMQ as basal polymer matrix when 5% weight loss was selected as measuring point. This kind of silicone rubber nanocomposite is a promising flame‐retardant polymeric material. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3275–3280, 2006     

聚氨酯／聚磷酸胺体系的阻燃及力学性能

应用热重量分析,水平燃烧,应力－应变和扫描电镜等实验手段,研究了聚氨酯／聚磷酸胺（ＰＵ／ＰＰＡ）体系的热分解特性以及阻燃和力学性能,实验结果表明,随阻燃剂ＰＰＡ添加量的增加,ＰＵ的热分解峰明显地移向 温,并与阻燃机理有关,在ＰＵ中加入ＰＰＡ可显著改善ＰＵ的阻燃性能,但同时也使的力不性强度明显下降。     

Effect of treated mica on rheological,cure, mechanical,and dielectric properties of ethylene propylene diene monomer (EPDM)/barium titanate (BaTiO3)/mica

In this study, mica, treated by three types of coupling agents, isopropyl trioleic titanate (NDZ105), 3‐aminopropyltriethoxysilane (KH550), and vinyltrimethoxysiloxane homopolymer (SG‐Si6490), were utilized to improve the properties of ethylene propylene diene monomer (EPDM)/barium titanate (BaTiO₃) composites. It is found that the addition of untreated mica can increase the complex viscosity, while the KH550 modified mica can reduce the complex viscosity. Compared to single usage of coupling agent SG‐Si6490, the hybrid usage of KH550 and SG‐Si6490 can further increase the tensile strength of EPDM/BaTiO₃/SG‐Si6490 treated mica (70/20/10) from 9.10 to 11.01 MPa (22% increase). The untreated mica can increase the interfacial polarity and improve the dielectric constant of EPDM/BaTiO₃ (70/30) from 7 to 9 at 40 MHz (28% increase). Moreover, the KH550 treated mica can enhance the thermal conductivity of EPDM/BaTiO₃ (70/30) from 0.323 W m^?1 K^?1 to 0.446 W m^?1 K^?1 (38% increase). In the meantime, the increased crosslink density caused by coupling agents can increase the volume resistivity of EPDM composites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44833.     

Flame retardancy and mechanical properties of ferrum ammonium phosphate–halloysite/epoxy polymer nanocomposites

To recycle the nitrogen (N) and phosphorus (P) from wastewater, ferrum ammonium phosphate (FAP)–halloysite nanotubes (HNTs) were synthesized with simulated wastewater containing N, P, and Fe pollutants as raw materials. The adsorption–chemical precipitation in situ method was used to synthesize the target products, and the optimal conditions for the synthesis of the FAP–HNTs were obtained. Fourier transform Infrared (FTIR) spectroscopy, energy‐dispersive spectroscopy (EDS), scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis were conducted to characterize the samples. The FAP particle size was 20–30 nm in the FAP–HNTs. The FTIR spectra demonstrated that a small amount of water in the FAP–HNTs promoted the curing reaction. The FAP–HNTs and Exolit OP 1230 (OP) were introduced into epoxy (EP) to prepare the polymer nanocomposites. The heat release rate (HRR) and flammability of the EP composites were tested by microscale combustion calorimetry and UL‐94 instruments. The mechanical properties of the EP composites also were tested by a tension testing system. The results indicate that the flame retardancy and mechanical properties of the EP composites were improved by FAP–HNT. The addition of FAP–HNT and OP gave rise to an evident reduction of HRR and a prolonged burning time for the EP. EP/FAP–HNT/OP (20) (where 20 is the loading weight percentage) passed the UL 94 V‐0 rating. The analysis of the char revealed the synergy of the FAP–HNTs and OP in reducing the flammability of the polymers. We concluded that these polymers show potential for applications in wastewater treatment and N/P recycling. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41681.     

Cure characteristics,morphology, and mechanical properties of ethylene–propylene–diene–monomer rubber/acrylonitrile butadiene rubber blends

Blends based on ethylene–propylene–diene monomer rubber (EPDM) and acrylonitrile butadiene rubber (NBR) was prepared. Sulfur was used as the vulcanizing agent. The effects of blend ratio on the cure characteristics and mechanical properties, such as stress–strain behavior, tensile strength, elongation at break, hardness, rebound resilience, and abrasion resistance have been investigated. Tensile and tear strength showed synergism for the blend containing 30% of NBR, which has been explained in terms of morphology of the blends attested by scanning electron micrographs. A relatively cocontinuous morphology was observed for 70 : 30, EPDM/NBR blend system. The experimental results have been compared with the relevant theoretical models. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Cure characteristics,morphology, mechanical properties,and aging characteristics of silicone rubber/ethylene vinyl acetate blends

Silicone rubber/ethylene vinyl acetate (SR/EVA) rubber mixes with different ratios were prepared by using dicumyl peroxide (DCP) and benzoyl peroxide (BP) as curing agents. The vulcanization characteristics such as cure kinetics, activation energy, and cure rate of the blends were analyzed. The effects of blend ratio and curing agents on the mechanical properties such as stress–strain behavior, tensile strength, elongation at break, tear strength, relative volume loss, hardness, flex crack resistance, and density of the cured blends have been investigated. Almost all the mechanical properties have been found to be increased with increase in EVA content in the blends particularly in DCP‐cured systems. The increment in mechanical properties of the blends with higher EVA content has been explained in terms of the morphology of the blends, attested by scanning electron micrographs. Attempts have been made to compare the experimental results, from the evaluation of mechanical properties, with relevant theoretical models. The aging characteristics of the cured blends were also investigated and found that both the DCP‐ and BP‐cured blends have excellent water and thermal resistance. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1069–1082, 2006     

Thermal,mechanical and morphological properties of surface‐modified montmorillonite‐reinforced Viton rubber nanocomposites

Thermal, mechanical and morphological properties of surface‐modified montmorillonite (OMMT)‐reinforced Viton rubber nanocomposites were studied. The surface of montmorillonite was modified with a column chromatography technique using quaternary long‐chain ammonium salt as an intercalant, which resulted in uniform exchange of ions between montmorillonite and the ion‐exchange resin, and increased the d‐spacing to 31.5 Å. This improved d‐spacing was due to the use of an ion‐exchange column of sufficient length (35 cm) and diameter (5 cm) with maximum retention time for exchange of ions. The Viton nanocomposites reinforced with OMMT (3–12 wt%) were prepared using a two‐roll mill and moulded in a compression moulding machine. Tensile strength increased 3.17 times and elongation at break from 500 to 600% for 9 wt% loading of OMMT in comparison to pristine Viton rubber. Thermogravimetric analysis revealed that the presence of OMMT greatly improved the thermal stability. This improvement in properties with increasing OMMT loading was due to insertion of rubber chains between the OMMT plates with good wetting ability. Overall, at an optimum OMMT loading of 9 wt%, the properties of the Viton rubber nanocomposites improved, and subsequently worsened at 12 wt% due to agglomeration of OMMT as revealed by scanning electron microscopy and atomic force microscopy images. © 2013 Society of Chemical Industry     

Effects of ammonium polyphosphate and triphenyl phosphate on the flame retardancy,thermal, and mechanical properties of glass fiber–reinforced PLA/PC composites

The purpose of this study is to increase of the flammability properties of the glass fiber (GF)–reinforced poly (lactic acid)/polycarbonate (PLA/PC) composites. Ammonium polyphosphate (APP) and triphenyl phosphate (TPP) were used as flame retardants that are including the organic phosphor to increase flame retardancy of GF‐reinforced composites. APP, TPP, and APP‐TPP mixture flame retardant including composites were prepared by using extrusion and injection molding methods. The properties of the composites were determined by the tensile test, limiting oxygen index (LOI), differential scanning calorimetry (DSC), and heat release rate (HRR) test. The minimum T_g value was observed for the TPP including PLA/PC composites in DSC analysis. The highest tensile strength was observed in GF‐reinforced PLA/PC composites. In the LOI test, GF including composite was burned with the lowest concentration of oxygen, and burning time was the longest of this composite. However, the shortest burning time was obtained by using the mixture flame retardant system. The flame retardancy properties of GF‐reinforced PLA/PC composite was improved by using mixture flame retardant. When analyzed the results of HRR, time to ignition (TTI), and mass loss rate together, the best value was obtained for the composite including APP.