Improve the mechanical property and flame retardant efficiency of the composites of poly(lactic acid) and resorcinol di(phenyl phosphate) (RDP) with ZnO‐coated kenaf

The kenaf coated with zinc oxide (ZnO) was prepared and characterized by X‐ray diffraction, scanning electron microscopy, and X‐ray photoelectron spectroscopy. The ZnO‐coated kenaf and the flame retardant resorcinol di(phenyl phosphate) were blended with poly(lactic acid) (PLA) by solution compounding and melt blending to prepare the flame‐retarded PLA composites. The thermal stability, the mechanical property, and the flame retardancy of the PLA composites were improved evidently. The tensile strength of the prepared PLA composites could reach up to 62.3 MPa in comparison with 55.4 MPa of the pure PLA. The dense and compact char residues were observed after the combustion of the PLA composites containing ZnO‐coated kenaf, whereas there were serious dripping phenomena and no char formation during the combustion of the pure PLA. The use of ZnO‐coated kenaf could increase flame retardant efficiency obviously. The mechanism of flame retardancy was discussed. Copyright © 2014 John Wiley & Sons, Ltd.     

Modified montmorillonite and its application as a flame retardant for polyester

A novel flame retardant composed of montmorillonite (MMT) and hexachlorocyclotriphosphazene (HCCP) was prepared in this study. MMT was chemically bonded with HCCP via a 3‐aminopropyltriethoxysilane (KH‐550) coupling agent. The structure was characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, and NMR. The preliminary application for improving the flame retardancy of poly(ethylene terephthalate) (PET) was investigated by means of the limited oxygen index, the vertical burning test, and thermogravimetric analysis. Scanning electron microscopy was used to investigate the morphology of the char residue. The results show that the novel flame retardant had excellent fire retardancy; that is, the sample achieved an increased UL‐94 V‐0 rating and limited oxygen index value of 31.5. The residue of the flame‐retarded PET increased to 14.7% compared to the 6.2% value of pristine PET. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39625.     

Synergistic effect of expandable graphite and aluminum hypophosphite on flame‐retardant properties of rigid polyurethane foam

A series of flame retarding rigid polyurethane foam (RPUF) composites based on expandable graphite (EG) and aluminum hypophosphite (AHP) were prepared by the one‐pot method. The properties were characterized by limiting oxygen index (LOI) test, cone calorimeter test, thermogravimetric analysis (TGA), real‐time Fourier transform‐infrared spectra (RT‐FT‐IR), X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), etc. The results indicate that both EG and AHP could enhance the flame retardency of RPUF composites. Besides, the flame retardant effect of EG was better than that of AHP. The results also show that partial substitution of EG with AHP could improve the flame retardency of RPUF, and EG and AHP presented an excellent synergistic effect on flame retardancy. What is more, compared with RPUF/20EG and RPUF/20AHP, the heat release rate (HRR) and total heat release (THR) of RPUF/15EG/5AHP were lower.TGA results indicate that partial substitution of EG with AHP could improve the char residue which provided better flame retardancy for RPUF composites. The thermal degradation process of RPUF composites and the chemical component of the char residue were investigated by RT‐FT‐IR and XPS. And the results prove that RPUF/15EG/5AHP had higher heat resistance in the later stage. Compared with the RPUF composites filled with EG, a better cell structure and mechanical properties were observed with the substitution of AHP for part of EG. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42842.     

Mechanical and piezo‐resistive properties of styrene–butadiene–styrene copolymer covalently modified with graphene/styrene–butadiene–styrene composites

As novel piezoelectric materials, carbon‐reinforced polymer composites exhibit excellent piezoelectric properties and flexibility. In this study, we used a styrene–butadiene–styrene triblock copolymer covalently grafted with graphene (SBS‐g‐RGO) to prepare SBS‐g‐RGO/styrene–butadiene–styrene (SBS) composites to enhance the organic solubility of graphene sheets and its dispersion in composites. Once exfoliated from natural graphite, graphene oxide was chemically modified with 1,6‐hexanediamine to functionalize with amino groups (GO–NH₂), and this was followed by reduction with hydrazine [amine‐functionalized graphene oxide (RGO–NH₂)]. SBS‐g‐RGO was finally obtained by the reaction of RGO–NH₂ and maleic anhydride grafted SBS. After that, X‐ray diffraction, X‐ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, and other methods were applied to characterize SBS‐g‐RGO. The results indicate that the SBS molecules were grafted onto the graphene sheets by covalent bonds, and SBS‐g‐RGO was dispersed well. In addition, the mechanical and electrical conductivity properties of the SBS‐g‐RGO/SBS composites showed significant improvements because of the excellent interfacial interactions and homogeneous dispersion of SBS‐g‐RGO in SBS. Moreover, the composites exhibited remarkable piezo resistivity under vertical compression and great repeatability after 10 compression cycles; thus, the composites have the potential to be applied in sensor production. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46568.     

Optical,electrical, and electrochemical properties of graphene based water soluble polyaniline composites

Polyaniline (PANI) is one of the most common polymers known for its conducting properties. However, poor water solubility limits its applications. In this work, PANI has been functionalized with sulfonic acid groups to produce sulfonated PANI (SPANI) offering excellent solubility in water. To compensate for the decrease of electrical conductivity due to functionalization, SPANI was combined with reduced graphene oxide (RGO) to form SPANI/RGO composites with interesting optical, thermal, and electrical properties. The composites have been characterized using X‐ray diffraction (XRD), field emission scanning electron microscopy, UV–vis absorption spectroscopy, Raman spectroscopy, Fourier‐transform infrared spectroscopy, X‐ray photoelectron spectroscopy, thermogravimetric analysis, cyclic voltammetry, and four probe electrical conductivity measurement. The SPANI/RGO composites show increased thermal stability, reduced optical band gap and improved electrochemical properties compared with the pure polymer. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42766.     

Microwave irradiation synthesis and characterization of RGO‐AgNPs/polystyrene nanocomposites

Polystyrene and reduced graphene oxide/silver (PSTY/RGO/AgNPs) nanocomposites were prepared via an in situ bulk polymerization method using two different preparation techniques. In the first approach, a mixture of silver nitrate, hydrazine hydrate, and polystyrene containing graphene oxide (PSTY/GO) were reduced by microwave irradiation (MWI) to obtain R‐(PSTY‐GO)/AgNPs nanocomposites. In the second approach, a mixture of the (RGO/AgNPs) nanocomposite, which was produced via MWI, and STY monomers were polymerized using an in situ bulk polymerization method to obtain PSTY‐RGO/AgNPs nanocomposites. The two nanocomposites were compared and characterized by Fourier transform infrared spectroscopy, X‐ray diffraction, X‐ray photoelectron spectroscopy, high‐resolution transmission electron microscopy, Differential scanning calorimetry, and thermogravimetric analysis. The results indicate that the nanocomposites obtained using the first approach, which involved MWI, exhibited a better morphology and dispersion with enhanced thermal stability compared to the nanocomposites prepared without MWI. POLYM. COMPOS., 35:2318–2323, 2014. © 2014 Society of Plastics Engineers     

Application of functionalized graphene oxide in flame‐retardant polypropylene

A surface functionalized graphene oxide (FGO) was prepared by a simple and efficient method of treating graphene oxide (GO) with pentaerythritol (PER) in water using an ultrasound process. After the PER was grafted onto the surface of the GO, the GO became hydrophobic instead of hydrophilic and precipitated as a dark brown material. The results of Fourier‐transform infrared analysis, X‐ray photoelectron spectroscopy, X‐ray diffraction, and transmission electron microscopy demonstrated that the PER had been successfully attached to the GO. Subsequently, the FGO was incorporated into the intumescent flame‐retardant‐polypropylene system. The presence of FGO improved the flame‐retardant efficiency as evidenced by the limiting oxygen index (LOI) and vertical burning test (UL‐94) test. Analysis by scanning electronic microscopy indicated that the FGO promoted the formation of a continuous, intact residual char layer on the surface of the polymer, which acts as an insulating barrier to protect the base material. As a result, it delayed the peak of heat release rate and increased the residual mass obtained on combustion of the polymer. J. VINYL ADDIT. TECHNOL., 21:278–284, 2015. © 2014 Society of Plastics Engineers     

石墨烯/碱式硫酸镁晶须/PVC复合材料的制备及性能表征

以改进的Hummers法制备还原氧化石墨烯(RGO),以RGO和碱式硫酸镁晶须(MHSHw)为填料,采用机械球磨法制备RGO/MHSHw/PVC复合粉料,经平板硫化机热压成型得三相复合板材。考察了RGO和MHSHw对复合材料电阻率、阻燃性能及力学性能的影响。结果表明:RGO具有很好的片层结构和导电性;当MHSHw添加量为5%,RGO添加量为1%时,RGO/MHSHw/PVC复合板材的表面电阻率为4×106Ω/square,比纯PVC下降8个数量级,达到了商业抗静电效果,拉伸强度达到最大值17.61 MPa,比纯PVC提高了44.04%,复合板材氧指数>33%,具有阻燃性能,得到力学性能优良兼具有抗静电和阻燃性能的复合材料。     

Modification of lignin and its application as char agent in intumescent flame‐retardant poly(lactic acid)

Urea‐modified lignin was prepared according to the Mannich reaction and well characterized by Fourier transform infrared spectrometer, elemental ananlyses, and scanning electron microscopy (SEM). Ammonium polyphosphate (APP) and urea‐modified lignin were added into poly(lactic acid) (PLA) as a novel intumescent flame‐retardant (IFR) system to improve flame retardancy of PLA. The flammability of IFR–PLA composites was studied using limiting oxygen index, UL‐94 vertical burning method and cone calorimeter test, and their thermal stability was evaluated by thermogravimetric analysis. The results showed that the urea‐modified lignin combined with APP exhibited much better flame retardancy and thermal stability than that of the combination of virgin lignin and APP. The improvement may be attributed to the better char morphology with more phosphoric char evidenced by SEM and X‐ray photoelectron spectroscopy. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Characterization and performance of dodecyl amine functionalized graphene oxide and dodecyl amine functionalized graphene/high‐density polyethylene nanocomposites: A comparative study

Dodecyl amine (DA) functionalized graphene oxide(DA‐GO) and dodecyl amine functionalized reduced graphene oxide (DA‐RGO) were produced by using amidation reaction and chemical reduction, then two kinds of well dispersed DA‐GO/high‐density polyethylene (HDPE) and DA‐RGO/HDPE nanocomposites were prepared by solution mixing method and hot‐pressing process. Thermogravimetric, X‐ray photoelectron spectroscopy, Fourier transforms infrared spectroscopy, X‐ray diffractions, and Raman spectroscopy analyses showed that DA was successfully grafted onto the graphene oxide surface by uncleophilic substitution and the amidation reaction, which increased the intragallery spacing of graphite oxide, resulting in the uniform dispersion of DA‐GO and DA‐RGO in the nonpolar xylene solvent. Morphological analysis of nanocomposites showed that both DA‐GO and DA‐RGO were homogeneously dispersed in HDPE matrix and formed strong interfacial interaction. Although the crystallinity, dynamic mechanical, gas barrier, and thermal stability properties of HDPE were significantly improved by addition of small amount of DA‐GO or DA‐RGO, the performance comparison of DA‐GO/HDPE and DA‐RGO/HDPE nanocomposites indicated that the reduction of DA‐GO was not necessary because the interfacial adhesion and aspect ratio of graphene sheets had hardly changed after reduction, which resulting in almost the same properties between DA‐GO/HDPE and DA‐RGO/HDPE nanocomposites. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39803.     

Physical wrapping of reduced graphene oxide sheets by polyethylene wax and its modification on the mechanical properties of polyethylene

A facile method to encapsulate the reduced graphene oxide (RGO) sheets physically with polyethylene (PE) wax was developed. The graphene oxide sheets were first wrapped with polyethylene wax, and reduced by hydrazine hydrate. The structure of the wrapped RGO was confirmed by means of Fourier transform infrared spectroscopy, X‐ray diffraction (XRD), and Raman spectroscopy. The PE wax‐wrapped RGO sheets were melt blended with PE to prepare PE/RGO nanocomposites. Transmission electron microscopy and XRD studies showed that this method could provide uniform dispersion of RGO sheets in the PE matrix. Scanning electron microscopy and Raman spectroscopy indicated that there was a strong interfacial interaction between the PE wax‐wrapped RGO sheets and PE matrix. Addition of 1 wt % RGO sheets in PE matrix led to a 48% increment in the yield stress and 118% increment in the Young's modulus, respectively. However, the elongation at break decreased with increasing RGO sheets loading content. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Ethylene vinyl acetate copolymer nanocomposites based on (un)modified sepiolite: Flame retardancy,thermal, and mechanical properties

Flame retardant ethylene‐vinyl acetate (EVA) nanocomposites were prepared by melt blending using unmodified and modified sepiolite. Modification process of sepiolite was carried out by using 3‐aminopropyltrimethoxysilane in water/ethanol medium. Thermal, mechanical, and flame retardancy properties of the prepared nanocomposites were evaluated and compared with each other. X‐ray diffraction and scanning electron microscopy indicated that sepiolite fibers are well‐dispersed in EVA matrix. By the addition of (un)modified sepiolite, both flame retardancy and thermal stability characteristics first improved, and then deteriorated, indicating a direct relationship between these properties. It was also found that sepiolite protects carbonyl groups of EVA from further degradation. Most interestingly, a simultaneous increase in both ductility and toughness was observed in the prepared composites. Whatever the evaluated properties were, whether the mechanical, thermal, or flame retardancy, the improved properties were more remarkable when modified sepiolite was utilized. POLYM. COMPOS., 38:1302–1310, 2017. © 2015 Society of Plastics Engineers     

壳聚糖/ZIF⁃67杂化物的制备及其对环氧树脂阻燃抑烟性能的影响

为了提高环氧树脂（EP）的阻燃抑烟性能,采用共沉淀法将类沸石咪唑酯骨架材料ZIF⁃67负载到壳聚糖（CS）表面,通过傅里叶红外光谱（FTIR）、X射线衍射（XRD）和扫描电子显微镜 （SEM）对其结构和形貌进行分析,结果表明杂化物CS⁃ZIF⁃67成功制备。将不同比例的CS⁃ZIF⁃67添加到EP中,研究其对EP阻燃抑烟性能的影响。结果表明,与纯的EP相比,CS⁃ZIF⁃67的加入可以提高EP复合材料的垂直燃烧UL 94等级和极限氧指数（LOI）、降低EP复合材料的热释放速率（HRR）和烟释放速率（SPR）,提高复合材料燃烧后的残炭量,CS⁃ZIF⁃67的加入可以有效提高EP的阻燃抑烟性能。对EP复合材料燃烧后的残炭进行SEM和Laman光谱分析。结果表明,CS⁃ZIF⁃67的加入,使得残炭的石墨化程度提高,EP燃烧时能形成更加致密的炭层,从而起到阻燃抑烟的作用。     

Preparation of expandable graphite with silicate assistant intercalation and its effect on flame retardancy of ethylene vinyl acetate composite

A halogen‐free intumescent flame retardant expandable graphite composite (EG), with an initial expansion temperature of 202°C and expansion volume of 517 mL g⁻¹, was successfully prepared via a facile two‐step intercalation method, i.e. using KMnO₄ as oxidant and H₂SO₄, Na₂SiO₃·9H₂O as intercalators. The prepared EG flame retardant was characterized by field emission scanning electron microscope, X‐ray diffraction spectroscopy, energy dispersive spectroscopy and Fourier transform infrared spectroscopy. Furthermore, flame retardancy and thermal property of various ethylene vinyl acetate copolymer (EVA) composites, including EVA/EG and EVA/EG/APP (ammonium polyphosphate) specimens, were studied through limiting oxygen index instrument (LOI), vertical combustion UL‐94 rating, thermal gravimetric and differential thermal analysis. The results indicate that the EVA/EG and EVA/EG/APP composites exhibit a better flame retardancy. Addition of EG at a mass fraction of 30% leads LOI of 70EVA/30EG composite improved to 28.7%. Even more, the synergistic effect between EG and APP improves the LOI of 70EVA/10APP /20EG composite to 30.7%. This synergistic efficiency is attributed to the formation of compact and stable layer‐structure, and the prepared EG can make EVA composite reach the UL‐94 level of V‐0. POLYM. COMPOS., 36:1407–1416, 2015. © 2014 Society of Plastics Engineers     

The preparation,characterization, and properties of silver nanoparticle reinforced reduced graphene oxide–poly(amidoamine) nanocomposites

A simple approach was employed to synthesize silver nanoparticle (Ag NP) reinforced reduced graphene oxide–poly(amidoamine) (Ag‐r‐RGO–PAMAM) nanocomposites. The structural changes of the nanocomposites with the PAMAM and Ag NPs were confirmed by Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, X‐ray diffraction, Raman spectroscopy, and scanning electron microscopy. In addition, the performance was characterized with thermogravimetric and electrical conductivity instruments. The results indicate that the Ag NPs are well dispersed in fine size on the surface of the RGO–PAMAM composites, which results in an increase of at least 38% in thermostability and a certain enhancement in electrical conductivity. It is worth noting that the electrical conductivity of the nanocomposites was approximately 5.88 S cm^?1, which was higher than that of RGO–PAMAM, and increases with the rising content of silver nanoparticles. Meanwhile, the Ag‐r‐RGO–PAMAM nanocomposites still maintain a favorable dispersion in organic solvents. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45172.     

An effective flame retardant for poly(ethylene terephthalate) synthesized by phosphaphenanthrene and cyclotriphosphazene

A novel flame retardant [9,10‐Dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxideÔtriphosphazene (DOPO–TPN)] based on phosphaphenanthrene and cyclotriphosphazene was synthesized and used to improve the flame retardancy of poly(ethylene terephthalate) (PET). The structure of DOPO–TPN was characterized by nuclear magnetic resonance, Fourier transform infrared spectroscope (FTIR), and elemental analysis. PET/DOPO–TPN composites with different amount of DOPO–TPN were prepared and the flame retardancy was determined by limiting oxygen index (LOI) and vertical burning test (UL‐94). With the incorporation of 5 wt % DOPO–TPN, the composite achieved a LOI value of 34% and UL‐94 V‐0 rating. The thermal properties of the PET/DOPO–TPN composites were investigated by thermogravimetric analysis. The flame retardant mechanism was investigated by pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS), FTIR, and scanning electron microscopy (SEM). The Py‐GC/MS results showed that DOPO based fragments would exist in the gas phase during the pyrolysis of PET/DOPO–TPN composites which demonstrated that DOPO–TPN could act through gas‐phase action to exert flame retardant effect. The results of FTIR and SEM demonstrated that DOPO–TPN could promote the formation of compact and intact char residues to inhibit the heat and combustible gas transmission in condensed phase. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45246.     

次磷酸铝与石墨烯对PBT的协效阻燃作用

将次磷酸铝（AHP）和石墨烯（RGO）协效应用于聚对苯二甲酸丁二醇酯（PBT）的阻燃处理。采用极限氧指数、垂直燃烧分析、微型量热分析、热失重分析等研究了PBT复合材料的阻燃性能。结果表明,适量RGO的加入能明显改善PBT的抗滴落性能; PBT/AHP-0.5 %RGO（质量分数,下同）样品的热释放速率峰值最低,从PBT/20 %AHP的518.7 W/g降低到433.0 W/g,下降了约16.52 %;RGO在合适的比例下可以促进PBT/AHP-0.5 %RGO样品残炭外表面形成较多数量,致密的囊泡,有效地阻碍了可燃性小分子的逸出,改善了材料的阻燃性能。     

Fire behaviour of polyester–clay nanocomposites

The aim of this study was on the one hand, to compare the fire behaviour of polyester/clay nanocomposites with that of the neat polymers added with the conventional flame retardant melamine isocyanurate (MIC) and on the other hand, to study the effect of the flame retardant added to the nanocomposites. Polyester/clay nanocomposites were prepared by using polybutylene terephthalate (PBT) and a co‐polyester elastomer as polymeric matrices and a commercial organoclay as filler. As verified by X‐ray diffractometry (XRD) and transmission electron microscopy (TEM) intercalated structures were obtained by mixing the molten polymer with the layered silicate in a corotating twin screw extruder. The fire behaviour of these materials was investigated by means of an oxygen consumption calorimetry (Cone Calorimeter). Peak heat release rate of 3‐mm thick samples measured at 50 kW/m² external heat flux was reduced by a factor of 2–3 by the addition of organically modified montmorillonite to the polymers. The further addition of MIC did not give a significant improvement in the behaviour of the materials. Copyright © 2005 John Wiley & Sons, Ltd.     

还原氧化石墨烯增强水泥基复合材料微观结构及力学性能

采用水热还原法制备了不同还原程度的还原氧化石墨烯(RGO),并将其添加到水泥浆体中,制得石墨烯增强水泥基复合材料。采用傅里叶变换红外光谱(FT-IR)、力学性能测试仪、扫描电子显微镜(SEM)对氧化石墨烯(GO)还原程度及水泥基复合材料的力学性能和微观结构进行测试。结果表明,在120℃水热条件下,控制不同还原时间可以得到不同还原程度的RGO;随着GO还原程度的提高,复合材料力学强度不断增加;RGO可使水泥更加密实,降低了水泥浆体的孔隙率,对水泥基复合材料起到增强增韧的作用。