Functionalized carbon nanotubes with oligomeric intumescent flame retardant for reducing the agglomeration and flammability of poly(ethylene vinyl acetate) nanocomposites

A novel oligomeric phosphorous–nitrogen‐containing intumescent flame retardant poly (2,6‐diaminopyridine spirocyclic pentaerythritol bisphosphonate) (PDSPB) is synthesized, and subsequently multiwalled carbon nanotube (MWNT)‐grafted oligomeric intumescent flame retardant, MWNT‐g‐PDSPB, is fabricated via chemical grafting reaction and characterized. The grafting reaction was characterized by FTIR, NMR, and XPS. After high‐density PDSPB (88 wt%) were attached to the MWNTs, core‐shell nanostructures with MWNTs as the hard core and PDSPB as the soft shell were formed. The resultant MWNT‐g‐PDSPB was soluble and stable in polar solvents, such as DMF and DMSO. MWNT‐g‐PDSPB has excellent thermal stability and charring ability. The TEM results showed that the functionalized MWNTs could achieve better dispersion in poly(ethylene vinyl acetate) (EVA) matrix. The residue char of MWNT‐g‐PDSPB is as high as 70 wt%, and the grafting of intumescent flame retardant of PDSPB can improve both the dispersion of MWNTs in polymer matrix and flame retardancy of the nanocomposites. POLYM. COMPOS., 2013. © 2012 Society of Plastics Engineers     

表面改性对LDPE/nano-ATH复合材料性能的影响

采用熔融共混法制备了低密度聚乙烯(LDPE)/纳米氢氧化铝(nano-ATH)复合材料,研究了nano-ATH表面改性前后对复合材料力学性能和阻燃性能的影响;利用扫描电镜(SEM)分析了nano-ATH表面改性前后在LDPE基体中的分散性。结果表明:表面改性nano-ATH使复合材料具有较高的拉伸强度和断裂伸长率;nano-ATH用量较少时,其表面改性与否对复合材料的阻燃性能基本没有影响;加入量较大时,表面改性nano-ATH使复合材料具有较好的阻燃性能,其在LDPE基体中的分散性也得到改善。     

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     

Effect of EPDM‐g‐MAH on the morphology and properties of PA6/EPDM/HDPE ternary blends

The formation of core‐shell morphology within the dispersed phase was studied for composite droplet polymer‐blend systems comprising a polyamide‐6 matrix, ethylene‐propylene‐diene terpolymer (EPDM) shell and high density polyethylene (HDPE) core. In this article, the effect of EPDM with different molecular weights on the morphology and properties of the blends were studied. To improve the compatibility of the ternary blends, EPDM was modified by grafting with maleic anhydride (EPDM‐g‐MAH). It was found that core‐shell morphology with EPDM‐g‐MAH as shell and HDPE as core and separated dispersion morphology of EPDM‐g‐MAH and HDPE phase were obtained separately in PA6 matrix with different molecular weights of EPDM‐g‐MAH in the blends. DSC measurement indicated that there may be some co‐crystals in the blends due to the formation of core‐shell structure. Mechanical tests showed that PA6/EPDM‐g‐MAH/HDPE ternary blends with the core‐shell morphology exhibited a remarkable rise in the elongation at break. With more perfect core‐shell composite droplets and co‐crystals, the impact strength of the ternary blends could be greatly increased to 51.38 kJ m^?2, almost 10 times higher than that of pure PA6 (5.50 kJ m^?2). POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Study on the flame retardancy of EVM/magnesium hydroxide composites optimized with a flame retardant containing phosphorus and silicon

A novel phosphorus‐silicon‐containing flame retardant, spirocyclic pentaerythritol bisphosphorate disphosphoryl chloride/9, 10‐dihydro‐9‐oxa‐10‐phosphaphanthrene‐10‐oxide/vinyl methyl dimethoxysilane (SPDV), was synthesized successfully and used for optimizing the flame retardancy of ethylene‐vinyl acetate copolymer (EVM) rubber/magnesium hydroxide (MDH) composites. The microstructure of SPDV was characterized and determined by Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy. Thermogravimetric analysis (TGA) showed that SPDV had good charring effect in air even at high temperature (800°C). The flame retardancy of the optimized EVM/MDH composites by SPDV was investigated by limiting oxygen index (LOI), cone calorimeter, and UL‐94 vertical burning tests. A higher LOI value (29.4%) and better UL‐94 rating (V‐0) can be achieved for the optimized EVM/MDH composite (EVM‐7) than EVM/MDH composite without SPDV (EVM‐3) with the total loading of additives. The HRR decreased and residual mass increased gradually as the loading of SPDV increased for the optimized EVM/MDH composites. There existed distinct synergistic intumescent flame‐retardant effect between SPDV and MDH in EVM matrix. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Core–shell structure design of pulverized expandable graphite particles and their application in flame‐retardant rigid polyurethane foams

Pulverized expandable graphite (pEG) and melamine ? formaldehyde (MF) resin core ? shell structure particles (pEG@MF) as specific flame retardants for rigid polyurethane foam (RPUF) were synthesized by encapsulating pEG particles with a layer of MF resin via in situ polycondensation. The initial feed weight ratio of pEG and MF prepolymer was found to be the key factor affecting the shell forming process, and the shell growth can be regarded as a combination of ‘raspberry‐like’ and conventional ‘core–shell’ formation mechanisms. With the encapsulation of a well formed MF shell, the expandability of pEG particles was significantly enhanced from 42 mL g^–1 to 76 mL g^–1 and thus the pEG@MF particles showed good flame‐retardant performance in RPUF. The RPUF/pEG@MF composites passed the V‐0 rate and the limiting oxygen index was remarkably increased from 21 to 28 vol% by adding only 10 wt% pEG@MF particles; both the expandability and available expandable graphite content played an important role in controlling the flame‐retardant performance of pEG@MF particles. With a loading of fine sized pEG@MF particles, desirable mechanical and thermal insulation properties of RPUF/pEG@MF composites were achieved by preserving the complete cell structure of RPUF and screening the high thermal conductivity of the pEG particles with the thermally inert MF resin shell. The exciting application of the novel pEG@MF particles indicates that the core–shell structure design of expandable graphite can serve as promising solution for fabricating halogen‐free flame‐retardant RPUF composites with high performance. © 2013 Society of Chemical Industry     

Preparation and flame retardancy of a novel flame‐retardant poly(ethylene‐co‐vinyl acetate)/aluminum hydroxide composites containing phosphorus

A novel flame‐retardant (SPDH) containing phosphorus was synthesized through the reaction of 10‐(2,5‐dihydroxyphenyl)‐9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide and synthesized intermediate product 3,9‐dichloro‐2,4,8,10‐tetraoxa‐3,9‐diphosphaspiro[5.5] undecane‐3,9‐dioxide, which was used for optimizing the flame retardancy of ethylene‐vinyl acetate copolymer (EVM) rubber/aluminum hydroxide (ATH) composites. The microstructure of SPDH was characterized and determined by Fourier transform infrared and nuclear magnetic resonance spectroscopy. Thermogravimetric analysis (TGA) showed that SPDH had good charring effect at high temperature (600°C). The flame retardancy of the optimized EVM/ATH composites by SPDH was investigated by limiting oxygen index (LOI), cone calorimeter, and UL‐94 vertical burning tests. A higher LOI value (29.8%) and better UL‐94 rating (V‐0) can be achieved for the optimized EVM/ATH composite (EVM‐7) than EVM/ATH composite without SPDH (EVM‐3) with the total loading of additives. The heat release rate decreased and residual mass increased gradually as the loading of SPDH increased for the optimized EVM/ATH composites. There existed distinct synergistic flame‐retardant effect between SPDH and ATH in EVM matrix. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Relationship between the distribution of organo‐montmorillonite and the flammability of flame retardant polypropylene

This article studies the relationship between the distribution of organically modified montmorillonite (OMMT) and the flammability of flame retardant polypropylene which consists of polypropylene (PP), brominated epoxy resin‐antimony oxide (BER‐AO) and OMMT. Polypropylene‐graft‐maleic anhydride (PP‐g‐MAH) was used to increase the polarity of PP and aid the dispersion of OMMT. Two model systems, PP/BER‐AO/OMMT and PP/PP‐g‐MAH/BER‐AO/OMMT composites, have been prepared by melt blending. TEM studies reveal a significant change in the distribution of OMMT for these two systems. For the first composites, OMMT platelets are aggregated in the BER‐AO domains, whereas for the second composites, OMMT platelets are dispersed in the PP matrix. The flame retardant properties of the second composite reflected by UL 94 vertical burning test and cone calorimetry are better than that of the first one. When OMMT platelets aggregate in BER‐AO domains as in the first composite, the BER‐AO associated with OMMT may agglomerate into long ribbon‐like structures during burning, inducing uneven distribution of BER‐AO. As a result, loose and uneven residues are formed at the end of combustion. In comparison, OMMT platelets dispersed in polymer matrix are more efficient at stabilizing the polymer and preventing aggregation of BER‐AO during burning, which induce thick and uniform char layers at the end of combustion. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Interfacial modification of high impact polystyrene magnesium hydroxide composites effects on flame retardancy properties

High impact polystyrene (HIPS)/magnesium hydroxide (MH) composites were prepared by melt‐blending. Two kinds of interfacial modifiers were used in this research, maleinated poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] (SEBS‐g‐MA) triblock copolymer and PS. The effects of the use levels of SEBS‐g‐MA on the flame retardancy of HIPS/elastomer/MH based on unmodified and PS‐modified surface were investigated by TEM, FTIR, and combustion tests (horizontal burning test and cone calorimetry). The combustion results showed that comparing composites containing unmodified MH, the flame retarding properties of composites containing PS‐modified MH were obviously improved. The increased performance can be explained that the PS covered on the surface of MH could further improve dispersion of the filler in matrix. Furthermore, there existed a critical thickness of interfacial boundary for optimum flame‐retarding properties in both ternary composites based MH and PS‐modified MH. When the interfacial boundary relative thickness is less than 0.53, the introduction of SEBS‐g‐MA can improve the dispersion degree, leading the improvement of flame retardancy properties. However, with the increase of interfacial boundary thickness, the SEBS‐g‐MA coating around MH acted as a heat and mass transfer barrier, leading to the reduction of flame retardancy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of core–shell zinc hydroxystannate nanoparticle–organic macromolecule composite flame retardant prepared by masterbatch method on flame‐retardant behavior and mechanical properties of flexible poly(vinyl chloride)

Macromolecule flame retardant melamine‐dicyandiamide‐formaldehyde‐phosphoric acid (denoted as MDFP) was used as the shell material to synthesize zinc hydroxystannate@MDFP (denoted as ZHS@MDFP), a novel composite flame retardant with core–shell structure, via masterbatch method. The morphology and structure of ZHS@MDFP were analyzed by means of transmission electron microscopy, X‐ray powder diffraction, Fourier transform infrared spectrometry, and thermal analysis. Moreover, the effect of ZHS@MDFP as a flame retardant on the flame‐retardant behavior and mechanical properties of flexible poly(vinyl chloride) (denoted as PVC) was investigated. It has been found that as‐synthesized ZHS@MDFP composite flame retardant has core–shell structure. Besides, as‐synthesized ZHS@MDFP as a core–shell flame retardant is superior to ZHS in increasing the limiting oxygen index and decreasing the smoke density rating of PVC, which is because the decomposition of MDFP shell as the blowing agent expands the char layer thereby improving the flame‐retarding capability of ZHS core. More importantly, ZHS@MDFP does not cause damage to the tensile strength and elongation at break of PVC matrix, which implies that the MDFP shell favors to improve the compatibility between ZHS and flexible PVC matrix. POLYM. ENG. SCI., 54:1983–1989, 2014. © 2013 Society of Plastics Engineers     

Characterizing composite of multiwalled carbon nanotubes and POE‐g‐AA prepared via melting method

Multiwalled carbon nanotubes (MWNTs) with acyl chloride functional groups and a metallocene polyethylene–octene elastomer (POE) or an acrylic acid‐grafted metallocene polyethylene–octene elastomer (POE‐g‐AA) were used to prepare hybrids (POE/MWNTs or POE‐g‐AA/MWNTs) using a melting method, with a view to identify a hybrid with improved thermal properties. Hybrids were characterized using Fourier transform infrared spectroscopy, ¹³C solid‐state nuclear magnetic resonance, X‐ray diffraction, thermogravimetry analysis, and scanning electron microscopy. MWNTs were purified using acid treatment, and results showed that ? COOH of MWNTs increased with acid treatment time and leveled off after 24‐h treatment. Much better dispersion and homogeneity of MWNTs was obtained with POE‐g‐AA in place of POE as the matrix. As a result, tensile strength at break of POE‐g‐AA/MWNTs was significantly improved even at 5 wt % MWNT content. Moreover, temperature of thermal decomposition for POE‐g‐AA/MWNTs was about 40–50°C higher than that for POE‐g‐AA, indicating higher thermal stability. This was because the carboxylic acid groups in POE‐g‐AA and the acyl chloride functional sites in MWNTs allow the formation of stronger chemical bonds. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1328–1337, 2007     

Dispersion,migration, and ‘network‐like’ structure formation of multiwall carbon nanotubes in co‐continuous,binary immiscible blends of polyamide 6 and acrylonitrile–butadiene–styrene copolymer during simultaneous melt‐mixing

Multiwall carbon nanotubes (MWNTs) were melt‐mixed in polyamide 6 (PA6) and acrylonitrile–butadiene–styrene (ABS) copolymer blends using a simultaneous mixing protocol in order to investigate the state of dispersion of MWNTs in PA6/ABS blends. The blend composition was varied from 40/60 (wt/wt) to 60/40 (wt/wt) in PA6/ABS blends, which showed ‘co‐continuous’ morphology in the presence of MWNTs. State of dispersion of MWNTs in these blends was assessed through bulk electrical conductivity measurements, morphological analysis, solution experiments, and UV‐vis spectroscopic analysis. MWNTs were subsequently modified with a novel organic modifier, sodium salt of 6‐aminohexanoic acid (Na‐AHA), to improve the state of dispersion of MWNTs. Blends with unmodified MWNTs exhibited the DC electrical conductivity in the range ～10^?11 to ～10^?5 S/cm, whereas blends with Na‐AHA‐modified MWNTs exhibited DC electrical conductivity in the range ～10^?7 to ～10^?5 S/cm. The reduction in MWNTs ‘agglomerate’ size (～73.7 μm for 40/60 blend with unmodified MWNTs to ～59.9 μm in the corresponding blend with Na‐AHA‐modified MWNTs) was observed through morphological analysis. The rheological studies showed increased complex viscosity and storage moduli in lower frequency region in case of blends with Na‐AHA‐modified MWNTs confirming a refined ‘network‐like’ structure of MWNTs. POLYM. ENG. SCI., 55:443–456, 2015. © 2014 Society of Plastics Engineers     

Effects of an intercalating agent on the morphology and thermal and flame‐retardant properties of low‐density polyethylene/layered double hydroxide nanocomposites prepared by melt intercalation

The effects of an intercalating agent on the morphology and thermal and flame‐retardant properties of low‐density polyethylene (LDPE)/layered double hydroxide (LDH) nanocomposites were studied with Fourier transform infrared spectroscopy, X‐ray diffraction, transmission electron microscopy, microscale combustion calorimetry, thermogravimetric analysis, and mechanical property measurements. X‐ray diffraction and transmission electron microscopy demonstrated that after intercalation with stearate anion (SA) or dodecyl sulfate anion (DS), organo‐LDH could be nanodispersed in an LDPE matrix with exfoliated structures or intercalated structures simultaneously with partially exfoliated structures, respectively, via melt intercalation. However, the unmodified LDH composites yielded only microcomposites. Microscale combustion calorimetry, thermogravimetric analysis, and dynamic Fourier transform infrared spectra showed the following order for the flame‐retardant and thermal properties: LDPE/SA‐modified LDH > LDPE/DS‐modified LDH > LDPE/NO₃‐modified LDH > LDPE. The higher performance of the LDPE/LDH nanocomposites with respect to flame retardance and thermal stability could be attributed to the better dispersion state of the LDH layers in the LDPE matrix and the greater hindrance effect of LDH layers on the diffusion of oxygen and volatile products throughout the composite materials when they were exposed to burning or thermal degradation. The tensile strength and elongation at break of the LDPE/LDH nanocomposites decreased to some extent because of the decrease in the crystallinity of the LDPE matrix. A transmittance test showed that the transparency of the exfoliated LDPE/SA‐modified LDH nanocomposite was very close to that of neat LDPE. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis,characteristic of a novel flame retardant containing phosphorus,silicon and its application in ethylene vinyl-acetate copolymer (EVM) rubber

A novel flame retardant (SPDV) containing phosphorus and silicon elements at the same time was synthesized. Spirocyclic pentaerythritol bisphosphorate disphosphoryl chloride (SPDPC) synthesized through simple dehydrochlorination reaction of pentaerythritol (PER) and phosphorus oxychloride (POCl₃) was introduced into 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)/ vinylmethyldimethoxy silane (VMDMS) oligomer (DV) to form a novel flame retardant. The structure and properties of SPDPC, DV and SPDV were characterized by FT-IR, NMR and TGA. After blended with EVM, the flame retardance of EVM/SPDV composites was estimated by cone calorimeter, limited oxygen index (LOI) and UL-94, and thermal stability was investigated using TGA. The morphological structure of the char formed after combustion in cone calorimeter was investigated by Scanning Electron Microscopy (SEM). The results indicate that the flame retardant and thermal stability were improved by incorporation of SPDV. The rich foamed char layers were observed in the residues after combustion in cone calorimeter test, which exactly benefits the thermal stability and flame retardant of EVM materials.     

Synergistic effect on flame retardancy and thermal behavior of polycarbonate filled with α‐zirconium phosphate@gel‐silica

A new kind of flame retardant (ZS) with layered α‐zirconium phosphate disks (α‐ZrP) as the core and inorganic flame retardant (gel‐silica, GS) to shield solid acid sites on the surface of α‐ZrP as the shell, was synthesized via a facile method. The incorporation effects of ZS with silicone resin on the thermal properties and flame retardance of PC composites were investigated. The presence of ZS could improve the thermal stability of PC matrix. With the addition of ZS contents increased to 3 wt %, the limiting oxygen index (LOI) of the composite was 32.3% and the vertical burning (UL‐94) test reached a V‐0 rating. However, with more contents of ZS, the LOI value decreased, and without the GS layer, the LOI value was decreased significantly as well. The synergism between the α‐ZrP core and gel‐silica shell, also with the silicone resin were found. Based on these results, the flame‐retardant mechanism was proposed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44829.     

Epoxy resin/phosphorus‐based microcapsules: Their synergistic effect on flame retardation properties of high‐density polyethylene/graphene nanoplatelets composites

Two types of microcapsule flame retardants are prepared by coating ammonium polyphosphate (APP) and aluminum diethylphosphinate (ADP) with epoxy resin (EP) as the shell via in situ polymerization, and blended with high density polyethylene (HDPE)/graphene nanoplatelets (GNPs) composites to obtain flame‐retardant HDPE materials. Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), and water contact angle results confirm the formation of core–shell structures of EP@APP and EP@ADP. The limiting oxygen index (LOI), vertical burning test (UL‐94), cone calorimetry, and Raman spectroscopy are employed to characterize the HDPE/GNPs composites filled with EP@APP and EP@ADP core–shell materials. A UL94 V‐0 level and LOI of 34% is achieved, and the two flame retardants incorporated in the HDPE/GNPs composite at 20 wt % in total play a synergistic effect in the flame retardancy of the composite at a mass ratio of EP@ADP:EP@APP = 2:1. According to the cone‐calorimetric data, the compounding composites present much lower peak heat release rate (300 kW/m²) and total heat release (99.4 MJ/m²) than those of pure HDPE. Raman spectroscopic analysis of the composites after combustion reveals that the degree of graphitization of the residual char can reach 2.31, indicating the remarkable flame retarding property of the composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46662.     

Reactive flame retardant with core‐shell structure and its flame retardancy in rigid polyurethane foam

With a shell of poly (methyl methacrylate‐co‐hydroxyl ethyl acrylate) (PMMA‐HA), microencapsulated ammonium polyphosphate (MHAPP) is prepared by in situ polymerization. The core‐shell structure of the reactive flame retardant (FR) is characterized by Fourier transform infrared (FTIR) and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS). The results of water leaching rate and water contact angle measurements show that ammonium polyphosphate (APP) is well coated by a hydrophobic shell. Due to the presence of active groups (–OH) and hydrophobic groups (–CH₃) in shell, MHAPP exhibits better compatibility, flame retardancy, and water resistance compared with neat ammonium polyphosphate (APP) in rigid polyurethane foam (PU). Compression strength of PU/MHAPP with suitable loading is higher than that of PU/APP and PU, the reason is that the active groups in shell can improve the compatibility of MHAPP in PU composite. From thermal stability and residue analysis, it can be seen that the presence of reactive flame retardant shows positive effect on thermal stability of PU composite at high temperature, results also indicate that MHAPP can promote the carbonization formation efficiency of PU composite during combustion process compared with APP. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42800.     

A facile strategy to fabricate microencapsulated expandable graphite as a flame‐retardant for rigid polyurethane foams

A facile strategy is reported for one‐step preparation of reactive microencapsulated expandable graphite (EG) for flame‐retardant rigid polyurethane foams (RPUF), which is based on in situ emulsion polymerization and the use of poly(glycidyl methacrylate) (PGMA) as reactive polymer shell. FTIR and SEM observations well demonstrate the formation of PGMA microencapsulated EG (EG@PGMA) particles. The encapsulation of PGMA shell significantly improves the expandability of EG particles from 42 to 70 mL g^?1. RPUF/EG@PGMA composite with only 10 wt % EG@PGMA loading reaches the UL‐94 V‐0 rating. The limiting oxygen indexes increase remarkably from 21.0 to 27.5 vol %. Additionally, the improved chemical and physical interaction enhance the interfacial bonding between EG and matrix, thus resulting in improved mechanical properties of RPUF/EG@PGMA. These attractive features suggest that the strategy proposed here can serve as a promising means to prepare highly efficient, reactive microencapsulated EG and corresponding good flame‐retarding RPUF with high mechanical properties. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42364.     

Evolution of phase morphology and ‘network‐like’ structure of multiwall carbon nanotubes in binary polymer blends during melt‐mixing

Polyamide6 (PA6)/acrylonitrile butadiene styrene copolymer (ABS) blends with unmodified multiwall carbon nanotubes (MWNTs) were prepared via melt‐blending in a conical twin‐screw micro‐compounder with varying melt‐mixing time. To improve the state of dispersion of MWNTs, non‐covalent organic modifiers for MWNTs have been utilized: sodium salt of 6‐amino hexanoic acid (Na‐AHA) and 1‐pyrene‐carboxaldehyde (PyCHO). PA6/ABS blends with MWNTs have shown a phase morphology transition from ‘matrix‐dispersed droplet’ type to ‘co‐continuous’ type as a function of melt‐mixing time with the exception of 40/60 PA6/ABS blend with PyCHO‐modified MWNTs. Non‐isothermal crystallization studies revealed the heterogeneous nucleating action of MWNTs through the presence of double crystallization exothermic peaks (at ～192^°C and >200^°C) while pure PA6 shows bulk crystallization peak at ～192°C. 40/60 and 60/40 (wt/wt) PA6/ABS blends with 5 wt% unmodified MWNTs exhibited electrical conductivity values of ～3.9 × 10^?11 S/cm and ～4.36 × 10^?6 S/cm, respectively. A significant enhancement in electrical conductivity was observed with Na‐AHA and PyCHO‐modified MWNTs (order of ～10^?6 and ～10^?4 S/cm, respectively). POLYM. ENG. SCI., 55:429–442, 2015. © 2014 Society of Plastics Engineers     

Grafting multi-elements hybrid polymer brushes on graphene oxide for epoxy composite with excellent flame retardancy

In this paper, a silicon-oxygen coupling agent (MPS) with a double bond is hydrolyzed with graphene oxide (GO) to obtain MPS-GO. The polymerization of MPS-GO with the phosphorus-containing monomer (HEPO) is initiated with 2,2′-Azobis(2-methylpropionitrile) (AIBN) to obtain multi-elements hybrid polymer brushes grafting graphene oxide (HM-GO). As a flame retardant, different amounts of HM-GO are added to obtain EP composites. In this system, the properties of composite flame retardant obviously increase with the increasing of HM-GO. The limiting oxygen index (LOI) value of composites with 4 wt% addition of HM-GO is 31.0%, while the LOI value of EP-0 is only 23.9%. And the peak heat release rate (PHRR) value is reduced from 515.8 W g⁻¹ of pure epoxy resin to 376.9 W g⁻¹. In addition, with the increase of HM-GO addition, the T_g value, flexural strength and flexural modulus of EP composites are improved. Through calculation, it is proved that the rising of T_g was due to the increase of crosslink density of the system. The flame retardant performance and mechanical properties of the composite materials are steadily improved, indicating that such flame retardants are dispersed well in the epoxy resin. HM-GO is an efficient macromolecular modified graphene oxide halogen-free flame retardant, which can improve both flame retardant properties and mechanical properties.