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     

Effect of halloysite nanotubes on thermal and flame retardant properties of polyamide 6/melamine cyanurate composites

In this study, polyamide 6 (PA6) with various contents of halloysite nanotubes (HNTs) and melamine cyanurate (MCA) were prepared by a twin‐screw extruder. The flame retardant and physical properties of PA6 composites were examined. X‐ray diffraction (XRD) patterns of PA6/HNTs and PA6/MCA/HNTs composites showed that HNTs as a nanoscale material dispersed in PA6 whether with MCA or not. Thermo gravimetric analyzer (TGA) results showed the presence of HNTs can improve thermal stability of PA6 and PA6/MCA composites. The incorporation of HNTs seemed to result the increase of crystallinity of PA6 and PA6/MCA composites from the differential scanning calorimetry (DSC) results. The combined of HNTs and MCA that leads to further improvements limiting oxygen index (LOI) value of PA6 to 31.7% exerted a positive effect on flame retardancy of PA6. What's more, some mechanical enhancements of PA6 with adding of HNTs were achieved and HNTs also made the tensile properties of PA6/MCA composites improved. POLYM. COMPOS., 36:892–896, 2015. © 2014 Society of Plastics Engineers     

Surface modification of halloysite nanotubes with l‐lactic acid: An effective route to high‐performance poly(l‐lactide) composites

To improve the interfacial bonding between halloysite nanotubes (HNTs) and poly(l ‐lactide) (PLLA), a simple surface modification of HNTs with l ‐lactic acid via direct condensation polymerization has been developed. Two modified HNTs were obtained: HNTs grafting with l ‐lactic acid (l‐HNTs) and HNTs grafting with poly(l ‐lactide) (p‐HNTs). The structures and properties of l‐HNTs and p‐HNTs were investigated. Then, a series of HNTs/PLLA, l‐HNTs/PLLA and p‐HNTs/PLLA composites were prepared using a solution casting method and were characterized by polarized optical microscopy (POM), field scanning electron microscopy, and tensile testing. Results showed that l ‐lactic acid and PLLA could be easily grafted onto the surface of HNTs by forming an Al carboxylate bond and following with condensation polymerization, and the amounts of the l ‐lactic acid and PLLA grafted on the surface of the HNTs were 5.08 and 14.47%, respectively. The surface‐grafted l ‐lactic acid and PLLA played the important role in improving the interfacial bonding between the nanotubes and matrix. The l‐HNTs and p‐HNTs can disperse more uniformly in and show better compatibility with the PLLA matrix than untreated HNTs. As a result, the l‐HNTs/PLLA and p‐HNTs/PLLA composites had better tensile properties than that of the HNTs/PLLA composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41451.     

PA66/TLCP/埃洛石纳米管三元复合材料的结构与性能

采用熔融共混方法制备了尼龙66(PA66)/热致液晶聚合物(TLCP)/埃洛石纳米管(HNTs)三元复合材料.结果表明,TLCP对PA66起到一定的增强增韧作用,加入HNTs后,PA66/TLCP/HNTs三元复合材料的弯曲性能明显提高,含有质量分数10%TLcP和5%HNTs的三元复合材料相比纯PA66,在冲击强度提高32.6%的同时,拉伸强度、弯曲强度、热变形温度分别提高了约16.3%、103%、22℃.采用差示扫描量热分析研究了复合材料中TLCP和HNT8对PA66结晶和熔融性能的影响,扫描电子显微镜照片和动态热机械分析表明,HNTs的加入改善了PA66与TLCP的相容性,TLCP在HNTs的作用下能够较好地原位成纤.     

Dendritic polyamidoamine-grafted halloysite nanotubes for fabricating toughened epoxy composites

Well-dispersed epoxy resin/halloysite nanotubes composites were prepared by functionalization of the HNTs surfaces using polyamidoamine generation-3 (HNTs-G3.0). A series of modified halloysite nanotubes with different generations of dendritic polyamidoamine (PAMAM) were prepared via a divergent synthetic process by repeating the Michael addition of methyl acrylate to superficial amino groups and the amidation of the resulting esters with ethylenediamine. The products were then characterized by means of FTIR, XPS, XRD and TGA. The results showed that PAMAM polymers are successfully grafted on the surface of HNTs and the grafting percentage of HNTs grafted with polyamidoamine generation-3 (HNTs-G3.0) is 27.21 %. The grafted PAMAM has no effect on the crystalline structure of HNTs. The morphology, interfacial interaction and mechanical properties of epoxy composites were investigated and correlated with the surface functionalization of HNTs. The observations of scanning electronic microscopy and transmission electron microscopy images showed that HNTs-G3.0 exhibited better dispersion than the p-HNTs. The interfacial interaction of the epoxy composites was studied by FTIR and DMA. It was found that dendritic polyamidoamine graft can effectively improve the interfacial interaction of the epoxy composites. With the improvement in particle dispersion and interfacial interaction through polyamidoamine generation-3 grafting, an increase of impact strength and fracture toughness was achieved, accompanied by enhancements of flexural strength and modulus. In particular, the impact strength and fracture toughness (K _IC) of composites with polyamidoamine generation-3 grafted HNTs were about 160 and 20 % higher than the values of functionalization halloysite nanotube system.     

Highly dispersed polyamide‐11/halloysite nanocomposites: Thermal,rheological, optical,dielectric, and mechanical properties

Bio‐based polyamide 11 and natural halloysite nanotubes (HNTs) were used for the preparation of PA‐11/HNT nanocomposites with varying nanotubes concentrations by melt extrusion using a masterbatch dilution process. The prepared nanocomposites were analyzed for microstructural changes, transparency, thermal stability, rheological behavior, dielectric, and mechanical properties. The HNT nanotubes are well dispersed in PA‐11 matrix in the studied composition range as shown by microscopy and spectrophotometry. Interestingly, good halloysite dispersion in PA‐11 matrix increases the tensile strength and Young modulus of PA‐11 without sacrificing the ductility. Highly dispersed nanotubes also bring favorable changes in the thermal stability, dielectric, and rheological characteristics of PA‐11. Additionally, glass transition temperature, crystallization temperature, and degree of crystallinity of the nanocomposites tend to increase with increase in nanotubes loading. Thus, PA‐11 can become a tailor‐made material with multifunctional characteristics, thanks to the addition of HNTs. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Natural inorganic nanotubes reinforced epoxy resin nanocomposites

Natural occurred nanotubes, halloysite nanotubes, were modified by silane and incorporated into epoxy resin to form nanocomposites. The morphology of the nanocomposites was characterized by transmission electron microscopy (TEM). Dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA) were performed on the nanocomposites. Flexural property and coefficient of thermal expansion (CTE) of the nanocomposites were also determined. Comparing with the neat resin, about 40% increase in storage modulus at glassy state and 133% at rubbery state were achieved by incorporating 12 wt% modified HNTs into the epoxy matrix. In addition, the nanocomposites exhibited improved flexural strength, char yield and dimensional stability. TEM examination revealed a uniform dispersion of the nanotubes in the epoxy resin. The remarkably positive effects of the HNTs on the performance of the epoxy resin were correlated with the unique characteristics of the HNTs, the uniform dispersion and the possible interfacial reactions between the modified HNTs and the matrix.     

Hemocompatibility and antifouling properties of PEGMA grafted Polyethersulfone/aminated halloysite nanotubes mixed matrix membrane

The aim of this study was to evaluate the permeation performance and hemocompatibility of polyethersulfone (PES) membrane after mixing with halloysite nanotubes (HNTs), followed by grafting poly (ethylene glycol) methyl ether metacrylate (PEGMA). HNTs were modified by (3-aminopropyl)triethoxysilane (APTES) to facilitate dispersion in PES matrix. Incorporation of 2wt% HNTs not only could increase water permeability of the PES membrane from about 580 to 840?L/m².h.bar, but also improved mechanical strength of the membrane and could be an appropriate sublayer for composite membrane preparation. Grafting PEGMA could inhibit proteins attachment and platelets adhesion on the PES mixed matrix membrane.     

PPS/PA66/HNTs复合材料的制备与性能研究

采用熔融共混方法制备了聚苯硫醚(PPS)/尼龙-66(PA66)/埃洛石纳米管(HNTs)复合材料,研究了其力学性能、热性能及其微观形态.结果表明:当PPS/PA66的比为60/40、HNTs的含量为30%时,复合材料具有较好的性能.复合材料的拉伸强度、弯曲模量及缺口抗冲击强度相对纯PPS分别提高了36.6%、163....     

Simultaneous improvement in strength,toughness, and thermal stability of epoxy/halloysite nanotubes composites by interfacial modification

This work investigated the effect of silane modification of halloysite nanotubes (HNTs) on the mechanical properties of epoxy/HNTs nanocomposites. Three kinds of silane coupling agents, including 3‐(2‐aminoethyl)‐aminopropyltrimethoxysilane (AEAPS), (3‐glycidyloxypropyl)‐trimethoxysilane (GPTMS), and octyltriethoxysilane (OTES), were employed. It was shown that the modified HNTs exhibited a better dispersion in the epoxy matrix compared with pristine one. Because of strong interfacial interaction between AEAPS modified HNTs and the epoxy matrix, the nanocomposites exhibited the highest glass transition temperature and modulus among all the samples. On the other hand, AEAPS and GPTMS modified HNTs/epoxy nanocomposites showed enhanced tensile strength and toughness. The toughing mechanisms were identified by the SEM micrographs of the fracture surfaces of the different kinds of samples. In this study, simultaneous enhancement of strength, toughness, and thermal stability of epoxy by the modified HNTs provides a novel approach to produce high‐performance thermosets. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43249.     

Morphological and mechanical behavior of chemically treated jute‐PHBV bio‐nanocomposites reinforced with silane grafted halloysite nanotubes

In this study, at first, thin films of poly(3‐hydroxybutyrate‐co?3‐hydroxyvalerate) (PHBV) nanocomposites were prepared by adding 1–3 wt % grafted halloysite nanotubes (G‐HNTs). Jute‐PHBV bio‐nanocomposites were then fabricated using these films and chemically treated jute fibers in a compression mold machine. The effect of treatment and modification on jute fiber and halloysite nanotubes (HNTs), and the change in their morphology was investigated using Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), scanning and transmission electron microscopy (SEM, TEM). Flexural and thermomechanical properties were determined using a three‐point bend test and dynamic mechanical analysis (DMA). The results showed separation of fiber bundles with rough fiber surfaces, and grafting of silane coupling agents on fibers and HNTs after the chemical treatment. As a result, a strong bonding was established between the PHBV, G‐HNTs and jute fibers that lead to significant improvements in flexural and thermomechanical properties of jute‐PHBV bio‐nanocomposites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43994.     

Novel epoxidized natural rubber toughened polyamide 6/halloysite nanotubes nanocomposites

A novel ternary epoxidized natural rubber (ENR-50) toughened polyamide 6/halloysite nanotubes (PA6/HNTs) nanocomposites were successfully prepared by extrusion followed by injection molding. The HNTs revealed a favourable interaction with the PA6 matrix as seen by the improvement in mechanical properties and presence of a new FTIR vibrational peak. The ENR-50 showed an improvement of the impact strength up to 300% with a super tough characteristic at only 15 wt% ENR-50. The naturally occurring nanotubes proved to be a suitable candidate to replace other synthetic nanotubes.     

Removal of methylene blue from aqueous solution by electrophoretically deposited titania‐halloysite nanotubes coatings

Two‐component suspensions of titania and halloysite nanotubes (HNTs) were prepared in ethanol with 0.5 g/L (optimum concentration) of polyethyleneimine (PEI) and different wt% of HNTs. Kinetics of Electrophoretic deposition (EPD) decreased with increasing the HNTs content in suspensions due to their less mobility compared with titania particles. HNTs reinforced the microstructure of coatings and reduced or completely prevented from cracking during drying and heat‐treatment steps. Removal of methylene blue (MB) via adsorption by HNTs coatings was faster than its photocatalytic degradation by titania coating. Dispersion of HNTs (up to ≈30 wt%) in the matrix of titania resulted in the synergistic catalytic effect in MB removal. The synergistic effect was because of the shorter traveling distance of MB molecules adsorbed on HNTs toward the photocatalytic active site of titania particles in composite coatings. However, the synergistic effect was destroyed with increasing the HNTs content in coating. Difference between the amount of MB removed by titania and composite coatings increased at longer times (≥60 minutes). Mass transfer of MB adsorbed on HNTs toward the photocatalytic active sites of adjacent titania particles can compensate the decline in the mass transfer from solution at longer times.     

Preparation,characterization, and mechanical/tribological properties of polyamide 11/Titanium dioxide nanocomposites

In this study, the effects of the surface chemical modification of titanium dioxide (TiO₂) nanoparticles and their addition into polyamide 11 (PA11) on the mechanical, dynamic‐mechanical, and tribological properties of PA11/TiO₂ nanocomposites were investigated. To improve the interfacial adhesion between the nanoparticles and the polymeric matrix, the surface of TiO₂ nanoparticles was modified with 3‐aminopropyl trimethoxysilane (ATPMS). Nuclear magnetic resonance (NMR), infrared spectroscopy (IR), and thermogravimetric analysis (TG) were used to evaluate the efficiency of the surface chemical modification of TiO₂ nanoxide. PA11/TiO₂ nanocomposites with 2 and 4 wt% of TiO₂ were prepared in an internal mixer. The interfacial adhesion between the matrix and the TiO₂ was evaluated by dynamic‐mechanical analysis (DMA), and the dispersion of nanoparticles was analyzed by scanning electron microscopy (SEM). The NMR spectrum of the modified TiO₂ exhibited peaks in the region between −55 ppm and −70 ppm, indicating disubstituted and trisubstituted chemical structures between alkoxysilano structures and TiO₂. Nanocomposites with modified TiO₂ exhibited the lowest tan δ peak values, which provide evidence that the chemical modification of the TiO₂ facilitated energy dissipation at the interface of TiO₂ with the PA11 matrix. Surface modification of the TiO₂ nanoparticles with ATPMS caused a greater reduction of the mass loss by abrasion when compared with nonmodified PA11/TiO₂ nanocomposites; this reduction reached approximately 70% in comparison with the mass loss of neat PA11. POLYM. COMPOS., 37:1415–1424, 2016. © 2014 Society of Plastics Engineers     

Synergistic flame‐retardant effect of halloysite nanotubes on intumescent flame retardant in LDPE

Synergistic flame‐retardant effect of halloysite nanotubes (HNTs) on an intumescent flame retardant (IFR) in low‐density polyethylene (LDPE) was investigated by limited oxygen index (LOI), vertical burning test (UL‐94), thermogravimetric analysis (TGA), cone calorimeter (CC) test, and scanning electronic microscopy (SEM). The results of LOI and UL‐94 tests indicated that the addition of HNTs could dramatically increase the LOI value of LDPE/IFR in the case that the mass ratio of HNTs to IFR was 2/28 at 30 wt % of total flame retardant. Moreover, in this case the prepared samples could pass the V‐0 rating in UL‐94 tests. CC tests results showed that, for LDPE/IFR, both the heat release rate and the total heat release significantly decreased because of the incorporation of 2 wt % of HNTs. SEM observations directly approved that HNTs could promote the formation of more continuous and compact intumescent char layer in LDPE/IFR. TGA results demonstrated that the residue of LDPE/IFR containing 2 wt % of HNTs was obviously more than that of LDPE/IFR at the same total flame retardant of 30 wt % at 700°C under an air atmosphere, and its maximum decomposing rate was also lower than that of LDPE/IFR, suggesting that HNTs facilitated the charring of LDPE/IFR and its thermal stability at high temperature in this case. Both TGA and SEM results interpreted the mechanism on the synergistic effect of HNTs on IFR in LDPE, which is that the migration of HNTs to the surface during the combustion process led to the formation of a more compact barrier, resulting in the promotion of flame retardancy of LDPE/IFR. In addition, the mechanical properties of LDPE/IFR/HNTs systems were studied, the results showed that the addition of 0.5–2 wt % of HNTs could increase the tensile strength and the elongation at break of LDPE/IFR simultaneously. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40065.     

A study on synergistic reinforcing effect of halloysite nanotubes/diatomite mixture-filled polymer (PP and PA6) composites

In this paper, the nanotubular halloysite nanotubes (HNTs)/disc-shaped diatomite mixture (HD) was used to study the synergistic reinforcing effect of the filler in polymer matrix (PP and PA6). The structure of the HNTs/diatomite mixture filler-filled polymer composites with different proportions of HNTs/diatomite was determined by XRD and SEM. The mechanical performance of the composites was extensively investigated. The results indicated that the HNTs/diatomite mixture filler with different shapes could significantly reinforce the mechanical performance of polymer regardless of whatever it was filled in — PP or PA6. The synergistic reinforcing effect of HNTs/diatomite mixture filler in polymer matrix was verified.     

Microstructural,mechanical, and thermal characteristics of recycled cellulose fiber‐halloysite‐epoxy hybrid nanocomposites

Epoxy hybrid‐nanocomposites reinforced with recycled cellulose fibers (RCF) and halloysite nanotubes (HNTs) have been fabricated and investigated. The dispersion of HNTs was studied by synchrotron radiation diffraction (SRD) and transmission electron microscopy (TEM). The influences of RCF/HNTs dispersion on the mechanical properties and thermal properties of these composites have been characterized in terms of flexural strength, flexural modulus, fracture toughness, impact toughness, impact strength, and thermogravimetric analysis. The fracture surface morphology and toughness mechanisms were investigated by SEM. Results indicated that mechanical properties increased because of the addition of HNTs into the epoxy matrix. Flexural strength, flexural modulus, fracture toughness, and impact toughness increased by 20.8, 72.8, 56.5, and 25.0%, respectively, at 1 wt% HNTs load. The presence of RCF dramatically enhanced flexural strength, fracture toughness, impact strength, and impact toughness of the composites by 160%, 350%, 444%, and 263%, respectively. However, adding HNTs to RCF/epoxy showed only slight enhancements in flexural strength and fracture toughness. The inclusion of 5 wt% HNTs into RCF/epoxy ecocomposites increased the impact toughness by 27.6%. The presence of either HNTs or RCF accelerated the thermal degradation of neat epoxy. However, at high temperature, samples reinforced with RCF and HNTs displayed better thermal stability with increased char residue than neat resin. POLYM. COMPOS. 2012. © 2012 Society of Plastics Engineers     

Compatibilizing Effect of Halloysite Nanotubes on Polyetherimide/Silicone Rubber Blend Based Nanocomposites

The present study deals with the preparation of nanocomposites comprising of polyetherimide (PEI) and silicone rubber reinforced with both unmodified and modified halloysite nanotubes (HNTs) by melt blending process with the aid of co-rotating twin screws extruder. The developed nanocomposites have been characterized by various sophisticated analytical instrument viz. TGA, DMA, SEM,TEM, FTIR and UTM. There is remarkable enhancement in various properties of the developed nanocomposites due to incorporation of modified HNTs. This can be attributed to fairly good dispersion of the HNTs in the polymer matrix resulting in reductions of filler-filler interaction.     

Surface‐modified halloysite nanotubes reinforced poly(lactic acid) for use in biodegradable coronary stents

Poly(lactic acid) (PLA) was reinforced halloysite nanotubes (HNTs) in this study. To improve dispersion and interfacial adhesion of HNTs within the PLA matrix, HNTs were surface modified with 3‐aminopropyltriethoxysilane (ASP) prior to compounding with PLA. PLA/ASP‐HNTs nanocomposites were characterized by differential scanning calorimetry (DSC), Fourier transfer infrared spectroscopy (FTIR), surface wettability, thermogravimetric analysis, transmission electron microscopy (TEM), and tensile testing. The hemocompatibility and cytocompatibility of PLA and PLA composites were investigated and the in vitro degradation process of PLA/ASP‐HNTs composites was investigated for a period of 6 months by gel permeation chromatography, FTIR, weight loss measurement, DSC, and tensile testing. PLA and all PLA composites were blood compatibile and non‐cytotoxic. TEM analysis revealed that HNTs agglomeration in PLA matrix was reduced by surface treatment with ASP. ASP‐HNTs had better reinforcing effect than unmodified HNTs evidenced by tensile testing. ASP‐HNTs appeared to increase the hydrolytic degradation process as measured by weight measurement. PLA/ASP‐HNTs composites displayed 12.1% weight loss and 30.6% average molecular weight reduction while retaining 74% of Young's modulus by the 24th week of degradation. Based on this data, the reinforcement of PLA using ASP‐HNTs may prove beneficial for applications such as biodegradable stents. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46521.     

Synthesis of poly(AA‐co‐AM) superabsorbent composites by reinforcement of halloysite nanotubes

A novel poly(acrylic acid‐co‐acrylamide)/halloysite nanotubes [PAA‐AM/HNTs] superabsorbent composite was synthesized by free radical polymerization with using HNTs as an inorganic additive. The composite was characterized by Fourier transform infrared spectroscopy, scanning electron microscope, and thermogravimetric analysis. The results revealed that HNTs and PAA‐AM were combined well together to form a porous structure with a pore size of about 10 μm, and HNTs were uniformly distributed in the composite. The thermal stability was improved by adding HNTs in the composite. The influences of contents of initiator and halloysite, neutralization degree of AA, and molar ratio of AM to AA on water absorbency were investigated. The water absorbency and the water retention capacity were improved after adding HNTs into PAA‐AM. The composite containing 10% HNTs had the highest water absorbency of 1276 g/g in distilled water. Moreover, PAA‐AM/HNTs composite also had a high swelling rate within 60 min and could maintain 78% initial swelling capability after five reswelled test. The substantial enhancement of swelling properties enables PAA‐AM/HNTs suitable for numerous practical applications. POLYM. COMPOS., 36:229–236, 2015. © 2014 Society of Plastics Engineers