Preparation,microstructure and thermal mechanical properties of epoxy/crude clay nanocomposites

To improve the performance/cost ratio of epoxy/clay nanocomposites, epoxy resin was reinforced with crude clay with the help of a silane modifier. The epoxy/crude clay nanocomposites were produced through a recently developed “slurry compounding” approach. The microstructure of the nanocomposites was characterized with X-ray diffraction (XRD), optical microscopy and transmission electron microscopy (TEM). The thermal mechanical properties were studied with dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). It has been shown that only 5 wt% of silane modifier is required to facilitate the dispersion and exfoliation of crude clay in epoxy matrix. The storage moduli and thermal stability were improved with the addition of crude clay.     

Ultrasound assisted synthesis of PMMA/clay nanocomposites: Study of oxygen permeation and flame retardant properties

PMMA/clay nanocomposites were synthesized by ultrasound assisted emulsifier-free emulsion polymerization technique. Ultrasound waves of different power and frequencies were applied to enhance the dispersion of the clay layers with polymer matrix. The structural information of the synthesized materials was studied by X-ray diffraction (XRD) and it was revealed that the interlayer spacing increased with clay loading. The magnitude of dispersion of the clay in the polymer matrix was detected by transmission electron microscopy (TEM). The Young’s modulus, breaking stress, elongation at break, toughness, yield stress and yield strain of the nanocomposites as a function of different clay concentrations and ultrasonic power were measured. Particle diameter of the nanocomposites was measured by laser diffraction technique. Oxygen permeability of the samples was studied and it was found that the oxygen flow rate was reduced by the combined effect of clay loading and ultrasound. The flame retardant property of the nanocomposites due to clay dispersion was investigated by measurement of limiting oxygen index (LOI).     

Epoxy based nanocomposites with fully exfoliated unmodified clay: mechanical and thermal properties

The unmodified clay has been fully exfoliated in epoxy resin with the aid of a novel ultrafine full-vulcanized powdered rubber. Epoxy/rubber/clay nanocomposites with exfoliated morphology have been successfully prepared. The microstructures of the nanocomposites were characterized by means of X-ray diffraction and transmission electron microscopy. It was found that the unmodified clay was fully exfoliated and uniformly dispersed in the resulting nanocomposite. Characterizations of mechanical properties revealed that the impact strength of this special epoxy/rubber/clay nanocomposite increased up 107% over the neat epoxy resin. Thermal analyses showed that thermal stability of the nanocomposite was much better than that of epoxy nanocomposite based on organically modified clay.     

Effect of flame retardants on flame retardant,mechanical, and thermal properties of sisal fiber/polypropylene composites

A flame retardant efficiency of flame retardants; ammonium polyphosphate (APP), magnesium hydroxide (Mg(OH)₂), zinc borate (Zb), and combination of APP with Mg(OH)₂ and Zb in sisal fiber/polypropylene (PP) composites was investigated using a horizontal burning test and a vertical burning test. In addition, maleic anhydride grafted polypropylene (MAPP) was used as a compatibilizer to enhance the compatibility in the system; i.e. PP-fiber and PP-flame retardants. Thermal, mechanical, and morphological properties of the PP composites were also studied. Adding the flame retardants resulted in improved flame retardancy and thermal stability of the PP composites without deterioration of their mechanical properties. APP and combination of APP with Zb effectively enhanced flame retardancy of the PP composites. No synergistic effect was observed when APP was used in combination with Mg(OH)₂. SEM micrographs of PP composites revealed good distribution of flame retardants in PP matrix and good adhesion between sisal fiber and PP matrix.     

Polymer/clay aerogel composites with flame retardant agents: Mechanical,thermal and fire behavior

Aerogel is a class of material characterized by its high void content and extreme lightness. Different polymer/clay aerogels have been prepared by a simply freeze–thaw process from a suspension with poly(vinyl alcohol) (PVOH) and clay (Na⁺-MMT). Low density polymer/clay aerogels modified with flame retardant agents were prepared using a similar approach. The addition of flame retardant agents slightly increased the apparent density of the final composites whereas the compression properties were reduced due to the decrease in the polymer/clay interfacial bonding. An exception was the sample containing Al(OH)₃ that exhibited higher modulus and stress at maximum deformation. Regarding thermal properties, the presence of ammonium polyphosphate (APP) or silica gel (SG) significantly slowed the rate of aerogel decomposition at the temperature range from 250 °C to 500 °C while the onset of polymer decomposition was not affected. Fire behavior was analyzed through cone calorimeter suggesting that either the presence of Al(OH)₃ or APP reduced the heat release rate of PVOH/clay systems.     

Intumescent flame retardant polyurethane/reduced graphene oxide composites with improved mechanical, thermal, and barrier properties

Intumescent flame retardant polyurethane (IFRPU) composites were prepared in the presence of reduced graphene oxide (rGO) as synergism, melamine, and microencapsulated ammonium polyphosphate. The composites were examined in terms of thermal stability (both under nitrogen and air), electrical conductivity, gas barrier, flammability, mechanical, and rheological properties. Wide-angle X-ray scattering and scanning electron microscopy indicated that rGO are well-dispersed and exfoliated in the IFRPU composites. The limiting oxygen index values increased from 22.0 to 34.0 with the addition of 18 wt% IFR along with 2 wt% rGO. Moreover, the incorporation of rGO into IFRPU composites exhibited excellent antidripping properties as well as UL-94 V0 rating. The thermal stability of the composites enhanced. This was attributed to high surface area and good dispersion of rGO sheets induced by strong interactions between PU and rGO. The oxygen permeability, electrical, and viscoelasticity measurements, respectively, demonstrated that rGO lead to much more reduction in the gas permeability (by ~90 %), high electrical conductivity, and higher storage modulus of IFRPU composites. The tensile strength, modulus, and shore A remarkably improved by the incorporation of 2.0 wt% of rGO as well.     

Structure and mechanical properties of polycarbonate modified clay nanocomposites

Polycarbonate (PC)/modified clay nanocomposites were prepared, in the absence and presence of different amounts of maleic anhydride grafted polypropylene (PP-g-MA), by direct melt blending. Their structures, as well as mechanical, morphological and thermal properties, were characterized by X-ray diffractometry (XRD), tensile testing, transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The XRD results of the PC/clay nanocomposites showed that they had intercalated structures, although some exfoliation was visible at low clay contents, that the gallery heights of the PC/clay nanocomposites were almost the same, and that some of the clay layers collapsed as a result of modifier decomposition at the high processing temperature. The XRD patterns of the PC/PP-g-MA/clay nanocomposites clearly show less intercalation and more exfoliation with increasing PP-g-MA content. These results were supported by TEM observations. Both the tensile strength and modulus show substantial improvements with both increasing clay and PP-g-MA contents, while the elongation at break substantially decreases, although the presence of PP-g-MA somewhat improves these values. All the nanocomposites have lower thermal stability than pure PC, but the presence of PP-g-MA seems to improve the thermal stability of these samples.     

Novel flame retardant zirconia-reinforced nanocomposites containing chlorinated poly(amide-imide): synthesis and morphology probe

In the present investigation, a thermally stable poly(amide-imide) (PAI) was synthesised from the polymerisation reaction of 4,4′-methylenebis(3-chloro-2,6-diethyl trimellitimidobenzene) as a chlorinated diacid with 4,4′-methylenebis(3-chloro-2,6-diethylaniline) using molten tetra-n-butylammonium bromide and triphenyl phosphite as a condensing agent and green media. This methodology offers enhancements for the synthesis of polymers with regard to yield of products, simplicity in operation, and green aspects by avoiding volatile solvents. From the chemical point of view, the chloride and ethylene groups impart to the polymer's chain increased solubility of obtained polymer in organic solvent. Then, the surface of zirconia nanoparticles (ZrO₂-NPs) was modified with 3-aminopropyltriethoxylsilane as a coupling agent. The obtained polymer and inorganic metal oxide NPs were used to prepare PAI/ZrO₂ nanocomposites through ultrasonic irradiation. The formation of PAI was confirmed by ¹H-NMR, FT-IR spectroscopy, and elemental analysis. The obtained polymer was synthesised with good yield (90%) and moderate inherent viscosity (0.48 dL/g). The resulting NP filled composites were also characterised by FT-IR, XRD, FE-SEM, TEM and TGA. The TEM and FE-SEM results indicated a high dispersion level of the nanoscale inorganic particles in the polymer matrix. In this article, ZrO₂-NPs are employed to improve flame retardancy of nanocomposites. TGA thermographs confirmed that the heat stability of the prepared NP-reinforced composites was improved in the presence of ZrO₂ nanocrystals.     

Single-wall carbon nanotubes-chitosan nanocomposites: Surface wettability,mechanical and thermal properties

Functionalized single-wall carbon nanotubes (f-SWCN) are dispersed in chitosan films by self-assembly of both components in aqueous media. This carbon form is a promising nanofiller to achieve nanocomposites with refined thermal, mechanical and surface features. In this study, we investigated the influence of functionalized single-wall carbon nanotubes concentration on the resulting properties of the nanocomposites structures. Functionalized single-wall carbon nanotubes are dispersed on a molecular scale in the polymeric matrix due to electrostatic interactions between both components. The thermal and mechanical properties have been characterized by thermogravimetric analysis and dynamic mechanical analysis, respectively, while their wettability is studied by water contact angle measurements. Mechanical resistance of the films is improved up to 18 % with the addition of functionalized single-wall carbon nanotubes, but the thermal stability is expressively reduced. A decrease in the surface hydrophobicity of 25 % is obtained after the inclusion of the nanofiller.     

Flame retardancy and thermal properties of epoxy acrylate resin/alpha-zirconium phosphate nanocomposites used for UV-curing flame retardant films

This paper reported the UV-curing flame retardant film, which consisted of epoxy acrylate resin (EA) used as an oligomer, tri(acryloyloxyethyl) phosphate (TAEP) and triglycidyl isocyanurate acrylate (TGICA) used as flame retardant (FR). The flame retardancy and thermal properties of films were reinforced by using alpha-zirconium phosphate (α-Zr (HPO₄)₂H₂O, α-ZrP). The morphology of nanocomposite film was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results showed that the organophilic α-ZrP (OZrP) layers were dispersed well in epoxy acrylate resin. Microscale Combustion Calorimeter (MCC), thermogravimetric analysis (TGA) and thermogravimetric analysis/infrared spectrometry (TGA-IR) were used to characterize the flame retardant property and thermal stability. It was found that the incorporation of TAEP and TGICA can reduce the flammability of EA. Moreover, further reductions were observed due to the addition of OZrP. The char residue for systems with or without OZrP was also explored by scanning electron microscopy (SEM).     

Preparation of thermally reduced graphene oxide and the influence of its reduction temperature on the thermal,mechanical, flame retardant performances of PS nanocomposites

In this article, we investigated the influence of thermally reduced graphene oxides (TGOs) at different reduction temperatures on the thermal, mechanical and flame retardant performances of polystyrene (PS). The results indicated that disordered expanded layer structure can be obtained as the reduction temperature increases from 200 to 500 and 800 °C (the resulted composites are named as PS/TGO2, PS/TGO5 and PS/GTO8, respectively), which could lead to better dispersion of TGO sheets in PS matrix. Dynamic mechanical thermal analysis showed that both the storage modulus and T_g of PS/TGO5 and PS/TGO8 nanocomposites are significantly improved compared with that of neat PS. Noticeable improvement in flame retardant performance were achieved with the addition of TGO5 and TGO8, particularly TGO8, due to the removal of the functional oxygen groups from GO and the barrier effect of intumescent and loosely structure of char layers.     

新型磷系阻燃剂的合成与表征及其阻燃性能初探

以甲苯、苯基硫代膦酰二氯(DCPPS)、1,6-己二胺为原料,高锰酸钾为氧化剂,通过四步反应合成了阻燃剂双(对-N-氨基己基-苯甲酰基)苯基氧化膦(BNBPPO)。用熔点I、R、元素分析等手段对合成的BNBPPO进行了表征,并且对各步的反应条件进行了优化。通过TG初步探讨了其热稳定性。在己内酰胺聚合成尼龙6时,加入该阻燃剂。实验表明,含有7%BNBPPO的尼龙6的氧指数从24提高到29.6。     

Poly(ethylene naphthalate)/clay nanocomposites based on thermally stable trialkylimidazolium-treated montmorillonite: thermal and dynamic mechanical properties

Thermally stable organically modified clays based on 1,3-didecyl-2-methylimidazolium (IM2C10) and 1-hexadecyl-2,3-dimethyl-imidazolium (IMC16) were used to prepare poly(ethylene naphthalate) (PEN)/montmorillonite (MMT) nanocomposites via a melt intercalation process. Examination by X-ray diffraction and transmission electron microscopy indicates that an intercalated nanocomposite was formed with IMC16-MMT, while unmodified MMT (Na-MMT) and IM2C10-MMT are generally incompatible with PEN. Thermogravimetric analysis reveals that the peak derivative weight loss temperature of the intercalated PEN/IMC16-MMT was more than 10 "C higher compared to neat PEN, PEN/Na-MMT, or PEN/IM2C10-MMT. Dynamic mechanical analysis also showed that a more significant improvement of the storage modulus was achieved in the better dispersed PEN/IMC16-MMT. The effect of annealing on the dynamic storage modulus of the hybrids is also investigated.     

可再生阻燃疏水复合纸板的制备及其力学性能

为了研制一种兼具阻燃性及疏水性并有优良力学性能的可再生复合纸板,本研究以聚磷酸铵（APP）-卡拉胶（KC）构建了膨胀型阻燃体系（IFR）,以正硅酸乙酯（TEOS）-甲基三甲氧基硅烷（MTMS）@氢氧化镁铝（MAH）作为协同阻燃剂、以硅烷偶联剂KH550（AEMO）@SiO₂作为疏水性填料、以可再生纸浆为基材,制备了APP-KC-[（TEOS-MTMS）@MAH]-（AEMO@SiO₂）复合纸板,并测得其力学性能;采用垂直燃烧实验和极限氧指数（LOI）表征纸板的阻燃效果;采用FE-SEM表征微观形貌;通过FTIR分析燃烧前后功能团变化;利用TG分析其热稳定性;采用接触角（CA）测试、滚动角（SA）测试等来测定其疏水性能。测试结果发现,复合纸板吸水率为1.78 g·m^-2、戳穿强度为6.4 J;边压强度为8.3 kN·m^-1、平压强度为360 kPa。采用优选配方（APP、KC、MTH、ATH的质量比为3∶2∶1∶1）时LOI达到32%;燃烧实验后得炭化长度为19 mm,续焰时间为0.5 s,灼焰时间为...     

Factors controlling mechanical properties of clay mineral/polypropylene nanocomposites

Effects of two factors on the mechanical properties of clay mineral/polypropylene nanocomposites were examined. The first factor is the presence of a small amount of poly(diacetone acrylamide) formed between clay mineral layers. This material was expected to separate effectively the stacked layer structure of the clay mineral on mixing with polypropylene. The stacked layer structure, however, was not separated sufficiently in spite of expansion of the interlayer distance of clay mineral, leading to poor improvement of the mechanical properties of the nanocomposite. Another factor is the kind of clay mineral. Montmorillonite and mica resulted in less favorable separation of the stacked structure than hectorite, but the resulting nanocomposites gave outstanding improvement of the properties. The stiffness of clay mineral layer was considered to influence the properties of the nanocomposite strongly.     

Carbon nanotubes dispersed polymer nanocomposites: mechanical,electrical, thermal properties and surface morphology

The various properties and surface morphology of the carbon nanotubes (CNTs) dispersed polydimethyl siloxane (PDMS) matrix were studied to determine their usefulness in various applications. The tensile strength, Young’s modulus and electrical breakdown strength of CNT/polymer composites were 0.35 MPa, 1.2 MPa and 8.1 kV, respectively. The thermal conductivity and dielectric constant for the material having 4.28 wt% CNT were 0.225 W m^?1 K^?1 and 2.329, respectively. The CNT/polymer composites are promising functional composites with improved mechanical and electrical properties. The scanning electron microscope analysis of surface morphology of PDMS/CNT composite showed that the rough surface texture on nanocomposite has large surface area with circular pores. The Fourier transform infrared spectroscopy showed the functional groups present in polymer nanocomposite.     

Preparation,mechanical and thermal properties of functionalized graphene/polyimide nanocomposites

Graphene oxide sheets with isocyanate functional groups (GONCO) were firstly synthesized and functionalized graphene/polyimide (FGS/PI) nanocomposites were subsequently prepared by typical solution casting and thermal imidization. The chemical changes of GONCO during the preparation of FGS/PI nanocomposites were carefully characterized by Fourier transfer infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses. As a result, the morphology analysis indicated that the FGS were dispersed in the PI matrix and were aligned more orderly with increasing the FGS contents. The tensile strength and the modulus of FGS/PI nanocomposites were significantly increased by 60% with a small quantity of 0.75 wt% FGS incorporated and decreased beyond that dosage. Moreover, the thermogravimetric analysis (TGA) results revealed that the thermal stability of PI was slightly improved by the incorporation of FGS.     

磷氮阻燃剂的合成及其应用

简要概述了近年来聚合型有机磷系、磷氮系阻燃剂的合成动向及阻燃特性,结合本实验室的工作,重点介绍了季戊四醇螺环磷酸酯类、笼状磷酸酯类及其它含磷-氮键的单体型膨胀阻燃剂的近期研究动态.     

Organic/inorganic flame retardants containing phosphorus,nitrogen and silicon: Preparation and their performance on the flame retardancy of epoxy resins as a novel intumescent flame retardant system

This paper presents the preparation of novel organic/inorganic flame retardants containing phosphorus, nitrogen and silicon (organic/inorganic FRs). The organic/inorganic FRs were highly water resistant, as suggested by the water contact angle and water solubility tests. The organic/inorganic FRs were then incorporated into epoxy resins (EP) at different phosphorus/nitrogen ratios and the flame retardancy of EP/FRs composites was characterized. The results showed that synergistic effects on the flame retardancy of EP composites existed between the DOPO-VTS and TGIC-KH. The char residues for EP/FRs composites were increased, and the highest char residues were obtained in air atmosphere (3.8 wt.%) when the DOPO-VTS/TGIC-KH is 4/1. The MCC results also showed that the THR of epoxy resins were also decreased when the DOPO-VTS/TGIC-KH is 4/1, which was in accordance with the highest LOI and UL-94 results. The SEM, FTIR, XPS and TG-FTIR results of pyrolysis products in both condensed and gases phases indicated that the strategy of organic/inorganic FRs combined condensed phase and gases phase flame retardant strategies such as the phosphorus–nitrogen synergism systems, the silicon reinforced effects in the condensed phase and DOPO flame retardant systems in the gases phase, resulting in significant improvements in the flame retardancy of epoxy resins.     

Graphite-like carbon nitride and functionalized layered double hydroxide filled polypropylene-grafted maleic anhydride nanocomposites: Comparison in flame retardancy,and thermal,mechanical and UV-shielding properties

Graphite-like carbon nitride (g-C₃N₄) and borate modified layered double hydroxides (LDH-B) were successfully fabricated by thermal pyrolysis and modified aqueous miscible organic solvent treatment methods, respectively. Then these nano-additives were introduced to prepare polypropylene-grafted maleic anhydride (PP-g-MA)/g-C₃N₄ and PP-g-MA/LDH-B nanocomposites using a modified solvent mixing strategy. Several important parameters of the nanocomposites including thermal, mechanical and UV-blocking properties were investigated. Results indicated that pure g-C₃N₄ exhibited 347.6 and 427.2 °C increase in onset decomposition temperature under air and nitrogen conditions, respectively, compared with LDH-B. In case of PP-g-MA nanocomposites, both T_-10 and T_-50 (the temperature at 10% and 50% weight loss, respectively) were improved by 14.6 and 27.7 °C, respectively, by the addition of g-C₃N₄ while those only increased by 2.3 and 17.8 °C upon introducing LDH-B. Furthermore, PP-g-MA/g-C₃N₄ system showed a remarkable increment (9.8 °C) in crystallization temperature while an increase of 4.2 °C for PP-g-MA/LDH-B nanocomposite. Introducing g-C₃N₄ and LDH-B into PP-g-MA led to a reduction of 28% and 19% in pHRR, respectively. It was noted that the incorporation of g-C₃N₄ caused significant improvement in storage modulus from 2445.0 MPa for neat PP-g-MA to 2783.5 MPa for PP-g-MA/g-C₃N₄ while that of PP-g-MA/LDH-B was dramatically decreased by 27.3%. Optical results indicated that PP-g-MA/g-C₃N₄ was rendered fascinating UV adsorption ability relative to PP-g-MA/LDH-B. It is expected that the novel two-dimensional nanomaterial could bring new creativity into polymer composites.