Catalytic synthesis of carbon nanotubes on clay minerals

Novel clay-carbon tube composites were synthesized by catalytic decomposition of acetylene over iron-catalyst centers supported on montmorillonite surfaces by ion-exchange. TEM and SEM micrographs show the growth of carbon tubes rooted to the clay surfaces, while the iron-nanoparticles (which catalyze the formation of carbon-nanotubes) are detected and characterized by Mössbauer spectroscopy, mainly as ferromagnetic cementite (Fe₃C). In the hybrid materials the clay retains its exchange properties making possible the preparation of clay-carbon nanotube derivatives that are valuable for various technological applications.     

Flame retardancy and thermal properties of novel UV-curing epoxy acrylate coatings modified by phosphorus-containing hyperbranched macromonomer

A novel phosphorus-containing hyperbranched macromonomer (PHM), successfully synthesized via Michael addition polymerization of tri(acryloyloxyethyl) phosphate (TAEP) with n-butylamine (BA), was blended with epoxy acrylate resin (EA) to prepare UV curable flame retardant coatings. The study of thermal degradation of these coatings revealed that PHM can catalyze the degradation of EA, contributing to the formation of thermally stable char layer. The residues of EA3 (which contains 45 wt.% PHM) at various temperatures were analyzed by X-ray photoelectron spectroscopy (XPS) and the results displayed that the formation of phosphorus-carbon structure can well protect the carbonaceous char from thermal-oxidative degradation at 800 °C. Besides, the investigation of the flammability illustrated that the addition of PHM increased the limiting oxygen index (LOI) value and reduced the peak heat rate release (HRR) and total heat release (THR).     

阻燃型玻纤增强PA10T复合材料的热氧老化性能

采用溴化环氧树脂对聚对苯二甲酰葵二胺(PA10T)进行改性,并通过熔融共混法制备阻燃型玻璃纤维(GF)增强PA10T复合材料,采用人工加速热氧老化手段,研究了热氧老化对其力学性能的影响,并用扫描电子显微镜(SEM)对复合材料的冲击断面形貌进行观察。结果表明,随热氧老化时间增加,复合材料的拉伸强度、弯曲强度和缺口冲击强度均下降明显,分子链松弛过程减弱;老化10 d后,复合材料的弯曲弹性模量仅略有下降而储能模量达到最大值,表明在热氧老化初期PA10T分子链之间发生了微交联,但随老化时间继续增加,两者均下降明显。SEM结果表明GF与树脂基体之间界面粘接作用的强弱是影响材料热氧老化性能变化的主要因素。     

聚乙烯/粘土纳米复合材料燃烧性能研究

使用锥形量热计、热重分析仪对聚乙烯(PE)／粘土纳米复合材料的燃烧性能进行了研究。结果表明，有机改性纳米粘土对PE燃烧性能有较大影响，随眷纳米粘土合量的增加，PE的热分解速率和最大热释放速率都明显下降，这对材料应用中的火灾安全性具有重要意义。     

Study on flammability of montmorillonite/styrene‐butadiene rubber (SBR) nanocomposites

The flammability of montmorillonite (MMT)/SBR nanocomposites, prepared by the technique of cocoagulating rubber latex and clay aqueous suspension, was investigated. Flammability studies, performed on the cone calorimeter, showed that the maximum heat release rate (HRR) of SBR decreased from 1987 to 1442 kw/m² with the introduction of nanoclay (20 phr). This nanocomposite had the lowest mass loss rate and the largest amount of char upon combustion compared with conventional SBR composites with the same clay loading and pure SBR. The permeability properties of MMT/SBR composites were also measured. It was deduced that the lowered permeability was responsible for the reduced mass loss rate and hence the lower HRR. Unfortunately, the oxygen index (OI) of the nanocomposites was not as high as expected. Combination of Mg(OH)₂ and clay was effective for the improvement of both mechanical properties and OI. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 844–849, 2005     

Dispersion and flame retardancy of ethylene vinylacetate/layered silicate nanocomposites using the masterbatch approach for cable insulating material

Ethylene vinylacetate (EVA) copolymer-based nanocomposites with maleic anhydride-grafted ethylene-vinylacetate (EVAgMA) and organically modified clay (o-clay) were prepared in a twin screw extruder by following a two-step melt compounding method. EVAgMA/o-clay masterbatches with various clay contents up to 50 wt% were examined, after which the masterbatch with the highest clay content was melt compounded with EVA for the preparation of EVA/o-clay nanocomposites containing specific amounts of clay. Further morphological dispersion of the clay particles by highly polar EVA and shearing was confirmed in the EVA/o-clay nanocomposites by X-ray diffraction (XRD) and transmission electron microscopy (TEM). These morphologies led to increased thermal properties in air as well as a considerable decrease in heat release rate (HRR). EVA/o-clay/MDH nanocomposites were also prepared using a high clay-bearing masterbatch to confirm the synergistic flame retardancy of clay as a co-additive in EVA/MDH composites. EVA/o-clay/MDH nanocomposites prepared by substituting o-clay for MDH showed significantly lower and wider HRR during combustion compared to EVA/MDH composite.     

The production of smectite clay/graphene composites through delamination and co-stacking

Layers from delaminated colloidal dispersions of two structurally different layered solids-octylamine-intercalated graphite oxide and cetyltrimethylammonium-intercalated smectite - could be costacked to obtain smectite clay/graphite oxide composites. The layers of the two parent solids were randomly stacked together in these composites. On thermal decomposition the graphite oxide sheets in the composites are reduced to graphene sheets resulting in clay/graphene composites. The composition is not uniform in these composites, which have many smectite-rich and carbon-rich regions. The clay component of the clay/graphene composites could be leached out to obtain exfoliated graphite.     

Flame retardant and mechanical properties of epoxy composites containing APP−PSt core−shell microspheres

Ammonium polyphosphate (APP)–polystyrene (PSt) core–shell microspheres (CSPs) were synthesized via in situ radical polymerization. The core–shell structure was confirmed by transmission electron microscope (TEM). The results of optical contact angle measurements demonstrated a significant improvement in hydrophobicity of the modified APP. The obtained APP–PSt CSPs were added into epoxy (EP) system with various loadings. Effects of CSP on flame retardancy, thermal properties, heat release rate (HRR), smoke production, and mechanical properties of EP/CSP composites were investigated by limiting oxygen index (LOI), UL‐94 tests, thermogravimetric analysis (TGA), cone calorimeter, and tensile test. LOI and UL‐94 indicated that CSP remarkably improved the flame retardancy of EP composites. TGA showed that the initial decomposition temperature and the maximum‐rate decomposition temperature decreased, whereas residue yields at high temperature increased with the incorporation of microspheres. Cone calorimetry gave evidence that HRR, peak release rate, average HRR, and smoke production rate of EP/CSP composites decreased significantly. The morphology of char residues suggested that CSP could effectively promote EP to form high‐quality char layer with compact outer surface and swollen inner structure. Tensile strength of EP was enhanced with the addition of CSP. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40218.     

Sustained antioxidant properties of epigallocatechin gallate loaded halloysite for PLA as potentially durable materials

Halloysite nanotube (HNT) was etched by hydrochloric acid, and epigallocatechin gallate (EGCG) was loaded into the etched HNT (HH) to prepare loaded antioxidant (HH-E) for polylactic acid (PLA) with improved thermal-oxidative stability. The loading process was confirmed by TGA and FT-IR, and the loading capacity was 16.15%. The presence of EGCG on the surface of etched HNT was further confirmed by nitrogen adsorption and TEM. The effect of loaded EGCG on thermal-oxidative stability of PLA was characterized by the change in OOT values of PLA after the aging process under 140°C. The results showed that HH-E increased OOT values of PLA from 231.2°C to 293.6°C at first, indicating that HH-E provided PLA with excellent thermal-oxidative stability. Furthermore, as can be seen from the trend of OOT changing over aging time, during the 14 days aging process, OOT values of PLA composites with HH-E decreased more slowly than that of PLA composites with EGCG alone, endowing PLA with sustainable thermal-oxidative stability. Further kinetic analysis showed that the apparent activation energy of the degradation process (E_a) of PLA composites with HH-E changed less than that of PLA composites with EGCG alone, which showed that the loading system provided PLA better sustainable stability. Moreover, the isothermal crystallization process of modified PLA was characterized by DSC and POM. The results showed that HH-E provided heterogeneous crystal nucleus for PLA, reducing the half crystallization time (t_0.5) and improvement of crystallization rate for PLA. These results prove that HH-E exhibited excellent performance in improving the thermal stability and crystallization property of PLA, showing multifunctional characterization.     

单体接枝改性炭黑填充NR复合材料的研究

采用单体接枝改性法制备炭黑填充型NR复合材料，并对其性能进行研究。结果表明，在NR胶乳与炭黑的混合体系中加入适当的单体M(BA，MMA或GMA)和引发剂，使单体M与NR大分子发生接枝反应的同时，与炭黑表面的活性基团发生反应，制备NR／M／炭黑复合材料；该复合材料的物理性能和耐热氧老化性能优异，热稳定性和抗湿滑性良好。     

Preparation of polystyrene/montmorillonite nanocomposites in supercritical carbon dioxide

The preparation of polystyrene (PS)/montmorillonite (MMT) composites in supercritical carbon dioxide (SC? CO₂) was studied. Lipophilic organically modified MMT can be produced through an ion‐exchange reaction between native hydrophilic MMT and an intercalating agent (alkyl ammonium). PS/clay composites were prepared by free‐radical precipitation polymerization of styrene containing dispersed clay. X‐ray diffraction and transmission electron microscopy indicated that intercalation of MMT was achieved. PS/clay composites have a higher thermal decomposition temperature and lower glass‐transition temperature than pure PS. The IR spectrum analysis showed that the solvent of SC? CO₂ did not change the structures of the PS molecules, but there were some chemical interactions between the PS and the clay in the composites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 22–28, 2005     

Thermal degradation mechanism of polycarbonate/organically modified montmorillonite nanocomposites

There were contradictory results about the effect of clay on polycarbonate (PC) thermal stability in previous reported papers. For ascertainment of the actual role of clay, PC nanocomposites were prepared by direct melt‐mixing PC with hexadecyl trimethyl ammonium chloride modified montmorillonite (OMT). The results of X‐ray diffractometry, transmission electron microscopy, and high‐resolution electron microscopy experiments present the formation of uniformly intercalated structure. Thermogravimetric analyses show the onset decomposition temperature of PC/OMT nanocomposites is earlier 65°C than neat PC. The mechanism of PC thermal decomposition effected by OMT was discussed in detail. It reveals that OMT can catalyze thermal degradation of PC macromolecular chains and decrease thermal stability of the nanocomposites. POLYM. COMPOS., 37:2301–2305, 2016. © 2015 Society of Plastics Engineers     

A kinetic analysis of the thermal-oxidative decomposition of expandable polystyrene

The kinetics of the thermal-oxidative decomposition of expandable polystyrene (EPS) was studied by a conventional thermogravimetric technique in various concentrations of oxygen from 0 to 21%. A kinetic model that accounts for the effects of oxygen concentration was proposed to describe the thermal-oxidative decomposition of EPS. The thermogravimetric analysis curve and its derivative have been analyzed by using differential and integral methods with modification of the Friedman and Coats-Redfern methods. The activation energy, the pre-exponential factor, and the reaction order for unreacted material and oxygen concentration have been determined. When oxygen was present, the activation energy was reduced significantly.     

Study on the Interfacial Behavior of Clay-Coated Carbon Fiber-Reinforced PEI Composites

In this article, based on the surface chemical treatment of carbon fiber, a clay coating process was developed for the surface modification of the carbon fiber to obtain a controlled interface between carbon fiber and polyetherimide (PEI) matrix in the composites system. SEM, XPS spectrum and contact angle measure reveal that the clay coating can improve the surface roughness of the carbon fiber surface for a favorable wettability with the matrix, which can also improve the interfacial adhesion of the composites. Experimental results show that the interlaminar shear strength (ILSS) and the three-point bending (TPB) of the composites reinforced by the carbon fiber coated with the clay have been enhanced.     

剑麻纤维/聚丙烯木塑复合材料的热氧老化性能研究

以剑麻纤维(SF)、聚丙烯(PP)为原料,经熔融共混、模压成型工艺制备木塑复合材料。探讨了SF/PP复合材料的力学性能、热性能随老化时间和SF含量的变化规律,借助扫描电镜对复合材料老化前后的冲击断面进行微观结构分析。结果表明:老化后复合材料的冲击强度、弯曲强度和弯曲模量随剑麻含量的增加而降低;同时,复合材料中PP相的结晶速率、结晶度也有所降低,但复合材料的热稳定性基本没有变化。     

Phosphorus and Silicon Containing Low‐Melting Organic–Inorganic Glasses Improve Flame Retardancy of Epoxy/Clay Composites

New low‐melting organic–inorganic glassy polymers containing phosphorus and silicon are synthesized by the reaction between phenylphosphonic acid and methyltrichlorosilane or methyltriethoxysilane. They possess both low‐softening points and high onset decomposition temperatures, which are favorable for preparing flame retardant composites. Although the glass by itself is sensitive to water, the composites are not significantly affected in that way. For glass/clay/epoxy composites glass transition temperature (T_g) as well as storage modulus increase with the glass amount. The glasses improve flame retardancy significantly due to flame inhibition and the formation of fire residue working as protection layer during burning. The total heat evolved is reduced by 23–28% for using 5–15 wt.% glass and the maximum HRR even by 58–48%. The latter effect decreases with increasing glass amount due to an adulterate residue deformation. The combination of glass and clay is proposed as a possible route to enhance flame retardancy.

     

A study of γ‐radiation‐crosslinked HDPE/EPDM composites as flame retardants

The dynamic flammability of flame‐retardant composites that consist of high‐density polyethylene (HDPE) and ethylene–propylene–diene rubber (EPDM) and other additives, and can be used as wire‐ and cable‐insulation materials, was studied before and after irradiation. The data for the heat‐release rate (HRR), the time to ignition, the specific extinction area and the concentrations of CO and CO₂ from the burning process of cone colorimeter tests were assessed. By blending HDPE with EPDM, the HRR of HDPE was reduced and the residue char of the composite increased. The HRR of HDPE/EPDM was further reduced and the residue char of HDPE/EPDM was further increased after irradiation. The oxygen index, mechanical properties, and thermal stability of the composites, and the morphology of the char formed in the cone calorimeter test, were also investigated. Copyright © 2004 Society of Chemical Industry     

Processing and properties of polymeric nano‐composites

Polymeric nano‐composites are prepared by melt intercalation in this study. Nano‐clay is mixed with either a polymer or a polymer blend by twin‐screw extrusion. The clay‐spacing in the composites is measured by X‐ray diffraction (XRD). The morphology of the composites and its development during the extrusion process are observed by scanning electron microscopy (SEM). Melt viscosity and mechanical properties of the composites and the blends are also measured. It is found that the clay spacing in the composites is influenced greatly by the type of polymer used. The addition of the nano‐clay can greatly increase the viscosity of the polymer when there is a strong interaction between the polymer and the nano‐clay. It can also change the morphology and morphology development of nylon 6/PP blends. The mechanical test shows that the presence of 5–10 wt.% nano‐clay largely increases the elastic modulus of the composites and blends, while significantly decreases the impact strength. The water absorption of nylon 6 is decreased with the presence of nano‐clay. The effect of nano‐clay on polymers and polymer blends is also compared with Kaolin clay under the same experimental conditions.     

Preparation of composites of laponite with alginate and alginic acid polysaccharides

Polymer/clay composites have several uses in fields such as engineering, agriculture, ceramics, surface coatings, absorbent materials, pharmaceuticals or catalysis. Polysaccharides, such as alginate and its acid derivatives, are biocompatible and biodegradable polymers, effective in the production of adsorbent systems, for encapsulation and controlled release of active ingredients such as drugs and fertilizers. In this work, alginate polysaccharide and alginic acid were used to form composites with laponite, both with the original clay or with clay previously functionalized with 3‐aminopropyltriethoxysilane. The properties of the composites prepared from laponite or functionalized laponite and alginic acid or alginate were compared. The interaction of laponite with alginic acid leads to composites with strong disorder in the clay structure. In all cases, composites with high contents of polysaccharides, with good thermal and mechanical properties, are obtained. Laponite‐derived composites showed high adsorption capability for Cr(III) and methylene blue from aqueous medium. Copyright © 2012 Society of Chemical Industry     

Flammability of polystyrene layered silicate (clay) nanocomposites: Carbonaceous char formation

Polymer layered‐silicate (clay) nanocomposites have not only the unique advantage of reduced flammability, but also improved mechanical properties. This is a key advantage over many flame retardants, which reduce flammability but also reduce the mechanical properties of the polymer. In our efforts to further understand the mechanism of flame retardancy with polymer‐clay nanocomposites, we investigated the effect of the clay, the loading level and polymer melt viscosity on the flammability of polystyrene‐clay nanocomposites. The nanoscale dispersion of the clay in the polymer was analysed by wide‐angle X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Cone calorimetry and gasification studies were used to evaluate the flammability of these nanocomposites. There were major reductions in peak heat release rates (HRRs), and increased carbonaceous char formation, for these nanocomposites. It was determined that while the viscosity of the PS nanocomposite played a role in lowering the peak HRR, the clay loading level had the largest effect on peak HRR. Finally, it was found that clay catalysed carbonaceous char formation, and the reinforcement of the char by the clay was responsible for the lowered flammability of these nanocomposites. Published in 2002 by John Wiley & Sons, Ltd.