Synthesis and foaming of water expandable polystyrene-clay nanocomposites

The typical process used to synthesize water expandable polystyrene (WEPS) was modified and applied to prepare water expandable polystyrene (PS)-clay nanocomposites (WEPSCN). The natural clay can be uniformly dispersed in water due to its hydrophilicity. It can be further carried into the styrene monomer by the formation of water-in-oil inverse emulsion. Via suspension polymerization, spherical PS beads with myriads of water/clay droplets inside were obtained. Upon heating via the hot medium, the PS matrix was expanded to form a cellular structure. Transmission electron microscopy results indicated that nanoclay forms a layer around the cell wall. The presence of nanoclay led to higher water content in the beads and reduced the water loss during storage.Using CO₂ as the co-blowing agent, foams with a bi-model structure and lower densities were obtained. Furthermore, CO₂ foaming offers an alternative method to utilize dried WEPS/WEPSCN beads. The presence of water cavities significantly enlarges the cell size and leads to a foam product with ultra-low density (∼0.03 g/cc) and low thermal conductivity.     

PP/超临界CO2连续挤出发泡成型

以超临界CO2为发泡剂,在连续挤出发泡过程中研究了超临界CO2用量对高熔体强度均聚聚丙烯(PP)发泡成型过程的影响.随着超临界CO2用量的增加,发泡挤出机口模压力降低,试样发泡倍率降低,泡孔尺寸变小,泡孔密度提高.在w(CO2)为3%,5%时,得到发泡倍率最高为13左右的PP发泡材料.w(CO2)为7%,发泡温度为12...     

Removal of carbon disulfide (CS2) from water via adsorption on active carbon fiber (ACF)

The primary objective of this paper was to demonstrate the suitability of ACF in effectively adsorbing CS₂ from water, and to compare its performance vs. that of GAC. Commercial ACF was modified to increase its specific surface and pore volume. CS₂ removal was studied by adding ACF to water containing CS₂ under varying conditions. The experimental results reveal that ACF is a potential adsorbent for capturing CS₂ under both equilibrium and dynamic adsorption/desorption conditions. The adsorption capacity of ACF was observed to considerably increase with the increase of CS₂ concentration: It was observed that the modified ACF exhibited greater adsorption for CS₂ than the GAC, and the mechanism for this difference was explored; The modified ACF showed a consistent performance within a pH range from 3-9; Under the experimental conditions, an modified ACF sample was adsorbed and desorbed by boiling water repeatedly without exhibiting any appreciable degradation in its adsorption performance.     

Extrusion foaming of polystyrene/carbon particles using carbon dioxide and water as co-blowing agents

Carbon particles such as platelet-like graphite (GR), spherically shaped activated carbon (AC), and tubular carbon nanofiber (CNF) were used as additives in extruded polystyrene (PS) foams with carbon dioxide (CO₂) and water as co-blowing agents. It was found that GR is the best additive for improving the thermal insulation performance of CO₂ based foam samples because of GR’s good absorption and reflectivity of infrared (IR) radiation. However, when the GR concentration was higher than 0.5 wt.%, the extruded foams exhibited large bubbles in the center of the foam and the extrusion line became unstable. By adding water carried by AC as a co-blowing agent, it was able to decrease the temperature in the center of the extruded foam, which successfully eliminated the bubble problem and achieved stable foam extrusion with good control of the foam density and cell morphology. Moreover, water carried by AC could also improve the mechanical performance of extruded foams containing CNF or GR. Water was not found in the extruded foams and the presence of water during extrusion did not affect the molecular weight and glass transition temperature of PS. Our results showed that a combination of AC as a water carrier and GR as an absorber and reflector of IR radiation can produce CO₂ based PS foams with good thermal insulation and mechanical properties, particularly with the presence of a small amount of CNF nanoparticles.     

Corrosion protection of iron in water by activated carbon fiber (ACF)

Commercial activated carbon fiber (ACF) was modified and employed to prevent iron corrosion in industrial water supply and circulation system. Static and dynamic experiments were carried out under varying conditions, including different pHs, different temperatures, different adsorbent quantities and different adsorbents. The primary objective was to experimentally demonstrate the suitability of ACF in effectively preventing iron corrosion in water under varying operating conditions, and compare its performance vis-à-vis to that of the other commercially available adsorbents, such as granular activated carbon (GAC) and powdered activated carbon (PAC). Iron sheet static corrosion simulation test as well as dynamic corrosion simulation test was performed to verify the idea. It was found out that ACF could significantly decrease the zeta potential (from 329 mV to 203 mV when 100 mg ACF was added to 200 ml water) and dissolved oxygen concentration (from 9.60 mg/l to around 9.18 mg/l when 200 mg ACF was added to 200 ml water) of the solution, thereby slowing down iron corrosion rate.     

Crystallinity development in cellular poly(lactic acid) in the presence of supercritical carbon dioxide

This article investigates the crystallinity development in cellular poly(lactic acid) (PLA) and the effect of the achieved crystalline content on its properties and microstructure. Carbon dioxide (CO₂) in its supercritical state was used as the expansion agent for three different grades of PLA that differed in terms of L‐lactic acid content. Cellular PLA was produced on a twin‐screw extrusion line using capillary dies of various diameters. The obtained crystalline contents were measured by differential scanning calorimetry and X‐ray diffraction techniques. The morphology of the cellular structures was examined using scanning electron microscopy. The crystallinity developed on expansion depended on L‐lactic acid content, on supercritical CO₂ concentration, polymer flow rate, and die diameter. Cellular PLA, with densities as low as 30 kg/m³, was obtained under the most favorable conditions. It was shown that the crystallinity development in PLA enhances its cellular structure formation and enables the fabrication of quality cellular materials at lower CO₂ concentration. The presence of PLA crystallites within expanded cell walls leads to a peculiar 2D‐cavitation phenomena observed only in the cell walls of semicrystalline foams. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Nanodispersions of carbon nanofiber for polyurethane foaming

Nanodispersions of polyurethane components with a three dimensional gelled network of filler is formed by the addition of a very small quantity of vapor grown carbon nanofiber (CNF). Reactive foaming of these nanodispersions produced polyurethane foams with superior properties. The kinetic profiles of polymerization and foaming reactions are not affected by the addition of filler. The cellular structure of nanocomposite foam becomes more uniform. Thermal conductivity and fire retarding tendency of the nanocomposite foams are superior at a very low loading of filler (1% by weight in components which corresponds to <0.5% by weight in foam). The filler did not open cells or induce structural defects.     

连续挤出发泡聚乳酸泡孔结构的影响因素

介绍了采用超临界CO2作为发泡剂,连续挤出聚乳酸泡沫塑料的方法。在不同的实验条件下,对聚乳酸进行挤出发泡,得到聚乳酸发泡样品。通过对样品的ESM照片的分析研究,得出了不同的发泡条件对挤出聚乳酸泡沫泡孔结构的影响。结果表明螺杆转速的增加使得泡孔数量增加,泡孔形态更加规整均匀。模头温度影响了泡孔形态,较高的温度会使得样品的泡孔形态受到不利的影响。水分的存在不利于聚乳酸发泡成为均匀发泡倍率高的泡沫制品。成核剂促进异相成核,使发泡样品的泡孔结构更加均匀,大大提高了聚乳酸泡沫塑料的泡孔密度。     

基于醇胺固定-释放二氧化碳原理的聚氨酯泡沫绿色制备

通过二乙醇胺（DEA）和二氧化碳反应制得一种氨基甲酸铵化合物（DEAC）。DEAC初始分解温度约为54℃,二氧化碳含量14.6%。将不同份数的DEAC作为反应型发泡剂添加到硬质聚氨酯发泡体系中制备泡沫材料,得到密度为90~150 kg·m^-3,压缩强度为0.02~1.65 MPa性能良好的泡沫材料。DEA在火力发电厂作为二氧化碳吸收剂以减少二氧化碳排放。因此,DEAC可以来源于火力发电厂的副产物,成本低廉。本研究为硬质聚氨酯泡沫的制备提供了一种新型的绿色、环保、经济的方法。     

反应型磷氮阻燃剂/可膨胀石墨复配阻燃聚氨酯泡沫

将反应型阻燃剂六(4-磷酸二乙酯羟甲基苯氧基)环三磷腈(HPHPCP)和可膨胀石墨(EG)复配,制备了阻燃聚氨酯泡沫,详细研究了复配阻燃剂对聚氨酯泡沫的物理力学性能、热稳定性以及阻燃性能的影响。结果表明,阻燃聚氨酯泡沫的密度和热导率随着复配阻燃剂中EG含量的增加而升高;压缩强度随着EG含量的增加呈现先增加后降低的趋势。热失重表明复配阻燃剂大大提高了聚氨酯泡沫的热稳定性。聚氨酯泡沫的初始分解温度(T_10%)从212.9℃,分别提高到222.0、231.2和243.2℃;700℃残炭量从7.6%分别提高到26.3%、31.6%和37.9%。聚氨酯泡沫的阻燃性能随着复配阻燃剂中EG含量的增加而提高。阻燃聚氨酯泡沫的极限氧指数从19%提高到29%,均能通过UL-94水平燃烧HF-1等级和垂直燃烧V-0等级。     

Preparation of microporous activated carbon and its modification for arsenic removal from water

Arsenic removal from water was investigated using activated carbon. The chemical activated carbon (CAC) prepared using H₃PO₄ from jute stick largely featured micropore structure with surface functional groups, while meso- and macropore structures were mainly developed in physical activated carbon (PAC). The CAC and PAC reduced arsenic concentration to 45 and 55 μg L⁻¹, respectively, from 100 μg L⁻¹ while iron-loaded CAC reduced to 3 μg L⁻¹, which is lower than the upper permissible limit (10 μg L⁻¹). The micropore structure of CAC along with complexation affinity of iron species towards arsenic species attributed to enhanced separation of arsenic.     

浅析碳捕捉推进绿水青山

建设绿色低碳的生态文明是关系人民福祉、关乎民族未来的大计,是实现中华民族伟大复兴中国梦的重要内容,随着煤化工行业的兴起,环境问题日益突出,煤化工的二氧化碳排放量很大。主要介绍了实行碳捕捉的必要性及方法。     

Application of TiO2-mounted activated carbon to the removal of phenol from water

TiO₂-mounted activated carbon was prepared through hydrolytic precipitation of TiO₂ from teraisopropyl orthotitanate and following heat treatment at 650–900 °C for 1 h under a flow of nitrogen. The removal of phenol from its aqueous solution under UV irradiation was measured on TiO₂-mounted activated carbons thus prepared. Although BET surface area of TiO₂-mounted activated carbons decreased drastically in comparison with the original activated carbon, the efficiency of phenol removal under UV irradiation was high. The sample heated at 900 °C, which consisted mainly of rutile phase, showed the highest total removal of phenol. Efficiency of phenol degradation is reduced because of phenol adsorption on the catalyst.     

Gallic acid water ozonation using activated carbon

The ozonation of gallic acid in water in the presence of activated carbon has been studied at pH 5. Hydrogen peroxide, ketomalonic and oxalic acids were identified as by-products. The process involves two main periods of reaction. The first period, up to complete disappearance of gallic acid, during which ozonation rates are slightly improved by the presence of activated carbon. The second one, during which activated carbon plays an important role as promoter, and total mineralization of the organic content of the water is achieved. The organic matter removal is due to the sum of contributions of ozone direct reactions and adsorption during the first period and to a free radical mechanism likely involving surface reactions of ozone and hydrogen peroxide on the carbon surface during the second period. There is a third transition period where by-products concentration reach maximum values and ozonation is likely due to both direct and free radical mechanisms involving ozone and adsorption. Discussion on the mechanism and kinetics of the process is also presented both for single ozonation and activated carbon ozonation.     

Determination of assimilable organic carbon (aoc) in ozonated water with acinetobacter calcoaceticus

The effect of ozone application in drinking water on the production of assimilable organic carbon (AOC) was evaluated. The typical procedure to determine AOC is suggested by van der Kooij, which is the method of bacterial growth measurement by colony‐forming units using the strain P17 and/or NOX. The bacterial indicator species used for this study is Acinetobacter calcoaceticus which was isolated and identified while ozonating Nakdong river water. This strain could never be isolated from the raw water, but this strain was the predominant isolate in the ozonated water. Within a short incubation time, this organism was found to replicate well on acetate and oxalate as the sole carbon sources. The yield coefficients of this organism for acetate and oxalate are the same order of magnitude as the value of P17 and NOX. With full‐scale experiments, A. calcoaceticus concentration was found to increase after ozonation, but did not decrease upon chlorination. In laboratory‐scale experiments with Yongsan river water, aldehyes were found to be produced in proportion to the ozone dose. The raw water contains low concentrations of aldehydes, but has a high AOC concentration. A correlation between aldehyde production and AOC production was observed in the tested water with ozonation.     

Growth of carbon nanofibers on activated carbon fiber fabrics

Activated carbon fiber fabrics, an excellent adsorbent, were used as catalyst supports to grow carbon nanofibers. Because of the microporous structure of the activated carbon fibers, the catalysts could be distributed uniformly on the carbon surface. Based on this concept, the carbon nanofibers can be grown directly on the activated carbon fiber fabrics. We demonstrate that carbon nanofibers with a diameter between 20 and 50 nm for most of the fibers can be synthesized uniformly and densely on activated carbon fiber fabrics, impregnated by nickel nitrate catalyst precursor, using catalytic chemical vapor deposition. Although the carbon nanofibers are not straight with a crooked morphology, they form a three-dimensional network structure. Structure characterizations by TEM and XRD indicate that the carbon nanofibers have a turbostratic graphite structure and the graphite layers are stacked with a herringbone structure.     

聚乙烯醇/微纤化纤维素复合微发泡材料的制备

通过溶液浇铸法制备了聚乙烯醇(PVOH)/微纤化纤维素(MFC)复合薄膜材料,以超临界二氧化碳(scCO₂)为物理发泡剂,采用间歇式降压法制备了一系列PVOH/MFC复合微发泡材料,主要讨论了在没有水分的影响下,不同发泡温度和时间以及MFC含量对PVOH/MFC复合微发泡材料的泡孔形貌、泡孔尺寸和泡孔密度的影响;同时,也对MFC的分散性和PVOH/MFC复合材料的流变性能和热性能对发泡行为的影响进行了研究。实验结果表明,均匀分散在PVOH基体中的MFC作为异相成核剂提高了气孔成核能力,且随着MFC含量的增加,泡孔尺寸降低,泡孔密度增大;并研究了发泡温度对PVOH/MFC复合材料的发泡形貌的影响,获得最优发泡温度。     

Improving the fire performance and smoke suppression of expandable polystyrene foams by coating with multi-dimensional carbon nanoparticles

Expandable graphite (EG) and modified multi-wall carbon nanotubes (ATH-MWNT) were introduced to expandable polystyrene (EPS) foams in order to improve its fire performance. The fire performance of EPS foams was evaluated by limiting the oxygen index (LOI), vertical burning (UL-94), and cone calorimetry tests. The results showed that the presence of 14.3% EG and 4.1% ATH-MWNT increased the LOI value from 18.0 to 30.3%, upgraded the UL-94 rating from no rating to V-0, completely eliminated melt dripping, and significantly decreased the peak heat release rate from 933 to 177 kW/m². Thermal analysis indicated that the thermal stability and char formation were improved by the presence of flame retardants. The char morphology was characterized by scanning electronic microscopy (SEM). It was suggested that the presence of EG and ATH-MWNT could form integrated char layers during combustion, which was beneficial to the formation of an intumescent protective char structure.     

Solid‐state microcellular high temperature vulcanized (HTV) silicone rubber foam with carbon dioxide

A series of microcellular high temperature vulcanized (HTV) silicone rubber foams were prepared using CO₂ as a physical blowing agent. Rheological properties, gas diffusive behavior, and foaming parameters of silicone rubber were investigated. The results show that saturation pressure has a significant effect on the diffusivity of CO₂ in HTV silicone rubber matrix. The gas concentration and diffusivity increase from 2.45 wt % to 3.24 wt %, and from 1.62 × 10^?5 cm²/s to 7.83 × 10^?5 cm²/s as the saturation pressure increases from 2 MPa to 5 MPa, respectively. The value of the gas diffusivity in HTV silicone rubber is almost 1000 times higher than that of the gas diffusivity in polyetherimide (PEI) matrix. Additionally, microcellular HTV silicone rubber foams with the smallest cell diameter of 9.8 μm and cell density exceeding 10⁸ cells/cm³ are achieved. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44807.     

CO2-原油体系发泡特性实验研究

为研究CO₂驱油田分离器内泡沫层产生及消除机理,设计了一套高压溶气原油泡沫测试系统,采用降压法研究了CO₂-原油体系的发泡特性。利用高速摄像机对泡沫产生至衰变的演变过程进行了记录,总结分析了不同降压阶段的气泡行为,研究了降压速率和搅拌速率对原油发泡特性的影响规律。研究发现,随压力降低,稳定存在气泡的直径增大,气泡位置上移,发泡行为更加剧烈;降压速率增加对降压阶段的发泡行为无明显影响,但会加剧稳定工作压力下的发泡行为;在转速小于等于120 r/min的条件下,搅拌速率增加会加剧降压阶段的发泡行为,但会加速稳定工作压力下的泡沫衰变。