Effect of fumed silica properties on the thermal insulation performance of fibrous compact

The particle properties play an important role in developing advanced thermal insulation board made by fumed silica. In this study, the effect of hydrophilic or hydrophobic on the thermal conductivity and fracture strength of the resultant insulation board was investigated. A higher thermal conductivity and higher strength were obtained in using hydrophilic particles. Very low thermal conductivity, below 0.02 W/m K, was achieved in using hydrophobic particles. The difference of thermal conductivity was mainly dominated by solid part. The decrease of thermal conductivity and increase of fracture strength were related to the bonding condition between particles in the boards.     

Simplified correlations of gypsum board thermal properties for simulation tools

The current work proposes for the first time an integrated set of simplified correlations for the thermal properties, i.e. effective thermal conductivity, effective specific heat and effective density, of commercial gypsum boards as a function of temperature that can be easily incorporated in dedicated computational tools in order to simulate the fire behavior of a gypsum board. The proposed correlations are based on experimental data purposely performed in the frame of this work, as well as on literature experimental data and theoretical approximations. The applicability and the accuracy of the correlations are established by simulating the fire behavior of various types of gypsum boards exposed to different fire conditions. For the validation of the developed correlations, an in‐house developed code is utilized, taking into account thermal properties produced by the proposed correlations. The predictions are compared with two published sets of experimental data, as well as with one experimental data set performed in the current work. The results indicate that the proposed correlations can be reliably utilized in computational tools in order to accurately predict the fire behavior of commercial gypsum boards. Copyright © 2014 John Wiley & Sons, Ltd.     

挤塑聚苯乙烯泡沫塑料(XPS)的主要性能及应用领域分析

详细介绍了挤塑聚苯乙烯泡沫塑料(XPS)的热导率、压缩强度、长期热阻、防潮性能等主要性能指标。阐述了XPS板材的主要应用领域,包括在建筑外墙外保温、屋面保温、地面保温、冷库保温、公路、铁路、渠道工程等领域的应用。详细分析了提高XPS板材阻燃性能的必要性和紧迫性,并提出了在含氢氯氟烃替换过程中XPS泡沫行业的发展趋势。     

SiO2气凝胶提高岩棉和玻璃棉性能的实验研究

以无水乙醇为溶剂,SiO₂气凝胶为溶质,制取SiO₂气凝胶改性溶液。采用浸润及常压干燥的方法制备岩棉/SiO₂气凝胶复合板和玻璃棉/SiO₂气凝胶复合板,研究不同质量分数的SiO₂气凝胶对复合板的短期吸水量、热导率及抗压强度的影响,并分析SiO₂气凝胶质量分数为8%时制备的岩棉/SiO₂气凝胶复合板和玻璃棉/SiO₂气凝胶复合板的改性效果,进而采用扫描电镜对复合板的微观形貌进行了表征。结果表明,SiO₂气凝胶均匀附着于无机纤维上,形成了较为稳定的复合体系;随着SiO₂气凝胶质量分数的不断增加,岩棉/SiO₂气凝胶复合板和玻璃棉/SiO₂气凝胶复合板的短期吸水量和热导率都逐渐减小,其抗压强度有一定的提升。比较改性后的岩棉和玻璃棉,后者的防水性能和抗压强度改善更明显。当SiO₂气凝胶质量分数达到8%时,岩棉/SiO₂气凝胶复合板和玻璃棉/SiO₂气凝胶复合板的短期吸水量较改性前分别下降了35.0%和36.2%,热导率分别下降了26.7%和18.3%,抗压强度分别提升了6.5%和102.9%。     

Effect of pulse electromagnetic coupling treatment on thermal conductivity of WC-8Co cemented carbide

In this study, investigations were conducted focusing on the WC-8Co cemented carbide. A dry turning test of TC4 titanium alloy with WC-8Co cemented carbide tool treated by pulsed electromagnetic coupling treatment (PEMCT) was conducted. Tool wear was observed and analyzed using a scanning electron microscope (SEM) and energy dispersive X-ray spectrometer (EDS). The thermal conductivity of WC-8Co cemented carbide before and after the PEMCT was measured using Hotdisk thermal conductivity analyzer. The finite element software, DEFORM, was used to simulate the cutting process, and the stable cutting temperature range was obtained. The high-temperature oxidation test was conducted in a muffle furnace to study the effect of the PEMCT on the oxidation resistance of WC-8Co cemented carbide. This study obtained the effect of the PEMCT on the thermal conductivity of tungsten cobalt cemented carbide. The results show that the PEMCT can reduce the adhesive, diffusion, and oxidation wear of the tools, thus, improving the wear resistance and service life of the tools. The PEMCT improves the thermal conductivity and diffusivity of WC-8Co cemented carbide. Moreover, the oxidation resistance of WC-8Co cemented carbide in high-temperature conditions can be improved.     

Preparation,characterization, and electrical properties of ZSM‐5/PEG composite particles

ZSM‐5/PEG composites were synthesized by a simple solution method with polyethylene glycol (PEG) and H‐ZSM‐5 zeolite (Si/Al = 11.4). The obtained composites were characterized using X‐ray powder diffraction and Fourier transform infrared spectroscopy. The obtained results indicated that the ZSM‐5 was physically combined with PEG. The thermal properties and thermal stability were investigated by thermogravimetric and differential thermal analyses. In situ electrical conductivity was used to follow‐up the changes in the electrical conductance during the heating of the ZSM‐5/PEG composite. It was found that ZSM‐5 is able to effectively enhance the electrical conductivity of PEG. The results showed that the obtained weight loss during the composite decomposition to charcoal is accompanied by a decrease in the electrical conductivity. Moreover, the removal of the formed charcoal is associated with an electrical conductivity increase. Calcining the ZSM‐5/PEG composite having a content of 30% results in many effects on the structural, textural, and electrical properties of the obtained products. POLYM. COMPOS., 35:1160–1168, 2014. © 2013 Society of Plastics Engineers     

空心玻璃微球隔热保温板的制备及其理化特性

将空心玻璃微球（hollow glass microspheres,HGM）与饱和硝酸铝溶液混合,经520℃保温30min热处理后制备出刚性保温板。测试了保温板的导热系数、抗压强度和燃烧性能,讨论了HGM粒子密度和平均粒径对保温板导热系数的影响。结果表明：保温板的导热系数随HGM粒子密度的下降而降低,当粒子的粒子密度为0.18 g/cm3时,保温板的导热系数为0.072 W/（m.K）,抗压强度为2.2 MPa;当HGM的平均粒径小于30μm时,保温板的实测导热系数与Dul＇nev提出的预测方程的计算结果相接近,HGM保温板的燃烧性能达到A1级不燃材料要求,可满足建筑保温和防火的要求。     

Fire behavior of regular and latent heat storage gypsum boards

This paper investigates the fire behavior of a regular and an energy storage gypsum board with latent heat storage characteristics when exposed to fire temperatures. Gypsum board samples, with and without a microencapsulated paraffin mixture phase change material, are studied at material and board level. At the material level, measurements of the physical properties, that is, mass and effective thermal conductivity, as a function of temperature, as well as differential scanning calorimetry experiments, in inert and oxidized environments, are performed. At the board level, specimens are inserted into a preheated oven, and the temperature evolution at preselected board locations is recorded. Both experimental procedures reveal significant information concerning the evolution of the various thermochemical processes taking place inside the gypsum boards during their heating. Results indicated the different fire behavior of the samples at different temperature ranges. At temperatures up to 300°C, the materials act as a fire retardant because of the dehydration of the free and chemically bound water contained in the gypsum boards. On the other hand, at temperatures higher than 300°C, the temperature rise within the samples is enhanced and accelerated because of the oxidation of the phase change material and their external finishing. Copyright © 2014 John Wiley & Sons, Ltd.     

Improved crack resistance and thermal conductivity of cubic zirconia containing graphene nanoplatelets

Composites of 8 mol.% yttria-stabilized zirconia (8YSZ) with graphene nanoplatelets (GNP) have been pointed as alternative interconnectors in SOFC due to their mixed ionic-electronic conduction. Here we show that GNP addition provides rising crack-resistance behavior, with long crack toughness up to 78% higher than that of 8YSZ, also improving its thermal conductivity (up to 6 times for the in-plane direction). Toughness versus crack length is measured for 7 and 11 vol.% of GNP using single edge V-notched beam technique and ultrashort pulsed laser notching; and thermal behavior is analyzed by the laser flash method. Materials also have highly anisotropic coefficient of thermal expansion. These properties contribute to enhance their performance under the harsh operating conditions of SOFC, as thermal residual stresses could be reduced while significantly improving the system mechanical stability. Moreover, the heat transfer may be enhanced especially along the interface direction which would increase the system efficiency.     

Characterization of cordierite based h-BN doped ceramics as an electronic substrate/circuit board material

In this study, h-BN was added to the cordierite composition obtained from zeolite, which was prepared by the determined stoichiometry to facilitate machinability and increase thermal conductivity. Sintering behavior, hardness, machinability, and thermal/electrical properties of the samples obtained by sintering the compounds at different times were investigated. Thanks to these features, it is aimed to use cordierite as an alternative material to integrated circuit substrates and electronic packaging materials. The produced samples were analyzed by X-ray diffraction analysis, examined by scanning electron microscopy, and field emission scanning electron microscopy. Afterward, thermal properties such as thermal diffusivity, thermal conductivity, and electrical properties such as electrical conductivity and dielectric permittivity were measured. The hardness and machinability of samples were investigated. Cordierite, spinel, glassy phase, and h-BN phase were detected, and it was observed that the blocky cordierite grains turned into equiaxed grains with the increase of the h-BN. According to the results obtained from the thermal conductivity test, it was seen that the h-BN additive increased the thermal conductivity value in general. In addition, it was determined that with the increase of h-BN, the hardness decreased, and the machinability properties of the samples improved.     

Measurement and prediction of thermal conductivity for hemp fiber reinforced composites

The thermal conductivity of hemp fiber reinforced polymer composites were studied from the steady state temperature drop across samples exposed to a known heat flux. The transverse and in-plane thermal conductivities for oriented and randomly oriented composites for different volume fractions of fiber were investigated. Experimental results showed that the orientation of fibers has a significant effect on the thermal conductivity of composites. To validate the experimental results, the heating tests for the thermal conductivity measurements were simulated by a finite element model using the thermal conductivity values obtained from the experiments. Predicted temperatures show close agreement with measured temperatures. Moreover, the experimental results of thermal conductivities of composites at different directions were compared with two theoretical models and illustrated good agreement between the obtained results and models. POLYM. ENG. SCI. 47:977–983, 2007. © 2007 Society of Plastics Engineers     

Thermal properties of gypsum plasterboard at high temperatures

Light timber frame wall and floor assemblies typically use gypsum‐based boards as a lining to provide fire resistance. In order to model the thermal behaviour of such assemblies, the thermo‐physical properties of gypsum plasterboard must be determined. The relevant literature and the chemistry of the two consecutive endothermic dehydration reactions that gypsum undergoes when heated are reviewed. The values determined for the thermo‐physical properties are modified to create smooth enthalpy and thermal conductivity curves suitable for input into a finite element heat transfer model. These values are calibrated within a reasonable range and then validated using furnace and fire test data. The type of plasterboard used in these tests is an engineered product similar to the North American type C board. The temperature at which the second dehydration reaction occurs is altered to be consistent with later research with little apparent affect on the comparison with test results. Values for specific heat, mass loss rates and thermal conductivity for gypsum plasterboard that are suitable for use in finite element heat transfer modelling of light timber frame wall and floor assemblies are recommended. Copyright © 2002 John Wiley & Sons, Ltd.     

An investigation into the thermal transport properties of PP/EPDM/clay nanocomposites using a new combined experimental/numerical method

This research work is devoted to the study of the thermal transport properties of nanocomposites based on PP/EPDM/Clay (Polypropylene/Ethylene Propylene Diene Monomer/Clay). Six different formulations were designed and the corresponding nanocomposites (with 0, 2, 4 and 6% of clay) were prepared via melt mixing. To achieve the goals, densities, specific heat capacities and thermal conductivities were measured as function of temperature and nanocomposites compositions. A new and novel methodology was developed to determine the thermal conductivity which was based on an inverse heat transfer problem. First, assuming a linear relationship for thermal conductivity, the transient heat transfer equation in a solid specimen was numerically solved. The obtained temperature profile was used as the input to an optimisation technique based on genetic algorithm and the parameters of the thermal conductivity relationship were found. The results showed that the specific heat increases both with increasing of temperature and clay contents. It is also increased with the addition of the rubber to the blend. In all samples, the thermal conductivity decreases with increasing of temperature with a linear relationship. In addition, at relatively constant ratios of PP/EPDM, thermal conductivity of nanocomposite and its sensitivity increase with temperature rise. Moreover, at constant value of clay content, the thermal conductivity is decreased with increase of rubber content. The explanations to above findings were also presented and discussed.     

挤塑板表面结构对导热系数的影响

通过对几种不同表面结构类型的挤塑聚苯乙烯泡沫塑料（XPS）板的导热系数进行检测并对数据进行分析和讨论。结果表明,表面开槽对XPS导热系数的影响较小,单面去除表皮次之,而双面去除表皮会明显降低XPS的导热系数。     

导热填料对NR/BR硫化胶的生热和导热的影响

研究了氧化锌、炭黑、石墨等几种导热填料对NR/BR硫化胶的生热和导热性能的影响。结果表明,提高氧化锌的用量可以减小硫化胶的损耗和压缩温升、提高导热系数;增加炭黑用量虽然提高导热系数,但炭黑的Payne效应、损耗和压缩温升等动态性能大幅度增加,表现出明显的逾渗现象,而导热系数、定伸应力、硬度等静态性能增加幅度较小;大粒径炭黑有利于提高硫化胶的导热系数、降低损耗和压缩温升,高结构度炭黑虽能提高导热系数,但是损耗和压缩温升增加。配方中加入氧化铝、氢氧化铝、石墨、煤灰、铝粉后,硫化胶的力学性能较差,Payne效应较弱,损耗和压缩温升明显降低,含有铝粉或石墨硫化胶的导热系数较高。     

Thermal properties and microstructure of gypsum board and its dehydration products: A theoretical and experimental investigation

This article addresses the thermal properties and the microstructure of gypsum boards produced from β‐hemihydrate by studying its dehydration process. Dehydration reaction of gypsum boards was investigated from both micro and macro levels, employing thermogravimetric analysis and a ventilated oven. A new dehydration mechanism of gypsum was proposed. The thermal properties of gypsum board such as enthalpy of reaction, specific heat capacity, and thermal conductivity were studied by differential scanning calorimetry and a heat transfer analyzer, respectively. The effect of void fraction and dehydration on thermal physical properties of gypsum board was investigated. The microstructure of the gypsum board at high temperature was studied with experiments and modeling. A model was proposed to describe the microstructure of a dehydrated system at high temperature, and experiments indicate its validity. Furthermore, the mechanical properties of gypsum at high temperature were investigated, and the effect of water content was discussed as well. Copyright © 2011 John Wiley & Sons, Ltd.     

Synergistic thermal conductivity enhancement of PC/ABS composites containing alumina/magnesia/graphene nanoplatelets

Graphene nanoplatelets (GNPs) have attracted considerable attention in the field of thermal management materials due to their unique structure and exceptional thermal conductive properties. In this work, we demonstrate a significant synergistic effect of GNPs, alumina (Al₂O₃), and magnesia (MgO) in improving the thermal conductivity of polycarbonate/acrylonitrile‐butadiene‐styrene polymer alloy (PC/ABS) composites. The thermal conductivity of the composites prepared through partial replacement of Al₂O₃ and MgO with GNPs could increase dramatically compared with that without GNPs. The maximum thermal conductivity of the composite is 3.11 W mK⁻¹ at total mass fraction of 70% with 0.5 wt% GNPs loading. It increases 60% compared with that without GNPs (1.95 W mK⁻¹). The synergistic effect results from the compact packing structure formed by Al₂O₃/MgO and the bridging of GNPs with Al₂O₃/MgO, thus promoting the formation of effective thermal conduction pathways within PC/ABS matrix. More importantly, together with the intrinsically high thermal conductivity of GNPs, boosted and effective pathways for phonon transport can be created, thus decrease the thermal resistance at the interface between fillers and PC/ABS matrix and increase the thermal conductivity of composites. POLYM. COMPOS., 38:2221–2227, 2017. © 2015 Society of Plastics Engineers     

Fire‐retarding properties of nanowollastonite in particleboard

Effects of wollastonite nanofibers on fire‐retarding properties of particleboard were studied here. Nanowollastonite (NW) was applied at 5%, 10%, 15%, and 20% based on the dry weight of wood particles. The size range of wollastonite nanofibers was 30 to 110 nm. Two application methods of NW were used: surface application (SA) in which NW was mixed with a water‐based paint and sprayed on the specimens, and internal application (IA) in which NW was mixed with the urea‐formaldehyde resin. Density was kept constant at 0.68 g/cm³ for all treatments. Specimens of 150 × 130 × 9 mm were prepared, and fire‐retarding properties were measured using 2 apparatuses: slide fire test apparatus and fixed fire test apparatus. The obtained results indicated that most fire‐retarding properties were improved with the increase in NW content up to 15% when applied internally. More than this amount resulted in decreasing of properties that was partly due to the less wood‐chips content and partly due to the absorption of resin by the NW fibers. Surface application showed higher improving effects on the properties. It can be concluded that SA of NW is more effective in improving fire‐retarding properties of particleboard; furthermore, 10% of NW is recommended as an optimum level of consumption.     

Effect of borax on the thermal and mechanical properties of ethylene‐propylene‐diene terpolymer rubber‐based heat insulator

The effect of Borax on the mechanical and ablation properties of three different ethylene‐propylene‐diene terpolymer (EPDM) compounds containing 20 phr carbon fiber, 20 phr Kevlar or 10 phr/ 10 phr carbon fiber/ Kevlar was investigated. All formulations contained 30 phr fumed silica powder and 10 phr paraffinic oil. It was found that adding Borax to the composite samples containing carbon fiber or Kevlar fiber or their mixture with an equal ratio can increase the tensile strength, elastic modulus and hardness with a slightly decrease in the elongation at break of the rubber samples. The results of thermogravimetry analysis (TGA) on the various samples showed significant increase in the char yield at 670°C by adding Borax to the rubber compounds. Moreover, ablation resistance of samples was also improved by increasing Borax content. Meanwhile, density and thermal conductivity of the insulator were also reduced up to about 10% when the carbon fiber was replaced with the Borax. The results indicated that composites containing Kevlar have high storage modulus and produce compact and stable char. EPDM rubber composite containing Borax (20 phr), carbon fiber (10 phr), and Kevlar (10 phr) showed thermal and ablative properties comparable with those of the asbestos‐ filled EPDM. The thermal conductivity and ablation rate of the above‐ mentioned sample were 0.287 W/m/K and 0.13 mm/s respectively. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41936.     

聚丙烯酸酯改性石墨及其对天然橡胶导热性能的影响

采用聚丙烯酸酯改性石墨,然后将其填充到天然橡胶中,研究了改性石墨对复合材料导热性能和力学性能的影响。结果表明,石墨经聚丙烯酸酯改性后降低了自身的聚集作用,同时由于其被包覆,受力时更不易分层滑移;表面粗糙度的提高及有机基团的增多使得石墨与橡胶间的结合作用增强,同时促成了更多导热网链和"桥接"导热通道的形成,从而提高了其填充天然橡胶的热导率和力学性能。石墨在改性时软硬段单体的配比影响其包覆效果,进而影响其填充天然橡胶的导热和力学性能;当石墨与改性单体的质量比为10/1、软硬段单体的质量比接近1/1时,所改性石墨填充天然橡胶的热导率较高,综合力学性能较好。