Preparation and properties of hollow glass bead filled silicone rubber foams with low thermal conductivity

Silicone rubber foams filled with various content and different particle size of hollow glass bead (HGB) were prepared by compression molding. It was revealed that compared with silica filled silicone rubber foams, HGB filled materials achieved higher foaming extent, lower thermal conductivity, and lower hardness, which can be significant for thermal insulation materials. For HGB filled materials, the morphology indicated the average cell size decreased with higher HGB content and larger particle size of HGB. The density, thermal conductivity, hardness and tensile strength increased with higher HGB content and larger particle size of HGB.     

空心玻璃微球含量对环氧复合泡沫塑料性能的影响

以空心玻璃微球（HGM）填充环氧树脂制备了密度为0.56~0.91 g/cm3的HGM/环氧复合泡沫塑料。研究了HGM含量对复合泡沫塑料黏度、力学性能、动态力学性能及隔热性能的影响。结果表明:表面偶联处理后增加了HGM的表面亲油性,改善了其与基体树脂间的相容性和界面性能,有利于HGM/环氧复合泡沫塑料性能的提高;体系黏度与HGM含量呈正相关,与温度呈负相关;随着HGM含量的增加,HGM/环氧复合泡沫塑料的压缩强度、弯曲强度和拉伸强度均有一定程度的降低,但是比强度变化不大,材料得到很大程度的轻质化;HGM的引入使得HGM/环氧复合泡沫塑料玻璃化转变温度向低温方向偏移,储能模量呈现先减小后增加的趋势,导热系数由纯环氧树脂的0.203 W/（m·K）减小到HGM含量为40wt%时的0.126 W/（m·K）。HGM/环氧复合泡沫塑料阻尼性能和隔热性能均有所提高。      

Enhancement in insulation and mechanical properties of PMMA nanocomposite foams infused with multi-walled carbon nanotubes

In this study, PMMA/CNTs composite materials with carboxyl-multi walled carbon nanotubes (c-MWNTs) or untreated MWNTs were prepared via in-situ bulk polymerization. The as-prepared PMMA/CNTs composite materials were then characterized by Fourier-Transformation infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM). The molecular weights of PMMA extracted from PMMA/CNTs composite materials and bulk PMMA were determined by gel permeation chromatography (GPC) with THF used as the eluant. The PMMA/CNTs composite materials were used to produce foams by a batch process in an autoclave using nitrogen as foaming agent. The cellular microstructure, insulation and compressive mechanical properties of PMMA/CNTs composite foams were also investigated in detail. Compared to neat PMMA foam, the presence of CNTs increases in cell density and reduces cell size. The insulation and compressive mechanical properties of PMMA/CNTs composite foams were found to improve substantially those of neat PMMA foam. In particular, 22.6% decrease in thermal conductivity, 19.7% decrease in dielectric constant and 160% increase in compressive modulus were observed with the addition of 0.3 wt% carboxyl-multi walled carbon nanotubes (c-MWNTs).     

Effect of multi-walled carbon nanotubes on mechanical,thermal and electrical properties of phenolic foam via in-situ polymerization

In this study, phenolic foam (PF)/multi-walled carbon nanotubes (MWCNTs) composites were fabricated by in-situ polymerization, and carbonized foams based on these PF foams were prepared and the electrical property was investigated. TEM results indicated excellent dispersion of MWCNTs in the phenolic resin matrix. Scanning electron microscope results indicated that PF composites exhibited smaller cell size, thicker cell wall thickness, and higher cell density, compared with pure PF. The incorporating of MWCNTs significantly improved the mechanical properties of PF. All PF composites showed a lower thermal conductivity versus pure PF. Moreover, the carbonized pure and composites PF exhibited open-cell three-dimensional skeleton carbon structure and the MWCNTs were well-dispersed on the surface of the skeletons. It is noteworthy that the introduction of MWCNTs significantly improved the electrical performances of foams and carbonized foams by construction of conductive MWCNTs network.     

Mechanical, thermal and electrical properties of aluminum nitride/polyetherimide composites

The mechanical, thermal and electrical properties of modified AlN/polyetherimide (PEI) composites were investigated. It revealed that the surface of AlN modified by silane could effectively increase the adhesion with matrix, which was beneficial for AlN to reinforce the polyetherimide matrix. After silane modification, the AlN showed good dispersion and wetibility in the polyetherimide matrix and imparted excellent mechanical, electrical and thermal properties. The tensile strength, modulus, electrical and thermal stability were improved with the increasing of AlN content. The tensile strength of AlN/PEI composites increased by 27% when 12.6 vol.% AlN was added to neat polyetherimide. The thermal conductivity of the 57.4 vol.% AlN/PEI composites increased three times compared with neat polyetherimide. Test results indicate that the silane grafted AlN incorporated into the polyetehetimide matrix effectively enhance the thermal stability, thermal conductivity and mechanical properties of the polyetherimide composites.     

纤维增强发泡保温复合材料的制备与性能

为了增强玻化微珠/水泥发泡保温复合材料的力学性能和保温性能,通过掺加改性物理泡沫降低发泡保温复合材料的密度和导热系数,采用改性纤维对发泡保温复合材料进行增强。研究了纤维增强发泡保温复合材料的力学性能和耐水性能,并利用扫描电镜对试样内部微观形貌进行观察,探讨了改性泡沫和改性纤维对发泡保温复合材料的增强机制。结果表明,掺加泡沫明显降低了发泡保温复合材料的密度和导热系数,当泡沫掺量为1.05 mL/g时,试样密度和导热系数分别为186 kg/m³和0.056 W/（m·K）。泡沫改性可有效改善发泡保温复合材料的强度和软化系数,掺加改性泡沫试样的抗折强度、抗压强度和软化系数较掺加乳胶粉试样的分别提高了21.05%、21.43%和13.56%。改性纤维可显著提高发泡保温复合材料的强度和软化系数,掺加改性纤维试样的抗折强度、抗压强度和软化系数较掺加未改性纤维试样的分别提高了25.93%、13.51%和8.33%。     

一种新型隔热涂料的制备及性能研究

以苯丙乳液为成膜剂,硅烷偶联剂处理后的中空玻璃微珠为功能隔热填料合成新型的隔热涂料。结果表明,用硅烷偶联剂预处理中空玻璃微珠后涂料附着力能提高1个级别;涂层导热系数随中空玻璃微珠粒径的增加呈现先减小后增大的趋势,当中空玻璃微珠的粒径为58μm左右时导热系数比其它粒径制得涂料的导热系数降低6%～28%;随涂膜厚度的增加,隔热效果增强,但当涂膜厚度增大到0.3mm时,继续增加涂膜厚度,隔热效果几乎不再增强;当中空玻璃微珠含量小于10%时,热反射率随中空玻璃微珠在隔热涂料中含量的增加显著增加,超过10%后,热反射率增加速率减缓,当达到12%时,涂料的热反射率值最高,继续增加玻璃微珠含量,热反射率几乎不增加。     

基于常温干燥法的纤维素基泡沫制备及性能分析

传统的石油基泡沫难以降解,因而带来环境污染和安全问题。纤维素基泡沫借助其可生物降解的天然特性,逐渐成为研究热点。然而,目前的成型技术在很大程度上依赖于干燥条件（如冷冻干燥和超临界干燥）,存在干燥耗时长、成本高的问题,因而难以实现泡沫的规模化生产。为解决此问题,提出一种常温干燥制备可再生纤维素基泡沫的新方法。以纸浆纤维为主料、纳米纤维素为黏结剂、聚乙烯醇作为纤维分散剂和泡沫助剂,经过充分混合、发泡、排水和干燥后,制成纤维素基泡沫。最后,测试泡沫密度、孔隙率,分析导热性能、力学性能。结果表明：制备的纤维素基泡沫具有密度低（(0.015±0.002)~(0.028±0.004) g/cm3）、孔隙率高（>98%）、热导率低（(0.060±0.003)~(0.069±0.003) W/(m·K)）等特点。纤维素基泡沫在80%应变下的最大应力值为59.366 kPa,比其他文献报道的类似纳米纤维素基泡沫高37.1%。未来,纤维素基泡沫有望替代石油基泡沫,在冷链运输过程中对产品进行缓冲保护和隔热保温。     

Processing of Kaolinite and Alumina Loaded in Natural Rubber Composite Foams

Composite natural rubber foams were successfully prepared from the vulcanization of natural rubber in a sulfur curing system. The natural rubber matrix phase was added with chlorinated polyethylene, kaolinite, and alumina. The morphology of natural rubber composite foams was altered when a gas was generated at the vulcanization temperature of 150°C to obtain open and closed cell structures. Furthermore, the kaolinite and alumina reinforced the mechanical properties and increased the thermal resistance of the composite foams. The composite foams were light in weight and had good thermal, mechanical, and electrical properties, suitable for energy absorption, thermal insulation, and structural uses.     

复合烧结助剂对Si3N4陶瓷力学性能和热导率的影响

Si₃N₄陶瓷因兼具优异的力学和热学性能, 成为第三代半导体陶瓷基板的首选材料之一。本研究以7种不同离子半径的稀土氧化物(RE₂O₃, RE=Sc、Lu、Yb、Y、Gd、Nd、La)与非氧化物(MgSiN₂)作复合烧结助剂, 通过热压烧结和退火热处理制备了高强、高热导Si₃N₄陶瓷, 并系统研究了复合烧结助剂中RE₂O₃种类对Si₃N₄陶瓷物相组成、微结构、力学性能和热导率的影响规律。热压后Si₃N₄陶瓷力学性能优越, 其中添加Nd₂O₃-MgSiN₂的样品弯曲强度达到(1115±49) MPa。退火处理后Si₃N₄陶瓷的热导率得到大幅提升, 呈现出随稀土离子半径减小而逐渐增大的规律, 其中添加Sc₂O₃-MgSiN₂的样品退火后的热导率从54.7 W·m^-1·K^-1提升至80.7 W·m^-1·K^-1, 提升了47.6%。该结果表明, 相较于国际上通用的Y₂O₃-MgSiN₂和Yb₂O₃-MgSiN₂烧结助剂组合, Sc₂O₃-MgSiN₂有望成为制备高强度、高热导Si₃N₄陶瓷的新型复合助剂。     

Effect of Porosity and Cell Size on the Dynamic Compressive Properties of Aluminum Alloy Foams

The dynamic mechanical properties of open-cell aluminum alloy foams with different relative densities and cell sizes have been investigated by compressive tests.The strain rates varied from 700 s^-1 to 2600 s^-1.The experimental results showed that the dynamic compressive stress-strain curves exhibited a typical three-stage behavior:elastic,plateau and densification.The dynamic compressive strength of foams is affected not only by the relative density but also by the strain rate and cell size.Aluminum alloy foams with higher relative density or smaller cell size are more sensitive to the strain rate than foams with lower relative density or larger cell size.     

芳香族聚酰亚胺泡沫的隔热性能研究

利用DMTA和自制热导测试仪测试了4种自制芳香族聚酰亚胺泡沫的玻璃化转变温度(Tg )、静态温度下的热导率(λ)和动态温度作用下的隔热性能;分析了一定厚度的聚酰亚胺泡沫的密度和温度影响热导率的规律;考察了聚酰亚胺泡沫在动态温度下的隔热性能.结果表明:单体(尤其是二胺)刚性越大,聚酰亚胺泡沫的玻璃化转变温度越高;在密度为50～140kg/m3范围内,聚酰亚胺泡沫的密度对热导率的影响较小;在温度为50～350℃范围内,温度的升高使聚酰亚胺泡沫的热导率增加;在动态温度下,聚酰亚胺泡沫表现出明显的热滞后性.     

Lignin particle- and wood flour-reinforced phenolic foams: Friability,thermal stability and effect of hygrothermal aging on mechanical properties and morphology

In the present work, the effect of lignin particles and wood flour weight fractions incorporated on friability and thermal stability of a phenolic foam was determined. In addition, the effect of hygrothermal aging on compressive mechanical properties and cell size of the materials was studied. The incorporation of lignin particles decreased friability of the phenolic foam; whereas, wood flour increased it. The influence of both reinforcements on thermal stability of the material was very low. Although the reduction in mechanical properties of reinforced foams was higher than for the unreinforced material after hygrothermal aging, modulus and strength of the reinforced foams were still superior to those of the unreinforced material. Hygrothermal aging did not influence cell size of the foams studied. The material which exhibits the best combination of features was 8.5 wt.% lignin particle-reinforced phenolic foam.     

THE NUCLEATION OF MICROCELLULAR THERMOPLASTIC FOAM: PROCESS MODEL AND EXPERIMENTAL RESULTS

Microcellular polymer foams exhibit greatly improved mechanical properties compared to standard foams due to the formers' small bubble size. Typical microcellular foams have bubbles with diameters on the order of 10 microns and volume reductions of 30 to 40%. The presence of these bubbles acts to increase the impact strength of a microfoamed structure to six or seven times that of solid parts of the same linear dimensions due to crack blunting and increased craze initiation in the cell walls.

The first step in designing techniques to manufacture parts of microcellular foam is a complete understanding of the bubble nucleation process. To this end, a theoretical model for the nucleation of microcellular foams in thermoplastic polymers has been developed and experimentally confirmed. This model explains the effect of various additives and processing conditions on the number of bubble nucleated. At levels of secondary constituents below their solubility limits, an increase in the concentration of the additive or the concentration of gas in solution with the polymer increases the number of bubbles nucleated. Nucleation in this region is homogeneous. Above the solubility limit of additives, nucleation is heterogeneous and takes place at the interface between second phase inclusions and the polymer. The number of bubbles nucleated is dependent on the concentration of heterogeneous nucleation sites and their relative effect on the activation energy barrier to nucleation.     

添加剂对NiFe2O4尖晶石性能的影响

研究了3种添加剂对NiFe2O4尖晶石性能和微观结构的影响.对试样的体积密度、三点抗弯强度、抗热震性、导电率进行了测试,并结合SEM和EDX进行了微观结构分析.结果表明,添加剂M使试样的体积密度变化最快,含有3%M试样的抗弯强度较纯尖晶石提高了25MPa,添加T的试样热震性最好,添加剂M和T均能提高试样的导电能力.     

应用于包装领域的明胶泡沫性能研究

目的 制作和表征基于明胶的生物基可堆肥降解泡沫材料,并应用于包装领域。方法 明胶泡沫通过机械发泡和在周围环境中干燥制成。研究明胶含量、表面活性剂含量以及发泡温度对泡沫最大发泡倍率(MER)、收缩、密度、结构以及压缩性能的影响。此外,研究不同明胶含量样品的导热率。结果 研究的3个因素对泡沫性能和结构有显著影响。MER值和收缩是黏度相关,并极大地影响泡沫密度、力学性能以及热导率。增加明胶含量制造出了密度和压缩强度更高的泡沫(由于MER值更低)。表面活性剂质量分数从0.75%增加到1.5%由于发泡性提升造成泡沫密度轻微下降。然而,进一步将表面活性剂质量分数提升至3%造成黏度显著增加、MER值下降,从而导致泡沫密度增加。更高的发泡温度可以得到更高的MER,但是由于液态泡沫稳定时间更长,收缩程度更大,泡沫密度更大。结论 明胶泡沫展现出作为低密度传统塑料泡沫(密度小于30 kg/m³)环保替代品极具潜力的性能。研究成功实现了明胶泡沫的低热导率〔0.038～0.039 W/(m.K)〕和相对较低的收缩程度。     

玻璃纤维增强体形式对酚醛泡沫性能的影响

针对酚醛泡沫脆性大、强度低等缺点,采用3种不同增强形式的玻璃纤维增强体,即短切玻璃纤维(SGF)、酚醛树脂浸渍固化的玻璃纤维针(GFN)及三维间隔连体织物,对酚醛泡沫进行增强.研究了纤维含量和纤维长度对酚醛泡沫压缩性能的影响规律,对比了不同增强形式纤维增强酚醛泡沫复合材料的压缩性能与保温性能.结果表明:当SGF长度为3 mm,与基体质量比为5%时,SGF增强酚醛泡沫的比压缩强度最佳,较纯泡沫的提高了21%;GFN(长度5 mm,与基体质量比为25%)增强酚醛泡沫的比强度提高8%;三维间隔连体织物增强酚醛泡沫的比强度虽略有下降,但其压缩强度(0.239 MPa)达到了承重类酚醛泡沫的要求.SGF和GFN增强的酚醛泡沫的热导率与纯酚醛泡沫的相比略有上升,但仍符合高效保温材料的要求;三维间隔连体织物增强酚醛泡沫的热导率上升明显.     

热处理时间对聚甲基丙烯酰亚胺(PMI)泡沫结构和性能的影响EI北大核心CSCD

以甲基丙烯酸丁酯(BMA),丙烯酰胺(AM)为反应单体,丙烯酸(AA)作为第三单体和交联剂,在不同热处理时间下,通过自由基本体聚合制备聚甲基丙烯酰亚胺(PMI)泡沫。采用傅里叶变换红外光谱(FT-IR)、扫描电子显微镜(SEM)、热重分析(TGA)、差示扫描量热分析(DSC)等手段对其结构和性能进行表征。结果表明:随着对BMA/AM/AA共聚物热处理时间增加,分子链间发生重排反应生成六元酰亚胺环,经过交联固化后得到PMI泡沫,其特征吸收峰与文献值能较好地吻合。泡沫热处理5 h后得到孔径为100~200μm致密硬质闭孔泡沫,其力学性能良好,压缩强度为8.160 MPa,拉伸强度达到12.95 MPa。泡沫的玻璃化转变温度(Tg)为255℃,热失重10%时热分解温度Td10高达280℃,345℃时泡沫仍能残留80%以上,其导热系数为0.05424 W/(m·K),说明对共聚物热处理5 h后得到了具有优异的耐高温性能和隔热性能的泡沫。     

Thermal conductivity improvement of composite carbon foams based on tannin-based disordered carbon matrix and graphite fillers

Carbonaceous porous matrices were prepared from a tannin-based resin by physical foaming, having improved thermal properties by addition of various kinds and various amounts of graphite fillers. The resultant composite carbon foams presented much higher thermal conductivity, making them suitable for hosting phase-change materials with the aim of using them in seasonal storage applications. These materials were investigated in terms of porous structure, thermal and mechanical properties. It was shown that, unlike what was a priori expected, smaller particles were far more suitable for getting conductive, strong and porous matrices. The smaller were the particles, the better were the results. These findings were explained and justified, making such biomass-based composite carbon foams interesting and cheap candidates for thermal storage applications.     

Microstructure and properties of metakaolin-based inorganic polymer foams

A mixture of 70 % metakaolin and 30 % blast furnace slag powders, employed as the raw material, is mixed with different alkaline activating solutions in the production of metakaolin-based inorganic polymer foams (MIPF) with various densities ranging from 0.4 to 1.0 g/cm³ using a mechanical foaming process. The microstructures of metakaolin and slag powders, inorganic binder, and MIPF specimens are characterized by using XRD, FTIR, and image analyses. The effects of stirring time, water/binder ratio, and foaming agent on the properties of inorganic binders are also evaluated. Moreover, the pore size distributions, thermal and mechanical properties of the MIPF specimens are obtained by conducting a series of measurements and then compared with each other. Based on the experimental results, it is found that the measured cell length, cell wall thickness, compressive strength, flexural strength, and coefficient of thermal conductivity of the MIPF specimens are significantly affected by their densities.