不同孔隙结构的硅海绵材料及其力学性能研究

采用不同方法制备了密度和孔隙率相近、孔隙结构不同的2种硅海绵材料,并表征了其孔隙结构的差异,研究了2种孔隙结构明显不同的硅海绵材料在力学性能方面的差异。研究结果表明：硅海绵材料的孔隙结构对断裂强度、断裂伸长率、压缩应力应变及压缩应力松驰等力学性能有较大的影响。     

挤出硅橡胶海绵的力学性能研究

采用化学发泡、挤出成型方法制备出硅橡胶海绵长条.比较了硅橡胶海绵不同部位的泡孔尺寸与力学性能.结果表明,硅橡胶海绵不同部位的密度、硬度、拉伸强度、扯断伸长率、压缩应力松弛和压缩应力-应变曲线性能表现出较好的一致性.白炭黑、发泡剂用量较高,硫化剂用量较低的硅橡胶海绵的硬度、拉伸强度、压缩应力松弛较高,扯断伸长率较低.两种硅橡胶海绵的压缩永久变形性能均优异,而且呈现较好的一致性.     

混炼胶品种对硅橡胶海绵的结构和性能的影响

采用3种不同混炼胶，通过化学发泡方法制作了硅橡胶海绵。分别比较了3种海绵的泡孔结构与密度、硬度、拉伸强度、压缩应力松弛、压缩应力应变性能。实验结果表明，混炼胶的性能、海绵的密度是影响海绵材料力学性能的重要因素。     

EVA改性硅橡胶海绵

中国工程物理研究院的赵祺等人将100份甲基乙烯基硅橡胶与30份2^#白炭黑共混均匀后,加入适量的乙烯-乙酸乙烯酯（EVA）,在120℃下混炼均匀;冷却后加入硫化剂、发泡剂,返炼均匀,在160℃下模压硫化发泡,制成了EVA改性硅橡胶海绵。加入约10％的EVA可以大幅度提高硅橡胶海绵的拉伸强度,而其压缩应力松弛变化不大;通过调整EVA的用量,可以得到具有不同压缩模量、不同压缩应力应变性能的硅橡胶海绵。     

挤出发泡MVQ海绵的结构与性能

采用挤出发泡方法制备甲基乙烯基硅橡胶(MVQ)海绵,研究白炭黑、硫化剂和发泡剂用量对MVQ海绵泡孔结构和性能的影响.结果表明:MVQ海绵中含有大量闭孔结构,不同密度海绵的泡孔尺寸及分布密度存在差异;采用较低用量的白炭黑和发泡剂、较高用量的硫化剂可以得到密度和硬度较大的MVQ海绵;MVQ海绵的压缩应力松弛率随着密度的增大呈现先增大后减小的趋势,在密度为0.61 Mg·m-3时达到极大值18％;在低应力区域内,密度较大的试样应力增幅比密度较小的试样大.     

硅橡胶泡沫泡孔结构与压缩应力松弛性能的相关性

中国工程物理研究院的丁国芳等人研究了氧化锌晶须对硅橡胶泡沫泡孔疏密程度及其对材料力学性能的影响,研究了泡沫密度和混合泡孔结构对材料的压缩应力松弛性能的影响。结果表明,随着氧化锌晶须用量的增加,泡孔疏密程度在增大,硅橡胶泡沫材料拉伸强度和扯断伸长率也在变大。硅橡胶泡沫密度在0．56—0．58g／cm^3范围内时压缩应力松弛性能最佳;在相对密度不变的情况,具有混合泡孔结构的硅橡胶泡沫材料的压缩应力松弛性能更好。     

硅橡胶泡沫泡孔结构与压缩应力松弛性能的相关性

中国工程物理研究院的丁国芳等人研究了氧化锌晶须对硅橡胶泡沫泡孔疏密程度及其对材料力学性能的影响,研究了泡沫密度和混合泡孔结构对材料的压缩应力松弛性能的影响。结果表明,随着氧化锌晶须用量的增加,泡孔疏密程度在增大,硅橡胶泡沫材料拉伸强度和扯断伸长率也在变大。硅橡胶泡沫密度在0．56—0．58g／cm^3范围内时压缩应力松弛性能最佳;在相对密度不变的情况,具有混合泡孔结构的硅橡胶泡沫材料的压缩应力松弛性能更好。     

3D打印制备氧化锌晶须增强有机硅泡沫

制备了氧化锌晶须增强的硅橡胶墨水,利用3D打印技术特有的图案化能力,将硅橡胶墨水打印成有序、开孔的有机硅泡沫材料,实现了发泡过程和硫化过程的分离,获得了泡孔结构均匀和压缩力学性能可控的泡沫材料。相比于传统发泡材料,该泡沫材料的压缩应力-应变曲线展现出明显的压缩应力平台区,有利于各种应力缓冲应用。     

低发泡倍率硅橡胶海绵结构及性能的影响因素

简要介绍了过氧化二苯甲酰硫化的低发泡倍率硅橡胶海绵胶料的配方、制备方法、海绵结构及力学性能。结果表明,硫化剂用量、硫化助剂、发泡温度、胶料可塑度和生胶相对分子质量对海绵硫化发泡效果的影响较大。硫化助剂会影响海绵的硫化返原,而胶料温度对海绵密度和硬度有一定的影响。低发泡倍率海绵为典型的闭孔结构,海绵压缩量大,模量低,拉伸强度低（〈0.8MPa）,伸长率高,压缩永久变形小,应力伸长率大,回弹性优。     

分子结构对室温硫化硅橡胶泡沫材料影响的研究

采用不同苯基结构或含量的端羟基聚有机硅氧烷为生胶,制备了4种密度相近的室温硫化硅橡胶泡沫材料,就生胶分子结构对硅橡胶的硫化特性、泡沫材料的泡孔结构及压缩性能的影响进行了研究。结果表明,端羟基聚有机硅氧烷分子中的苯基对室温硫化硅橡胶的硫化性能以及泡沫材料的泡孔结构和压缩性能有明显的影响,苯基的位阻效应会降低胶料的硫化速率,有利于获得泡孔细小均匀的泡沫材料,同时降低泡沫材料的应力松弛率。     

PVA纤维改性酚醛泡沫的研究

为了改善酚醛泡沫的性能,选用聚乙烯醇(PVA)纤维作为酚醛泡沫的增强材料,研究了不同PVA纤维含量和长度对酚醛泡沫的泡孔结构、压缩性能、弯曲性能的影响。结果表明,PVA纤维可以有效改善酚醛泡沫的力学性能和泡孔结构,随着PVA纤维含量的增加,酚醛泡沫的力学性能呈现先增大后减小的趋势。当PVA纤维的用量为酚醛树脂质量的3%时,酚醛泡沫的力学性能达到了最大值,泡孔结构达到了小且均匀的状态。PVA纤维的长度对酚醛泡沫的泡孔结构也有一定的影响,当PVA纤维长度为6 mm时,酚醛泡沫具有最好的泡孔结构,但PVA纤维长度增加时,酚醛泡沫的压缩性能、弯曲性能减小。     

磁场取向镀镍碳纳米管/聚氨酯复合泡沫材料的制备及性能

在磁场作用下通过一步法原位聚合制备了磁场取向镀镍多壁碳纳米管/聚氨酯复合泡沫材料.通过透射电镜、扫描电镜等表征了泡沫材料的结构,并测试了材料的压缩性能和吸声性能.结果表明:镀镍碳纳米管可使聚氨酯泡沫材料的泡孔更均匀.在磁场作用下,镀镍碳纳米管取向能显著提高材料的压缩强度,当碳纳米管的质量分数为1.0%时,其压缩强度为纯PU泡沫材料的3倍.同时,取向镀镍碳纳米管/PU复合泡沫材料的吸声性能也得到了进一步提高.     

蒸馏水含量对三明治结构硬质聚氨酯泡沫性能的影响

采用异氰酸酯、聚酯多元醇、发泡剂（水）等原料通过一体发泡成型技术制备出一种新型的三明治泡沫夹心复合材料。利用热重分析、扫描电子显微镜等对不同水含量（质量分数分别为0、0.5 %和1.0 %）的硬质聚氨酯泡沫材料的泡孔直径、密度、热导率、压缩性能、三点弯曲和热力学性能等做了研究,进而确定提高硬质聚氨酯性能的最佳工艺。结果表明,随着水含量的增加,硬质聚氨酯泡沫材料泡孔直径增大,密度变小,热导率降低,保温性能提高,而压缩性能和三点弯曲却呈下降趋势;综合考虑硬质聚氨酯泡沫材料泡孔结构和良好的保温隔热及弯曲等力学性能,其最佳含水量为0.5 %。     

水声耐压反声材料的研制

通过配方与工艺研究,研制了一种低密度、高压缩强度,同时具有较低声速的聚氨酯泡沫作为反声障板芯材,能满足300m水深潜艇反声障板的要求。对制备原理、其压缩强度、预压缩力,孔径和孔结构对声速的影响,开孔方法,异氰酸酯种类对孔径的影响也进行了讨论。     

Flammability properties and mechanical performance of epoxy modified phenolic foams

This work has been mainly focused on the development and optimization of the processing methodology to produce epoxy modified phenolic foams. This study analyzes the relation between the composition and the structure as well as the mechanical and flammability performance of epoxy‐phenolic (E‐P)‐based foams. Phenolic foams modified with different types and compositions of epoxy resin were successfully synthesized and characterized, showing uniform pore structure. Two epoxy resins were used for this approach. One is regular diglycidyl ether of bisphenol A (Epon 826) type and the other is a brominated bisphenol A (DER 542), which has halogen groups in the structure to improve the flammability properties of the resulting foams. Cone calorimeter (ASTM E 1354) was used to measure the heat release rate, the time to ignition, and other flammability properties of the E‐P foams with different types of epoxy resins, under well‐controlled combustion conditions. The mechanical performance of the system was studied and compared with competing foams, such us phenolic, epoxy, and polyurethanes, in aspects of compression, friability, and shear performances. Compared with conventional phenolic foams, E‐P foams exhibit significant improvement in mechanical performance, lower friability and similar resistance to flame. These results demonstrate the potential of the E‐P foam as a flame resistant and high performance core material for sandwich structure. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1399–1407, 2007     

Effects of high-temperature exposure on properties of lightweight geopolymer foams incorporating diatomite powders

A kind of metakaolin-based geopolymer foams incorporating diatomite powders (GKGP) with open cellular was presented by addition of diatomite powder via hydrogen peroxide method. Impacts of high-temperature exposure on the microstructure, pore structure, and mechanical properties of the GKGP samples were investigated. The GKGP foams achieved a typical amorphous phase structure at room temperature. Open porosity of the samples reached approximately 74%. After high-temperature exposure treatment, the KGP matrix is basically transformed into leucite crystal phase. The compression strength of the leucite foams was also enhanced with increasing temperature to 1200℃ (9.28 MPa). The lightweight foamed GKGP samples with high open porosity might have great potential for membranes and industries, etc.     

Optimized pore structure and high permeability of metakaolin/fly-ash-based geopolymer foams from Al– and H2O2–sodium oleate foaming systems

Geopolymer foams have been widely studied as adsorbents owing to their high specific surface areas, high heavy metal immobilization efficiencies, low cost, environmental friendliness, and resource-recycling benefits. In this study, geopolymer foams with different pore structures were prepared from Al– and H₂O₂–sodium oleate foaming systems, and their chemical properties, pore structures, and permeabilities were characterized. The effects of the foaming agent type and surfactant content on the crystal structure and chemical bonding of the materials were analyzed by X-ray diffraction analysis and Fourier-transform infrared spectroscopy, and the pore morphology and structural characteristics were characterized by morphological observations, three-dimensional (3D) reconstruction, and compression tests. Numerical simulations were also carried out to study the structural characteristics of the 3D-reconstructed pores. Furthermore, variations in the permeability coefficient and flow characteristics were tested and analyzed by experiments and simulations. The pores in the geopolymer from the H₂O₂–sodium oleate foaming system tended to be more connected, whereas those in the Al–sodium oleate geopolymers were more complete and closed. The highly connected pore structure facilitates the even diffusion of the solution and effectively increases the amount of adsorption sites. These properties are significant for adjusting the adsorption capacity of geopolymer foams as adsorption monoliths.     

Recycling of aluminum beverage cans for metallic foams manufacturing

This paper proposes recycling beverage cans (aluminum cans) to reduce the manufacturing cost of metallic foams, while it is discussed the effects of the alloying elements that reinforce the metallic matrix in resistance to compression, due mainly in part to the formation of the phase β-Al₆(FeMn). The manufacturing process used for the metallic foams was the Alporas modified, using an excess of 10 wt% pure calcium. This allowed not only to modify viscosity of the molten alloy but also to obtain important quantities of the reinforcing phase Al₄Ca. Once obtained, the foams were characterized using techniques including differential thermal analysis, optical microscopy, scanning electron microscopy, chemical analysis and compression tests. Additionally, Image J software was used to determine the percentage of porosity and the average pore size of the metallic foams. Foam density was calculated by immersion in water using the Archimedes principle. The results showed that foams manufactured with beverage cans have a homogeneous porous structure with an average porosity of 80%, an average pore size of 3 mm, a specific gravity 0.4 and a compressive strength of 22 MPa. These results are superior to those obtained in foams manufactured with pure aluminum as well as alloying foams such as Al–12Si–0.6Mg (A413), and Al–1Mg–0.6Si (A356).     

Effect of pore size distribution on compressive behavior of moderately expanded low‐density polyethylene foams

We investigated the effect of the pore size distribution on the compressive behavior for moderately expanded elastic polymer foams. Unlike well‐expanded foams, moderately expanded foams have heterogeneous cellular structures and their mechanical properties can depend on the heterogeneity of cellular structures. To clarify the effect of the pore size distribution on mechanical properties, we prepared a series of low‐density polyethylene (LDPE) foams with different pore size distributions and relative densities as models of moderately expanded elasitc polymer foams. We performed the microscope observations and the uniaxial compression tests of the moderately expanded LDPE foams. The compressive behavior of a foam was primarily determined by the relative density, but we found that the compressive behavior also depends on the pore size distribution, especially in the collapse region. In the collapse region, the compressive stress–strain curves showed clear dependence on the heterogeneities of cellular structures. The broader cell distribution resulted in the stronger strain dependence of the stress in the collapse region. We show that we can reasonably predict the compressive stress–strain curves from the pore size distributions. POLYM. ENG. SCI., 59:510–518, 2019. © 2018 Society of Plastics Engineers