2,3,3’,4’-联苯四酸二酐硬质聚酰亚胺泡沫材料的结构与性能

系统研究了在含2,3,3’,4’-联苯四酸二酐(a-BPDA)的聚酰亚胺(PI)泡沫材料体系中,计算相对分子质量、二胺分子结构、二酐分子结构对聚酰亚胺泡沫材料性能的影响。研究发现,对于a-BPDA/m-PDA/NA体系,计算相对分子质量为1500时,可以制备得到性能优良的硬质耐高温聚酰亚胺泡沫材料,其玻璃化转变温度高于350℃,闭孔率大于88%,压缩强度为1.34 MPa。在该体系中,部分引入ODPA,可提高材料的韧性;当n(BTDA)∶n(a-BPDA)=5∶5时,泡沫材料不但拥有高的耐热性能和力学力学性能,同时还具有良好的韧性。     

1,4-丁二醇降解聚酯产物的发泡工艺研究

利用废弃聚酯的降解产物制备聚氨酯泡沫,优化了聚氨酯泡沫的制备工艺。其中,最佳工艺为:降解产物为10份,催化剂的用量为1.0~1.1份,水的用量为1.0~1.1份,异氰酸酯的用量为20份。该工艺条件下得到的泡沫密度小、压缩强度高、热性能稳定。工艺优化后聚氨酯泡沫的密度为62kg/m3,压缩强度为400~420kPa,初始热分解温度为250~260℃。     

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.     

聚乙烯醇纤维对碱矿渣泡沫混凝土性能的影响

以水玻璃为激发剂,制备干密度为350kg/m~3的碱矿渣泡沫混凝土,为提高碱矿渣泡沫混凝土的韧性,降低干燥收缩,本工作研究了聚乙烯醇(PVA)纤维对碱矿渣泡沫混凝土干密度、强度、折压比、吸水率和干燥收缩性能的影响。结果表明:PVA纤维对碱矿渣泡沫混凝土干密度无明显影响;PVA纤维掺量为0.6~1.2kg/m~3时,碱矿渣泡沫混凝土的抗折强度和折压比明显增加,韧性得到明显改善;碱矿渣泡沫混凝土吸水率也低于未掺纤维的泡沫混凝土;PVA纤维掺量大于0.6kg/m~3时,碱矿渣泡沫混凝土的干燥收缩显著降低;综合碱矿渣泡沫混凝土性能及经济性等因素,碱矿渣泡沫混凝土中PVA纤维最优掺量为0.6kg/m~3。     

1,4-丁二醇降解废弃涤纶短纤

采用1,4-丁二醇降解废弃涤纶短纤,研究了其降解的工艺条件,降解温度控制在190~228℃。降解产物通过减压蒸馏提纯,蒸馏温度为220~250℃,然后用提纯后的产物制备聚氨酯泡沫,并研究了该泡沫的性能。用红外光谱分析了降解产物的结构;用差示扫描仪表征了降解产物的熔点约为203℃,聚氨酯泡沫的熔点有所升高;用热重分析仪研究了产物及聚氨酯泡沫的热性能;用万能材料试验仪测试了泡沫的压缩载荷。     

硬质聚氨酯泡沫材料制备及表征

为了提高废弃资源的利用率,减少废弃聚酯对环境的污染,以乙二醇、废弃聚酯纤维、醋酸锌为原料降解聚酯纤维,制得对苯二甲酸乙二醇酯(BHET)单体,并用其制备硬质聚氨酯泡沫材料。探讨了泡沫催化剂对硬质聚氨酯泡沫材料密度和压缩性能的影响。结果表明,当原料配比一定时,催化剂用量为0.25g时,制得的硬质聚氨酯泡沫具有较低的密度为109kg/m~3,较高的压缩强度为1363kPa。     

聚醚TSU-450L和聚醚H303复配制备硬质聚氨酯泡沫及性能研究

聚醚TSU-450L与聚醚H303复配和异氰酸酯按一定质量比混合,HFC-365/227作发泡剂,经催化发泡固化制备硬质聚氨酯泡沫(RPUF)。产物用红外光谱(FT-IR)、热失重(TGA)和扫描电镜(SEM)表征。实验表明,组合聚醚(TSU-450L∶H303=7∶3,质量比)和异氰酸酯质量比为1∶1.25,表观密度45kg/m~3,导热系数0.026W/(m·k),耐热性120℃,吸水率0.025g/cm~3,抗压强度0.33MPa。结果显示制备的RPUF达到埋地钢质管道防腐保温层技术规范。     

三元共聚聚酰亚胺结构胶的合成及性能研究

以2,2-双[4-(4-氨基苯氧基)苯基]丙烷(BAPP)和4,4′-二氨基二苯甲烷(MDA)作为二胺单体,3,3′,4,4′-二苯酮四酸二酐(BTDA)作为二酐单体,N-甲基砒咯烷酮(NMP)为溶剂,通过常规的两步法经热亚胺化合成了三元共聚型聚酰亚胺结构胶。采用傅里叶变换红外光谱表征了聚合物的结构;热重-差热分析(TG-DTA)表明,所合成的聚酰亚胺具有良好的热稳定性,在N2气氛中起始降解温度接近500℃,800℃质量保持率大于50%。单搭接拉伸剪切测试结果表明,所得聚酰亚胺结构胶对不锈钢片的室温粘接强度(LSS)高达14.13MPa,350℃下的拉伸剪切强度达1.91MPa。     

羧基碳纳米管增强酚醛泡沫的压缩性能及热性能

研究了羧基碳纳米管(CNT-COOH)增强酚醛泡沫复合材料的制备工艺、微观结构、压缩性能和热性能,并结合红外光谱和泡沫在不同压缩应变下的变形破坏形貌,探讨了CNT-COOH对酚醛泡沫的增强机制。结果表明,CNT-COOH作为异相成核剂,使酚醛泡沫泡孔的平均尺寸减小,泡孔密度增大; 随着酚醛泡沫中CNT-COOH含量增加,CNT-COOH/酚醛泡沫复合材料的压缩模量和压缩强度提高。红外分析表明,CNT-COOH可能未与酚醛泡沫发生固化反应。CNT-COOH/酚醛泡沫复合材料在不同压缩应变下的SEM分析表明,CNT-COOH位于泡孔的孔壁上,并通过CNT-COOH/酚醛泡沫的界面传载作用承受了一定载荷,增强了泡沫的力学性能。热重分析和垂直燃烧试验表明,CNT-COOH作为稳定剂,降低了泡沫的热降解速率,使其热稳定性和阻燃性能均略有提高。     

含有氢键的聚酰亚胺薄膜的制备和性能表征

以对硝基苯甲酸为原料,通过酰氯化、酰化、还原反应成功合成了4,4’-二氨基苯酰替苯胺(DBN),DBN分别和3,3’,4,4’-联苯四酸二酐(BPDA)、均苯四甲酸二酐(PMDA)通过两步法缩聚制备出聚酰亚胺薄膜,用红外(FT-IR),差示扫描量热仪(DSC)和热重分析(TGA),拉伸测试表征其结构和性能,结果表明,成功合成了含有酰胺键的聚酰亚胺薄膜,并且酰胺键的N-H分别和酰亚胺环中的C-N和C=O形成了氢键。将其与4,4’-二氨基二苯醚(ODA)聚酰亚胺薄膜相比,对应二酐(BPDA和PMDA)分别和DBN制备的聚酰亚胺薄膜表现出了优异的热性能和耐溶剂性,尤其是拉伸强度有了显著的提高。     

Mesophase AR pitch derived carbon foam: Effect of temperature, pressure and pressure release time

For the carbon foam production, mesophase pitch pellets are heated up in a reactor in an aluminum mold to specified pressures and finally pressure released to obtain green carbon foam samples. The green foams were then stabilized and carbonized. The effects of various temperatures, pressures and pressure release times on production of carbons foams are investigated. The samples are subjected to SEM, mechanical testing, mercury porosimetry analysis and bulk density determination for characterization. For the processing temperatures of 553, 556, 566 and 573 K, the densities of the foams produced were 380, 390, 410 and 560 kg/m³ respectively. The compressive strengths of the respective samples were increased from 1.47, to 3.31 MPa for the lowest and highest temperatures. The processing pressures were 3.8, 5.8, 6.8 and 7.8 MPa. The bulk density and the compressive strength of the carbon foams produced were changed from 500 to 580 kg/m³, and 1.87 to 3.52 MPa for the lowest and highest pressures respectively. Pressure release times of 5 s, 80 s, 160 s and 600 s are used to produce different carbon foam samples. The densities and the comprehensive strengths measured for the highest and lowest pressure release times changed from 560 to 240 kg/m³ and 3.31 to 2.16 MPa respectively. The pore size distribution of all of the products changed between 0.052×10^-6m and 120×10^-6m. Increase in temperature and pressure increased the bulk density and compressive strength of the carbon foams. The mercury porosimetry results show % porosity increase with increasing temperature and pressure. On the other hand, increase in pressure release time decreased the bulk density, compressive strength of the carbon foam.     

Dynamic compression of cellular cores: temperature and strain rate effects

Cross-linked polyvinyl chloride closed-cell foams were examined under quasi-static and high strain rate compression loading using a servo-hydraulic testing machine and a modified split Hopkinson pressure bar apparatus consisting of polycarbonate bars for strain rates up to 1900 s⁻¹. Three foam densities were examined viz. 75, 130, and 300 kg/m³. Each core density has been subjected to compressive loading at room and elevated temperatures. A reverse trend in failure modes was observed when moving from room to elevated temperatures at high strain loading, which was not found in quasi-static testing at elevated temperatures. Accordingly, post-impact tests were conducted to evaluate the residual strength of the foam cores subject to elevated temperatures and HSR. Results of the post-impact test revealed that the foam cores are still capable of taking some loading. The residual strength of cores was fairly constant regardless of temperature therefore recovery of volume does not signify an increase in residual strength of cores.     

Properties of new polyimide foams and polyimide foam filled honeycomb composites

New polyimide foams and polyimide foam filled honeycombs are currently being developed at NASA, its licensee Sordal Inc. (USA) and Newmet (UK) under the trade name Solrex®. These materials are foreseen for Space, Aerospace, Maritime & Medicine applications. In this paper selected properties of these new materials with different densities are described. The investigated key properties are compression strength, thermal conductivity and moisture gain. The dependence of these properties on density, temperature and thermal cycling is discussed. Limits of the used characterisation methods are discussed. Possible applications are defined.     

不同单体配比聚甲基丙烯酰亚胺泡沫的制备与性能

以甲基丙烯酸(MAA)和丙烯腈(AN)为单体,通过加热结合超声的方法引发反应,快速制备了不同单体配比的聚甲基丙烯酰亚胺(PMI)泡沫。通过傅里叶变换红外光谱、热重分析、动态力学热分析、垂直燃烧、极限氧指数(LOI)和扫描电镜对PMI泡沫结构、热性能、燃烧性能和形貌进行表征,同时对PMI泡沫的力学强度进行分析。结果表明,高温下氰基与羧基通过重排异构化反应生成酰胺键,制备的PMI泡沫具有良好的成炭性能和较高的玻璃化转变温度,LOI随AN含量的增加而提高,泡沫呈蜂窝状结构,孔径在0.1~0.3 mm之间。力学性能分析表明,PMI泡沫具有较高的力学强度,50.1 kg/m 3的PMI泡沫的拉伸强度、弯曲强度和压缩强度分别为1.85 MPa、2.71 MPa和3.74 MPa。     

Effect of hollow sphere size and size distribution on the quasi-static and high strain rate compressive properties of Al-A380–Al2O3 syntactic foams

Metal matrix syntactic foams are promising materials for energy absorption; however, few studies have examined the effects of hollow sphere dimensions and foam microstructure on the quasi-static and high strain rate properties of the resulting foam. Aluminum alloy A380 syntactic foams containing Al₂O₃ hollow spheres sorted by size and size range were synthesized by a sub-atmospheric pressure infiltration technique. The resulting samples were tested in compression at strain rates ranging from 10^?3 s^?1 using a conventional load frame to 1720 s^?1 using a Split Hopkinson Pressure-bar test apparatus. It is shown that the quasi-static compressive stress–strain curves exhibit distinct deformation events corresponding to initial failure of the foam at the critical resolved shear stress and subsequent failures and densification events until the foam is deformed to full density. The peak strength, plateau strength, and toughness of the foam increases with increasing hollow sphere wall thickness to diameter (t/D) ratio. Since t/D was found to increase with decreasing hollow sphere diameter, the foams produced with smaller spheres showed improved performance. The compressive properties did not show measurable strain rate dependence.     

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。     

前驱体热解氮化硼/碳化硅复相泡沫陶瓷的抗氧化与高温隔热性能研究

以聚碳硅烷(PCS)和三甲胺基环硼氮烷聚合前驱体(PBN)进行共聚合制得复合前驱体, 以此为原料采用高压裂解发泡技术制备了一种氮化硼/碳化硅(BN/SiC)复相开孔泡沫陶瓷. 由包含不同比例组分的起始前驱体所制得的泡沫陶瓷的孔隙直径在1~5 mm, 体积密度在0.44~0.73 g/cm³之间. 对该陶瓷材料的微观结构和性能的研究表明, 由于BN相的引入使得BN/SiC复相泡沫陶瓷在800~1100℃的抗氧化性能有了显著的提高; 其压缩强度随着引入BN比例的增加而提高, 约为纯SiC泡沫陶瓷的5~10倍. 其中以组分重量比为1:1的起始复合前驱体所制备BN/SiC复相多孔陶瓷在1500℃时的导热系数仅为4.0 W/(m·K); 对其进行隔热性能测试, 材料热面中心温度为1400℃时, 其背面中心温度仅为280℃; 采用有限差分法数值模拟背部升温历程, 将其有效导热系数代入计算模型, 得到材料背部中心温度升温历程的数值模拟结果, 与实际升温历程基本一致.     

负泊松比三明治结构填充泡沫混凝土的面内压缩性能

为改善负泊松比三明治结构的受压破坏模式且提高其缓冲吸能能力,提出一种填充泡沫混凝土的新型复合三明治结构。在负泊松比结构中填充不同密度(409 kg/m3、575 kg/m3、848 kg/m3、1 014 kg/m3)的泡沫混凝土得到负泊松比填充结构,并对无填充负泊松比结构、负泊松比填充结构和泡沫混凝土对照试块在准静态压缩下的破坏模式和吸能特性进行比较。根据荷载-位移关系和破坏模式得到以下结论:当填充物密度较小时,负泊松比填充结构能够将填充物的泊松比限制在较小的数值,胞元表现出内凹的变形模式,结构发生逐渐被压实的压缩破坏;当填充物密度较大时,结构发生“X”型剪切破坏,塑性铰区域和剪切带附近的胞壁发生断裂破坏;泡沫混凝土填充物的密度越大,填充结构的压实应变越小,吸收的能量越多,但当填充物密度超过一定值后,填充物密度的增加对负泊松比填充结构能量吸收能力的提升作用不再明显,结构的比吸能降低。      

Compressive behaviour of open cell Al–Al2O3 composite foams fabricated by sintering and dissolution process

Abstract

The sintering and dissolution process (SDP) was used to produce the fine open cell Al–Al₂O₃ composite and pure Al foams with the relative density of 0·25–0·40 and the pore size of 112–400 μm. The composite foam exhibited much higher yield strength and Young's modulus than the pure Al foam, and thus had an elevated plateau stress. Moreover, the composite foam showed a unique dependence of the compression stress on the pore size, i.e. it increased with increasing pore size, which was quite different from that for the common metal foams.