超临界流体技术制备聚合物开孔发泡材料的研究进展

开孔发泡材料以其独特三维骨架形态广泛应用于吸音材料、生物医药材料、光学材料和过滤薄膜材料等领域。超临界流体(scCO2、scN2)具有溶解度大、无毒环保、价格低廉和临界点易于达到等诸多优点,作为一种绿色物理发泡剂在制备开孔发泡材料领域有巨大的潜力,利用超临界流体微孔发泡制备开孔发泡材料也成为当前的研究热点。综述了利用超临界流体技术制备开孔发泡材料的最新国内外研究进展,阐述了开孔发泡的机理、制备方法以及其应用领域,最后对目前利用超临界流体微孔发泡制备开孔材料存在的问题进行分析和展望。     

PP/PP-g-MAH/MMT纳米复合材料微孔发泡的研究

通过熔融共混法制备聚丙烯/马来酸酐接枝聚丙烯/蒙脱土(PP/PP-g-MAH/MMT)纳米复合材料母粒。利用"二次开模"法注塑成型制得PP/PP-g-MAH/MMT纳米复合微孔发泡材料。研究了MMT和PP-g-MAH的用量对纳米复合微孔发泡材料发泡质量的影响。结果表明:5%的MMT和6%的PP-g-MAH有较好的协同效应,微孔发泡材料发泡倍率最大,泡孔平均直径最小,泡孔密度较大,泡孔尺寸分布范围较窄。     

超临界CO2发泡工艺对聚乳酸微孔纳米复合材料泡孔结构的影响

利用超临界CO_2作为物理发泡剂,采用高压釜间歇发泡法,制备了聚乳酸/聚丁二酸丁二醇酯/氧化锌(PLA/PBS/ZnO)微孔纳米复合材料,研究了超临界CO_2微孔发泡过程中,发泡温度、保压压力和释压速率对PLA/PBS/ZnO微孔纳米复合材料泡孔结构的影响。结果表明:发泡温度对微孔纳米复合材料泡孔结构的影响显著且与纳米复合材料熔体强度密切相关,温度相对过高或过低,都会引起聚合物熔体强度和表面张力的变化而导致无法得到均匀密集的泡孔,当体系的发泡温度为90℃时,复合材料的泡孔平均直径最小,泡孔密度最大,泡孔尺寸分布最集中;保压压力对泡孔结构的影响体现在超临界CO_2的溶解度和发泡体系的黏度上,保压压力较低时得到的泡孔平均尺寸较大且分布不均匀,当保压压力为16 MPa时,复合材料的泡孔平均直径最小,泡孔密度最大,泡孔尺寸分布最集中;释压速率决定着发泡初始阶段的成核效率,随着释压速率的升高,复合材料的泡孔平均直径减小,泡孔密度显著增大,泡孔数量增多且尺寸分布更集中。     

微孔发泡聚合物泡孔形貌控制的研究进展

使用超临界流体技术制备微孔发泡聚合物,泡孔形貌是影响微孔聚合物性能的关键因素。针对微孔发泡聚合物泡孔形貌控制,即增加泡孔密度、减小泡孔直径、均化泡孔尺寸分布,从工艺条件、基体性质、共混改性、纳米添加剂、外加力场等影响因素出发,综述了近年来微孔发泡聚合物泡孔形貌控制的研究进展;最后展望了微孔发泡聚合物的前景。     

柑橘皮渣/淀粉基复合发泡材料的纳米改性研究

目的在柑橘皮渣/淀粉基复合材料中添加纳米材料,对其进行纳米改性研究。方法分别将质量分数为1%,3%,5%,7%等4种纳米蒙脱土添加到柑橘皮渣/淀粉复合材料中,采用双螺杆挤出制备复合发泡材料,并检测复合发泡材料的膨胀率、表观密度、压缩强度、吸湿性能、微观结构和红外光谱。结果添加质量分数为1%和3%的纳米蒙脱土,均能显著增强复合发泡材料的压缩强度,且添加质量分数为3%的纳米蒙脱土,能使复合发泡材料具有最大膨胀率、最低表观密度和丰富的泡孔结构,而添加质量分数为5%和7%的纳米蒙脱土,并不利于复合发泡材料的挤出成型。结论添加适量的纳米材料可以提高柑橘皮渣/淀粉基复合材料的发泡效果,增强力学性能。     

EP含量对PP/PP-g-MAH/EP微孔发泡复合材料发泡行为及力学性能的影响

采用化学发泡法制备了聚丙烯/聚丙烯接枝马来酸酐/环氧树脂(PP/PP-g-MAH/EP)微孔复合发泡材料,研究了EP粉体含量对其发泡行为及力学性能的影响。结果表明,EP粉体在发泡过程中起异相成核作用,且与PP-g-MAH反应形成的交联网络结构提高了复合材料的熔体强度,从而显著改善了泡孔结构。随着EP含量增加,微孔发泡材料的拉伸强度、弯曲强度和冲击强度都呈现先增大后减小的趋势。当EP含量为5%时,复合材料的泡孔尺寸最小,泡孔密度最大,泡孔分布最均匀,微孔发泡材料的冲击强度最大;当EP含量为1%时,拉伸强度、弯曲强度最大,发泡材料的综合力学性能最佳。     

聚合物介孔复合材料研究进展

无机介孔材料在催化、吸附领域已经得到了广泛的应用.聚合物介孔复合材料是指将介孔材料以各种方式加入聚合物基体中得到的杂合材料,是介孔材料崭新的应用领域.介绍了聚合物介孔复合材料所使用的主要介孔材料类型,概括了聚合物介孔纳米复合材料的制备方法,包括单体原位聚合和与聚合物共混方法,重点阐述了其作为功能复合材料、药物缓释材料、...     

弹性体对微发泡聚丙烯复合材料发泡行为的影响

以化学发泡为主线,在聚丙烯(PP)基体中添加弹性体三元乙丙橡胶(EPDM)制备微发泡聚丙烯复合材料。利用旋转流变仪、差示扫描量热法和扫描电镜等手段,系统地研究EPDM对微发泡PP材料发泡行为的影响。结果表明,EPDM的加入提高了PP材料的熔体强度,对PP材料发泡质量有明显改善;同时使PP复合材料的降温结晶峰向高温移动,能有效抑制泡孔的变形及并泡等恶化现象。当EPDM的质量分数为20%时,泡孔形态较为理想,其泡孔直径和泡孔密度分别为14.43μm,2.49×10⁷cm^-3。与未加EPDM的微发泡PP复合材料比较,EPDM的加入能够拓宽发泡PP复合材料的发泡温度窗口,发泡温度范围为180~195℃。     

纤维对微发泡聚丙烯复合材料发泡行为的影响

采用化学发泡法注塑成型工艺制备了微发泡聚丙烯(PP)/纤维复合材料,通过流变理论和纤维与树脂的界面行为,研究了玻璃纤维(GF)、芳纶纤维(AF)和碳纤维(CF)对微发泡聚丙烯复合材料发泡行为的影响。结果表明,纤维的加入可以有效改善微发泡PP材料的泡孔结构,改善效果CFGFAF,这归因于纤维的成核能力和PP/纤维复合材料流变性能的综合作用;比表面积越大、长度越短和分散性越好的纤维可以提供更多的成核点位置,从而可以获得具有较小泡孔尺寸和较大泡孔密度的微发泡材料。     

纳米蒙脱土对木粉/聚丙烯复合材料发泡性能的影响

采用高压釜间歇式发泡法,结合超临界CO₂微孔发泡技术制备了发泡木粉-纳米蒙脱土(NMMT)/聚丙烯(PP)复合材料。通过对复合材料的结晶行为、流变性能、泡孔形貌及压缩性能进行分析,主要研究了NMMT对其微孔结构及力学性能的改善作用。结果表明:NMMT的引入使木粉/PP复合材料中PP基体的结晶速率加快,结晶度减小,有利于发泡均相体系的形成和泡孔生长;PP分子链的运动受到NMMT片层的抑制作用,导致木粉/PP复合材料的熔体弹性提高,泡孔合并与塌陷的现象减少,发泡材料的平均泡孔直径从30.4 μm降低至20.3 μm,并且泡孔尺寸的均匀性得到明显改善,压缩强度和模量分别提高了187%和223%。      

Fabrication,properties,and applications of open-cell aluminum foams:A review

Open-cell metallic foams or porous metals have a distinctive combination of excellent structural performance and superior functional characteristics,such as their light weight,energy absorption,sound absorption,heat dissipation,and electromagnetic shielding.As a primary representative of metallic foams,aluminum foam has developed into a new engineering material with many unique applications in the fields of aerospace,automotive industry,petrochemical industry,building materials,and etc.This paper summarizes the fabrication methods,properties,and applications of open-cell aluminum foams.The current status and development trends are also introduced.     

Strain-rate effects in Ni/Al composite metal foams from quasi-static to low-velocity impact behaviour

Metal foams are used as absorbers for kinetic energy but predominantly, they have only been investigated under quasi-static load-conditions. Coating of open-cell metal foams improves the mechanical properties by forming of Ni/Al hybrid foam composites. The properties are governed by the microstructure, the strut material and geometry. In this study, the strain-rate effects in open-cell aluminium foams and new Ni/Al composite foams are investigated by quasi-static compression tests and low-velocity impact. For the first time, drop weight tests are reported on open-cell metal foams, especially Ni/Al composite foams. Furthermore, size-effects were evaluated. The microstructural deformation mechanism was analysed using a high-speed camera and digital image correlation. Whereas pure aluminium foams are only strain-rate sensitive in the plastic collapse stress, Ni/Al foams show a general strain-rate sensitivity based on microinertia effects and the rate-sensitive nano-nickel coating. Ni/Al foams are superior to aluminium foams and to artificial aluminium foams with equal density.     

Anisotropic polyurethane foam with Poisson'sratio greater than 1

Anisotropic polymer foams have been prepared, which exhibit a Poisson's ratio exceeding 1, and ratios of longitudinal to transverse stiffness exceeding 50. The foams are as much as 20 times stiffer in the longitudinal direction than the foams from which they were derived. The transformation process involved applying to open-cell polyurethane foam an axial strain of 25 to 45%, at a temperature above the softening point, followed by cooling under axial strain. This revised version was published online in November 2006 with corrections to the Cover Date.     

Open-cell cavity-integrated injection-molded acoustic polypropylene foams

In this study, a commercially available foam injection-molding machine was enhanced with a mold opening technique to produce polypropylene open-cell acoustic foams. Gas counter-pressure was used to improve the cell morphology and uniformity of the injection-molded foams. Their structure and thickness were controlled by applying different degrees of mold opening. The sample structure, the cell morphology, and the acoustic behavior of the foams were characterized. A foamed structure with an open-cell content of 67% and an expansion ratio of 4.6 was obtained when the mold was opened by 4.5 mm. Although further opening of the mold did not significantly increase the open-cell content, it triggered crack creation in the middle of the foams, where the creation of cavities was also facilitated. The injection-molded foams with a cavity and a high open-cell content, presented remarkable acoustic properties: a peak absorption coefficient of 0.95 was observed for foam with a 73% open-cell content and a 9 mm cavity. An automated system was also developed to perforate the acoustic foams, and the acoustic properties of foams both with and without perforation were studied. While perforating the foams widened their absorption coefficient frequency spectrum, it did not improve their transmission loss.     

开孔泡沫金属压缩实化特性研究

对开孔泡沫金属微结构实化过程进行分析,理论分析表明开孔泡沫金属的实化应变不但与其相对密度成幂律关系,而且还与泡沫金属的单元结构特征密切相关.由此提出了一种用于描述相对密度较低的开孔泡沫金属压缩实化特性的数学模型,在该模型中泡沫结构和筋条材料对泡沫金属实化特性的影响以材料常数的形式体现,理论分析结果与试验结果完全一致.     

纤维素基可生物降解共混高分子材料的制备和性能

综述了近年来以纤维素为共混组分制备可生物降解高分子材料的研究进展,重点介绍了纤维素或纤维素衍生物与其它天然高分子(壳聚糖、蛋白质、淀粉等)以及可降解合成高分子(聚乙二醇、聚己内酯、聚乳酸等)共混材料的制备和性能,揭示了纤维素基可生物降解材料在某些应用领域替代石油基材料的潜力.     

开孔与闭孔泡沫铝的压缩力学行为

研究了开孔与闭孔两种胞孔结构不同、制备工艺不同的泡沫铝在准静态压缩载荷下的压缩响应曲线.结果表明:开孔与闭孔泡沫铝压缩应力-应变曲线均具有多孔泡沫材料明显的三阶段特征,即线弹性段、塑性屈服平台段及致密段;相对密度对泡沫材料的力学性能(如杨氏模量、屈服强度)有很大影响;在准静态下,开孔泡沫铝表现出明显的应变率效应,而闭孔泡沫不如开孔敏感;泡沫铝材料表现为弱的各向异性;胞孔结构影响两种泡沫材料的压缩响应曲线.     

开孔泡沫金属热传输性能研究进展

介绍了开孔泡沫金属的结构特点,分别从紧凑型换热器、相变储能系统、热管以及催化反应器四个方面的应用分析了国内外开孔泡沫金属热传输性能应用研究现状,指出了泡沫金属在这些领域应用的前景和存在的问题,提出了今后开孔泡沫金属热传输性能的研究及应用方向。     

Mechanical selection of foams and honeycombs used for packaging and energy absorption

The volume of foams used in packaging is enormous. Proper design requires identification of the correct material and selection of the correct density for each particular application. The vast amount of data in the literature is in need of a systematic analysis and a compact presentation. In this paper, the energy-absorption data of each class of cellular materials (such as open-cell elastic foams) are normalized and presented in a single diagram. Diagrams of this type are termed packaging-selection diagrams, and the optimal density of a cellular material can be obtained from them once the maximum permitted stress of the packaging is known. This new approach offers greater generality and simplicity than existing methods, such as the Janssen factor or energy-absorption diagrams.     

生物可降解高分子多孔微球制备与应用的研究进展

生物可降解高分子多孔微球可以在体内降解并且无毒副作用,已经被广泛应用于药物控制释放、组织工程等领域,它们的制备及应用是近年来的研究热点。概述了生物可降解高分子多孔微球的几种制备方法及其应用领域,并对生物可降解高分子多孔微球的未来发展前景进行了展望。