微孔聚合物皮层厚度测量的扫描声显微方法

微孔发泡是一种有广泛应用前景的聚合物改性方法.皮层的存在对微孔结构材料的性能有很大的影响,皮层厚度的测量、工艺控制和理论计算是微孔材料加工中的主要问题.文章介绍了一种测量微孔聚合物皮层厚度的新的有效方法--扫描声显微(SAM)方法,并测量了微孔聚苯乙烯和微孔聚碳酸酯的皮层厚度.     

热致相分离法制备聚偏氟乙烯微孔膜的研究

热致相分离法是一种制备聚合物微孔材料的有效方法.介绍了聚合物初始浓度、稀释剂、降温速率、成核剂、萃取剂等因素对热致相分离法制备聚偏氟乙烯(PVDF)微孔材料的影响,并对热致相分离法制备聚偏氟乙烯(PVDF)微孔膜的最新研究进展进行了介绍.     

基于相分离制备高分子微孔材料的新探索

对制备聚合物微孔膜的相分离法进行了评述.简介了课题组几种基于相分离制备聚合物微孔材料的新探索,包括热致相分离,冷冻诱导相分离,聚合致相分离,基板诱导共混聚合物的有规相分离.     

微孔材料的研究进展

微孔材料因其特有的微观结构而具有特殊的性能,在很多领域都有应用或应用前景.综述了微孔材料的特殊性能和其在多领域的应用,以及微孔分子筛、微孔膜、微孔泡沫、微孔陶瓷、微孔淀粉泡沫等常见微孔材料的性能和制备方法,并介绍了微孔材料的常见分类方法.     

共轭微孔聚合物研究进展

共轭微孔聚合物(CMPs)有制作方法简单多样、比表面积大、物理化学稳定性好、结构形貌可调等特点,因此受到广泛关注。近年来,共轭微孔聚合物的多种合成方法和新应用成为了研究热点,CMPs主要用途包括超级电容器、非均相催化、化学传感器、太阳能界面蒸发、抑菌材料、阻燃材料。重点介绍了共轭微孔聚合物的多种合成方法以及CMPs的多种应用领域,并且对目前合成CMPs的难点进行总结。     

锂离子电池用微孔型聚合物电解质的研究进展

对新一代锂离子电池,特别是动力型电池用微孔型聚合物电解质膜材料的制备方法以及几类典型的聚合物电解质膜的特点进行了归纳和总结;比较了这一领域里萃取法、倒相法和直接造孔法的技术与工艺特点;用材料在实际电池中的机械强度、吸液率、耐高温性能、导电性能和电化学窗口宽度等指标考察了3种主要类型--单相型、两相型和复合型微孔聚合物电解质的各自优势与缺点;对微孔聚合物电解质的研制前景和开发趋势进行了展望.     

微孔结构氟聚合物铁电驻极体的制备及其热稳定性研究

描述了一种微孔结构氟聚合物铁电驻极体的制备方法，利用准静态方法测量了该功能膜的压电系数如，并通过等温衰减和热刺激放电电流谱的测量研究了凼，的热稳定性。结果表明，这类氟聚合物铁电驻极体膜的准静态压电系数d33与热压时间有关；与聚丙烯（PP）压电驻极体膜相比较，氟聚合物压电驻极体膜不但具有更高的压电活性，而且呈现更优良的热稳定性。     

CO2激光加工微孔膜关键加工参数

目的解决CO_2激光加工微孔膜实际生产中难以快速、精确地确定不同孔径微孔加工参数的问题,指导微孔膜包装材料的工程应用。方法在激光功率为6~30 W、打孔时间为0.4~4 ms的条件下,加工厚度为0.04,0.06,0.07 mm的PP包装薄膜和厚度为0.035,0.05,0.07 mm的PE包装薄膜,测量微孔孔径、孔长,分析处理试验数据。结果在厚度为0.035~0.07 mm的PP/PE薄膜上加工出了直径为50~400μm微孔,在厚度为0.06 mm的PP薄膜上加工出了直径为53~257μm、孔长为100~161μm的微孔。结论激光加工微孔膜,孔径随激光功率、打孔时间的增加而增大,调节激光功率和打孔时间均可获得不同孔径微孔;加工PE薄膜所需的激光能量显著大于PP薄膜;薄膜厚度越大,打孔所需的激光能量越高;微孔孔长相对于薄膜厚度有所增加,且微孔孔径越大,孔长增量越大。     

热致相分离法制备聚烯烃微孔膜

热致相分离（TIPS）法是目前制备聚合物微孔膜的重要方法之一。其制膜方法简单有效，突破了传统非溶剂诱导相分离制膜方法对膜材料本身的限制。介绍了热致相分离法制备微孔膜的基本步骤，综述了近年来采用热致相分离法制备聚烯烃微孔膜的研究现状及进展。     

双层刮膜法中聚砜膜结构的控制和性能研究

同时刮膜法是一种利用涂层与支撑层分离来制备高表面开孔率微孔膜的方法.本文采用同时刮膜法制备PSf微孔膜,考察了底层制膜液中聚砜的浓度、添加剂PVPK-90含量、凝胶浴温度以及PEI涂层厚度等参数对膜结构和性能的影响.结果表明,PSf溶液中聚合物浓度增大使溶液的黏度明显增大,同时膜表面凹洞数目减少,孔径减小,且水通量减少...     

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.     

聚丁二酸丁二醇酯离聚物微孔发泡性能

聚丁二酸丁二醇酯(PBS)综合性能优越,但因熔体黏度低而难以用于制备微孔塑料。论文采用离子化改性提高PBS熔体黏度,用于超临界二氧化碳(sc-CO_2)发泡。将丁二酸与丁二醇预缩聚后,添加二乙醇胺盐酸盐和二异腈酸六亚甲基酯(HDI)进行扩链反应,制备氨基离子浓度(UIC)为1%~5%的PBS离聚物(PBSUI),再以sc-CO_2发泡制备PBSUI微孔塑料。采用动态流变仪和X射线衍射测试PBSUI的流变行为和结晶性能,随着UIC的增加,由离子簇聚集产生的物理交联提高了PBSUI的熔体黏度和松弛时间,发泡前后PBSUI结晶度和球晶的直径均降低。扫描电镜结果表明,随着UIC增加,PBSUI泡孔由圆形转变为多边形,泡孔平均直径(D)、壁厚和开孔率下降,而泡孔密度(N_f)和发泡倍率则上升。当UIC为3%,PBSUI的D为2.05μm,N_f达1.73×10~(10)cm~(-3),发泡倍率超过10,由离子簇聚集引起的物理交联和异相成核作用,显著提高了PBSU的发泡性能,获得了泡孔形态良好的微孔泡沫塑料。     

模压法制备微孔发泡聚碳酸酯片材

为制备采用微孔挤出法、微孔注射法及常规发泡方法难以制备的薄型微孔发泡聚碳酸酯(PC)片材,首次采用具有制备周期短、工艺简单、操作容易、制备价格低廉等优点的模压法,通过快速降温降压制备了薄型微孔发泡PC片材,并探讨了加工参数对泡孔结构的影响,利用显微镜对泡孔结构进行了表征.实验结果表明:随着发泡时间的增加,泡孔尺寸先增加后恒定不变,泡孔密度先增加后降低;随发泡压力的增加,泡孔尺寸快速减小后变化不大,泡孔密度先快速增加后变化较小;随着发泡温度的增加,泡孔尺寸快速增加,泡孔密度快速降低;随活化比的增加,泡孔尺寸先减小后增加,泡孔密度则先增加后降低.通过控制发泡时间、发泡压力、发泡温度、活化比等加工参数可以控制微孔发泡PC的泡孔结构.     

聚氨酯泡沫夹心板的结构与频率响应特性

制备了一系列三明治式聚氨酯(PU)泡沫夹心板,研究了聚氨酯泡沫的组成和结构与频率响应特性之间的关系.结果表明:聚氨酯泡沫夹心板的灵敏度以及频宽与材料的组成和孔径、孔隙率、开闭孔率、厚度等结构因素以及皮层材料性质有关.芯层聚合物分子组成决定材料的阻尼性能,在很大程度上决定声能的输出;芯层空气含量越高,具有阻尼性质的聚合物含量少,音板灵敏度高;声波经过材料时摩擦阻力小,灵敏度高;材料的反射界面增加,声能损耗增大.     

Numerical prediction of the foam structure of polymeric materials by direct 3D simulation of their expansion by chemical reaction based on a multidomain method

The quality of thermosetting polymer foams (like polyurethane foam, used for example in automotive industry) mainly depends on the manufacturing process. At a mesoscopic scale, the foam can be modelled by the expansion of gas bubbles in a polymer matrix with evolutionary rheological behaviour. The initial bubbles correspond to germs, which are supposed quasi-homogeneously distributed in the polymer. An elementary foam volume (∼1 mm³) is phenomenologically modelled by a diphasic medium (polymer and immiscible gas bubbles). The evolution of each component is governed by equations resulting from thermodynamics of irreversible processes: the relevant state variables in gas, resulting from chemical reaction creating carbon dioxide (assimilated then to a perfect gas), are pressure, temperature and conversion rate of the reaction. The number of gas moles in each bubble depends on this conversion rate. The foam is considered as a shear-thinning viscous fluid, whose rheological parameters evolve with the curing reaction, depending on the process conditions (temperature, pressure). A mixed finite element method with multidomain approach is developed to simulate the average growth rate of the foam during its manufacture and to characterize the influence of the manufacturing conditions (or initial rheological behaviour of the components) on macroscopic parameters of the foam (cell size, heterogeneity of porosity, wall thickness).     

波纹腹板增强泡沫夹芯复合材料结构准静态压缩吸能特性

随着车船运输量与日俱增,由此引发的车船撞击结构物的事故频发,造成严重的生命财产损失与结构破坏,亟需为桥梁等结构物设置防护吸能装置。该文提出了一种新型波纹腹板增强泡沫夹芯复合材料吸能结构。该复合结构以聚氨酯泡沫为芯材,玻璃纤维增强复合材料(Glass fiber reinforced polymer,简称GFRP)为面板,在波纹型泡沫的间隙铺设双轴向玻璃纤维布,利用真空导入工艺成型。通过波纹腹板增强泡沫夹芯复合材料结构的准静态压缩试验,研究了波纹腹板与面板壁厚以及波长对夹芯结构破坏模式、承载能力以及吸能特性的影响。试验结果表明：腹板壁厚较大、波长较短的试件吸能效果最优。此外,对试验工况进行了有限元数值模拟,分析了腹板壁厚与泡沫密度因素对试件承载力的影响,为其在防撞领域的应用提供一定依据。     

Aluminum integral foam castings with microcellular cores by nano-functionalization

The goal of the present work is the refinement of the pore morphology of aluminum integral foam castings. Integral foam molding, a modified high pressure die casting process, is used where a mixture of melt and blowing agent particles (magnesium hydride, MgH₂) is injected at high velocity into a permanent steel mold. At the mold surface, decomposition of the blowing agent and pore formation is suppressed due to the high solidification rate whereas solidification of the core is much slower allowing blowing agent decomposition, pore nucleation, and growth. Blowing agent particles not only act as gas suppliers but also represent pore nuclei. Thus, microcellular foam cores can be attained by increasing the number of MgH₂ particles. But increasing the number of powder particles by powder milling strongly decreases the flowability and strong particle agglomeration as a result of the increasing cohesive forces leads to inhomogeneous foams. Flowability of the powder can be restored by coating it with SiO₂-nano-particles resulting in a homogeneous microcellular foam morphology.     

汽车座椅聚合物泡沫座垫非线性弹性-阻尼特性建模研究

该文探讨了汽车座椅聚合物泡沫座垫的非线性弹性-阻尼特性的一种建模方法及过程。首先进行了泡沫座垫的动态力学特性实验测试,根据座垫的非线性动态特性特征选择了模型的表达式,再通过大量实验数据对其进行了参数辨识,建立了座垫的一种非线性弹性-阻尼特性数学模型,表达了座垫的动态载荷与变形位移、速度的关系。另一方面,进行了实际人体在座垫上的正常坐姿体压分布测试,参考体压分布状态进行了座垫的离散化,建立了泡沫座垫的垂向非线性弹性-阻尼特性的离散化模型,可更好地模拟座椅-乘员系统的人体角振动响应特性。最后进行了所建立的聚合物泡沫座垫动态特性模型在座椅-乘员系统多体动力学响应模拟分析中的应用验证。     

Influence of microstructural heterogeneity on the scaling between flow stress and relative density in microcellular Al–4.5 %Cu

We explore the influence of the metal microstructure on the compressive flow stress of replicated microcellular 400-μm pore size Al–4.5 wt%Cu solidified at two different solidification cooling rates, in the as-cast and T6 conditions. It is found that the yield strength roughly doubles with age-hardening, but does not depend on the solidification cooling rate. Internal damage accumulation, measured by monitoring the rate of stiffness loss with strain, is similar across the four microstructures explored and equals that measured in similar microcellular pure aluminium. In situ flow curves of the metal within the open-pore microcellular material are back-calculated using the Variational Estimate of Ponte-Castañeda and Suquet. Consistent results are obtained with heat-treated microcellular Al–4.5 wt%Cu and are also obtained with separate data for pure Al; however, for the as-cast microcellular Al–4.5 wt%Cu, the back-calculated in situ metal flow stress decreases, for both solidification rates, with decreasing relative density of the foam. We attribute this effect to an interplay between the microstructural and mesostructural features of the microcellular material: variations in the latter with the former held constant can alter the scaling between flow stress and relative density within microcellular alloys.     

Cell nucleation in solid-state polymeric foams: evidence of a triaxial tensile failure mechanism

The mechanism for nucleation phenomenon in solid-state microcellular foams is identified as a solid-state failure process. This process originates at internal flaws within the gas-polymer matrix, where it is induced by the presence of a state of hydrostatic tensile stress within the polymer matrix. The hydrostatic tensile stress is caused by the presence of the saturating gas within the polymer. The nucleation phenomenon is thermally activated at the effective glass transition temperature of the gas-polymer mixture. At this critical temperature, the hydrostatic tensile stress within the gas-polymer mixture is sufficient to cause the polymer matrix to fail, thereby creating a foam cell nucleus. In general, the nucleation sites are observed to be flat, approximately circular, fracture sites. After the appearance of the initial fracture, gas diffuses from the gas-polymer matrix into the fracture. The fracture seam inflates during the growth process, in which growth begins with the appearance of a disk shaped fracture and concludes with an approximately spherical cell. The results and conclusions presented herein suggest a new avenue to explain the cell nucleation phenomena observed in this process.