聚丙烯硬弹性膜的挤出流延工艺及拉伸成孔性

以某进口均聚聚丙烯(PP)(PP1)为原料,通过挤出流延工艺制备了PP1硬弹性膜并在130℃下对其进行热处理,研究了挤出温度、流延辊转速及温度、热处理温度和时间等工艺参数对PP1硬弹性膜弹性回复率的影响,得到了最佳工艺条件,即挤出温度为195℃、流延辊温度及转速分别为90℃,26 r/min,热处理温度和时间分别为145℃,30 min。将该工艺应用于分子量及其分布与PP1基本相似的国产PP(PP2),发现由此工艺制备的PP2硬弹性膜的弹性回复率可达94.6%,与PP1硬弹性膜相差不大。通过冷热单向拉伸将PP1和PP2硬弹性膜制备成微孔膜,发现两者具有相似且优异的微孔结构。在此基础上,通过扫描电子显微镜研究了冷热拉伸工艺参数对PP2微孔膜拉伸成孔性的影响。结果表明,当冷拉伸倍数为15%,热拉伸倍数为100%,冷热拉伸速率均为50 mm/min时,制备的PP2微孔膜形成了完整规则的多孔结构。     

填充改性聚四氟乙烯拉伸多孔膜的研究进展

选择聚四氟乙烯(PTFE)拉伸多孔膜作为论述对象,概述了聚四氟乙烯的特征性能以及聚四氟乙烯拉伸多孔膜的改性技术现状,并针对聚四氟乙烯拉伸多孔膜改性后功能的不同,着重地介绍了相关填充改性的聚四氟乙烯拉伸多孔膜的技术方法。最后,还对聚四氟乙烯拉伸多孔膜的改性研究存在的问题及发展方向进行了合理的展望。     

氟化工专利精选

<正>多孔聚四氟乙烯膜的制造方法以及多孔聚四氟乙烯膜该多孔聚四氟乙烯膜表现出了优异的耐化学品性和耐热性,并且具有高孔隙率和优异的尺寸稳定性。该制造多孔聚四氟乙烯膜的方法的特征在于包括拉伸步骤,其中在低于氟树脂的熔点的温度下,沿纵向和(或)横向拉伸含有聚四氟乙烯作为其主要成分的氟树脂片状成形体,从而形成多孔氟     

铝阳极氧化多孔膜功能化应用的新趋向

铝阳极氧化形成的具有独特结构的多孔膜的功能化，近年来正逐渐引起人们的重视，在用于研制诸如分离膜及分离催化膜，光学元件，磁化膜材料，选择性吸收膜等功能材料方面，已显示出良好的应用前景。铝阳极氧化多孔膜的功能化为研制新型功能材料开辟了又一新途径。     

热处理条件对聚丙烯流延基膜取向片晶结构及拉伸成孔性的影响

摘要：为了优化挤出流延单向拉伸法制备聚丙烯微孔膜的工艺,以温度、时间和基膜受到的张应力做为热处理条件变量,通过DSC、FTIR、SEM、电子材料试验机和透气率测试仪等方法表征流延基膜的取向片晶结构参数和微孔膜的孔结构,考察热处理条件对聚丙烯流延基膜取向片晶结构和拉伸成孔性的影响。研究表明,随热处理温度从120℃提高到145℃,基膜的取向片晶结构得到改善,硬弹性增强,拉伸成孔性能变好;随热处理时间延长,基膜的结晶度、片晶厚度及取向程度不断提高,取向片晶结构趋于完善,当热处理时间达到30min后,取向片晶结构的完善程度接近稳定;在热处理过程中对基膜施加适当张应力可以提高基膜的片晶取向程度和硬弹性,改善其拉伸成孔性。     

膜材料的选择和几种反渗透膜

本文列举了一些膜材料选择中可供参考的物理参数和它们之间的相互关系。据聚合物链节的硬、软,亲水和疏水等特性以及对一些性能优良的膜材料的分子结构的分析,提出了一个初步的膜材料结构模型。对离子交联的聚丙烯酸反渗透膜以及磺化聚苯撑氧和聚乙烯醇互聚物反渗透膜的制备和性能进行了简要地阐述。最后,扼要地介绍了多孔的和复合的反渗透荷电膜在理论和实践方面的发展及这两种膜间的不同的性能。     

含有增强纤维的多孔滤膜Murase，Kei等（Mitsubishi Rayon Co．，Ltd，Japan）WO 02 24，3l5 2002，3，28 32页（日文）

该多孔膜具有良好的分离性能、高渗透性和高机械性能，特别是拉伸破坏强度高。该多孔膜由一多孔元件和增强纤维构成，该多孔元件从一个表面到另一个表面分布有大量的孔。增强纤维呈线型地连续存在于与渗透方向垂直的膜表面。在多孔元件的两个表面部位，一个表面在包括表面的横断面区域有增强纤维，而另一表面在包括表面在内的横断面区域无增强纤维。     

多孔离子传导电池隔膜研究进展

具有高离子选择性和高电导率的离子传导膜对于以新能源为主体的新型电力系统（如液流电池、燃料电池、锂电池等）至关重要。近年来，研究者们提出了构建多孔离子传导膜以应对传统隔膜普遍存在的离子选择性和电导率之间的权衡效应。本综述从无机多孔离子传导膜、有机多孔离子传导膜以及多孔离子传导复合膜三个方面简要概述了近年来多孔离子传导膜作为电池隔膜的最新研究进展，总结了多孔离子传导膜在液流电池、燃料电池、锂电池等新能源电池中的前沿性工作，并指出未来多孔离子传导电池隔膜的研究将重点关注多孔膜结构的调控、高性能多孔膜材料的开发以及多孔膜在新型电池中的应用。     

双向拉伸膜

双向拉伸膜是目前为止应用最成功的PLA膜，经过双向拉伸并热定型的PLA膜耐热温度可提高到90℃，强度、韧性明显改善，故双向拉伸是改善PLA材料应用特性的最佳方法之一，该类膜可用于鲜花包装、信封透明窗口膜、糖果包装等等。     

生产硬弹性PP单丝的关键技术

随着塑料制刷业的兴起,硬弹性PP单丝(φ0,8～1mm)的需求量越来越大.由于用途上特殊的硬弹性需求,其生产技术也不同一般.目前,国内仅有几家企业能够生产,本文根据生产实践,研究讨论了硬弹性单丝的生产技术.1 硬弹性PP单丝的特殊性与通常单丝相比,硬弹性PP单丝直径大且具有较高的弯曲刚性和弯曲变形回弹性.已知PP单丝的硬弹性受分子量大小,结晶度高低,球晶完善程度,单丝内部空穴多少(大小)等因素影响,除此之外在很大程度上还取决于PP分子取向度.经验表明PP拉伸比≥19时,单丝的硬弹性达到理想范围.如此大的拉伸比,要求用较粗的拉伸条(如φ1mm单丝需要用φ4.3～4.5mm粗的拉伸     

Plasticizer effect of dibutyl phthalate on the morphology and mechanical properties of hard elastic poly(vinylidene fluoride) fibers

To improve the structure and hard elasticity of poly(vinylidene fluoride) (PVDF) fibers, a small amount of the plasticizer dibutyl phthalate (DBP) was added to PVDF. The PVDF/DBP blend fibers were prepared by melt spinning and subsequent annealing. The crystalline structure and thermal properties of the blend fibers were analyzed in terms of the long‐period lamellar spacing, crystal structure, and degree of crystallinity with X‐ray diffraction, differential scanning calorimetry, and small‐angle X‐ray scattering. The results indicated that stacked crystalline lamellae, which were aligned normal to the fiber axis, existed in the blend fibers, and they were in the form of an α‐crystal phase. The total crystallinity of the blend fibers was higher than that of the pure PVDF fibers, and it reached its highest value when the DBP concentration was 2 wt %; then, it decreased with an increase in the DBP content. The morphology and mechanical properties of the fibers were also investigated with scanning electron microscopy and electronic tensile experimentation. The results of scanning electron microscopy apparently exhibited a small porous structure on the surface of the blend fibers, and the more DBP there was in the PVDF fibers, the more porous structure was obtained. Mechanical experiments indicated that the fibers with a 5 wt % concentration of DBP had better elastic recovery and breaking strain than the pure PVDF fibers. These results all indicated that DBP‐modified PVDF fibers have potential applications in preparing microporous membranes by a melt spinning and stretching process. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effects of stretching on crystalline phase structure and morphology of hard elastic PVDF fibers

The phase characteristics and morphology of stretched hard elastic poly(vinylidene fluoride) (PVDF) fibers were investigated by X‐ray diffraction (XRD) and wide‐angle and small‐angel X‐ray scattering (WAXS and SAXS). It was indicated that α and β phases coexisted in stretched PVDF fibers, stretching assisted in α to β phase transformation. The β/α ratios of stretched PVDF fibers were affected by stretching temperature, rate, and ratio. The β phase content of stretched PVDF fibers had an abrupt increase when stretched near 70°C, and then it decreased with increasing stretching temperature. Besides, the β/α ratio of PVDF fibers increased with stretching rate and ratio. The total crystallinity of PVDF fibers did not change much even on different stretching conditions. WAXS results indicated that the unstretched and stretched PVDF fibers all exhibited three strong equatorial streaks, with d‐spacing (0.964, 0.488, and 0.439 nm) and (0.946, 0.494, and 0.480 nm), which suggested that PVDF fibers still remained the crystalline reflections of c‐axis orientation even after being stretched. The long periods of stretched PVDF fibers, calculated from SAXS curves, increased from 19.04 to 39.75nm. On the basis of these results, the β transformation mechanism of stretched PVDF fibers was also discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2254–2259, 2007     

低温冷拉对具有排核片晶结构的PVDF微孔膜成孔的影响

采用聚偏氟乙烯（PVDF）材料制备锂电池用微孔膜,使用熔体挤出拉伸法制备了预制膜片,通过牵伸比的调节成功获得了拥有排核片晶结构的预制膜片。结果表明,该预制膜具有沿着流动方向的高取向度。退火后,在拉伸预制膜成孔的过程中,由于PVDF松弛时间较短,即使预制膜具有排核片晶结构,在常温下的成孔效果也较差;根据时温等效原理,降低冷拉时的拉伸温度,可以达到与提高松弛时间同样的效果;对比室温下冷拉和-20 ℃低温下冷拉膜片的扫描电子显微镜照片,低温冷拉后的膜片具有更多的孔结构和更好的孔分布情况,并初步探索了低温拉伸条件对于成孔促进作用的成孔机理。     

拉伸流动场诱导PVDF/BaTiO3流延膜结晶行为研究

利用挤出流延过程中的拉伸应力场对聚偏氟乙烯/钛酸钡(PVDF/BaTiO3)复合材料进行原位非等温拉伸试验,研究了拉伸比及BaTiO3用量对PVDF/BaTiO3流延膜结晶结构和介电性能的影响。广角X射线衍射结果表明,PVDF/BaTiO3复合膜的取向程度明显大于纯PVDF。X射线小角衍射结果显示:对于纯PVDF,第二个散射峰的强度随拉伸的进行而不断提高,在拉伸比为1.5时,其强度明显超过第一个散射峰;加入BaTiO3后,第一个散射峰的强度比纯PVDF明显提高,而第二个散射峰的强度也随拉伸比的提高而增强。复合膜的组成相同时,其介电常数随拉伸比的提高而减小,而介电损耗随拉伸比的提高而增大。     

多孔膜基材对等离子体接枝膜微观结构的影响

采用等离子体诱导接枝聚合法,在有机聚偏氟乙烯(PVDF)膜、尼龙(N6)膜和无机多孔阳极氧化铝(PAA)膜上接枝甲基丙烯酸(MAA),系统地研究了多孔膜基材及接枝工艺条件对接枝开关膜微观结构的影响。结果发现,对于PVDF基材膜,单体溶液脱气次数越多接枝率越大。对于不同类别的多孔膜基材,采用相同工艺条件接枝时,N6膜的接枝率高于PVDF膜,PAA膜接枝率最低。在接枝率相近的时候,接枝层在PVDF膜整个断面孔内和表面均存在,而N6膜则主要集中在表层。在PAA膜上接枝时发现,等离子体照射功率的强弱对基材膜的影响很大,当功率超过50W时,PAA膜表层就会被刻蚀而导致膜的质量减轻。     

Superhydrophobic polyvinylidene fluoride/graphene porous materials

We demonstrated a simple method to produce superhydrophobic polyvinylidene fluoride (PVDF)/graphene porous materials. The hybrid PVDF/graphene gel was formed by the diffusion of non-solvent (methanol or water) into PVDF/graphene suspension in N,N-dimethylformamide (DMF). By carefully replacing DMF in aged gels by water, gel samples were freeze-dried to produce skinless porous materials. This drying method effectively avoids pore-shrinkage because of the capillary force in the drying process of gels, giving porous materials with high specific surface area and surface roughness. Furthermore, compared with pure PVDF porous materials, the addition of small amount of graphene in hybrid gels not only influences the crystallization of PVDF, but also leads to a dramatically morphology change which significantly increases their surface roughness in nanoscale, thus generating superhydrophobic porous PVDF/graphene materials.     

制膜基底对非溶剂致相转化法PVDF膜结构与性能的影响

以聚偏氟乙烯(PVDF)/N,N-二甲基乙酰胺–辛醇/水为制膜体系,采用干、湿相转化法制膜。考察了制膜基底对膜结构、表面浸润性和透过性能的影响。对膜样品的XRD测试表明,具有一定粗糙度的砂纸基底对液态膜具有粘附限制作用,在成膜过程中的液–固分相与液–液分相的竞争中占据更大优势。在适当粗糙度的砂纸基底上可以制得底面高度疏水且透过性能良好的PVDF微孔膜。     

Lamellar crystalline structure of hard elastic HDPE films and its influence on microporous membrane formation

The development of hard elastic high-density polyethylene (HDPE) precursor films and its influence on the microporous membrane formation have been investigated. As a first step, the HDPE precursor films with ‘row-nucleated lamellar crystalline’ structure were prepared by applying elongation stress to the HDPE melt during T-die cast film extrusion and subsequently annealing the extruded films. This unusual crystalline structure was analyzed in terms of lamellar crystalline orientation, long-period lamellar spacing, crystallite size, and degree of crystallinity. The processing (melt extension and annealing temperature)-structure (lamellar crystalline structure)-property (hard elasticity) relationship of HDPE precursor films was also investigated. The uniaxial stretching of hard elastic HDPE precursor films induces the bending of crystalline lamellae, which leads to the formation of micropores between them. The observation of morphology and air permeability for the HDPE microporous membranes have revealed that the well-developed porous structures characterized by superior air permeability were established preferably from the precursor films prepared by the high stress levels and the high annealing temperatures. Finally, the relationship between the hard elasticity of HDPE precursor films and the air permeability of corresponding microporous membranes was discussed.     

无机粒子改性聚偏氟乙烯超滤膜的研究进展

聚偏氟乙烯(PVDF)作为一种常见的超滤、微滤、渗透蒸发薄膜材料,具有优良的热稳定性、化学稳定性、疏水性及生物相容性等,在生物、医药等各个领域均表现出良好的应用前景。近年来,PVDF复合多孔膜的制备及应用成为材料界的研究热点,但由于PVDF材料具有较低的表面能,使其具有疏水性,存在过滤压力大、薄膜易受污染等问题,限制了其使用范围,因此需要对PVDF膜材料进行亲水改性。为此,在详细介绍PVDF结构及性能的基础上,总结了不同无机粒子改性PVDF复合多孔膜的最新研究进展,归纳了其常用制备方法及工艺,展望了PVDF复合材料的发展前景及研究方向。