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聚偏氟乙烯(PVF2)至少有四种晶相结构,即α、β、γ和δ相,PVF2的压电性和热电性直接依赖其β相结构。 本工作报导以特殊的熔体拉伸方法制备不同组成偏氯乙烯(VF2)和四氟乙烯(VF4)的共聚物高取向薄膜与对其结构的研究结果。 相似文献
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研究了不同组成的苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)的相形态与粘弹弛豫.用透射电子显微镜(TEM)表征了SBS的形态,结果显示,几种SBS均呈层状结构,随着苯乙烯含量的降低,聚苯乙烯(PS)相的尺寸稍有减小,而聚丁二烯(PB)相尺寸明显增大.用动态流变学方法考察了不同温度下SBS嵌段大分子的弛豫行为,结果表明,苯乙烯含量减少,PS相玻璃化转变和有序-无序转变温度均降低;苯乙烯含量少的,在有序-无序转变过程中呈现出高且宽的损耗峰,表明有序-无序转变过程中能量的耗散主要由两相溶合时分子链间的内摩擦所决定,分子链越长,内摩擦越大,能量耗散越大. 相似文献
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非晶PET等温结晶后,用DSC、WAXD、SAXS、密度和透射电镜等方法,考察了结晶PET在升温过程中的结构变化,进一步证实了过程中发生部分熔融再结晶;同时形态也起了明显变化:片晶增厚,片晶侧向尺寸增大,由节瘤状晶粒堆砌部分地转变为典型的片晶堆砌,构成片晶的微晶尺寸增大,晶体趋于完善,折迭表面的规则折迭增加。这样,在等温结晶时生成的结构状态转变为更稳定的形态,因而相应地在DSC曲线上出现两个熔融峰。 相似文献
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Through the preparation of PVDF membranes using various nonsolvent coagulation baths following the phase inversion process, the influence of alcohol-based nonsolvents on the formation and structure of PVDF membranes were investigated. The light scattering and light transmission measurements were used to characterize the equilibrium phase diagram and the gelation speed, respectively. The locations of the crystallization-induced gelation boundaries for various systems and precipitation processes were explained from the corresponding thermodynamic and kinetic parameters. It was found that the better affinity between alcohol-based nonsolvents and DMAc solvent caused the gelation boundaries further away from the PVDF-DMAc axis with the coagulation bath varying from water, methanol, ethanol to iso-propanol. Due to the lower exchange rate of DMAc and alcohols, the delayed demixing took place for the membrane-forming using alcohols as baths, and the delayed time became longer when the coagulation bath was changed from methanol, ethanol to iso-propanol. The characterization results of membranes indicate that the influence of nonsolvents on the phase diagram and the precipitation process are in agreement with those on the membrane morphology. The better thermodynamic stability and a low exchange diffusion rate of PVDF/DMAc/alcohols favor the liquid-solid phase separation in gelation process, and therefore yield the membranes with a porous upper surface, a particular bottom surface and symmetrical structure. 相似文献
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PHBV电纺纤维结构与形态的研究 总被引:11,自引:0,他引:11
利用电纺丝法制备了超细聚 β 羟基丁酸戊酸酯 (PHBV)纤维 ,通过扫描显微镜 (SEM)、差热分析(DSC)、宽角X射线衍射和偏振红外吸收光谱对产品进行了结构与形态的表征 .研究了纺丝过程中溶液浓度、电压和接收距离 3个参数对纤维形态的影响 .结果表明 ,溶液浓度是决定性的 ,只有高于一个定值才能获得单一的纤维产品 .与流延成型的PHBV相比 ,电纺丝具有较高的取向度和结晶度 .原因可能是 ,电场力下喷丝震荡过程中带来的拉伸作用从而引起分子链的规整排列 相似文献
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研究了玻璃基板作用下极性高聚物为低组分的共混物薄膜在退火条件下相形态的发展过程 .选用聚苯乙烯 (PS) 聚甲基丙烯酸甲酯 (PMMA)与聚苯乙烯 (PS) 聚ε 己内酯 (PCL)两个体系 ,在玻璃基板上Spin Coating成膜后退火 .由于共混物薄膜中极性相对较大的高聚物组分 (PMMA和PCL)相对于极性较小的PS组分对玻璃基板具有更好的润湿性 ,所以在上述的两个共混薄膜体系中其相形态分别显示PMMA和PCL在低组分比例下最终发展成为连续相 .利用扫描电镜以及元素分析很好地验证了以上的结论 ,并且对其机理进行了解释 .此外 ,改变PS的分子量与PCL共混 ,研究了组分粘度对薄膜相形态发展的影响 .结果表明 ,PS组分粘度越大 ,共混物薄膜相结构发展速度越慢 相似文献
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聚丙烯β型球晶形态及成因的探讨 总被引:9,自引:0,他引:9
本文主要采用扫描电子显微镜,对主含夕球晶的iPP,或其与LDPE共混的试样的表面、切面、热处理样,紫外线及光、热老化样等大量试样中的β球晶形态进行了观察,结合前人工作,对iPPβ球晶的形态及成因,提出了一些新的看法。 相似文献
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聚丙烯力学性能与等规度及形态的关系 总被引:2,自引:0,他引:2
在单轴拉伸的条件下,在聚丙烯的四种不同球晶尺寸及堆集状态中,研究了等规度对力学性能的影响,并用偏光显微镜研究了不同球晶的拉伸变形机构。 一般地讲,等规度对聚丙烯力学性能是有影响的,但不及球晶尺寸和堆集状态的影响那么重要。不同球晶的聚丙烯在力学性能上的差别与其在拉伸变形机构上的差别密切相关。 相似文献
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HIPS-g-GMA相容剂对PC/HIPS共混物相容性的影响* 总被引:3,自引:0,他引:3
将两种或两种以上聚合物进行共混是获得性能优异合金材料的简单而有效的途径[1,2 ] .但是大多数聚合物共混时 ,由于混合焓ΔH >0且混合熵ΔS非常小 ,导致混合自由能大于零 ,故大多数共混体系是不相容的 .而对于不相容的共混 ,由于两相间的界面张力大 ,两相间形成锐形界面 ,两相之间的界面粘结力低 ,导致材料性能很差 .为了改善两相间的相容性 ,需要加入相容剂[3 ,4 ] .绝大多数增容剂是嵌段或接枝共聚物 .这类增容剂分子量较大 ,在加工条件下 ,由于其粘度较大往往难于迁移到两相的界面处 ,起不到应有的增容作用 .聚合物反应加工技术是近 2… 相似文献
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本文主要研究了在溶液聚合中,用两种加料方式对嵌段聚醚氨酯(SPEU)本体形态结构的影响。由透射电镜观察的结果发现,在预聚反应过程中采用两种加料方式,其最终聚合产物(SPEU)都具有明显的两相结构;加料方式不同主要影响SPEU中分散相的形态和其内的聚集态结构:(1)采用将端羟基的聚四次甲基醚(PTMEG)溶液滴加到4,4′-二苯基甲烷二异氰酸酯(MDI)的溶液中,俟反应完成后再滴加入扩链剂(Extender)的加料方式所制得的SPEU其分散相在形态上呈现为小棒条状,这种分散微区的宽度一般在10—60nm范围内,从选区电子衍射结果证明这种微区的结构是结晶的。(2)而采用将MDI的溶液滴加到PTMEG溶液中,俟反应完成后再滴加Extender的加料方式所制备的SPEU其分散相在形态上呈现为球形,它们的直径多在100至300nm范围内,由电子衍射证明这种分散微区的结构是无定形的。 相似文献
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水性聚氨酯及其接枝共聚物分散液颗粒的形态研究 总被引:10,自引:0,他引:10
通过自乳化法合成了水性聚氨酯 ,并用甲基丙烯酸甲酯对其进行了接枝共聚 .用动态光散射对其胶束粒径进行了测量 ,并用透射电镜对胶束的粒子形态进行了观察 ,研究结果表明 ,胶束粒子的粒径与聚氨酯结构中的二元醇组成有密切的关系 ,亲水性二元醇合成的聚氨酯胶束粒径比疏水性二元醇合成的要大 ;随聚丙二醇含量增多 ,接枝共聚反应更易进行 ,且接枝后的胶束粒径比接枝前增大 ,但随丙二醇含量增加 ,接枝共聚反应难以进行 ,且胶束粒径接枝前后变化不大 ,并有减小的趋势 ;随聚氨酯分子侧链的柔顺性增加 ,主链的刚性增强 ,胶束粒子易发生微相分离 ,形成壳 核结构 相似文献
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分子力学和分子动力学方法研究不同变质程度烟煤的分子结构 总被引:1,自引:0,他引:1
采用分子力学和分子动力学模拟方法 ,研究了不同变质程度烟煤的三维分子构型和能量参数。结果表明 :随变质程度的增加 ,煤分子内平行的芳香片层结构增大。不同变质程度烟煤分子在团聚前后的成键相互作用能仅略有变化 ,其中扭转能Et 的变化相对较为显著 ,并且扭转能随煤阶的增加呈逐渐减小的趋势。非成键作用能 ,特别是超过三个原子的范德华作用能 ,是煤中的重要相互作用能 ,是模型分子团聚的重要驱动力 ,对于烟煤分子聚集状态的形成起着决定性的作用。同时随煤阶的升高 ,超过三个原子的范德华作用能逐渐增加。模型分子的总势能随煤阶的变化呈两头高、中间低的趋势 ,与煤的一些宏观物理性质有一定的相一致性。 相似文献
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In this paper, the morphology, sedimentary structure, bioherm--building mollusk assem-blages and their growing and piling-up models of modern oyster bioherms in the estuariesof the Zimaigou and Xiaoqing Rivers are described and expounded, the environmentalconditions for the development of oyster bioherms, such as the dynamical geomorphicbackground, water depth, hydrodynamic factors and ecological conditions in the estuaries,are analyzed, the relationship of the successively seaward migrating of oyster biohermswith average annual sea-level changes and the erosion--accretion processes in the estuariesare probed and explained, and the geological significance of oyster bioherms in the studyof Quaternary marine environmental evolution is presented. 相似文献
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郭福祥 《中国科学B辑(英文版)》1992,(8)
The paper discusses the characteristics of the trigonioidacean evolution, including stagecharacter, pattern of the punctuated equilibria, periodic reappearance phenomenon of similarmorphology and synchronous orientation parallelism.This indicates that the trigonioida-ceans were themselves the material foundation cf their evolution.It is pointed out that thecharacteristics reflect the regularity of their genetic material mutations. 相似文献
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The study of terranes has already become an important subject in research of the Circum-Pacific continental margin. This paper discusses proper understanding of the terrane conception and identifies existence of the Nadanhada terrane according to its difference from the neighbouring massifs in terms of evolutionary history, tectonic background, and deformation features, and to the fault-contact relation between them; analyzes the paleogeographic position variation of the Nadanhada terrane during the Triassic to late Jurassic and the period when the terrane was attached to the ancient continental marging; finally discusses the consequential effects of theterrane accretion from the observed tectonic events after terrane collage. 相似文献
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TIME-TEMPERATURE-MISCIBILITY AND MORPHOLOGY OF POLYOLEFIN BLENDS 总被引:1,自引:0,他引:1
Miscibility and crystallization have been studied for polypropylene-polyethylene and polyethylene-polyethyleneblends. In the case of the polypropylene blends the composition of interest is 20% polypropylene. At this composition thepolypropylene has been found to be soluble in linear low density polyethylene but insoluble in high, low and very lowdensity polyethylenes. The miscibility has been concluded from the crystallization kinetics and polarised optical microscopywith a hot stage. Polyethylene-polyethylene blends have been formed from polymers with similar average branching contentbut where they have different melting temperatures. Important consequences are to introduce long branches into apolyethylene that only has short branches, and to modify the morphology of a polyethylenes so that haze, gloss and strainhardening are improved. Polyethylene blends must be developed after careful consideration of the branch content anddistribution within each of the constituents. It is not sufficient to simply blend polyethylenes, with the desired range ofproperties, without regard to the miscibility of the blend composition. 相似文献