应用溶剂刻蚀法研究聚乙烯的交联结构

应用四氯化碳溶液和三氯甲苯溶液为溶剂对交联聚乙烯表面结构及断面结构进行刻蚀处理，利用扫描电镜对聚乙烯的交联结构进行观察。结果表明，聚乙烯断面结构用三氯甲苯溶液刻蚀50h处理后，可清晰地观察到其交联结构。     

涂料树脂交联技术的最新进展

通过专利文献和研究报告的调查，评论了溶剂型和水性涂料交闻技术的最新进展，（１）降低挥发性有机化合物（ＶＯＣ）含量：（２）用无毒交联剂替换有毒的多异氰酸酯；（３）汽车面漆防酸雨；防擦伤；（４）节能的低温化；（５）更高的性能。各种新交联体系已开发出来以代替现行体系．诸如氨基树脂固化，多异氰酸酯固化和封闭型多异氰酸酯固化。一些采用新体系的商业产品已投放市场。     

热氧老化对特种氟橡胶交联结构及力学性能的影响

采用加速老化实验方法对特种氟橡胶密封材料的热氧老化性能进行了研究,获得了不同老化温度及老化时间对特种氟橡胶力学性能和交联结构的影响规律。研究结果表明,氟橡胶在热空气中老化时随老化温度的升高和老化时间的延长,材料的拉伸强度、硬度降低,100%定伸应力先增加后减小,拉断伸长率先减小后增大,回弹性和压缩永久变形增大。材料的交联密度先增加后减少,表明氟橡胶在热氧老化初期以交联为主,在老化后期以降解为主。     

交联结构对苯类吸收树脂性能的影响

采用悬浮聚合法制备了球形苯类吸收树脂,研究了交联剂用量与树脂的吸收倍率、交联密度和凝胶分数之间的关系,探讨了交联结构对树脂吸收和释放动力学的影响,并采用扫描电镜考察了树脂的微观形貌。结果表明:随着交联剂用量的增加,吸收树脂的凝胶分数和交联密度不断增大,吸收倍率出现峰值;随着交联密度的提高,吸收树脂对甲苯的吸收速率和释放速率均减慢,吸收动力学常数与释放扩散系数都不断降低;树脂对甲苯的吸收动力学过程符合准一级动力学方程;得出了形式简洁的吸收树脂释放动力学方程,能够很好地描述吸收树脂释放甲苯的动力学行为;吸收树脂的交联结构稳定,再生重复使用10次以后树脂微球的大小、形貌和吸收倍率均无明显变化。     

交联结构的表征及其对硫化胶性能的影响

主要介绍硫黄硫化橡胶交联键类型和交联密度的表征方法以及交联结构对硫化胶性能的影响。表征交联键类型的方法主要有化学探测剂法、固体核磁共振法、校准曲线法和光谱分析法等,其中化学探测剂法比较成熟,而固体核磁共振法作为新技术具有很大的潜力。表征交联密度的方法主要有化学测定法、平衡溶胀法、力学测定法、核磁共振法和透射电子显微镜法等,其中平衡溶胀法是一种经典方法,核磁共振法也得到了广泛应用。     

高分子材料微观形态结构的扫描电镜研究

利用扫描电镜对聚乙烯(PE)、丙烯腈-丁二烯-苯乙烯共聚物(ABS)等高分子材料填料的分散性及表面与断裂界面进行了研究。结果表明,扫描电镜能够详细观察研究高分子材料的表面结构、微观相分离等,便于表征高分子材料微观结构形态,是分析高分子材料微观结构形态的有效手段。     

生物质焦表面形貌SEM研究

采用扫描电镜对生物质焦的表面形貌进行研究。扫描电镜实验结果表明,生物质在制焦后,表面粗糙度提高,比表面积增大,孔隙更加发达。焦样表面形貌的特征主要是由生物质种类决定的,在扫描电镜下,稻壳焦样表面有锯齿状不规则的突起,但是开口在表面的孔很少;树叶焦样表面有不规则的孔;玉米杆焦样有如同蜂窝状的表面结构,表面孔十分丰富;棉花杆焦样有着絮状的表面结构,表面孔也较明显。热解温度对焦样表面形貌的影响不大。     

Characterization of modified polypropylene by scanning electron microscopy

Characterizing the morphology of modified multiphasic polymer systems, as are often applied for improving the impact strength, is normally a complicated and tedious task. Nevertheless, knowledge about the volume fraction and particle‐size distribution of the elastomer phase is important for the specific development of high‐impact systems. Direct production in the reactor enables only indirect control of these two quantities. Computer‐controlled scanning electron microscopy in combination with image processing allows an automated measurement of both all the necessary particle parameters (size distribution, shape, orientation, etc.) and the elastomer content of the material. Since bulk materials are used for the investigation, additionally, three‐dimensional information about the structure of the material can be gained by simply varying the electron energy, without the necessity to resort to multiple slices. This information is especially important in the case of particles with extremely irregular shapes, as obtained, for example, by strong agglomeration of the modifier particles. The mathematical routines used for calculation of the particle‐size distributions from the measured profile‐size distributions cannot be applied in such cases. The method was tested for several materials with significantly different compositions, both immediately after molding and also after a subsequent thermal relaxation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1152–1161, 2000     

Isothermal titration calorimetry, transmission electron microscopy, and field emission scanning electron microscopy of a main-chain viologen polymer containing bromide as counterions

The interaction of a main-chain viologen polymer containing bromide as counterions with water and aqueous potassium bromide over a broad range of concentrations was studied with isothermal titration calorimetry. The dilution process of this polymer was endothermic as opposed to flexible poly(sodium acrylate) and poly(sodium styrenesulfonate). This result may be related to the different mechanism of hydration of pyridinium and bromide groups in the main chain. It also exhibited aggregation phenomenon in both water and aqueous potassium bromide solutions as detected by transmission electron microscopy like other flexible and rigid-rod polyelectrolytes. As the polymer concentrations in aqueous solutions increase, the aggregated polymer exhibited more defined ordered structures than random structures observed at low polymer concentrations. Field emission scanning electron microscopy also revealed the effect of variation of concentration of aqueous potassium bromide on the morphology of the polymer matrix. At increasing concentrations of aqueous potassium bromide, the polymer structures became more ordered than those in low concentrations.     

High-resolution scanning electron microscopy for the characterization of supported metal catalysts

A scanning electron microscope with a short-focal-length immersion lens and subnanometer resolution has been used to characterize several oxide-supported metal particle catalysts. Nanometer-sized metal particles in the Pt/TiO₂ and Pd/SiO₂ systems could be imaged with best clarity at the upper end of the operating voltage range (20–30 kV). However, visibility depended upon an adequate yield of secondary electrons relative to the support: small Pt particles on CeO₂ could not be located by secondary electron imaging. Best visibility of the surface topography of the support was obtained at lower accelerating voltages.     

Determination of organic sulphur in raw and chemically cleaned coals by scanning electron microscopy and energy dispersive X-ray spectrometry

Scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS) is a useful method to evaluate chemical cleaning processes and to obtain values of the organic sulphur remaining in cleaned coals. Pressed pellets can be used when the cleaning process has made the coal too heterogeneous to analyse by the conventional epoxy mounting method. The SEM-EDS analysis time is the same for both methods, whereas the preparation of pellets is much easier than that of epoxy mounts. The overall analysis time should therefore be decreased by using the pellet technique.     

Microscopic lamellar organization in high-density polyethylene banded spherulites studied by scanning probe microscopy

Surface topography and lamellar aggregation structure of high-density polyethylene (HDPE) banded spherulites were investigated by scanning probe microscopy. HDPE films were prepared by isothermal crystallization at various crystallization temperatures from the melt. Polarizing near-field scanning optical microscopic (NSOM) observations for the HDPE films revealed submicron-scale correlation between surface topography and birefringence of banded spherulites. The height profile of the film surface along the spherulitic radius periodically changed corresponding to the intensity profile of transmitted light along the radius of the extinction ring. This correlation was more clearly observed in the topographic and NSOM images of permanganic etched PE films. Therefore, it was apparently suggested that the crystallographic c-axis of the orthorhombic unit cell was parallel and perpendicular to the film surface at the peak and the valley in the surface corrugation of the banded spherulite, respectively. The band spacing obtained by polarizing NSOM and atomic force microscopy (AFM) was comparable to that determined by polarizing far-field optical microscopic observation under crossed nicols. The band spacing and the peak-to-valley height difference in the corrugation increased with an increase in isothermal crystallization temperature. AFM observations directly indicated local lamellar orientation and stacking manner.     

The quantitative analysis of nano-clay dispersion in polymer nanocomposites by small angle X-ray scattering combined with electron microscopy

The main objective of this work is to propose a new approach for the quantitative analysis of the degree of dispersion of clay particles in the polymer matrix by small angle X-ray scattering (SAXS) combined with electron microscopy. Due to the low temperature processibility and good thermal stability, poly[(butylene succinate)-co-adipate] (PBSA) was chosen as a model polymer matrix for this study. The nanocomposites of PBSA with four different weight percentages of organically modified montmorillonite (OMMT) loadings were prepared via melt-blending method. The dispersed structure of the clay particles in the PBSA matrix was studied by SAXS. Results show that the clay particles are nicely dispersed in the case of all nanocomposites. However, with a systematic increase in clay loading, the dispersed clay structure of the nanocomposites changes from a highly delaminated to a flocculated and then to a stacked intercalated one. The probability of finding neighboring clay particles in the PBSA matrix as well as their thickness was calculated using the Generalized Indirect Fourier Transformation technique developed by Glatter and the modified Caillé theory proposed by Zhang. The morphology of the nanocomposites was also extensively studied by scanning transmission electron microscopy (STEM). In the case of all nanocomposites, SAXS results were in good agreement with STEM observations. Finally, a correlation between the predicted morphology of nanocomposites and their melt-state rheological properties is reported.     

Deformation behavior of nanocrystalline titania particles accessed by complementary in situ electron microscopy techniques

The mechanical behavior of nanostructured spherical submicrometer titania particles was studied by in situ uniaxial compression experiments in the scanning and transmission electron microscope (SEM and TEM). Mesoporous and amorphous titania particles were prepared by a wet chemical sol‐gel approach. To obtain nanocrystalline (nc) single‐phase anatase and rutile particles the amorphous particles were crystallized by high‐temperature annealing. For each sample the deformation behavior of at least 50 particles was investigated by in situ compression experiments in the SEM. In all cases an elastic – predominantly plastic deformation behavior accompanied by crack initiation at exceptionally high engineering strain values of several percent were observed. Crack propagation presumably along grain boundaries and a Weibull distributed fracture stress was shown for all nc particles. Complementary in situ TEM experiments and ex situ analysis of focused ion beam prepared particle cross‐sections were carried out to identify the underlying deformation mechanisms. Grain rotations and grain sliding are observed for nc anatase particles during in situ compression and are further identified to be linked to a densification of the mesoporous particle structure. Our dedicated preparation and quantitative in situ characterization methodology provides an excellent basis for a better understanding of the mechanical behavior of advanced ceramics.     

Determination of lamellae in segmented polyurethanes by electron microscopy

The morphology of segmented polyurethane was studied with an electron microscope. Polymers were obtained by the prepolymer method from poly(ethylene adipate), 4,4-diphenylmethane diisocyanate and 1,4-butanediol. The unstained sample showed spherulites with fibrillar structure. Attempts were made to enhance the contrast in order to study the fibrillar structure more thoroughly. The staining method used to study the structure of lamellae is described.