透明成核剂作用下的等规聚丙烯的结晶形态

利用偏光显微镜观察了等规聚丙烯（iPP）在透明成核剂TM-3作用下的等温结晶形态，并与普通成核剂苯甲酸钠的影响作了对比。结果表明：等温和等成核剂含量条件下，含有TM-3样品的最佳结晶完善程度出现在结晶时间为10h时；其他条件相同时，TM-3／iPP样品的最佳结晶完善程度出现在140℃；而TM-3／iPP样品的结晶完善程度在成核剂含量为0．3％（质量分数）时最好。作为一种新型成核剂，TM-3的成核机理不再是简单的异相成核，而是提供少量而有效的生长点，使PP链段进行附着生长。结果证实，TM-3具有明显促进iPP球晶生长的能力。     

The semi-automatic nucleator

The nucleator is a well-established manual stereological method of estimating mean cell volume from observations on random cell transects through reference points of the cells. In this paper, we present an automated version of the nucleator that uses automatic segmentation of the boundaries of the cell transects. An expert supervises the process. If the segmentation is judged to be satisfactory, an estimate of the cell volume is calculated automatically on the basis of the whole cell transect. In the remaining cases, the expert intervenes and uses the classical nucleator. The resulting estimator is called the semi-automatic nucleator. In this paper, we study the statistical properties of the semi-automatic nucleator. Formulae for the bias and mean square error are derived. The semi-automatic nucleator may have a small bias but will still in most cases be more efficient than the classical nucleator. Procedures for estimating bias and mean square error from a pilot study are provided. The application of the semi-automatic nucleator is illustrated in a study of somatostatin positive inhibitory interneurons which were genetically labelled with green fluorescent protein (GFP). The cells were sampled with an optical disector. The centre of mass in a central cell transect was used as reference point. It is found in this study that the number of cells needed for obtaining, for instance, a 5% precision of the estimate of mean cell volume is 150 and 189 for the semi-automatic and the classical nucleator, respectively. Taking into account that the time spent analysing one cell is shorter for the semi-automatic nucleator than for the classical nucleator, the semi-automatic nucleator is superior to the classical nucleator.     

玻璃纤维增强高结晶PP的研究

考察了玻璃纤维(GF)增强高结晶聚丙烯(PP)的力学性能,发现高结晶PP/GF的力学性能较普通PP/GF的提高15%～18%;同时考察了不同增容剂对高结晶PP/GF的力学性能的影响,均聚接枝物拉伸强度、弯曲强度较高,共聚接枝物的冲击强度较高;另外发现在PP/GF中加入山梨醇型α成核剂、芳酰胺类β成核剂后,两者对其性能有较大影响,使其力学性能降低40%以上。     

Interactions between sorbitol-type nucleator and additives for polypropylene

The thermal properties of a sorbitol-type nucleating agent (viz. 1,2,3-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonitol (TBPMN)) were examined in this study, and the influence of common processing additives assessed. In addition, we describe a novel approach to monitor in situ the self-assembly of the nucleator in presence of additives by optical microscopy. The performance of sorbitol compounds is closely associated to their chemical structure and ability to self-assemble. TBPMN formed elongated fibrils from the melt under inert atmosphere, in molted polypropylene, or in presence of antioxidants. However, calcium stearate (CaSt) and glycerol monostearate hampered growth, and yielded thinner fibrils. In presence of the additives, melting point depression of the nucleator occurred, and resulted in a lower degree of crystallinity upon cooling. Performance evaluation of the nucleator in polypropylene blends revealed an increased crystallization temperature when antioxidants were present, while CaSt inhibited nucleator activity. The effect of mono-glycerides was found highly dependent on the processing conditions. Noteworthy, blends containing all the additives displayed the highest performance. This study highlights the importance of the preparation method of polymer additive blends to achieving the best performance in the final product. Characterization was performed by thermogravimetric analysis, Fourier-transform infrared spectroscopy, optical microscopy, and differential scanning calorimetry.     

透明聚丙烯的研究进展

聚丙烯（PP）作为一种热塑性树脂,具有良好的性能,并且价格低廉,被广泛应用于各种领域,尤其是透明PP以其优异的光学和力学性能,近年来吸引了越来越多研究者的重视。本文概述了透明PP在国内外的研究发展情况,介绍了PP增透改性的主要途径（包括添加透明剂、直接合成透明PP、共混改性等）,并对各种改性方法的优缺点进行总结,对于进一步研究PP的透明改性具有一定的指导意义。     

Non‐uniform systematic sampling in stereology*

Non‐uniform systematic sampling designs in stereology are studied. Various methods of constructing non‐uniform systematic sampling points from prior knowledge of the measurement function are presented. As an example, we consider area estimation from lengths of linear intercepts. The efficiency of two area estimators, based on non‐uniform sampling of parallel lines, is compared to that of the classical 2D Cavalieri estimator, based on uniform sampling, in a sample of planar profiles from transverse sections of 41 small myelinated axons. The comparison is based on simulations. It is concluded that for profiles of this type one of the non‐uniform sampling schemes is more efficient than the traditional uniform sampling scheme. Other examples where non‐uniform systematic sampling may be used are in area estimation from lines emanating from a fixed point, area estimation from concentric circles or spirals and curve length estimation from sweeping lines. It is shown that proportional‐to‐size sampling is a special case of non‐uniform systematic sampling. Finally, the effect of noise in the observations is discussed.     

A novel highly efficient β‐nucleating agent for polypropylene using nano‐CaCO3 as a support

In order to increase the isotactic content of β‐nucleated polypropylene (β‐iPP) and decrease the cost of its production, the investigation and development of novel highly efficient β‐nucleators are important issues. Nano‐CaCO₃ was used as a support to prepare a supported β‐nucleator, nano‐CaCO₃‐supported calcium pimelate. Fourier transform infrared spectral analysis shows that an in situ chemical reaction takes place between nano‐CaCO₃ and pimelic acid. Differential scanning calorimetry results indicate that the crystallization and melting temperatures of β‐phase in supported β‐nucleator‐nucleated iPP are higher than those of calcium pimelate‐nucleated iPP. The β‐nucleating ability of the supported β‐nucleator is little influenced by the cooling rate and crystallization temperature over a wide range. The decreased content of pimelic acid in the supported β‐nucleator slightly decreases the crystallization temperature of iPP but it has no influence on the content of β‐phase in nucleated iPP. A novel supported β‐nucleator has been successfully synthesized via pimelic acid supported on the surface of CaCO₃. The crystallization temperature of iPP and melting temperature of β‐phase in iPP nucleated using the supported β‐nucleator are higher than those of iPP nucleated using calcium pimelate. The concept of a supported nucleator will provide a new way to increase the efficiency of polymer additives and to decrease the amounts of them that need to be used by using nanoparticles as supports. Copyright © 2010 Society of Chemical Industry     

高熔体流动速率抗冲共聚聚丙烯M30RH的开发

在环管聚丙烯(PP)装置上利用非对称外给电子体技术和直接聚合法生产了高熔体流动速率抗冲共聚PP M30RH。通过工艺改造、优化操作参数、筛选后期活性更高的DQC602型催化剂、采用使PP刚韧平衡性更好的成核剂VP-101B,实现了M30RH的大批量稳定生产。与用降解法生产的国内同类PP相比,M30RH无异味、不发黄,刚韧平衡性好,在洗衣机和汽车零部件专用改性树脂等领域得到广泛应用。     

成核剂对聚甲醛结构与性能的影响

利用差示扫描量热仪、偏光显微镜和力学性能测试研究了不同成核剂对聚甲醛(POM)结构和性能的影响。结果表明,选用的无机成核剂均能有效地减小POM球晶尺寸,提高POM的结晶峰温度及缺口冲击强度,其中以滑石粉的成核效果最为显著。滑石粉使POM最大结晶温度由141.2℃提高到145.5℃,球晶平均尺寸约为未加成核剂的POM球晶尺寸的1/4,缺口冲击强度从5.12 kJ/m2增加到6.21 kJ/m2。     

耐热高抗冲聚丙烯结晶行为及微观形态研究

β成核剂能对聚丙烯进行改性,考察β成核剂改性共聚聚丙烯的结晶行为及微观形态。结果表明,β成核剂只改变β晶型含量,对β晶型内部结构没有影响,且对共聚聚丙烯中α晶型的影响不明显。偏光显微镜观察发现,辐射β球晶和环带β球晶均呈略微彩色,有明显Maltese黑十字。