试样缺口对悬臂梁缺口冲击强度测试结果的影响研究

选择聚碳酸酯（PC）、均聚聚丙烯（PP）、聚氯乙烯（PVC）和聚丙烯腈-丁二烯-苯乙烯树脂（ABS）四种原材料作为研究对象,对比研究试样缺口差异对悬臂梁缺口冲击强度测试结果的影响。结果表明,PC材料的注塑试样和机铣试样的冲击强度均值相同,但是前者的波动明显高于后者;而对于均聚PP,注塑试样的冲击强度明显高于机铣试样;另外相比于PVC,缺口加工方式、缺口加工速度以及缺口剩余宽度对ABS材料的冲击强度结果影响不大。     

聚丙烯材料简支梁缺口冲击性能的时温效应研究

将聚丙烯(PP)树脂在一定注塑工艺条件下制备成用于简支梁冲击测试的样条,分别为ISO注塑A型缺口冲击样条和无缺口样条(然后通过铣缺口机机械加工成A型缺口冲击样条),通过摆锤冲击试验仪进行简支梁缺口冲击强度测试,研究共聚型PP材料注塑缺口和铣缺口冲击性能的时温效应.结果表明,共聚型PP材料铣缺口在标准环境下调节,简支梁缺...     

不同条件对聚碳酸酯缺口冲击强度测试结果的影响

以纯聚碳酸酯(PC)、阻燃PC和阻燃增韧PC试样为研究对象,研究了ISO 7391–2,ASTM D256和ISO180三种标准测试的悬臂梁缺口冲击强度差异,同时探讨了缺口制作方式和退火处理(135℃,2h)对缺口冲击强度测试结果的影响。结果表明,不同PC试样采用ASTM D256标准测试的缺口冲击强度较ISO 7391–2稍高,而采用ISO 180标准测试的缺口冲击强度最低。偏光应力仪和扫描电子显微镜测试结果表明,由于ISO 180标准规定的试样厚度相对较大,试样产生了过大的残余应力,加之阻燃PC中阻燃剂与PC的相容性较差,进而导致采用ISO 180标准测试的阻燃PC缺口冲击强度测试数据极低。实际应用中尽量选用断裂行程短、试样厚度大的ISO 180标准对改性PC试样的缺口冲击强度进行测试,其更能体现材料的缺陷和实际韧性。采用机铣缺口测试的缺口冲击强度稍高,而采用模塑缺口测试的缺口冲击强度离散系数小,数据稳定性更好。退火处理虽可消除试样的内部应力,但会导致试样边缘位置应力集中更加明显,退火处理后各试样的缺口冲击强度测试数据均大幅度降低。     

一种新型抗缺口敏感性/自愈合水凝胶的制备与表征

氧化石墨烯由于其杰出的机械、电学、光学等性能,是一种较为理想的2D合成材料。在水凝胶网络中引入氧化石墨烯复合材料,不仅能极大地增强水凝胶的韧性和机械性能,还使得材料具有一些特殊的性质。使用氧化石墨烯生长金纳米颗粒并通过巯基-金可逆键吸附N,N′-双(丙烯酰)胱胺作为交联剂可以合成具有均匀结构的聚丙烯酰胺水凝胶。这种方法合成的水凝胶其拉断时拉伸应力超过2MPa,拉伸应变超过2500%;且当材料具有缺口时,其仍能保持一定的机械性能(在具有1/4缺口时,该水凝胶拉断时拉伸应变接近2000%,拉伸应力接近1MPa);切断的材料在断口处经近红外光照射2min后,材料自愈合。其自愈合后拉伸应变超过2000%,拉伸应力超过1MPa。     

聚合物的非线性光学研究—原理及材料

近年来，有机非线性光学材料引起了放大学者们的极大兴趣，特别是有机高分子材料因其固有的性质（如机械性能、加工性能）倍受重视，在世界范围内已展开了广泛的探索研究工作。本文将简要叙述非线性光学材料的发展概况，在介绍有机非线性光学原理及材料的设计原则之后，主要对高分子非线性光学研究状况、结构、应用和发展前景进行了综述。     

Charge Density Distribution,Electrostatic Properties,and Impact Sensitivity of the High Energetic Molecule TNB: A Theoretical Charge Density Study

A quantum chemical calculation and a charge density analysis have been performed on the energetic molecule trinitrobenzene (TNB) to characterize its bond strength and to relate the bond topological parameters with the impact sensitivity. The optimized geometry of the molecule was calculated by the density functional method B3P86 with the basis set 6‐311G**. The bond topological analysis predicts a significantly low bond electron density (∼1770 e nm⁻³) as well as Laplacian of electron density (−1.67×10⁶ e nm⁻⁵) for C N bonds. This low value of the Laplacian indicates, the charges of these bonds are highly depleted, which confirms that these are the weakest bonds in the molecule. The N=O bonds bear a high negative value of Laplacian, reflecting that the bond charges are highly concentrated. The isosurface of the molecular, electrostatic potential (ESP) shows large electronegative regions at the vicinity of  NO₂ groups. Further analysis of ESP in the bonding region allows predicting the impact sensitivity. A sound relationship has been found between the ESP at the mid point of the bonds and its bond charge depletion. The positive ESP at the mid points of highly charge depleted C NO₂ bonds reveals that these bonds are the sensitive bonds in the molecule.     

Simple Relationship for Predicting Impact Sensitivity of Nitroaromatics,Nitramines, and Nitroaliphatics

This paper describes the development of a simple model for predicting the impact sensitivity of nitroaromatics, benzofuroxans, nitroaromatics with α‐CH, nitramines, nitroaliphatics, nitroaliphatics containing other functional groups, and nitrate energetic compounds using their molecular structures. The model is optimized using a set of 86 explosives for which different structural parameters exist. The model is applied to a test set of 120 explosives from a variety of the mentioned chemical families in order to confirm the reliability of a new method. Elemental composition and two specific structural parameters, that can increase or decrease impact sensitivity, would be needed in this new scheme. The predicted impact sensitivities for both sets have a root mean square (rms) of deviation from experiment of 23 cm, which shows good agreement with respect to the measured values as compared to the best available empirical correlations.     

EPDM/LLDPE/CB复合导电体系热敏特性研究

研究了ＥＰＤＭ／ＬＬＤＰＥ／ＣＢ复合型导电高分子材料电阻率的温度依赖性,炭黑含量的依赖性及热功率特性。确定了制备热敏导电材料的最佳ＥＰＤＭ用量。实验表明,在体系临界组成和ＥＰＤＭ含量（质量）１０～２０份时,炭黑粒子能得到较均匀分布,室温电阻率较低,且具有强ＰＴＣ效应,适于制作ＰＴＣ热敏材料。     

多硝基芳香化合物撞击感度的量子化学研究

采用了ＰＭ３方法对一系列多硝基芳香类化合物进行了几何构型的全优化和平衡几何构型下的电子结构计算，结果表明，对于引发键为Ｃ－ＮＯ２的炸药分子，Ｍｕｌｉｋｅｎ键级顺序与实测的Ｈ５０顺序一致。Ｔｅｔｒｙｌ中引入ＮＨ２后，分子中的－Ｎ（ＣＨ３）（ＮＯ２）基团被活化。     

Quantum Chemistry Derived Criteria for Impact Sensitivity

Energetic materials are a special and important kind of substance. Impact sensitivity, which refers to the vulnerability to explosion under external stimuli, measures the safety and reliability of an energetic material and is a critical property. Various efforts have been made to rationalize the impact sensitivity of different types of energetic materials. Since a chemical explosion is a chemical reaction dominated phenomenon, a comprehensive understanding of such explosive processes requires detailed information of chemical bonding and molecular interaction. Quantum chemistry provides a modern theory of chemical bonding and computational quantum chemistry is a powerful tool to investigate chemical phenomena. Even at the very beginning of computational quantum chemistry, researchers in the field of energetic materials have begun to apply quantum chemistry to explosive properties. In this paper we review the quantum chemistry studies on impact sensitivity and examine various quantum chemistry derived parameters used to rationalize the impact sensitivity ordering of various energetic materials.     

A New General Correlation for Predicting Impact Sensitivity of Energetic Compounds

This paper describes an improved simple model for prediction of impact sensitivity of different classes of energetic compounds containing nitropyridines, nitroimidazoles, nitropyrazoles, nitrofurazanes, nitrotriazoles, nitropyrimidines, polynitroarenes, benzofuroxans, polynitroarenes with α‐CH, nitramines, nitroaliphatics, nitroaliphatic containing other functional groups, and nitrate energetic compounds. The model is based on some molecular structural parameters. It is applied for 90 explosives, which have different molecular structures. The predicted results are compared with outputs of complex neural network approach as one of the best available methods. Root mean squares (rms) of deviations of different energetic compounds are 24 and 49 cm, corresponding to 5.88 and 12.01 J with 2.5 kg dropping mass, for new and neural network methods, respectively. The novel model also predicts good results for eight new synthesized and miscellaneous explosives with respect to experimental data.     

A Device for Testing Thermal Impact Sensitivity of High Explosives

A drop‐weight instrument is described to investigate the impact sensitivity of high explosives at elevated temperatures. This test is typically performed to discover potential safety aspects of either newly synthesized materials of unknown behavior. Normally, drop‐weight impact sensitivity tests are conducted at room temperature, since high explosives are often stored or handled at room temperature. The instrument described here has the capability of heating the samples from ambient to 300 °C prior to impact. The thermal impact sensitivities of PETN, TATP, HMX, and silver azide (AgN₃) as a function of temperature are obtained. The phase transition of HMX can clearly be observed by a significant decrease in the impact height in situ.     

Statistical Assessment Methods for the Sensitivity of Energetic Materials

The joint research project Particle Processing and Characterization was started in March 2003 under the EUROPA ERG1 Arrangement, with the objective to study the influence of crystallization and processing techniques on particle quality and its implication for the formulation of PBX with IM behavior. As sensitivity assessment is a crucial task of the project, impact sensitivity tests of HMX and RDX samples have been performed at two different laboratories, and several statistical techniques have been tested in addition to the standard BAM “1/6” and Bruceton “up and down” methods.     

低渗透油藏储层敏感性研究

储层保护是油田开发必须研究的课题,而保护储层最主要的就是要搞清楚油层可能的伤害类型,以及伤害的程度,从而采取相应的对策。在储层伤害评价研究中,储层敏感性评价是最主要的手段之一。依据行业标准,通过室内试验研究储层”五敏”性,为低渗透油藏开发作出建设性指导意见。