Properties of fresh and hardened concrete

The present paper reviews the literature related to the properties of fresh and hardened concrete published after the previous (12th) International Congress on the Chemistry of Cement held in Montreal in 2007.Workability and fundamental rheological properties, reversible and non-reversible evolution, thixotropy, slump loss, setting time, bleeding, segregation and practical issues related to formwork filling and pressure, are addressed among the properties of fresh concrete.Among hardened concrete properties compressive strength and other mechanical and physical properties of hardened concrete, such as tensile strength, elastic properties, shrinkage, creep, cracking resistance, electrical, thermal, transport and other properties are covered. Testing, interpretation, modeling and prediction of properties are addressed, as well as correlation with properties of fresh concrete and durability, effects of special binders, recycled and natural aggregates, fiber reinforcement, mineral and chemical admixtures. Special attention is given to the properties of hardened lightweight and self-compacting concrete.     

The structure and properties of solid gelatin and the principles of their modification

The structure and properties of gelatin in the solid state are discussed with respect to the structural, chemical and polymeric characterization of gelatin. Also the influence of casting conditions on the structural characteristics of gelatin, the relationship between the physico-mechanical properties of gelatin and the conformational state of the gelatin macromolecules and the effect of water on the structural and mechanical properties of gelatin are discussed. The effect of heat on the structural transformations and properties of gelatin are considered with reference to structural transformations, physico-mechanical properties, physico-chemical properties, internal stress and relaxation properties. The principles of modification of the physico-mechanical properties of gelatin are discussed, in particular the physical modification, physico-chemical modification and finally chemical modification.     

偏摩尔性质的图示分析

通过对二元混合物的摩尔性质与组分的摩尔分数的关系曲线进行分析,不仅可以明确混合物的摩尔性质,纯组分1和组分2的摩尔性质,而且可以明确组分1和组分2的偏摩尔性质。此外还可以对摩尔性质表达偏摩尔性质的公式进行推导,为学习偏摩尔性质的理解与应用提供帮助。     

Classification of properties of elastomers using the “optimum property concept.” I. Introduction

An attempt is made to distinguish properties of elastomers by types. “Basic properties of materials” or “network properties” in elastomers are properties which either increase or decrease from the liquid to the solid state of materials or over the range of the “elastomeric plateau” of elastomers. From these are distinguished properties that exhibit characteristic maxima and are therefore “maximum properties” or bivalued properties. Mechanical failure properties show the characteristics of “maximum properties.” The maxima in “maximum properties” generally do not coincide. This noncoincidence of the maxima with a change in a “basic property of a material” has major theoretical and practical implications, for example, it is the cause of the crossovers in the relative performance rating of materials under different test conditions. The implications of this noncoincidence of the failure property maxima on the relevance of correlations between these properties are discussed. A change in the testing conditions is reflected in a shift of the optimum value in a “basic property of a material” with respect to a specific “maximum property.” Data and certain conclusions in the literature are interpreted on the basis of this concept. Examples of the limitations of the validity of mathematical relationships are presented. Also, a definition of the term “state of cure” is proposed and a suggestion for the rating of severities of test equipment and applications of elastomeric materials recommended. The effect of increased degrees of crosslinking for a series of polymers and crosslinking agents is assessed. It is suggested that the “mechanisms” of failure properties will remain elusive if their rationalization is attempted on the basis of other failure properties, e.g., the mechanism of abrasion on that of tear strength or cut growth. The main purpose of this proposal is to provide support for a drastic reduction in laboratory testing by identifying those properties which can lead to different relative ratings in routine evaluations and actual applications. A more empirical approach to materials evaluations is recommended based on the calibration of laboratory instrumentation with respect to specific applications. A de-emphasis of routine evaluations of materials on the basis of their “maximum properties” seems to be justified.     

笼型倍半硅氧烷基聚合物的制备和结构性能以及应用

笼型倍半硅氧烷基聚合物是一种典型的多面体有机／无机分子复合物材料,因其具有优异的光、电、热、磁、声、力学和化学相容性等性能,所以近年来被引入较为尖端的技术领域进行研究和应用。本文归纳总结了笼型倍半硅氧烷基聚合物的现行制备方法,讨论了笼型倍半硅氧烷结构对材料性能的影响。最后,对笼型倍半硅氧烷基聚合物材料的应用领域和发展趋势进行了说明。     

Effect of processing conditions on the structure and properties of polypropylene spunbond fabrics

The structure and properties of a spunbond fabric are determined by numerous process variables. The development of fiber morphology is influenced and controlled by extrusion and quenching conditions. The properties of the fabric are the result of the properties of the filaments, their arrangement in the web, and the bonding conditions. It is therefore critical to understand the relationship between the process conditions and the properties of the fabrics produced. This study was conducted to investigate the effects of some of the important process variables on the structure and properties of the filaments and ultimately on that of the fabrics. Process variables such as polymer throughput rate, cooling and suction air speed, web basis weight, and bonding temperature were investigated. Filament samples were collected before bonding and were analyzed for various properties such as crystallinity, crystallite size, birefringence, density, thermomechanical stability, and tensile properties. The fabric samples were analyzed for tensile properties, tear strength, stiffness, and crystallinity. Ruptured strips obtained from the tensile test were observed with a scanning electron microscope to understand the failure mechanism. The results were statistically analyzed to evaluate the effect of process variables on the properties and to predict the properties for different process conditions. The findings are helpful in determining the optimum processing conditions so as to achieve the desired properties. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2355–2364, 2005     

不同比例甲醇汽油对橡胶的溶胀影响研究

研究了丁腈橡胶(NBR)、氟橡胶(FKM)及氢化丁腈橡胶(HNBR)等三种典型橡胶在不同比例甲醇汽油中的理化性能与机械性能变化,并与乙醇汽油体系的溶胀进行了对比研究。实验结果表明:NBR在不同甲醇比例的浸泡体系中,尺寸、质量及体积变化率均小于6%,且尺寸变化率最小,基本维持在3%以下;溶胀后NBR的机械性能下降显著。FKM各项理化性能及机械性能在汽油中的变化均最小,在M30甲醇汽油体系中最大,且随着时间延长,其理化性能变化逐渐增大,而机械性能则无明显变化;在相同条件下,FKM的理化性能及机械性能变化均大于NBR与HNBR,而NBR与HNBR的变化趋势基本一致;NBR在甲醇汽油中的溶胀程度与其在乙醇汽油中基本相当。     

Predicting mechanical properties of acrylonitrile-butadiene-styrene terpolymer in injection molded plaque and box

A methodology to predict mechanical properties in injection molded parts has been developed. Knowledge of part properties before actual molding and testing will be of immense help to part and mold designers in modification of design. This methodology involved the application of connectionist learning systems, injection molding computer simulation, and experimental evaluation of mechanical properties, to relate the thermomechanical history of injection molded parts to the resulting part properties of injection molded parts are dependent upon their thermomechanical history which in turn is greatly influenced by the processing conditions and part geometry. As the relationships between engineering properties and thermomechanical history are complex and highly nonlinear, the methodology developed was based on a backpropagation neural network algorithm that provided the means for a nonparametric mapping between the part properties and thermomechanical history. The proposed methodology has been successfully applied to two geometries, plaque and box. This methodology provides designers with the ability to predict mechanical properties in injection molded parts when significant thermomechanical history can be obtained from injection molding simulation.     

Mechanical properties of rigid thermoplastic foams—Part I: Experimental considerations

The through-thickness variation in the porosity of structural foam material is known to result in different “material properties” when mechanics based on homogeneous materials is used to interpret data from standard tensile and bend tests. Unresolved issues relating to structural design include the specification of the most useful test specimen, the identification of useful material properties, and the application of these properties to part design and analysis. This paper develops procedures for determining the mechanical properties of rigid thermoplastic structural foams, and for the application of these properties to the design of load-bearing components. Rather than molded specimens, it is suggested that specimens cut from large, edge-gated plates be used for determining mechanical properties of structural foams. By modeling foams as continuous but nonhomogeneous materials, it is shown that data from simple tensile and flexural tests can be used in structural analysis to systematically account for the through-thickness variation of material properties.     

Evaluation of dielectric cure models for an epoxy-amine resin system

The parallel-plate test fixture on a Rheometrics viscometer was electrically isolated so that the rheological and dielectric properties of a thermoset polymer system could be simultaneously measured. This enabled the relationship between the dielectric properties and the rheological properties to be directly examined. A close relationship was established between the dielectric properties (dipole relaxation time and specific conductivity) and the pre-gelation bulk viscosity. This relationship suggested that models similar in form to those used to describe the change in viscosity might be used to describe the changing dielectric properties. The limitations and advantages of two such models, which attempt to describe the time-temperature behavior of the dielectric properties, were then tested for use with a typical aerospace epoxy resin system.     

Microstructure dependent properties of polypropylene‐clay nanocomposites

The mechanical properties of melt processed polypropylene‐montmorillonite nanocomposites were studied as a function of clay content. The measurement of tensile properties at room temperature and dynamic mechanical properties over a wide temperature range reveal a decrease in modulus and tensile strength of the composite with increasing clay content. The origins of this anomalous result were examined in detail using X‐ray diffraction and differential scanning calorimeter, which averaged the microstructure over reasonable specimen volumes. Micromechanical models could be used to adequately describe the composite properties, provided appropriate properties for the matrix and particle were used. The matrix properties were found to affect the average properties significantly. © Wiley Periodicals, Inc. J Appl Polym Sci 103: 204–210, 2007     

Effect of annealing on the properties of poly(ether ether ketone)

The effect of annealing on the properties of poly(ether ether ketone) has been studied by changing annealing temperature and time. Crystallinity increases with annealing temperature, but is little affected by annealing time. Annealing time results suggest an improved crystalline perfection as annealing time increases. Higher crystallinity levels cause an increase in stress-related properties and a decrease in strain-related properties. Crystalline perfection, however, seems to produce an increase in stress-related properties, but it does not affect strain-related properties. Consideration has also been given to the effect of other possible parameters different from crystalline structure, such as crosslinking, on the variation of properties.     

Performance and properties of nonionic surfactants from linear secondary alcohols

Surfactants based on the linear secondary alcohols provide a new source of biodegradable detergents. The nonionic surfactants of these alcohols are discussed in relationship to their surfactant properties and performance in detergent formulations. The performance properties in detergent formulations are defined by the results of detergency and foam stability tests. The surfactant properties presented are viscosity, surface tension, wetting and alkaline color stability. The above properties of the nonionic surfactants from the linear secondary alcohols have been compared to the properties of the less degradable nonylphenol nonionics and to the nonionic surfactants from the linear alkylphenol, oxo alcohol and Ziegler alcohol hydrophobes.     

The structure of nonlinear blending models

Most empirically defined properties such as octane numbers blend non-linearly. That is, when measured properties of the components are combined in proportion to their amounts in the blend, the results can differ substantially from measured blend properties.Physical blending obeys certain common-sense rules of behavior. An example is that the order of mixing does not affect the properties of the result. Procedures for calculating blend properties, in order to reflect physical behavior, must therefore observe these same rules.This paper shows that all procedures obeying these rules must be of a certain form which can be thought of as consisting of three steps. In the first step component properties are “transformed” according to a fixed rule. In the second step transformed component properties are blended linearly. In the third step the same fixed rule (or its inverse) is applied to the results of the second step to give estimated blend properties.     

Produkteigenschaften und Verfahrenstechnik

Product properties and process engineering. The properties of solids are determined by their chemical composition, their state of dispersion, and their interfacial forces. They are largely responsible for the behaviour of the products during the manufacturing process and for the desired quality characteristics of the finished product. The aim of this survey is to illustrate the influence of particle size distribution and interfacial forces on product properties. The effects shown can be explained with the aid of a few physical modes. The first part shows how product properties can be adjusted to achieve a particular aim, principally by modifying the particle size. These include product-relevant properties such as filtration properties, miscibility, and potential for dust explosion, as well properties relevant to the (final) product such as colour and taste. As the particle size decreases, the forces acting between the particle become increasingly important. The second part of this article therefore focuses on those product properties which can be influenced by way of changes in the cohesive forces. Production-relevant properties are flow properties, bulk density, agglomeration behaviour; product-relevant properties are tablet stability and redispersibility of foods, dyes, etc. Among the cohesive forces, capillary forces deserve particular attention. The paper concludes with an account of their role in the manufacture and use of solids. The pore structure of an agglomerated solid is determined by capillary forces and the external forces required during the manufacturing process.     

Application of statistical mechanics to the analysis of various physical properties of elastomeric networks — a review

This paper examines the application of the statistical mechanics to the analysis of various physical properties of the elastomeric networks. The equilibrium properties of rubber-like networks are discussed, and also some dynamic properties, such as the relaxation spectrum of Gaussian networks. The paper covers a large spectrum of properties of polymer networks such as: fluctuations and chain dimensions in unimodal and bimodal network, effects of entanglements and constraints on the elastic properties of the network, segmental orientation, liquid-crystalline networks, small angle neutron scattering from networks, strain birefringence, elastic properties of filled networks, strain induced crystallization etc. The paper shows that the statistical mechanics can be successfully used to the analysis of almost all physical properties of rubber-like networks.     

Development of Short-Carbon-Fiber-Reinforced Polypropylene Composite for Car Bonnet

In this paper, short-carbon-fiber-reinforced polypropylene (SCF/PP) composites were prepared with melt blending and hot-pressing techniques. The tensile properties, flexural properties, hardness, and work of fracture (WOF) of this composite were investigated. Thermal stability of the composite was studied via the thermal gravimetric analysis (TGA). Finally, the mechanical properties of this composite were compared to mechanical properties of steel car bonnet in order to choose for car bonnet application. The properties of the composite prepared by 10% SCF/PP is comparable with the properties of carbon steel.     

PE抗菌食品保鲜膜的研制

先将抗菌粉体制成抗菌母料，然后将抗菌母料按一定比例添加至聚乙烯原材料中，通过混匀、吹塑等工艺制备了抗菌食品保鲜膜。研究了该抗菌食品保鲜膜的抗菌性能、物理机械性能、光老化性能和卫生理化性能。发现当抗菌母料的添加量为4％时，抗菌食品保鲜膜具有抗菌效果好、抗菌谱广等特点；而它的物理机械性能没有明显变化，光老化性能良好，且卫生理化性能均符合要求。     

EPDM/ENR共混胶力学性能的研究

探讨了三元乙丙橡胶(EPDM)和环氧化天然橡胶(ENR)的共混比、加料顺序、硫化体系对EPDM/ENR共混物的硫化特性、力学性能和耐热空气老化性能的影响。结果表明,共混比不同,共混胶的性能均有差异,且共混物的力学性能低于单组分的线性加和值,但综合比较而言,当EPDM/ENR=40/60时共混胶的力学性能较好;在所研究的四种加料顺序中,以配合剂先与EPDM制成母炼胶后再与ENR共混的这一种加料顺序下所得的共混物硫化胶的力学性能最好;采用半有效硫化体系所制得的共混物硫化胶的力学性能较好。     

Thermal and mechanical properties of nano-titanium dioxide-doped polyvinyl alcohol

Organic polymers exhibit poor thermal stability and inferior mechanical properties. Significant improvement in mechanical and thermal properties of polymers can be achieved by homogeneous distribution of inorganic materials preferably in nano size. In this study, these properties of polyvinyl alcohol were found to improve by addition of nano-titanium dioxide. Microwave irradiation method was used to prepare nano-titanium dioxide and doped in polyvinyl alcohol matrix to formulate the composite film. The spectral and morphological characterizations of the composites were carried out by the conventional techniques. Various mechanical properties were determined by Tinus Oisen universal testing machine. Thermal gravimetric analysis and differential scanning calorimetry were used for studying the thermal properties of the composites. Shift in decomposition temperature of polyvinyl alcohol indicated the enhanced thermal stability of polyvinyl alcohol. The composite also exhibited significant improvement in all the mechanical properties.