In this study the tensile stress/strain behavior of various consumer plastic thin film materials was measured using a low mass mechanical analyzer. Film thicknesses varied from 19 mm to 66 mm (0.75 mil to 2.6 mil). In this study the force applied to the samples was ramped at 0.05 N/min from 0.05 N to 1 N and sample strain was followed. All measurements were made at ambient conditions. The tensile behavior of the consumer products were compared qualitatively and quantitatively. Three mechanical phenomena were observed in the materials: linear elastic behavior, a strengthening or increase in modulus, and yielding or rapid elongation with minimal changes in stress. In the linear elastic region modulus was measured as defined by the inverse of the slope of the stress versus strain curve. Modulus values of 87 MPa to 6 GPa were observed.

Most military’s greases are formulated for use in severe service environments and multipurpose applications. To meet these requirements, the specifications usually require a wide operational-temperature range; excellent water and storage stability; good shear and oxidation stability; good antiwear and load carrying capacity; and rust and corrosion protection. These physical and chemical properties can change during storage and use. Most of these changes are interrelated and can eventually lead to lubrication failure.?

DSC is the most direct and sensitive approach for characterizing the thermodynamic parameters controlling noncovalent bond formation (and therefore stability) in proteins and other macromolecules. In an experiment requiring only a few micrograms of material, the protein is thermally unfolded, allowing the relationship between enthalpy and entropy of the denaturation process to be established in about one hour. Correlating thermodynamic properties to stability is necessary for the rational design of engineered proteins and protein therapeutics.

Greases are important lubricating systems that are very interesting to a rheologist since they often exhibit strongly time-dependent behavior [thixotropy], and are able to shear thin by several orders of magnitude in terms of they are to function as lubricants, and keep moving surfaces apart from each other, even at high relative velocities. Traditionally greases are measured in terms of base oil viscosity, pumpability [Lincoln Ventmeter] and via a penetrometer [amongst other tests!]. These test types all provide a single number or data points can be obtained under varying circumstances of say temperature or in that an unworked sample is compared with a worked sample, but too often the results form only a relative measure of the grease.

Thermoset polymers form the matrix in filled plastics and fiberreinforced composites used in a diversity of products. These range from consumer items and auto body panels to advanced composites for printed circuit boards (PCBs), aerspace structural components such as the Space Shuttle payload bay door and jet engine cowls and ducts, and expensive, high-performance sports equipment. Also, thermosets are used extensively as adhesives, molding compounds, and surface coatings, including protective solder masks for PCBs.

Creep recovery measurements on anionically polymerized polystyrenes and commercial low density polyethylene have been performed with a new magnetic bearing rheometer. Due to the very small residual torque, a key feature of the magnetic bearing rheometer, small recoverable compliance values in the linear viscoelastic regime could be accurately measured. The equilibrium compliance Je obtained is compared to the ratio of G’/G’’2, evaluated from oscillation measurements in the terminal region (low frequency). Excellent agreement could be found for the narrow distributed PS with a molecular weight from 13,000 to 330,000 g/mol. Finally the shear compliance of a commercial PS was converted to the dynamic moduli G’ and G’’ using approximation formulas by Schwarzl to extend the frequency range, large enough to fully describe the viscous and elastic behavior of the material.

The challenge for studying fast changing systems with rheology such as UV initiated polymerization and crosslinking is multifold. These materials react within seconds and the moduli change over 2 to 3 decades. UV lights must irradiate the sample homogeneously over a short time period and fast data acquisition. An option for UV curing, using parallel plate has been designed for the ARES rheometer. A fast data sampling device with a new correlator has been developed to provide up to 500 dynamic mechanical data points per second, so the modulus build up can be easily followed. Results are obtained for an acrylate-based pressure sensitive adhesive. The curing reaction is studied as a function of the sample gap, UV intensity and UV exposure time.

In an oscillation shear experiment, the material is subjected to either a sinusoidal strain or stress and the corresponding response is measured. The ratio of the output and input signals is referred to as the transfer function or material function (Figure 1). When a sinusoidal deformation or deformation rate is applied, the material’s response is the stress. The resulting material function is either the modulus or the viscosity; if a stress is applied and the strain measured, the material function is the compliance.

Although membrane proteins are very difficult to work with, ultra-sensitive calorimetry can over-come the limitations of many other physical characterization techniques to provide insights into the factors driving membrane protein/lipid assembly and controlling the stability of the conplexes.

Waterborne coatings do not have a priori, the same advantageous rheological properties as solvent-based coatings. If not formulated correctly, they are much inferior with regard to flow properties, leveling, application properties, film build, etc.. In order to obtain the desired performance, thickeners and rheological modifiers are added to improve waterborne paints. Conventional thickeners like cellulosics, high molecular weight polymers or inorganic clays increase the viscosity during application, but they provide poor spatter resistance and leveling to the paint. Associative thickeners are low molecular weight, water soluble polymers like modified alkali swellable emulsions, and provide overall good performance to a waterborne coating.

Rheological testing of thermoplastic materials can be performed on both solid samples and on melts. This is important because the choice of material form and physical state is more than a matter of convenience: Product performance issues usually are related to solid samples properties; process ability issues can be correlated with polymer melt properties. In either case, since rheology is an indirect and non-unique measurement of structure, the application of rheology to solving processing and product performance problems often reduces to comparative analysis of good and poor performing samples.

Fluid materials, by definition, are systems which flow when subjected to stress. How they respond to an input stress is the heart of rheological testing and may be a complex issue. There are many types of fluids: pure substances, mixtures, dispersions and solutions, falling into the categories of either simple or structured fluids. Each has its own unique behavior when subjected to stress. In general, when a material has a uniform phase, such as a solution or pure substance, it is referred to as a simple fluid. Materials which contain more than one phase, such as solid particles dispersed in a liquid, gas particles in foam or an emulsion of immiscible liquids are considered structured fluids since their rheological behavior is in general dominated by the interactions of the constituents.

Thermo-analytical experiments were used to characterize prepared Al?Mg and Al?Ti powders. Ignition temperatures for the Al?Mg powders vary from approximately 860 to 1060 K for the range of heating rates covered in the present ignition experiments. Kinetic correlations using Kissinger analysis were made to identify the reactions that may cause or contribute to ignition. Ignition for both Al?Mg and Al?Ti powders is associated with low-temperature, sub-solidus reactions.

Modulated thermomechanical analysis is shown to be a useful tool for determining thermodynamic and kinetic, reversing and nonreversing length changes in materials when these thermally induced events take place simultaneously. This ability to separate thermodynamic from kinetic events aids in the interpretation of the thermal curve, measures expansion and contraction taking place at the same time and provides a more accurate estimation of the glass transition temperature than the softening temperature. MTMA may have applications in other measurements where thermodynamic and kinetic length changes occur simultaneously. Such examples may include the softening of organic or inorganic glasses, heat set films and fibers, and shape memory alloys.

Modulated DSC is a powerful tool for materials characterization. Like any other precision technique, failure to use the optimum experimental conditions can result in sub-par performance. Following the suggestions listed in this paper should help you to design your MDSC experiment so that you derive the highest quality data.

The simple yet highly sophisticatd character of these instruments has a major drawback: their simplicity significantly increases the potential foor misinterpreting experimental results.

Starches are natural products used most extensively as thickening agents in the food industry, but are also widely employed in the adhesives, paper coatings, wood, packaging, and pharmaceutical industries. A fundamental rheological measurement conducted routinely on starches is the evaluation of the gelatinization process. This is accomplished by measuring the viscosity of the starch suspension, while heating and cooling under specific testing conditions. The resultant curve, referred to as the pasting curve, yields important starch performance parameters, including the pasting temperature, peak viscosity, holding strength, and final viscosity.

Materials such as coals, coal products (e.g., chars, briguettes) and activated carbons are a self-heating hazard in storage and transportation. Accordingly, work was carried out in the 1970’s (1,2) largely at the Fire Research Station in the UK, which led to the formulation of a test (3,4) for predicting whether or not a particular coal or carbon material was a self-heating hazard. The test wich is very widely used up to the present time, focuses on the quantity critical ignition temperature, and the present author has shown (5) that this is not the most suitable quantity around which to build such a test. The critical ignition temperature provides an indication of self-heating hazards only in the limit where all susceptible materials have the same activation energy (usual symbol E, units J mol-1) for their reaction with atmospheric oxygen. This is very far from the truth, and consequently the tests are unreliable.

A pharmaceutical compound (10 mg/mL) was dissolved at pH 4 and at pH 10, then both samples were simultaneously heated in a MC-DSC. Thermal activity was evident, indicative of chemical reactions occurring in the samples. Under basic conditions the reaction was endothermic, while in acidic conditions the reaction was exothermic. When the logarithm of the thermal activity was plotted versus the reciprocal temperature, it became apparent that there were at least two reaction pathways with different activation energies at pH 10, while at pH 4 there was only evidence of a single degradative reaction. This information would be very useful in designing traditional HPLC stability screening studies since under basic conditions, this compound should clearly be stressed at lower rather than higher temperatures.

Solvated systems can be studied by techniques such as moisture sorption, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and isothermal calorimetry. Although in theory any one of these techniques can provide adequate data on the energy changes associated with solvation or desolvation, in practice isothermal microcalorimetry often provides superior data on pseudo-polymorphs, especially when only small (milligram) samples are available, or when unexpected results are obtained from other thermal techniques. For example, TGA was unable to detect formation of a drug hydrate in the presence of lactose monohydrate since there was no net change in mass associated with exchange of water between the drug substance and the lactose excipient.

Microcalorimetry has been successfully applied to the study of electrochemical components and structural materials during the design and development of new batteries. The Ampoule form of the Microcalorimeter is ideally suited to the examination of the electrochemical materials in forms such as pastes, liquids, powders or even the entire battery. The method is non-destructive, Analysis of the activity of the components is fast; for example, a reaction normally taking several weeks or months can be observed within a few hours when using this technique. The variable full-scale readout range of the instrument ensures a sensitive measurement of the activity of a wide range of samples,

Although it is often assumed that the pH of a buffer solution remains constant during a differential scanning calorimetry (DSC) experiment, the pK of a buffer can in fact change signifi cantly between 0 oC and 100 oC. Such pH changes can result in sample denaturation, aggregation and precipitation that, in the absence of knowledge about the temperature stability of the buffer, could erroneously be ascribed solely to temperature-induced unfolding of the biomolecule.

It is well known that there is an equivalence of the effects of time and temperature on the rheological properties of viscoelastic materials1. At low temperatures a material will behave in the same fashion as at high frequency, and at high temperature the material will behave as it would at low frequency. Data in a range of temperatures over modest frequency ranges( see figure 1) can be collected and arranged to predict the behavior over a wider frequency range than possible in practical testing. Bear in mind that very low frequencies can take days or weeks for measurements, and ultra high frequencies cannot be measured by existing instruments. The modulus data can then be shifted horizontally along the abscissa to overlap forming a smooth curve. This approach allows the generation of master curves of modulus data spanning considerably wider ranges of time (frequency) and/or temperature than the range of the original data (see figure 2).

Traditionally, pure gum rubber rheological properties are tested and certified using the well-known Mooney viscometer according to ISO 289. This test is, in most of the cases, used for polymer choice for a specific recipe. Most rubber technologists recognize that this method fails to provide compound flow behavior information, especially when comparing polymers of identical ML(1+4) from various sources. Money Stress Relaxation has improved polymer source discrimination but is not widely adopted by polymer users although an increasing number of polymer suppliers are now providing this characteristic.

Injection molding big parts and complex shapes with rigid PVC is probably the most demanding PVC process in terms of melt viscosities. PVC is a material with physical and chemical characteristics that make it process slightly more difficult in comparison with other thermoplastics. The high viscosity contributes to the development of a high amount of heat when the material is subjected to the shear applied by the screw during the plasticization. The thermal instability of the compound results from the breakdown either when it is heated at temperatures higher than admissible or when it remains for too long at high temperature. Hence evaluating the material behavior in terms of its thermal stability and melt viscosity is important for end-users of PVC compounds. This paper attempts to assist engineers who are faced with the task of screening compounds from various suppliers, prior to full-scale evaluation of the compound in production machines.

本文阐述了如何用DSC分析方法应用于药物学开发 因为晶型结构的药物一般具有较好的储存稳定性，制药公司一般偏好采用结晶的化合物作为新药的配方组成成分。然而通常遇到的问题是药物容易形成多种结晶结构的多晶型。因为多晶型在物理性质上存在很大的差异，例如由溶解速率的不同而导致的生物活性上的不同，因此控制药物的浓度和晶型形式就显得尤为重要。

DSC是在定义的气氛下测量样品发生转变时的温度与热流随温度或时间变化的函数关系；MDSC是在传统DSC上的提高，它将总的热流分解成可逆热流(热容)和不可逆(动力学)组分。可逆的信号包括热容，例如玻璃化转变和熔化；不可逆热流信号包括动力学成分，如结晶、结晶的完整性和重结晶、以及固化和分解等。

一个医药公司想比较两种洗液的扩散速度，以确定不同配方的作用效果。可是两种洗液的量非常少，难以用合适的方法进行表征。

Although membrane proteins are very difficult to work with, ultra-sensitive calorimetry can overcome the limitations of many other physical characterization techniques to provide insights into the factors driving membrane protein/lipid assembly and controlling the stability of the complexes.

因为药物晶体具有很好的储存稳定性，药物公司在新药物配方中倾向采用结晶化合物。然而经常碰到的问题是药物存在多种结晶形式，即通常所说得多晶型。由于多晶型的每种晶型的物理性质、比如分散速率和生物活性有很大的不同，因此控制结晶的形势和含量显得十分重要。