Processing history

Tool life tests are used to evaluate the effects of changes in tool materials, cutting variables, processing history, workpiece composition, or workpiece microstmcture. Tool life, T, and cutting speed, can be related by the following equation ... 

Because of the effects of impurity content and processing history, the mechanical properties of vanadium and vanadium alloys vary widely. The typical RT properties for pure vanadium and some of its alloys are hsted in Table 4. The effects of ahoy additions on the mechanical properties of vanadium have been studied and some ahoys that exhibit room-temperature tensile strengths of 1.2 GPa (175,000 psi) have strengths of up to ca 1000 MPa (145,000 psi) at 600°C. Beyond this temperature, most ahoys lose tensile strength rapidly. 

Since TPEs typically consist of two incompatible phases at service temperature, the hnal properties of TPEs are influenced by the properties of the individual phases and the interface. It is therefore necessary to consider several factors, like the constituents nature, their molecular weight and relative amounts, processing history, etc., to understand the properties of TPE. The influences of various factors on TPEs properties are discussed below. 

Polymer structure and formulation. As an example, Woo et al. [7] measured OIT values for series of commercial PVC resins and polyester thermoplastic elastomers (TPEs). The researchers used the ASTM D3895-80 procedure, but substituted air as the oxidising gas instead of pure oxygen. A dependency on thermal processing history of the TPE film samples appeared to influence the measured OIT in the PVC study, chemically different chain ends affected polymer stability and hence OIT values. 

The work on the electrochemical generation of a solution of ceric sulphate from slurry of cerous sulphate in 1-2 M sulphuric acid was abandoned by BCR due to difficulties encountered in handling slurried reactants. A 6kW pilot reactor operated at 50 °C using a Ti plate anode and a tungsten wire cathode (electrolyte velocity about 2ms 1) produced 0.5 M Ce(S04)2 on the anode with a current efficiency of 60%. The usefulness of Ce(IV) has been limited by the counter anions [131,132], Problems include instability to oxidation, reactivity with organic substrates and low solubility. Grace found that use of cerium salts of methane sulfonate avoids the above problems. Walsh has summarized the process history, Scheme 6 [133],... 

Scheme 6. Process history of indirect naphthoquinone synthesis using electrogenerated Ce(IV) [133]...

Charcoal production, from wood, 26 360 Chardonnet, Hilaire de, 11 248 Chardonnet process, history of,... 

Mineral sources, lanthanide and yttrium distribution in, 14 6311 Mineral spirits, solvent for cosmetics, 7 832 Minerals processing, history of, 16 596t. 

Rubber Chemistry and Technology 65,No.5,Nov./Dec.l992,p.932-55 INFLUENCE OF COMPOSITION AND PROCESSING HISTORY ON THE CELLULAR MORPHOLOGY OF THE FOAMED OI.EFINIC THERMOPLASTIC ELASTOMERS Dutta A Cakmak M Akron,University... 

To conclude this section on polymols, we should note that we have used the term polymer almost exclusively to refer to organic macromolecules. The term plastic refers not only to organic substances of high molecular weight, but also to such substances that at some point in their manufacture have been shaped by flow. Thus, the term plastic is more specific than the term polymer, and this term carries with it an indication of its processing history. As we will see in Chapter 7, there are many materials that can be considered polymers, yet are formed by routes other than melt processing. 

It is known that the structures present in a polymer reflect the processing variables and that they greatly influence the physical and mechanical properties. Thus, the properties of polymeric materials are influenced by their chemical composition, process history, and the resulting morphology. Morphological study usually requires two preparatory steps prior to the study itself selection of instrumental techniques and development of specimen preparation techniques. Structural observations must be correlated with the properties of the material in order to develop an understanding and applications of the material. Figure 22.1 illustrates the types of optical microscope (OM) techniques commonly used to examine polymer specimens [2]. 

Available data from process history and testing clearly identified... 

The effective magnitude of cohesive effects depends primarily on two factors the intensity and nature of the cohesive forces (e.g., electrostatic, van der Waals, capillary) and the packing density of the material (which determines the number of interparticle contacts per unit area). This dependence on density is the source of great complexity cohesive materials often display highly variable densities that depend strongly on the immediate processing history of the material. 

Fig. 9. Phase diagram showing the temperature versus the copolymer composition. The dashed areas correspond to the transition region. The frontiers among the different regions depend on sample preparation as well as on sample thermal and processing history. The fraction of ferroelectric phase, Ff, increases with increasing PVF2 content...

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