INDEX elevated temperatures

ISO 4589-3 Plastics—Determination of Burning Behavior by Oxygen Index-Elevated-Temperature Test, ISO, Geneva, Switzerland, 1996. 

The mineral talc is extremely soft (Mohs hardness = 1), has good sHp, a density of 2.7 to 2.8 g/cm, and a refractive index of 1.58. It is relatively inert and nonreactive with conventional acids and bases. It is soluble in hydroduoric acid. Although it has a pH in water of 9.0 to 9.5, talc has Lewis acid sites on its surface and at elevated temperatures is a mild catalyst for oxidation, depolymerization, and cross-linking of polymers. 

Over the years many attempts have been made to provide some measure of the maximum service temperature which a material will be able to withstand without thermal degradation rendering it unfit for service. Quite clearly any figure will depend on the time the material is likely to be exposed to elevated temperatures. One assessment that is being increasingly quoted is the UL 746B Relative Temperature Index Test of the Underwriters Laboratories (previously known as the Continuous Use Temperature Rating or Index). 

Eor amine-containing polymers, DMF is often a good choice of solvent. DMF can also be a good choice for polymers of higher carboxylic acid content. However, DMF does present some experimental difficulties. It must be run at an elevated temperature, typically 60°C, because of its viscosity. Also, because most polymers have a much lower refractive index response in DMF, the signal-to-noise ratio for a polymer in this solvent is diminished versus the same ratio for common acrylates in THF. 

The separation was carried out on a TSKgel Amide-80 column 4.6 mm i.d. and 25 cm long with a mobile phase consisting of a 80% acetonitrile 20% water mixture. The flow rate was 1 ml/min and the column was operated at an elevated temperature of 80°C. The saccharides shown were 1/ rhamnose, 2/ fucose, 3/ xylose, 4/ fructose, 5/ mannose, 6/ glucose, 7/ sucrose and 8/ maltose. The analysis was completed in less than 20 minutes. These types of separations including other biomonomers, dimers and polymers are frequently carried out employing refractive index detection. 

The SEC mechanism demands only an isocratic (constant composition) solvent system with normally a single solvent. The most frequently used organic solvents are THF, chloroform, toluene, esters, ketones, DMF, etc. The key solvent parameters of interest in SEC are (i) solubility parameter (ii) refractive index (iii) UV/IR absorbance (iv) viscosity and (v) boiling point. Sample solutions are typically prepared at concentrations in the region of 0.5-5 mg mL-1. In general an injection volume of 25-100p,L per 300 x 7.5 mm column should be employed. For SEC operation with polyolefins chlorinated solvents (for detector sensitivity and increased boiling point) and elevated temperatures (110 to 150 °C) are required to dissolve olefin polymer. HFIP is the preferred solvent for SEC analysis of polyesters and polyamides. 

ISO 4589-3 1996 Plastics - Determination of burning behaviour by oxygen index - Part 3 Elevated-temperature test... 

In most cases, calibration curves were determined at ambient or elevated temperatures using the Waters 150C High Temperature Gel Permeation Chromatograph which includes a sensitive refractive index detector. Otherwise, a modular system consisting of a Waters Model M6000A Solvent Delivery System, a Waters Model U6K Injector and a Waters Model 401 Refractometer, were used at ambient temperature. The mobile phase at room temperature was... 

White crystal or granule strong saline taste no odor slightly hygroscopic density 2.429 g/cm at 25°C refractive index 1.712 subhmes at elevated temperatures vapor pressure 54.75 torr at 300°C and 758.2 torr at 395°C highly soluble in water 60.6 g and 75.5 g/100 mL at 0° and 20°C, respectively—solubility increasing approximately 16 to 18 g/100 mL for every 20°C increase in temperature. 

Reconstruction of all the three low-index faces of Au single crystal under elevated temperature has been described in several papers. This subject has been discussed in detail by Dakkouri and Kolb [335], as well as (also for other metals) by Kolb [336], and Gao et al. [337, 338]. A recent concise review of Au reconstruction, including experimental details of the surface preparation, has been published by Trasatti and Lust [4]. 

Liquids with equal solubility parameters are miscible, there is no heat of mixing. With increasing difference of <5, two phases coexist, which become miscible at elevated temperature, at the critical consolute temperature Tc. Tc increases with the difference of the <5 s and with the mean molar volume of the two liquids. Another polarity scale was recently introduced by Middleton and co-workers13 based on the bathochromic shift of UV-visible 2max. The obtained spectral polarity index ranks the solvents at one end of the scale is the nonpolar perfluorohexane and at the opposite the highly polar and acidic l,l,2,3,3.3-hexafluoropropan-2-ol. The latter is much more polar than its hydrocarbon analog. 

A short guard column containing the same stationary phase as the analytical column is placed before the analytical column to protect it from contamination with particles or irreversibly adsorbed solutes. A high-quality pump provides smooth solvent flow. The injection valve allows rapid, precise sample introduction. The column is best housed in an oven to maintain a reproducible temperature. Column efficiency increases at elevated temperature because the rate of mass transfer between phases is increased. Mass spectro-metric detection provides quantitative and qualitative information for each substance eluted from the column. Ultraviolet detection is most common and it can provide qualitative information if a photodiode array is used to record a full spectrum of each analyte. Refractive index detection has universal response but is not very sensitive. Evaporative light scattering responds to the mass of each... 

ISO 4589-3, Plastics—Determination of Burning Behaviour by Oxygen Index—Part 3 Elevated-Temperature Test, International Organization for Standardization, Geneva, Switzerland. 

Some of the test methods being used to measure the processing stability of polypropylene include melt flow drift measurements at elevated temperatures using an extrusion plastometer (melt indexer), melt viscosity retention measurements using a torque rheometer, retention of melt flow after repeated extrusions, and injection molded spiral test measured by the flow in inches at various temperatures and the retention of melt flow of the injected spirals. The nine commercial resins were evaluated by these methods. 

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