Test method temperature index

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. 

The pour point (ASTM D-97, IP 15) is the lowest temperature at which the fuel oil will flow under specified conditions. The maximum and minimum pour point temperatures provide a temperature window where a petroleum product, depending on its thermal history, might appear in the liquid as well as the solid state. Pour point data can be used to supplement other measurements of cold flow behavior, and the data are particularly useful for the screening of the effect of wax interaction modifiers on the flow behavior of petroleum. The pour point should not be confused with the freezing point, which is an index of the lowest temperature at which the crude oil will flow under specified conditions. Test methods (ASTM D-2386, ASTM D-5901, ASTM D-5972, IP 434, IP 435) for the freezing point are not usually applicable to fuel oil but are more applicable to diesel fuel and aviation fuel. 

Two methods (ASTM D-1218, ASTM D-1747) are available for measuring the refractive index of viscous liquids. Both methods are limited to lighter-colored samples for best accuracy. The latter test method (ASTM D-1747) covers the measurement of refractive indexes of light-colored residual fuel oil at temperatures from 80 to 100°C (176-212°F). Temperatures lower than 80°C (176°F) may be used provided that the melting point of the sample is at least 10°C (18°F) below the test temperature. This test method is not applicable, within reasonable standards of accuracy, to liquids having darker residual fuel oil (having a color darker than ASTM Color No. 4 ASTM D-1500). 

Long-term behavior of insulation systems can be estimated after the temperature index has been determined by the impregnated twisted pair test (IEC 172, criterion breakdown voltage) or helical coil test (IEC 1033, Method B, criterion bond strength). The two tests lead to differing results that do not correlate and the end user of the system enameled wire/impregnating resin has to decide which test is applicable for his electrical appliance. It is important to choose a suitable combination of materials and to ensure close cooperation between manufacturers of electrical insulating materials and those who later process them. 

The properties of a resin which can be determined by simple test methods are shown in Table 18. The solids content of a resin usually is determined by the so-called dish method at 120°C for 2h [different times and sometimes lower temperatures (105°C) are often used as several variations of this method exist]. Even if it is a rather simple test, some deviations in the results might occur because not only does all water present as solvent in the liquid adhesive resin evaporate, but also a further condensation reaction with further water elimination takes place. Both liberate condensation water and this additional water is evaporated as well. The more severe the conditions during drying, the lower the solids content measured. Also some details of the test, such as the type of oven, the number of dishes in the oven at the same time, or recirculation of air or not, can influence the results of the test. The refractive index can be used as a quick method for the determination of solids content, however, the correlation between these two charaeteristie resin values is sometimes rather poor and not the same for all resins. The density is oifly important when using volumetric adhesive dosing systems, but not as a quality parameter of the adhesive. 

As an example, there could be confusion concerning the relationships between relative humidity index, heat distortion temperature (HDT), and warp temperature. These tests provide specific information, and there is generally no correlation of their results. Clarifications of these tests are given in their respective test-method descriptions. 

In this small-scale test method, 460-mm (18-in.) x 150-mm (6-in.) wide and up to 25-mm (1-in.) thick vertical sample is used. The sample is exposed to a temperature of 670 + 4 °C at the top from a 300-mm (18-in.) x 300-mm (12-in.) inclined radiant heater with top of the heater closest to and the bottom farthest away from the sample surface. The sample is ignited at the top and flame spreads in the downward direction. In the test, measurements are made for the arrival time of flame at each of the 75-mm (3-in.) marks on the sample holder and the maximum temperature rise of the stack thermocouples. The test is completed when the flame reaches the full length of the sample or after an exposure time of 15-min, whichever occurs earlier, provided the maximum temperature of the stack thermocouples is reached. Flame spread index (7s) is calculated from the measured data, defined as the product of flame spread factor, F, and the heat evolution factor, Q. 

Melt Index A single point identification of resin melt viscosity, measured in grams per 10 minute period passing through a specific orifice size at a cenain temperature, as dictated by test method ASTM D1238. 

The reference temperature NDT, RTf, is also an index temperature used as a normalization tool to compare the behaviour of different materials and different heats of materials. The RTndt is determined according to procedures outUned in the ASME Boiler and Pressure Vessel Code (ASME, 2013 a) and is a combination of the NDT temperature and Charpy impact test results. Briefly, the RTndt is the higher of either the NDT temperature or Tso - 60°F (33 C), where T q is the temperature at which three Charpy impact specimens achieve energy and lateral expansion values of at least 50 ft-lb (68 J) and 0.035 in. (0.89 mm), respectively. A more detailed discussion of this reference temperature can be found in Chapter 1. Similarly, for WWER RPVs, the CVN-based temperature called the critical temperature of brittleness, 21, is used as a reference temperature. These references are discussed in subsequent sections as used for various test methods. 

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