ASTM D6090-17 pdf download.Standard Test Method for Softening Point Resins (Mettler Cup and Ball Method).
6. Calibration of Apparatus Using a Primary Standard
6.1 This step, required only occasionally, is designed to establish that the temperature indicated by the instrument is in agreement with a known standard. A special cup with a bottom orifice of2.8 mm is used instead ofthe one specified for testing the resin. N OTE 1—The stainless steel ball is not used during calibration.
6.2 Reagent—Use either analytical reagent or primary stan- dard grade benzoic acid for the calibration. As this material is hygroscopic, it must be stored in a tightly sealed container, and replaced with fresh material from a newly opened supply if hydration or other contamination is suspected. 6.3 Procedure: 6.3.1 Filling the Sample Cup—Place the cup on a clean, flat surface and fill it with benzoic acid crystals. Hand press the material into the cup with a 9.2-mm rod of dowel stock or equivalent. Refill and repeat the pressing step until the cup is filled with benzoic acid. Remove any crystals from the exterior of the cup.
6.3.2 Heating—Preheat the measuring cell to 121°C, and maintain it at that temperature. Place the cartridge assembly containing the benzoic acid in position in the measuring cell, taking care that the slits for the light beam are properly positioned. With the instrument set in the dropping point mode, start the required method, which includes a waiting period of 30 s to allow temperature equilibration between the measuring cell and sample followed by an automatic temperature ramp of 0.2°C/min. The temperature will rise steadily at the correct rate until the drop point is reached, and then remain steady on the readout.
6.3.3 Cleaning—Immediately remove the cartridge assem- bly. Check to determine that the sample has passed through the light beam and no pre-triggering has occurred. Ifa malfunction is suspected, the entire procedure must be repeated. Inspect the apparatus carefully to ensure that no residue remains. Wash the cartridge parts with a suitable solvent to remove the last traces of the residue.
6.3.4 Interpretation—If the result is not 123.5 6 0.5°C, repeat the test. If the second value remains outside of the acceptable range, repeat the test using a fresh sample of benzoic acid. If the results remain outside of the acceptable range, the instrument requires recalibration or repair. Consult the manufacturer’s instruction manual.
7. Instrument Check of Apparatus Using a Secondary Standard
7.1 The primary calibration standard, benzoic acid, might not have a dropping point similar to the softening point of the resin being tested. In such cases, it is desirable to calibrate the instrument using a secondary standard having a dropping point similar to that of the test sample. Materials suitable for use as secondary standards are listed, but are not limited to those, in Table 1. Demonstration of conformance to the dropping point of benzoic acid should be completed before a secondary standard is read.
7.2 Follow the same procedure as in 6.3.2 and 6.3.3 but start about 3°C below the actual dropping point of the secondary standard. 8. Preparation of Sample
8.1 Fold the tab on an oil-free disposable aluminum weigh- ing dish to a horizontal position and pinch a pour spout into the dish directly opposite the tab. Weigh 5 to 10 g of resin into the dish.
8.2 Place the dish and sample on a preheated hot plate and cover with a 600-mL or larger beaker. Heat the sample until it is almost melted.
8.3 Remove the beaker from the hot plate, grasp the tab with forceps or needle-nose pliers, and stir the sample with a probe-type thermometer until it is completely melted and homogeneous. Avoid entraining air into the sample melt. ASTM D6090 pdf download.