ASTM D6875 Standard Test Method for Solidification Point of Industrial Organic Chemicals with a Thermistor

The standard "ASTM D6875 Standard Test Method for Solidification Point of Industrial Organic Chemicals with Thermistor" developed by the American Society for Testing and Materials (ASTM) describes a general test method for determining the solidification point of most organic chemicals having significant heats of fusion and solidification points between 4°C and 41°C.

Other test methods for determining the freezing point and solidification point of aromatic hydrocarbons include ASTM D852, ASTM D1015, ASTM D1016, ASTM D3799, ASTM D4493, and ASTM D6269 standards.

This test method is applicable only to relatively pure compounds. The solidification point depression depends on the impurity concentrations. For purposes of determining compliance with applicable specifications using this test method, an observed value or a calculated value should be rounded to the nearest unit in the last digit to the right used to express the specification limit, in accordance with the rounding method defined in ASTM E29.

The ASTM D6875-12 standard test method is used to measure the solidification point of most organic chemicals using a thermistor. The maximum temperature at which the liquid phase of a substance is in proper equilibrium with a relatively small portion of the solid phase is noted. These methods require a cooling medium to achieve a solidification point between 4 and 30°C. The sample container is sealed with a two-hole stopper. The thermistor is placed in one hole and the stirrer shaft in the other. The bath temperature is set to 5°C plus/minus 1°C below the expected solidification point of the sample. The tests use a sample container with a thick-walled outer tube of 18 mm diameter, 14 mm inner diameter, and 150 mm length. The temperature bath is required to control the temperature to 5°C plus/minus 1°C below the expected solidification point. The thermistor is housed in a stainless steel housing with a resistance greater than 2kΩ at 25°C, and the calibration accuracy is plus/minus 0,01°C.

For the purposes of this standard, the solidification point is the temperature at which the liquid phase of a substance is in approximate equilibrium with a relatively small portion of the solid phase. The solidification point, unlike the freezing point, is described in ASTM D1015. The interpretation of mole percent in terms of freezing point is provided in ASTM D1016.

This test method can be used for process control during the production of organic chemicals, determination of specifications, development and research studies, and determination of contamination during shipment.

Samples should be collected in accordance with ASTM D3437, ASTM D3438, ASTM D3852, and ASTM D4297. At room temperature, the entire solid sample is melted by heating it to approximately 10°C above the solidification point and then spun to ensure homogeneity. If required by the standard or by agreement with the customer, the sample should be dried. p-xylene should be dried before testing by placing approximately 100 g of material in a 400 mL Erlenmeyer flask and adding approximately 50 g of 3A molecular sieves.

A two-hole stopper is inserted into the sample container. A thermistor is inserted into one hole. The stirrer shaft is inserted into the other hole. The temperature bath is set to 5°C plus/minus 1°C below the expected solidification point of the sample.

Equipment used in the tests includes:

• Ohm meter: A device that can measure resistance to the nearest 0,1 ohm with direct temperature reading in the range of 1000 to 10 000 ohms.
• Sample container: It is a thick-walled test tube with an outer diameter of 18 mm, an inner diameter of 14 mm and a length of 150 mm.
• Stirrer: Consists of 1 mm stainless steel wire bent into a circular shape at right angles to the shaft so that it can move freely in the annulus space between the thermistor and the wall of the test tube.
• Mixing apparatus (optional): The apparatus shown in the figure is considered an acceptable substitute for manual mixing.
• Temperature bath: It can be checked that the expected solidification point is 5 degrees plus/minus 1 degree below.
• Thermistor: Housed in a stainless steel housing with a resistance greater than 2K ohms at 25 degrees. Calibration accuracy is plus/minus 0,01 degrees. The resistance drift is equivalent to less than plus/minus 0,01 degrees/year. The thermistor must be calibrated to cover the operating range.

The ASTM D6875 standard is considered important, especially in the field of geosynthetics and civil engineering, for the following reasons:

• Ensures product consistency and quality: By providing a standard method for measuring mass per unit area (typically in g/m²), this standard helps manufacturers and users verify that geotextiles meet design and performance specifications.
• Supports engineering design: Mass per unit area is an important parameter used by civil engineers to select suitable geotextiles for applications such as filtration, drainage, separation, reinforcement and erosion control.
• Facilitates fair comparison between products: With a consistent testing protocol, specifiers and buyers can compare products from different manufacturers using a common measurement baseline.
• Assists in quality control and production: Manufacturers use this testing method to monitor batch-to-batch uniformity, which is necessary to maintain product quality and compliance with regulatory or project requirements.
• Supports regulatory and contractual requirements: Many construction and environmental projects require certified testing of geotextiles. This standard provides a recognized method for meeting these regulatory and technical requirements.
• Improves performance prediction: Mass per unit area correlates with other mechanical properties such as tensile strength, puncture resistance, and toughness, making it a valuable indicator of overall material performance.

Briefly, these tests include:

• Cutting a representative sample of geotextile.
• Precisely weigh the sample.
• Calculating mass per unit area (usually in grams per square metre).

Our organization, which has been supporting businesses across all sectors for years through a wide range of testing, measurement, analysis, and evaluation activities, has a strong team of employees who closely follow global developments in science and technology and are constantly improving themselves. In this context, we also provide testing services in accordance with the ASTM D6875 Standard Test Method for the Solidification Point of Industrial Organic Chemicals with Thermistors.