Moisture Testing with ASTM D6980-17

Introduction

The ASTM D6980-17 standard is important for making sure plastics are of good quality and work well. It’s all about checking how much water is in the plastic. If there’s too much water, it can cause problems as water makes plastic weaker. It can crack, bend, or break more easily with pressure application. Also, when plastics soak up water, they might change size. This can change their shape and make them not work properly.

Using significant water while making plastic items like shapes or tubes can lead to problems like bubbles, holes, or rough surfaces. Water can also make some plastics break down quicker. This also indicates the fragility of plastics. So, it’s important to monitor the moisture content in plastics throughout the manufacturing process. ASTM D6980-17 helps measure the moisture in plastics consistently. Thus ensuring integrity and longevity.

Scope of ASTM D6980-17

ASTM D6980-17 is a standard that explains how to find moisture in plastics. This is done by checking how much weight they lose. This method works for many kinds of plastics. These include those that melt with heat, harden when cooled, and stretch. It helps us measure the water content in the plastic.

The ASTM D6980-17 test is designed for:

• Measuring the moisture in plastic to a miniscule amount, as low as 50 milligrams per kilogram, is the same as 50 parts per million (ppm).

• Providing a control mechanism to ensure material quality during production and post-processing stages.

• Facilitating acceptance testing for plastic materials to verify adherence to moisture content specifications.

Procedure

The ASTM D6980-17 procedure follows a specific sequence:

• Sample Preparation: To get a sample ready, we chop or grind up the plastic into tiny bits or powder. This helps it dry out faster. Then, we weigh out a precise amount of the sample using a super accurate scale.

• Sample Placement and Heating: The weighed sample is placed on a clean, dry weighing dish specifically designed for the test apparatus. The dish and sample are loaded into a preheated and equilibrated heating chamber within the testing instrument. The heating chamber reaches and maintains a specific temperature according to the type of plastic being tested. The standard typically recommends temperatures well below the plastic material’s melting or decomposition point to avoid unintended material loss.

• Monitoring Weight Loss: At predetermined time intervals, the sample and dish assembly are removed from the heating chamber and weighed using the analytical balance. The weight loss is meticulously recorded at each interval.

• Drying to Constant Weight: Keep heating, weighing, and recording data until the weight stops changing. That means all the moisture that can be removed has been taken out.

Data Analysis

Once the drying process reaches a constant weight, the moisture content (M) of the plastic sample is calculated using the following formula:

M = (Wo – Wd)/Wo * 100 percent

where:

M: Dampness content of the plastic sample, communicated as a rate.

Wo: Beginning load of the sample before drying (mg).

Wd: Last sample weight after drying to consistent weight (mg).

This calculation provides a quantitative measure of the moisture content present in the plastic material. The resulting value can then be compared to the specified moisture content limits for the particular plastic material or application requirements.

Sample Size

ASTM D6980-17 does not prescribe a specific sample size. However, it recommends selecting a sample size that offers a balance between sufficient surface area for efficient moisture release and maintaining representative properties of the bulk material. The chosen sample size should also be suitable for the capacity of the weighing dish and the analytical balance used in the testing process.

Further Analysis

The ASTM D6980-17 method is useful for measuring moisture in plastics, but other methods can be used in certain cases. Here are some other techniques:

1. Karl Fischer Titration (ASTM D6444): This method uses a chemical reaction to accurately measure moisture in a sample, especially good for materials with very low moisture levels.

2. Karl Fischer Coulometry (ASTM E1532): Similar to Karl Fischer Titration but with automated features and electrochemical detection, which can make the analysis faster.

3. Gravimetric Analysis with Desiccant: This involves placing the plastic sample with a moisture-absorbing material and measuring the weight gain of the desiccant. It’s less accurate but cheaper and good for rough estimates.

Choosing the right way to measure moisture depends on several things:

• Accuracy Needed: If you need precise results, methods like ASTM D6980-17 or Karl Fischer are often best.

• Material Characteristics: Some plastics need special methods because they react to heat or chemicals.

• Cost and Time: Methods like Karl Fischer can be more expensive and take longer than ASTM D6980-17.

Conclusion

Tracking moisture levels is crucial for ensuring the quality and effectiveness of plastic materials in different industries. The ASTM D6980-17 standard provides a reliable method. It measures moisture content by observing weight loss. Knowing how to conduct this test, analyze the data, and consider sample size aids in using this method for material assessment. Apart from the ASTM D6980-17 method, other techniques such as Karl Fischer Titration and Desiccant Gravimetric Analysis can be employed based on the specific application requirements.

Choose Infinita Lab 

Infinita Lab is your go-to place for material testing. We give you easy access to many certified labs all over the USA. We test different materials like metals and plastics to ensure high quality and speed up research and development. With our knowledge and modern facilities, we provide reliable and precise results for all your material testing needs.