How to test the quality of extrusion rubber material?

As a trusted supplier of extrusion rubber materials, ensuring the quality of our products is of utmost importance. High - quality extrusion rubber materials are crucial for a wide range of applications, from automotive components to industrial seals. In this blog, I will share some effective methods to test the quality of extrusion rubber materials.

Physical Property Testing

Hardness Testing

Hardness is one of the most fundamental physical properties of rubber materials. It can significantly affect the performance of the extrusion rubber product. A durometer is commonly used to measure the hardness of rubber. There are different types of durometers, such as Shore A and Shore D, which are suitable for different hardness ranges of rubber.

For softer extrusion rubber materials, Shore A durometer is typically used. The test involves pressing the indenter of the durometer onto the surface of the rubber sample. The hardness value is then read directly from the scale on the durometer. A consistent hardness value within the specified range indicates a high - quality rubber material. If the hardness varies significantly across the sample, it may suggest uneven mixing during the manufacturing process or improper curing.

Tensile Strength and Elongation Testing

Tensile strength and elongation are important indicators of a rubber material's ability to withstand stretching forces without breaking. To conduct this test, dumbbell - shaped rubber samples are prepared according to the relevant standards (e.g., ASTM D412). The samples are then placed in a tensile testing machine, which gradually applies a pulling force until the sample breaks.

The maximum force applied before the breakage is recorded as the tensile strength, usually expressed in units of megapascals (MPa). Elongation at break is measured as the percentage increase in the length of the sample compared to its original length. High - quality extrusion rubber materials should have appropriate tensile strength and elongation values. For example, in automotive applications, rubber seals need to have sufficient tensile strength to maintain their integrity under various operating conditions, and adequate elongation to accommodate movements without tearing.

Density Testing

Density is another physical property that can be used to assess the quality of extrusion rubber materials. The density of a rubber material can be measured using a density meter. A consistent density value within the expected range is a sign of a homogeneous material. Deviations in density may indicate the presence of voids, inclusions, or improper formulation.

If the density is lower than expected, it could mean that there are air bubbles or other voids in the rubber, which can weaken the material and reduce its performance. On the other hand, a higher - than - normal density may suggest the presence of excessive fillers or improper mixing of ingredients.

Chemical Property Testing

Chemical Resistance Testing

Extrusion rubber materials are often exposed to various chemicals in their applications. Therefore, testing their chemical resistance is crucial. This can be done by immersing rubber samples in different chemicals for a specified period (e.g., 24 hours, 7 days) at a controlled temperature.

After the immersion period, the samples are removed, dried, and their physical properties, such as hardness, tensile strength, and volume change, are measured again. A high - quality rubber material should show minimal changes in these properties when exposed to the relevant chemicals. For example, in industrial applications where rubber seals are used to contain chemicals, good chemical resistance ensures long - term performance and reliability.

Aging Resistance Testing

Aging can significantly affect the performance of extrusion rubber materials over time. To test aging resistance, rubber samples are subjected to accelerated aging conditions, such as high - temperature and high - humidity environments. For example, samples can be placed in an aging oven at a specified temperature (e.g., 70°C) for a certain number of hours.

After the aging process, the physical properties of the samples, such as hardness, tensile strength, and elongation, are measured again. A high - quality rubber material should show only minor changes in these properties after aging. If the material becomes brittle or loses a significant amount of its mechanical properties, it may not be suitable for long - term applications.

Microstructural Analysis

Microscopic Examination

Microscopic examination can provide valuable information about the internal structure of extrusion rubber materials. A scanning electron microscope (SEM) or an optical microscope can be used to observe the rubber's microstructure.

Under the microscope, the presence of agglomerated fillers, voids, or inhomogeneous distribution of rubber polymers can be detected. For example, if the filler particles are not well - dispersed, it can lead to weak points in the material and reduce its overall performance. A high - quality rubber material should have a uniform microstructure with well - dispersed fillers and no visible defects.

Fourier - Transform Infrared Spectroscopy (FTIR)

FTIR is a powerful analytical technique used to identify the chemical functional groups present in a rubber material. By analyzing the infrared absorption spectrum of a rubber sample, we can determine the type of polymers, additives, and curing agents used in the formulation.

This technique can be used to verify the composition of the extrusion rubber material and detect any impurities or unexpected chemical components. For example, if a rubber material is supposed to be made of a specific type of rubber polymer but the FTIR spectrum shows the presence of other polymers, it may indicate a quality issue in the manufacturing process.

Specialized Rubber Material Testing

Testing of High Resilience Fluorosilicone Rubber

High resilience fluorosilicone rubber is known for its excellent resilience and resistance to high temperatures and chemicals. In addition to the general tests mentioned above, specific tests for high - resilience properties are required.

One such test is the compression set test. A rubber sample is compressed to a certain percentage of its original thickness and held under compression for a specified time at a specific temperature. After the compression period, the sample is released, and the percentage of permanent deformation is measured. A high - quality high - resilience fluorosilicone rubber should have a low compression set value, indicating that it can quickly recover its original shape after being compressed.

Testing of Conductive Fluorosilicone Rubber

Conductive fluorosilicone rubber is used in applications where electrical conductivity is required, such as in electronic devices. The key test for this type of rubber is the measurement of electrical conductivity.

A four - point probe method is commonly used to measure the electrical resistivity of the rubber sample. The resistivity value should be within the specified range for the intended application. In addition, the stability of the electrical conductivity over time and under different environmental conditions should also be tested.

Testing of Fluorosilicone Rubber Adhesive

Fluorosilicone rubber adhesive is used to bond rubber components together or to other materials. To test its quality, adhesion strength testing is essential.

A lap - shear test can be used to measure the adhesion strength between two bonded rubber or rubber - to - substrate samples. The samples are prepared by applying the adhesive between the bonding surfaces and curing it according to the recommended procedure. The bonded samples are then placed in a tensile testing machine, and a shear force is applied until the bond fails. The maximum force applied before the failure is recorded as the adhesion strength. A high - quality fluorosilicone rubber adhesive should have sufficient adhesion strength to ensure a reliable bond.

Conclusion

Testing the quality of extrusion rubber materials is a comprehensive process that involves multiple aspects, including physical property testing, chemical property testing, microstructural analysis, and specialized testing for different types of rubber materials. By conducting these tests, we can ensure that our extrusion rubber materials meet the highest quality standards and are suitable for a wide range of applications.

If you are in need of high - quality extrusion rubber materials, we are here to provide you with the best products and services. We welcome you to contact us for procurement and further discussions. Our team of experts is ready to assist you in finding the most suitable rubber materials for your specific needs.

References

• ASTM D412 - Standard Test Methods for Vulcanized Rubber and Thermoplastic Elastomers - Tension
• ASTM D2240 - Standard Test Method for Rubber Property - Durometer Hardness
• Various technical literature on rubber materials and testing methods from industry - recognized sources.