How do you evaluate mechanical properties of conductive polymers through mechanical testing?

1 Types of mechanical tests

Different types of mechanical tests can be used to measure various aspects of the mechanical behavior of conductive polymers. For instance, a tensile test applies a uniaxial force to stretch a sample until it breaks, allowing for the measurement of the stress-strain curve, the modulus of elasticity, the yield strength, the ultimate tensile strength, and the elongation at break. Compression tests use uniaxial force to squeeze a sample until it deforms or fails, and can measure the compressive modulus, the compressive strength, and the buckling behavior. Bending tests apply a force to bend a sample until it fractures or deflects, providing insight into the flexural modulus, flexural strength, and bending stiffness. Fatigue tests employ a cyclic load to a sample until it fails due to repeated stress, allowing for the determination of fatigue life, fatigue limit, and fatigue crack growth rate. Finally, an impact test applies a sudden and high-speed force to a sample until it breaks or absorbs energy; this test measures impact strength, impact toughness, and fracture toughness.

2 Preparation of samples

Prior to conducting any mechanical test, it is critical to prepare the samples correctly in order to guarantee consistent and reliable results. Considerations such as shape and size, surface quality, and orientation and alignment of the samples should all be taken into account. Samples should conform to the test method and testing machine specifications, have a smooth and clean surface without any defects, and have a consistent and well-defined orientation relative to the direction of the applied force. Additionally, the shape and size of the samples can influence the stress distribution and failure mode of the material, while surface quality can impact its mechanical performance. Similarly, orientation and alignment can affect anisotropy and electrical conductivity.

3 Execution of tests

When performing any mechanical test, it is essential to follow standard procedures and protocols to ensure accurate and reproducible results. The testing machine should be calibrated and verified to apply the required force, displacement, speed, frequency, or energy to the samples. Additionally, the testing machine should be equipped with sensors, transducers, or cameras to record the relevant data and parameters of the test. The testing environment should also be controlled and monitored to maintain the desired temperature, humidity, pressure, or atmosphere for the samples. This is necessary as it can affect the thermal expansion, the moisture absorption, and the oxidation of the material. Lastly, it is important to select and adjust the testing parameters to suit the purpose and scope of the test. These parameters can include load, strain, strain rate, cycle number, impact velocity, or notch geometry of the test. Such parameters can affect deformation, fracture, and fatigue of the material.

4 Analysis of results

After completing any mechanical test, it is necessary to analyze the results and interpret them in relation to the properties and the performance of the material. Data processing, comparison, and interpretation are all important factors to consider. Data processing involves filtering, smoothing, averaging, or fitting the data with appropriate models or equations. Data comparison requires calculating, ranking, or normalizing the data with suitable criteria or indicators. And data interpretation involves identifying, correlating, or predicting the relationships between the structure, the composition, the morphology, and the conductivity of the material. All of these steps are necessary for understanding the advantages and disadvantages of the material.