Dynamic Mechanical Analysis (DMA) of polymer materials, are you familiar with it?

In your daily work, do you ever have questions like: How to study the damping performance of materials? How to investigate the mechanical properties of composite materials at high temperatures? How to research the elastic properties of rubber materials at low temperatures? How to study the curing process and process parameters of thermosetting resins? Dynamic Mechanical Analysis (DMA) is an effective method for studying the relationship between polymer molecular chain movement, structural changes, and performance. DMA, short for Dynamic Thermomechanical Analysis, is a technique that tests the mechanical properties of materials as they change with temperature (time or frequency) under the influence of oscillating stress or strain in a programmatically controlled temperature environment.

During DMA testing, changes in mechanical properties such as storage modulus, loss modulus, and loss factor of polymer materials occur as temperature and frequency change. These changes are depicted as a series of steps or peaks on the spectrum, each representing a molecular motion or chain segment relaxation process within the material. DMA is widely used in determining the glass transition temperature (Tg), studying the low-temperature performance, heat resistance, damping performance, and material compatibility of polymer materials.

**Glass Transition Temperature (Tg) **

DMA testing the glass transition temperature (Tg) is based on the principle that the mechanical properties (such as storage modulus) of polymer materials undergo a sharp change during the glass transition process. This change is typically several orders of magnitude, making DMA sensitive to measuring the glass transition process of materials. Compared to other methods like DSC and TMA for Tg testing, DMA offers advantages such as high sensitivity and closer approximation to real-world material application scenarios. DMA is particularly suitable for samples that are difficult to test with DSC or TMA, such as materials with high filler content, highly cross-linked thermosetting materials, and samples where the glass transition process overlaps with other effects like relaxation, as illustrated in Figure 1. While it is challenging to detect the glass transition in DSC testing, DMA can effectively characterize it.

Figure 1: Comparison of Glass Transition Temperature Testing between DSC (top) and DMA (bottom)

Damping performance

Damping performance is a crucial characteristic of polymer materials used for damping, sound insulation, and buffering, where they dissipate solid mechanical vibrations into heat. Such materials are commonly referred to as damping materials. Due to the specificity of their applications, these materials require significant mechanical loss. DMA testing directly provides curves of mechanical loss as a function of temperature, frequency, or time. By comparing the differences in damping performance of polymer materials under specific conditions, DMA analysis plays a vital role in the research, selection, and improvement of damping materials.

Compatibility

To enhance the comprehensive performance of polymer materials, blending modification methods are often employed. Generally, a blend composed of two or more materials may form either a homogeneous or multiphase structure, depending on the degree of compatibility. The curves obtained from DMA testing can significantly characterize the compatibility of materials. As shown in Figure 2, a typical multiphase structure is illustrated. In cases where two components are not entirely compatible, the blend may form two phases, resulting in multiple loss peaks in the DMA loss factor curve. Studying the compatibility of blends can verify the effectiveness of polymer blending modifications, analyze the effects of material processing on performance, and investigate failures caused by compatibility issues.

In certain technical fields, surfaces and surface analysis are significant, including: Photoemission Process

When atoms or molecules absorb X-ray photons, they emit electrons. The kinetic energy (KE) of these electrons depends on the photon energy (hν) and the binding energy (BE), which is the energy required for the electron to leave the surface.

Figure 2: DMA Curve of Sample with Poor Compatibility

The DMA curve of the sample with poor compatibility. In addition to the applications listed above, DMA can also evaluate various properties of polymer materials, such as softening temperature, viscoelastic behavior (stress relaxation, creep), aging behavior, secondary transitions, cold resistance, heat resistance, crystallization, etc. Through in-depth analysis of DMA data, it can also guide product design and material usage, material selection and optimization, product defect evaluation (failure analysis), and predict the service life of polymer materials.