The storage and loss modulus of tires has usually been measured using Dynamic Mechanical Analysis or DMA. This testing technique is able to accurately measure both properties, which help predict rolling resistance and wet traction. Important information for tire manufacturers. Here spatially resolved DMA is demonstrated using oscillatory indentation with an iNano indentation system produced by Nanomechanics, Inc.
Materials and Methods
测试样品是从普利司通轮胎中取出的，并嵌入了环氧座。然后将表面抛光以准备它进行纳米引导实验。在本实验中进行的测试期间，使用了inano的聚合物包选项。直径为100 µm的扁平冲头用于进行基于接触的DMA测量。将测试的目标区域放置在两个钢带之间。进行了21次动态压痕测试，每次测试都进行了100 µm。在每个测试地点，系统将打孔面压成完全接触，然后分别测量了由E'和e”代表的存储和损耗模量。测量是通过以1至200 Hz的频率振荡缩进器来进行测量。Inano系统测量了DMA性能，这是位置和频率的函数。
图1。Cross-section of the tire sample embedded in epoxy, polished and ready for testing. The multiple polymer layers are apparent in the cross-section. A vector of tests was performed along the yellow line across the sample, proceeding upward.
Table 1.Test Inputs.
| Frequency sweep |
泊松的比例 |
Target Dynamic Displacement |
Pre-test compression |
打孔直径 |
| 1-200 Hz |
0.499 |
50 nm |
0.1 µm |
107.4 µm |
Results and Discussion
It was found that the storage modulus decreased for test sites closer to the outer part of the tire. About half-way across the testing area, the storage modulus decreased sharply; this indicated a very different material would be present at that location. It was found that the storage modulus increased with frequency at all tested positions.
The storage and loss moduli increased steadily and significantly with frequency. However, the loss modulus increased more as a function of frequency. In the real world this would mean that the tire material would damp more energy at higher frequencies. As polymers manifest time-temperature correlation, they will exhibit analogous behavior with temperature. This means that both the storage and loss moduli are likely to increase with decreasing temperature. The loss modulus will become more dominant as temperature decreases.
结论
与传统DMA相对于基于接触的DMA测试具有更大的优势。如本实验中用于测量轮胎横截面的局部复杂模量的振荡凹痕技术所示。与传统的DMA测试不同，测试只需要一个平坦的表面，该测试需要特定几何样品。使用Inano系统快速且自动化测试。另一个优点是测量值是局部的，揭示了性质的重要空间变化。
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