热塑料弹性体（TPE）是一类独特的材料，可提供类似橡胶的最终特性，并结合简单的塑料加工。欧洲杯足球竞彩这些材料没有欧洲杯足球竞彩固化，因此具有降低的加工和能源成本。TPE家族包括一系列材料，例如热塑甲烷（TPU），热塑料硫酸盐欧洲杯足球竞彩（TPV）和热塑料橡胶（TPR）等。本文详细介绍了TPR的块共聚物。
TPR includes block co-polymers such as Styrene-Ethylene-Butylene-Styrene (SEBS) and Styrene-Butadiene-Styrene (SBS). SEBS is a fully saturated form of SBS with improved stability and weather-ability. The average molecular weight of these polymers is very high which prevents the materials from freely flowing. As a result, the viscosity measurements using capillary rheometers are hard to perform.
使用振荡性休斯仪对样品的表征
An oscillatory rheometer consisting of a closed cavity test chamber is the most appropriate test instrument for evaluating TPR samples. Other suitable instruments include the RPA flex and RPS elite. TPR’s with high to very high AMW do not flow upon melting. Such polymers can be sintered above melt temperature to produce a repeatable test piece. Pressure can be directly achieved in closed cell oscillatory rheometers.
The TPR materials act as a purely elastic material even under melting conditions, owing to their high molecular weight. This characteristic is illustrated in the Figure 1. While considering the viscosity power law model, η = k •ɣ̇(n-1), the pseudo plasticity index “n” is close to zero and (n-1) = -0.87 which is a property of quasi-purely elastic materials.
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Figure 1.Purely elastic characteristic of TPR materials
Moreover, a Newtonian viscosity plateau occurs at frequencies below that measured byoscillatory rheometers.However, like a differential scanning calorimeter, dynamic testing can also be performed under a testing mode.
This type of testing monitors the viscoelastic properties of the material while continuously changing temperatures, and measures complex modulus (G*), and phase (δ) which provides useful data on hardness and transitions.
图2显示了图表说明了95°C附近的主要过渡δ峰。该过渡称为PS玻璃过渡温度（TG）。该图说明了由于添加的加工油的类型或水平变化，TG的变化。另外，还观察到120°C和150°C之间的二次过渡。G*的图可以从G*与G*轴的温度相比实现，从而实现了TPR固态硬度的确定。图3显示了G*与温度的图。
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Figure 2.Graph illustrating the main transition δ peak around 95°C
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Figure 3.Graph of G* versus temperature
Conclusion
闭塞oscillatory rheometerneeds to be programmed as below to carry out this analysis:
- 将SEB作为粉末或颗粒加载到底部的模具上，并在待机模式下关闭仪器。连续重复此过程，直到样品清晰为止，这表明在Spew通道中存在小物质闪光灯。将多余的材料放在样品上后，再次开始测试。
- 以中等频率和非常低应变的方式振荡样品以稳定材料行为。记录S和S”检查固定条件。
- 以中等频率进行可变的温度测试，并以1°C/min的温度速率从200°C到80°C。较高的温度速率可以降低过渡幅度。
- g*的绘图g*与G*的对数尺度上的温度仅在g*临时高原与在相同温度下的硬度成正比的地方
- 绘图切线δ与温度在线性尺度上
This information has been sourced, reviewed and adapted from materials provided by TA Instruments.
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