Grease, Finding Temperature Transitions In Greases Using Viscosity Measurements

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Lubricating products such as greases need to be workable in all environments that the application may be used. This can include extremely low temperatures such as farming equipment in Siberia, or vehicles used at the South Pole (-40ºC).

Cooling Effects

冷却后，油脂中的不同馏分将单独冻结，并且在tanδ值中应明显相应的峰。与tanδ峰并行，复杂的粘度（η*）当然会增加。

图1。Variation in viscosity and phase changes with temperature.

Interpretation Of Results

上面的振荡结果清楚地表明了C.-10ºC和C.-50ºC的TAN三角洲曲线峰的每个组件的冰点。粘度还显示了两个单独的“滴”与相变为变化。因此，从复杂的粘度可以看到样品在任何特定温度下的可行性。

Measuring Temperature Induced Phase Changes

This mechanically assessed phase change is likely to be around 10ºC higher than that measured by differential scanning calorimetry (DSC), because the phase change is frequency dependent and a DSC sample is at rest.

但是，由于大多数润滑剂制造商需要在低温下确定油脂材料的工作范围，因此通过风湿计测量的TG（或冰点）通常更相关。

Conclusion

可以使用Bohlin CVO准确地测量熔点和玻璃过渡温度，其中发生在-150ºC和550ºC之间。

测量条件

Samples	油脂和高分子量润滑剂
几何学	PP15锯齿状和具有低温延长单元的强制气体延长温度电池（使用液体N2）
单频振荡
Strain	0.005
频率	1Hz
初始压力	100 Pa
Temperature range	30ºC to -70°C (or working temperature)

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