Advanced Materials Engineering Group, IRC Polymer Laboratory, School of Engineering, Design & Technology, University of Bradford, Bradford BD7 1DP, United Kingdom.
Micron. 2013 Jan;44:174-8. doi: 10.1016/j.micron.2012.06.004. Epub 2012 Jun 16.
Visco-elastic behaviour at the nano-level of a commonly used polymer (PET) is characterised using atomic force microscopy (AFM) at a range of temperatures. The modulus, indentation creep and relaxation time of the PET film (thickness=100 μm) is highly sensitive to temperature over an experimental temperature range of 22-175°C. The analysis showed a 40-fold increase in the amount of indentation creep on raising the temperature from 22°C to 100°C, with the most rapid rise occurring above the glass-to-rubber transition temperature (T(g)=77.1°C). At higher temperatures, close to the crystallisation temperature (T(c)=134.7°C), the indentation creep reduced to levels similar to those at temperatures below T(g). The calculated relaxation time showed a similar temperature dependence, rising from 0.6s below T(g) to 1.2s between T(g) and T(c) and falling back to 0.6s above T(c). Whereas, the recorded modulus of the thick polymer film decreases above T(g), subsequently increasing near T(c). These visco-elastic parameters are obtained via mechanical modelling of the creep curves and are correlated to the thermal phase changes that occur in PET, as revealed by differential scanning calorimetry (DSC).
使用原子力显微镜（AFM）在一系列温度下对一种常用聚合物（PET）的纳米级粘弹性行为进行了表征。PET 薄膜（厚度=100μm）的模量、压痕蠕变和弛豫时间对实验温度范围为 22-175°C 的温度高度敏感。分析表明，从 22°C 升高到 100°C 时，压痕蠕变的幅度增加了 40 倍，在玻璃-橡胶转变温度（T(g)=77.1°C）以上的上升速度最快。在较高温度下，接近结晶温度（T(c)=134.7°C）时，压痕蠕变降低到接近 T(g)以下温度的水平。计算出的弛豫时间也表现出类似的温度依赖性，从 T(g)以下的 0.6s 上升到 T(g)和 T(c)之间的 1.2s，然后在 T(c)以上又回落到 0.6s。然而，厚聚合物薄膜的记录模量在 T(g)以上增加，随后在 T(c)附近增加。这些粘弹性参数是通过对蠕变曲线进行力学建模获得的，并与 PET 中发生的热相变化相关联，这是通过差示扫描量热法（DSC）揭示的。
