Nano-scale temperature dependent visco-elastic properties of polyethylene terephthalate (PET) using atomic force microscope (AFM)

• Published in: Micron (Oxford, England : 1993) Vol. 44; pp. 174 - 178
• Main Authors: Grant, Colin A., Alfouzan, Abdulrahman, Gough, Tim, Twigg, Peter C., Coates, Phil D.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.01.2013
• Subjects: Atomic force microscopy; Creep; Creep (materials); crystallization; differential scanning calorimetry; Indentation; Nanoindentation; Nanomaterials; Nanostructure; Polyethylene terephthalate; Polyethylene terephthalates; Relaxation time; temperature; Viscoelasticity; Polyethylene terephthalate; Atomic force microscopy; Creep; Nanoindentation
• ISSN: 0968-4328; 1878-4291
• DOI: 10.1016/j.micron.2012.06.004

► AFM based characterisation on common recyclable semi-crystalline polymer PET. ► Observation of topographic surface changes with increasing temperature. ► Nano-mechanical analysis of the polymer using creep indentation. ► Correlation of nano-mechanical properties with phase changes in the polymer. 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=100μm) 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 (Tg=77.1°C). At higher temperatures, close to the crystallisation temperature (Tc=134.7°C), the indentation creep reduced to levels similar to those at temperatures below Tg. The calculated relaxation time showed a similar temperature dependence, rising from 0.6s below Tg to 1.2s between Tg and Tc and falling back to 0.6s above Tc. Whereas, the recorded modulus of the thick polymer film decreases above Tg, subsequently increasing near Tc. 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).