Application Note B-TA1053
Introduction
For polyethylene (PE) and polyvinyl chloride (PVC), which are used as food wraps, the thermal expansions by TMA were compared in a dry atmosphere and a humidity-controlled atmosphere at 25°C and 80% relative humidity.
Measurement and analysis example
As samples, PE film (thickness: 15 μm) and PVC film (thickness: 10 μm) were cut into strips of 5 mm width and 15 mm length. TMA measurements were performed in a tensile load mode at 20 mN with a heating rate of 2°C/min.
Figure 1: Comparison of thermal expansion rates of PE under dry atmosphere and 25°C, 80% relative humidity atmosphere
Figure 2: Comparison of thermal expansion rates of PVC under dry atmosphere and 25°C, 80% relative humidity atmosphere
For PE, no significant difference in thermal expansion due to humidity was observed, suggesting low humidity dependence.
For PVC, shrinkage reflecting film stretching during manufacturing is observed in the range of 50°C to 75°C. However, under 80% relative humidity, the shrinkage is smaller (i.e., expansion is larger), indicating a strong dependence on humidity.
Thus, by measuring thermal expansion under various relative humidity conditions, it is possible to evaluate the dependence of film properties on humidity.
