EVA Film Sample
In this example, DSC measurements* were carried out on an EVA film sample of approx. 7 mg with the DSC 204 F1 Phoenix®® at heating rates of 10 K/min. These DSC experiments were performed at the Federal Institute for Materials Research and Testing ("BAM"), Germany.
In the 1st heating (blue curve), the Glass Transition TemperatureThe glass transition is one of the most important properties of amorphous and semi-crystalline materials, e.g., inorganic glasses, amorphous metals, polymers, pharmaceuticals and food ingredients, etc., and describes the temperature region where the mechanical properties of the materials change from hard and brittle to more soft, deformable or rubbery.glass transition temperature at -28°C (inflection point) is followed by an EndothermicA sample transition or a reaction is endothermic if heat is needed for the conversion.endothermic double peak between 50°C and 100°C. This melting behavior can be correlated to a lamellar thickness distribution. The ExothermicA sample transition or a reaction is exothermic if heat is generated.exothermic peak at 158°C indicates the exothermic crosslinking reaction. Noticeable is the rather low reaction enthalpy (-14.15 J/g) in comparison to epoxy resins (typically between -400 J/g and -500 J/g).
In the 2nd heating (red curve), the glass transition occurred at almost the same temperature. The endothermic double peak between 40°C and 80°C
has changed to a broad shoulder with its maximum at 63°C. The higher the crystal thickness, the higher the Melting Temperatures and EnthalpiesThe enthalpy of fusion of a substance, also known as latent heat, is a measure of the energy input, typically heat, which is necessary to convert a substance from solid to liquid state. The melting point of a substance is the temperature at which it changes state from solid (crystalline) to liquid (isotropic melt).melting temperature. Therefore, the change from a peak into a broad shoulder is an indication of a distribution of crystals with reduced thickness as a consequence of the thermal treatment in the 1st run. No exothermic reaction peak is present in the 2nd run, indicating that the crosslinking process was finished after the 1st heating.
*Our thanks to Dr. W. Stark and M. Jaunich from the Federal Institute for Materials Research and Testing ("BAM") in Berlin for the measurements and discussion. The results are published in Polymer Testing 30 (2011) 236-242.