Rheological and Thermal Behavior of High-Density Polyethylene (HDPE) at Different Temperatures
- 1 Polymer Science and Technology Laboratory, Chemical Engineering Department, Engineering School, Federal University of Minas Gerais, Belo Horizonte, Brazil
- 2 Polymer Science and Technology Laboratory, Chemical Engineering Department, Engineering School, Federal University of Minas Gerais, Belo Horizonte, Brazil
- 3 Polymer Science and Technology Laboratory, Chemical Engineering Department, Engineering School, Federal University of Minas Gerais, Belo Horizonte, Brazil
- 4 Polymer Science and Technology Laboratory, Chemical Engineering Department, Engineering School, Federal University of Minas Gerais, Belo Horizonte, Brazil
- 5 Polymer Science and Technology Laboratory, Chemical Engineering Department, Engineering School, Federal University of Minas Gerais, Belo Horizonte, Brazil
- 6 Polymer Science and Technology Laboratory, Chemical Engineering Department, Engineering School, Federal University of Minas Gerais, Belo Horizonte, Brazil
Abstract
In the present work, rheological properties of HDPE samples were measured at temperatures of 150°C, 190°C and 230°C. It was shown, by oscillatory tests, at low frequencies, that, for temperatures of 150°C and 190°C, there was a predominance of the viscous behavior over the elastic one. At 230°C, there was a predominance of the elastic contribution, and there was an increase of the molar mass compared with the ones obtained from the tests at 150°C and 190°C. The results obtained from the temperature ramp oscillatory test showed that, up to around 248°C, the viscous behavior prevailed, the opposite being observed at higher temperatures. At 230°C the sample showed significantly lower values of strain when compared with the ones observed at 150°C and 190°C. Oxidative induction time (OIT), melting point and degree of crystallinity were determined by differential scanning calorimetry (DSC). The DSC results and the rheological measurements showed a completely different behavior for the HDPE samples at 230°C compared with the 150°C and the 190°C ones, suggesting that HDPE, at the temperature of 230°C, underwent thermo-oxidative degradation with the initial predominance of crosslinking.
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