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.
Parrondo, A., Allen, N.S., Edge, M., Liauw, C.M., Fontán, E. and Corrales, T. (2002) Additive Interactions in the Stabilization of Film Grade High-Density Polyethylene. Part I: Stabilization and Influence of Zinc Stearate during Melt Processing. Journal of Vinyl & Additive Technology, 8, 75-89. http://dx.doi.org/10.1002/vnl.10349
Erbetta, C.D.C., Silva, M.E.S.R., Freitas, R.F.S. and Sousa, R.G. (2013) Evaluation of Thermal, Chemical and Rheological Properties of High Density Polyethylene (HDPE) Additives with Pro-Degrading Agent, after Processing. Proceedings of the 12th Brazilian Congress of Polymers, Florianópolis, 22-26 September 2013, 1-4.
Cruz, S.A., Farah, M., Zanin, M. and Bretas, R.E.S. (2008) Evaluation of Rheological Properties of Virgin HDPE/ Recycled HDPE Blends. Polímeros: Ciência e Tecnologia, 18, 144-151. http://dx.doi.org/10.1590/S0104-14282008000200012
Guimaraes, M.J.O.C., Coutinho, F.M.B., Rocha, M.C.G., Bretas, R.E.S. and Farah, M. (2003) Rheology of High Density Polyethylene Toughened with Elastomeric Polyethylene. Polímeros: Ciência e Tecnologia, 13, 135-140. http://dx.doi.org/10.1590/S0104-14282003000200013
Pinheiro, L.A., Chinelatto, M.A. and Canevarolo, S.V. (2004) The Role of Chain Scission and Chain Branching in High Density Polyethylene during Thermo-Mechanical Degradation. Polymer Degradation and Stability, 86, 445-453. http://dx.doi.org/10.1016/j.polymdegradstab.2004.05.016
Hinsken, H., Moss, S., Pauchet, J. and Zweifel, H. (1991) Degradation of Polyolefins during Melt Processing. Polymer Degradation and Stability, 34, 279-293. http://dx.doi.org/10.1016/0141-3910(91)90123-9
Scuracchio, C.H, Bretas, R.E.S. and Isayev, A.I. (2004) Blends of PS with SBR Devulcanized by Ultrasound: Rheology and Morphology. Journal of Elastomers and Plastics, 36, 45-75. http://dx.doi.org/10.1177/0095244304039913
Moss, S. and Zweifel, H. (1989) Degradation and Stabilization of High Density Polyethylene during Multiple Extrusions. Polymer Degradation and Stability, 25, 217-245. http://dx.doi.org/10.1016/S0141-3910(89)81009-2
Azevedo, J.B., Chávez, M.A. and Rabello, M.S. (2010) The Effect of a Crosslinking Agent on the Morphology and Physical and Mechanical Properties of Polymer Foams Based on EVA and EPDM. Polímeros: Ciência e Tecnologia, 20, 407-414. http://dx.doi.org/10.1590/S0104-14282011005000002
Hoàng, E.M., Allen, N.S., Liauw, C.M., Fontán, E. and Lafuente, P. (2006) The Thermo-Oxidative Degradation of Metallocene Polyethylenes: Part 2: Thermal Oxidation in the Melt State. Polymer Degradation and Stability, 91, 13631372. http://dx.doi.org/10.1016/j.polymdegradstab.2005.07.018