Assessment of rheological behavior of secondary polymeric raw materials in the conditions corresponding to processing of polymers by method of extrusion and injection molding

摘要

In the present work, rheological behavior of polymeric raw materials in the conditions corresponding to processing of polymers by the methods of extrusion and injection molding is modeled. Mixes based on secondary polypropylene and the following polymers: secondary polyethylene of low pressure LDPE-276 and secondary polyethylene of high pressure HDPE-?20 were used as a polymeric basis. The composites were obtained in a melt using the laboratory station “PlastographEC” (Brabender, Germany) in 15?min at a load of 200?N, temperature of 180?°C and screw speed of 30?revolutions per minute. Rheological measurements were taken in the oscillation mode on a modular dynamic rheometer Haake MarsIII at 220?°C in an oscillation frequency range from 0.01 to 100?Hz. It is revealed that with an increase in content of the second polymer in the mix an increase in the values of complex viscosity of the melt always takes place. This is apparently due to the fact that the samples of the second polymers in all cases were characterized by a higher value of the melt viscosity, than the secondary polypropylene. In addition,an increase in the content of the second polymer in the mix led to an increase in the values of exponent n in the frequency dependence of the viscosity that confirms the strengthening of the dependence of viscosity on the frequency of oscillations and a deviation of melt viscosity of composition from the behaviour typical of a Newtonian liquid. It is shown that compositions based on mixes of polypropylene with HDPE-20 and LDPE-276 can be fairly easily processed at high shear rates, while the enhanced interaction of polymers will provide them improved deformation and strength characteristics.