Dynamic rheological properties for HDPE/CB composite melts

A study on the dynamic viscoelastic properties of carbon black (CB)-filled high-density polyethylene (HDPE) in the molten state was carried out. When the temperature was above 180degreesC in an air atmosphere, the storage modulus G', loss modulus G, and loss tangent 8 showed particular characteristics. In the low-frequency region, the modulus increased with increase of the testing time while the tan 5 obviously decreased. Also, the higher the temperature, the more notable was the change. We can detect these changes from the deviation of G' (G) against to plots from the linearity and the appearance of a characteristic plateau phenomenon. The width and height of the modulus plateau increased with increase of the temperature. When temperature was below 180degreesC, the testing time and the temperature had no effect on the viscoelastic parameters of HDPE. However, if we used 99% nitrogen gas as the atmosphere, substituting for air, the viscoelastic parameters revealed an undiscernible change, different from that in an air atmosphere. No changes were found under the protection of the antioxidant B215. This phenomenon indicated that HDPE can be oxidized at a temperature higher than 180degreesC. Nitrogen gas and an antioxidant agent can prevent HDPE from crosslinking. (C) 2003 Wiley Periodicals, Inc.