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Effect of carbon black on time dependence of the melt flow index
Author(s) -
Schreiber H. P.,
Rudin A.
Publication year - 1967
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1967.070110704
Subject(s) - carbon black , melt flow index , materials science , polyethylene , thioether , extrusion , adsorption , carbon fibers , thermodynamics , instability , capillary action , composite material , polymer , polymer chemistry , chemical engineering , chemistry , organic chemistry , mechanics , copolymer , natural rubber , physics , composite number , engineering
Time dependence in the melt indexing of polyolefins stabilized against thermally induced changes is well known, the prevalent effect being an increase in melt index toward a steady‐state value. The melt index of polyethylenes compounded with carbon black has been found to decrease, in some cases radically, although oxygen uptake data show no evidence of thermal instability. The melt index–time plot can be restored to its normal shape by adding excess quantities of a standard thioether antioxidant. Data are rationalized by assuming that polyethylene adsorbs on the available pigment surface, forming a crosslink network. The thioether antioxidant, however, may adsorb preferentially, thereby restoring the normal response of the polymer to forces resulting in its capillary extrusion. The results emphasize the contribution of chain orientation effects to the time dependence of melt index.