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Rheological properties of mixtures of molten polymer and fluorocarbon blowing agent. I. Mixtures of low‐density polyethylene and fluorocarbon blowing agent
Author(s) -
Han Chang Dae,
Ma ChinYuan
Publication year - 1983
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.1983.070280234
Subject(s) - blowing agent , fluorocarbon , polymer , materials science , rheology , viscosity , polyethylene , capillary action , composite material , polymer blend , polymer chemistry , copolymer , polyurethane
The viscosities of mixtures of low‐density polyethylene and fluorocarbon blowing agent were determined from the measurement of wall normal stress along the longitudinal axis of a capillary die. For the study, three different grades of commercial high‐pressure low‐density polyethylene were used, together with the following fluorocarbon blowing agents, dichlorodifluoromethane (FC‐12), dichlorotetrafluoroethane (FC‐114), and blends of FC‐12 and FC‐114. In the experiment, blowing agent concentration and melt temperature were varied for each combination of polymer and blowing agent employed. Analysis of the experimental data has led to a correlation between the viscosity reduction factor (VRF) and the blowing agent concentration, in which VRF is defined as the ratio of the viscosity of polymer‐blowing agent mixture to that of the polymer alone. It was found that the correlation obtained is independent of shear rate and temperature and dependent upon only the type of fluorocarbon blowing agent. The practical significance of the correlation is discussed. We have shown that the entrance pressure drop obtained in the absence of phase separation in the entrance region may be used as a measure of the elastic properties of mixtures of fluorocarbon blowing agent and low‐density polyethylene resin.