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Particle size and molecular weight effects on the melt flow of emulsion PVC
Author(s) -
Berens A. R.,
Folt V. L.
Publication year - 1969
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760090105
Subject(s) - die swell , materials science , extrusion , slippage , composite material , particle size , shear rate , rheometer , particle (ecology) , melt flow index , rheology , chemical engineering , polymer , oceanography , engineering , copolymer , geology
Abstract The melt flow behavior of straight emulsion‐polymerized PVC in a capillary extrusion rheometer has been found to depend upon both the molecular weight and the particle size of the sample. Observations of flow‐rate, post‐extrusion swell, and extrudate appearance, as functions of extrusion temperature and pressure, suggest that both molecular deformation and particle slippage are involved in the flow mechanism. The relative importance of these two modes of flow varies with extrusion conditions and with the PVC molecular weight and particle size. Particle slippage is favored by large particle size, high molecular weight, and low temperature and by a shear stress above a critical yield value. Apparent melt viscosity, swelling, and roughness are minimized under conditions corresponding to the maximum contribution of particle slippage. In the proper range of temperature and shear rate, straight emulsion PVC yields smooth, low‐swell extrudates of excellent physical properties.