Premium
Melt viscosity of acrylic copolymers
Author(s) -
Nagai Tohru,
Kimizuka Yuichi,
Nakamura Etsuko,
Seto Jun'etsu
Publication year - 1984
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.1984.070291123
Subject(s) - shear rate , materials science , shearing (physics) , polymer chemistry , apparent viscosity , reduced viscosity , composite material , methyl methacrylate , shear (geology) , thermodynamics , capillary action , copolymer , newtonian fluid , viscosity , polymer , physics
The melt flow behavior of methyl methacrylate (MMA) copolymerized with methyl acrylate (MA) was measured and analyzed in terms of the molecular structure of the copolymers. Measurement was done by using a capillary rheometer in the shear rate range from 6 × 10 0 to 3 × 10 3 s −1 and in temperatures from 160°C to 280°C. The Newtonian flow pattern appeared in lower shear rate and higher temperature regions. However, with increasing shear rate at lower temperature, viscosity decreased to a constant slope on a logarithmic scale. The melt fracture arose at the critical shearing stress point S c of 6 × 10 6 dyn/cm 2 . A die swell also appeared in the shear rate range larger than 1 × 10 6 dyn/cm 2 , and its maximum value was two times larger than that of the capillary diameter. The decrease in viscosity with increasing shear rate is explained in terms of the apparent energy of activation in flow E α * . E α *also decreases with increasing shear rate. The exponential relation of E α *to η is maintained in the higher shear rate. The lowering of viscosity in lower shear rate, however, is attributed to not only the change in E α *but also the change in the volume of flow unit. The melt viscosity increases in inverse proportion to the MA content in the copolymers which form more flexible chains. Syndiotactic form of MMA has increased viscosity, caused by the rigidifying of segmented chains, rather than the strengthening of intermolecular interaction.