Abstract
A method proposed earlier has been extended to estimate complete flow curves or rheograms of engineering plastics. Master curves that are independent of the grade and temperature have been generated and presented for acrylics, polyacetal, nylons, polyethylene terephthalate, polycarbonate and polysulfone. The influence of the various molecular parameters on the viscosity behaviour of polymer melts have been explained rationally. More specifically, the effects of chain branching and of chain rigidity on the master curve of a resin type have been elucidated with reference to polyacetal and polysulfone, respectively. The method presented here can be used effectively by processors of engineering plastics.
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Abbreviations
- F :
-
force due to the weight of piston and load (dynes)
- l :
-
length of nozzle (cm)
- L :
-
load (kg)
- M e :
-
molecular weight between entanglement points along a polymer molecule
- MFI:
-
melt flow index (gm/10 min)
- n :
-
slope of the shear stress versus shear rate curve on log-log scale
- Q :
-
flow rate (cm3)
- R N :
-
radius of nozzle (cm)
- R P :
-
radius of piston (cm)
- T 1 :
-
temperature at condition 1 (K)
- T 2 :
-
temperature at condition 2 (K)
- T g :
-
glass transition temperature given in table 2 (K)
- T s :
-
standard reference temperature (=T g + 50 K)
- \(\dot \gamma \) :
-
shear rate (sec−1)
- η :
-
apparent viscosity (poise)
- ρ :
-
density of the polymer (gm/cm3)
- τ :
-
shear stress (dynes/cm2)
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NCL Communication Number 2926.
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Shenoy, A.V., Saini, D.R. & Nadkarni, V.M. Rheograms for engineering thermoplastics from melt flow index. Rheol Acta 22, 209–222 (1983). https://doi.org/10.1007/BF01332373
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DOI: https://doi.org/10.1007/BF01332373