Practical Rheology and Its Role in Polymer Processing. By Tim Womer. Outline . Definitions Basic Equipment Viscosity vs. Shear Rate Curves What they tell us How we can use them Melt Index: “What is it?” Moisture?. RHEOLOGY. The Science of Deformation and Flow of Matter.
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The Science of Deformation and Flow of Matter
from “ ”
Heracleitus, 5th Century B.C.
“All Things Flow”
vj = 2 eijeij
tij = tji
= 2 eij
-Mathematics is complicated
Viscosity [ Pa s ]
Windows of the Cathedral of
Chartres in France have “Flowed”
since they were Produced 600
IF YOU WAIT LONG ENOUGH
Glass behaves like Fluids !!!
Definition: A state of molecular structure in some resins attributed to the existence of solid crystal with a definite geometric form. Such structures are characterized by uniformity and compactness.
Definition: Devoid of crystallinity or stratification. Most plastics are amorphous at processing temperatures, many retaining this state under all normal conditions
The flow characteristic of 50 wt. motor oil at 50°F in the winter versus its flow characteristic when it is drained out of the oil pan after the motor has been warmed up to 200°F
n = .3
n = .5
Materials with different
Viscosity shear thinning
(Power-law Index Role)
The terms “melt index” (MI), “melt flow rate” (MFR) and “melt flow index” (MFI) refer to the same test. MFR was introduced to replace MFI. The term MFI is used to refer to the flow rate of PE obtained under Condition 190/2.16 (formally know as Condition E). The use of such terms is not encouraged for other materials. It is suggested, by ASTM D 1238 that the term melt flow rate (MFR) be used for other plastic materials.
app = 2.4 MFIWhat does MFI mean? Not Much!