ISSN:
0032-3888
Keywords:
Chemistry
;
Chemical Engineering
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
A method is proposed to describe the processing history in extrusion dies and its influence on the state of the polymer after processing. The approach differs from conventional processing analysis, which uses the shear viscosity function to calculate pressure drop vs flow rate relations. The approach also differs from heuristic analysis which tries to find empirical correlations between rheological observations and processing behavior. The method is applied to the flow in annular extrusion dies. An integral constitutive equation is chosen to calculate the flow and to describe the flow history at the die exit as memorized. In the analysis, the kinematics are locally approximated by isothermal steady shear flow. The velocity and the velocity gradient are used to determine the Finger strain tensor, the path lines, and the residence times of the deforming material elements. Measures of the state of the polymer at the die exit are chosen to be the stress ratio N1/2τ12 and the free recovery. The free recovery calculations presume that the extrudate is chopped into small volumes of homogeneous flow history. The results of the calculations show the polymer very sensitively reacts to small changes of the die geometry. Important applications of this analysis are film blowing and blow molding, where the extensional behavior during the blowing process outside the die depends greatly on the preceding shaping process inside the die.
Additional Material:
11 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pen.760210608
