Phenomenological Studies On Extrusion Swell Of Polymer Melt Through Conical Short Dies

Rheology is a subject which studies the flowing phenomenon and consequent deformation disciplinary of material. In the field of macromolecule physics, synthesized the plastics, elastics and viscoelastic deformation of macromolecule and developed polymer rheology. Along with polymer materials coming rapidly into national economy's each domains, and with more and more high request to products made of polymer in quality and output, complicated processing technics problems in actual manufacture are come forth, and these problems arose great attention to study on viscoelastic behavior of polymer.This paper regards polymer's extrusion swell in the process of extruding as researching object, uses phenomenological study theory and tensor analyzing means, infer the polymer melt's extrusion swell in conical short die from theoretics aspect and gained the resolution answer of it. This paper also study from theoretic influence of the geometry structure on the polymer's extrusion swell, calculate the polymer's extrusion swell in conical short die by in taking the entrance angle of extrusion die, the flowing nature convergent angle, the recoverable elastic strain and the ratio of length to diameter in the straight segment; discuss the influence of convergent extensional flowing of polymer melt and shear flowing on the polymer's extrusion swell. So conclusions are inspired as following: the polymer's extrusion swell is developed mainly by the extrusion die's entrance convergent flowing. This paper set forth that the polymer melt's extrusion swell in extrusion die is affected nearly by elastic reversion, relaxation time and stick time. The theory brought forward by this paper is according preferable with the experiment.This paper uses low density polyethylene(LDPE) as experiment material, introduces different conical short extrusion dies with different entrance angles and different ratio of length to diameter in the straight segment. Large numbers of extrusion swell experiment were done using extruder. Through these experiments, the relationship between extrusion swell and some factors such as extrusion die's entrance angle, ratio of length to diameter in the straight segment, shear rate and so on. Also using extrusion dies with zero ratio of length to diameter in the straight segment and big ratio of length to diameter in the straight segment separately in the experiment to cite the fact that extensional deformation of convergent flowing can bring intense entrance elastics effect. The experiment results shows that the extensional deformation's elastic reversion aroused by convergent flowing of polymer melt in the die entrance is the main reason for extrusion swell; in the die with big...