Flow-induced crystallization of linear polyethylene above its normal melting point

1976 ◽  
Vol 16 (7) ◽  
pp. 512-525 ◽  
Author(s):  
Victor Tan ◽  
Costas G. Gogos
Keyword(s):  
Melting Point ◽  
Linear Polyethylene ◽  
Normal Melting Point ◽  
Induced Crystallization ◽  
Flow Induced Crystallization

Flow-Induced Crystallization of High-Density Polyethylene

1995 ◽  
Vol 60 (10) ◽  
pp. 1733-1740 ◽  
Author(s):  
Ivan Fortelný ◽  
Jana Kovářová ◽  
Josef Kovář
Keyword(s):  
High Density Polyethylene ◽  
Molar Mass ◽  
Maximum Temperature ◽  
Capillary Viscometer ◽  
Linear Polyethylene ◽  
Shear Rates ◽  
Melting Temperatures ◽  
Dsc Measurements ◽  
Induced Crystallization ◽  
Flow Induced Crystallization

Crystallization induced by flow in the capillary viscometer was studied for four grades of linear polyethylene. From rheological and DSC measurements it follows that crystallization was induced in all samples under study at temperatures higher than melting temperatures of the same samples crystallized at rest. The maximum temperature of flow-induced crystallization increases with increasing molar mass of polyethylene. Flow-induced crystallization of injection moulding grades of polyethylene only takes place in a limited interval of shear rates. This effect is explained as a consequence of the shear rate distribution in the capillary.

scholarly journals A novel approach to the study of extensional flow-induced crystallization

2021 ◽  
Vol 96 ◽  
pp. 107060
Author(s):  
Juliana Amirdine ◽  
Thouaïba Htira ◽  
Nicolas Lefevre ◽  
René Fulchiron ◽  
Nathalie Mathieu ◽  
...  
Keyword(s):  
Extensional Flow ◽  
Novel Approach ◽  
Induced Crystallization ◽  
Flow Induced Crystallization

Simulation of film blowing including flow-induced crystallization

2001 ◽  
Vol 45 (5) ◽  
pp. 1085-1104 ◽  
Author(s):  
Antonios K. Doufas ◽  
Anthony J. McHugh
Keyword(s):  
Film Blowing ◽  
Induced Crystallization ◽  
Flow Induced Crystallization

Prediction of normal melting point of pure substances by a reference series method

AIChE Journal ◽  
2013 ◽  
Vol 59 (10) ◽  
pp. 3730-3740 ◽  
Author(s):  
Neima Brauner ◽  
Mordechai Shacham
Keyword(s):  
Melting Point ◽  
Series Method ◽  
Reference Series ◽  
Pure Substances ◽  
Normal Melting Point

Elastomer Structures and ‘Cold Crystallization’

1979 ◽  
Vol 52 (1) ◽  
pp. 207-212 ◽  
Author(s):  
M. Bruzzone ◽  
E. Sorta
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Melting Point ◽  
Natural Rubber ◽  
Crystallization Rate ◽  
Cold Crystallization ◽  
Structural Defects ◽  
Strain Induced Crystallization ◽  
Induced Crystallization

Abstract In a great number of applications an ideal elastomer should satisfy, to a certain extent, both of the following requirements: (1) nearly instantaneous crystallization upon application of strain (strain induced crystallization) and (2) slow or no crystallization when cooled at the temperature of maximum crystallization rate (cold induced crystallization). A noteworthy case of (2) is elastomer crystallization in a strained state. The connection between the points (1) and (2) has not been clearly understood up to now, but it is known that some crystallizable elastomers fulfil the requirements of both (1) and (2) better than others. From an experimental point of view, cold induced crystallization kinetics are substantially easier to measure than those of very fast strain induced crystallization. The phenomenon of cold induced crystallization in natural rubber, NR, has been known since the very beginning of elastomer technology and the tendency of natural rubber to crystallize by cooling has been overcome by crosslinking it with sulphur (vulcanization) without impairing its ability to crystallize by stretching (Goodyear, 1836). The synthesis of cis-polyisoprenes (IR) and cis-polybutadiene (BR) of different microstructural purity (different cis content) gave the possibility of changing the crystallization rate. It has also been reported that the very fast cold crystallization of trans-polypentenamer (TPA) could be reduced by lowering the trans content. The same fact had been observed earlier for trans-polychloroprene. There is a general agreement in postulating that the reduction of the crystallization rate, obtained either by cross-linking or by chain regularity reduction, can be linked with the lowering of the melting point. In both cases the low level of structural defects introduced in the chains does not affect the glass transition temperature in such a way as to vary the crystallization rate. The aim of this paper is to emphasize the importance of the variations of the glass transition temperature and melting point on the elastomeric cold crystallization rate and the way these may be used in planning new elastomer structures.

Sign in / Sign up

Export Citation Format

Share Document