Healing of knit lines in injection-molded liquid crystalline polymers

2007 ◽  
pp. 57-62 ◽  
Author(s):  
K. Engberg ◽  
U. W. Gedde
Keyword(s):  
Liquid Crystalline ◽  
Liquid Crystalline Polymers ◽  
Crystalline Polymers ◽  
Injection Molded

Investigation of Structure-Property Relationships Between Crystal Orientation and Dielectric Behavior in Liquid Crystalline Polymers

2017 ◽  
Author(s):  
Anthony Sullivan ◽  
Anil Saigal ◽  
Michael A. Zimmerman
Keyword(s):  
High Performance ◽  
Liquid Crystalline ◽  
Driving Forces ◽  
Liquid Crystalline Polymers ◽  
Dielectric Behavior ◽  
Dielectric Anisotropy ◽  
Shear Direction ◽  
Structure Property ◽  
Crystalline Polymers ◽  
Injection Molded

Liquid crystalline polymers (LCP’s) make up a class of high performance materials, which derive favorable mechanical, chemical, and electrical characteristics from their long-range molecular order. The unique LCP microstructure gives rise to anisotropic bulk behavior and an understanding of the driving forces behind this morphology is essential to the design of manufacturing processes for isotropic material production. In this investigation, the crystalline orientation in injection molded LCP plaque samples was measured using 2D wide-angle x-ray scattering (WAXS). The direction of preferred alignment was observed from the WAXS scattering patterns and the degree of orientation in the material was quantified using an order parameter and an anisotropy factor. In addition, the dielectric constant was measured with respect to the mold direction (MD) and transverse direction (TD). To investigate the effects of processing on hierarchal structure in the material, and the resulting macroscopic properties, plaques of two different thicknesses were analyzed, both as-injection molded and with the skin layer mechanically removed. It is shown that preferred orientation along the shear direction in the LCP samples corresponds to dielectric anisotropy, and increasing sample thickness, or conversely, mechanically removing the shear aligned layer, results in a more isotropic dielectric response.

Knit line fractures in injection molded liquid crystalline polymers

1990 ◽  
Vol 30 (24) ◽  
pp. 1620-1627 ◽  
Author(s):  
K. Engberg ◽  
A. Knutsson ◽  
P.-E. Werner ◽  
U. W. Gedde
Keyword(s):  
Liquid Crystalline ◽  
Liquid Crystalline Polymers ◽  
Crystalline Polymers ◽  
Injection Molded

Bulk and surface molecular orientation distribution in injection-molded liquid crystalline polymers: Experiment and simulation

2010 ◽  
Vol 50 (9) ◽  
pp. 1864-1877 ◽  
Author(s):  
Jun Fang ◽  
Wesley R. Burghardt ◽  
Robert A. Bubeck ◽  
Susan M. Burgard ◽  
Daniel A. Fischer
Keyword(s):  
Molecular Orientation ◽  
Liquid Crystalline ◽  
Liquid Crystalline Polymers ◽  
Orientation Distribution ◽  
Crystalline Polymers ◽  
Injection Molded ◽  
Experiment And Simulation

Structure-property relations of liquid crystalline polymers

1987 ◽  
Vol 45 ◽  
pp. 460-463
Author(s):  
Linda C. Sawyer
Keyword(s):  
Solid State ◽  
Liquid Crystalline ◽  
Structural Model ◽  
Crystalline Polymer ◽  
Liquid Crystalline Polymers ◽  
Mechanical Anisotropy ◽  
Structure Property ◽  
Preparation Methods ◽  
Crystalline Polymers ◽  
Extended Chain

Recent liquid crystalline polymer (LCP) research has sought to define structure-property relationships of these complex new materials. The two major types of LCPs, thermotropic and lyotropic LCPs, both exhibit effects of process history on the microstructure frozen into the solid state. The high mechanical anisotropy of the molecules favors formation of complex structures. Microscopy has been used to develop an understanding of these microstructures and to describe them in a fundamental structural model. Preparation methods used include microtomy, etching, fracture and sonication for study by optical and electron microscopy techniques, which have been described for polymers. The model accounts for the macrostructures and microstructures observed in highly oriented fibers and films.Rod-like liquid crystalline polymers produce oriented materials because they have extended chain structures in the solid state. These polymers have found application as high modulus fibers and films with unique properties due to the formation of ordered solutions (lyotropic) or melts (thermotropic) which transform easily into highly oriented, extended chain structures in the solid state.

Factors affecting microstructural scale in liquid crystalline polymers

1990 ◽  
Vol 48 (4) ◽  
pp. 220-221
Author(s):  
Christine M. Dannels ◽  
Christopher Viney
Keyword(s):  
Liquid Crystalline ◽  
Liquid Crystalline Polymers ◽  
Factors Affecting ◽  
Crystalline Polymers ◽  
Thermal Expansion Coefficients ◽  
Low Thermal Expansion ◽  
Lower Viscosity ◽  
Fine Microstructure ◽  
Planar Orientation ◽  
Strength And Stiffness

Processing polymers from the liquid crystalline state offers several advantages compared to processing from conventional fluids. These include: better axial strength and stiffness in fibers, better planar orientation in films, lower viscosity during processing, low solidification shrinkage of injection moldings (thermotropic processing), and low thermal expansion coefficients. However, the compressive strength of the solid is disappointing. Previous efforts to improve this property have focussed on synthesizing stiffer molecules. The effect of microstructural scale has been overlooked, even though its relevance to the mechanical and physical properties of more traditional materials is well established. By analogy with the behavior of metals and ceramics, one would expect a fine microstructure (i..e. a high density of orientational defects) to be desirable.Also, because much microstructural detail in liquid crystalline polymers occurs on a scale close to the wavelength of light, light is scattered on passing through these materials.

Statistical physics of liquid-crystalline polymers

1988 ◽  
Vol 156 (11) ◽  
pp. 427 ◽  
Author(s):  
A.N. Semenov ◽  
Alexei R. Khokhlov
Keyword(s):  
Statistical Physics ◽  
Liquid Crystalline ◽  
Liquid Crystalline Polymers ◽  
Crystalline Polymers

Processing Studies of Blends of Polypropylene with Liquid Crystalline Polymers

1991 ◽  
Author(s):  
A. Datta ◽  
J. P. De Souza ◽  
A. P. Sukhadia ◽  
D. G. Baird
Keyword(s):  
Liquid Crystalline ◽  
Liquid Crystalline Polymers ◽  
Crystalline Polymers
Sign in / Sign up

Export Citation Format

Share Document