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Bulk and surface molecular orientation distribution in injection‐molded liquid crystalline polymers: Experiment and simulation
Author(s) -
Fang Jun,
Burghardt Wesley R.,
Bubeck Robert A.,
Burgard Susan M.,
Fischer Daniel A.
Publication year - 2010
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.21710
Subject(s) - materials science , polymer , fourier transform infrared spectroscopy , thermotropic crystal , composite material , attenuated total reflection , orientation (vector space) , optics , chemical physics , geometry , chemistry , liquid crystalline , physics , mathematics
Bulk and surface distributions of molecular orientation in injection‐molded plaques of thermotropic liquid crystalline polymers (TLCPs) have been studied using a combination of techniques, coordinated with process simulations using the Larson‐Doi “polydomain” model. Wide‐angle X‐ray scattering was used to map out the bulk orientation distribution. Fourier Transform Infrared Attenuated Total Reflectance (FTIR‐ATR) and Near‐Edge X‐ray Absorption Fine Structure (NEXAFS) were utilized to probe the molecular orientation states to within about ∼5 μm and ∼2 nm, respectively, of the sample surface. These noninvasive, surface‐sensitive techniques yield reasonable self‐consistency, providing complementary validation of the robustness of these methods. An analogy between Larson‐Doi and fiber orientation models has allowed the first simulations of TLCP injection molding. The simulations capture many fine details in the bulk orientation distribution across the sample plaque. Direct simulation of surface orientation at the level probed by FTIR‐ATR and NEXAFS was not possible due to the limited spatial resolution of the simulations. However, simulation results extracted from the shear‐dominant skin region are found to provide a qualitatively accurate indicator of surface orientation. Finally, simulations capture the relation between bulk and surface orientation states across the different regions of the sample plaque. POLYM. ENG. SCI., 50:1864–1877, 2010. © 2010 Society of Plastics Engineers