Thermomechanical processing environment and morphology development of a thermotropic polymer liquid crystal

We have studied a longitudinal polymer liquid crystal consisting of poly(ethylene terephthalate) (PET) and p‐hydroxybenzoic acid, namely PET/0.6PHB, where 0.6 is the mole fraction of the second component. The material was injection molded with systematic variations of the melt and mold temperatures...

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Bibliographic Details
Published in:Journal of applied polymer science 2010-03, Vol.115 (5), p.2991-3004
Main Authors: Viana, Júlio C., Simões, Ricardo, Mano, João F., Oliveira, Maria. J., Denchev, Zlatan Z., Brostow, Witold, Cunha, António M.
Format: Article
Language:English
Subjects:
Applied sciences
Exact sciences and technology
Injection molding
Injection moulding
Liquid crystals
Machinery and processing
Mathematical analysis
Mathematical models
Melts
Morphology
Moulding
Orthogonal arrays
Plastics
Polyethylene terephthalates
Polymer industry, paints, wood
polymer liquid crystal
processing
Technology of polymers
thermomechanical environment
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Summary:We have studied a longitudinal polymer liquid crystal consisting of poly(ethylene terephthalate) (PET) and p‐hydroxybenzoic acid, namely PET/0.6PHB, where 0.6 is the mole fraction of the second component. The material was injection molded with systematic variations of the melt and mold temperatures and injection flow rate using design of experiments based on a Taguchi orthogonal array. Thermomechanical environment defined by local melt temperatures and shear rates and stresses imposed during processing was estimated by computer simulations of the mold‐filling phase. The morphology of the moldings was characterized by optical and scanning electronic microscopy, wide‐ and small‐angle X‐ray scattering, and differential scanning calorimetry. An analysis of variance approach identified the significant processing variables and their contributions to variations of morphological parameters. The processing environment affects strongly the melt viscosity, and there is a strong thermo‐mechanical coupling. The result is a complex multilaminated and hierarchical microstructure, whose morphological features are very sensitive to the processing conditions. Relationships between local thermomechanical variables (rather than global ones) and the morphological parameters are established. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
ISSN:0021-8995
1097-4628
1097-4628
DOI:10.1002/app.30087