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Linear Viscoelastic Properties (linear + viscoelastic_property)

Distribution by Scientific Domains

Polymers and Materials Science	87%

Selected Abstracts

Engineering investigations on the potentiality of the thermoformability of HDPE charged by wood flours in the thermoforming part

POLYMER ENGINEERING & SCIENCE, Issue 8 2009
F. Erchiqui
A dynamic finite element method is used to analyze the thermoformability of composites containing wood and a thermoplastic matrix for five different proportions of wood flour. Linear viscoelastic properties can be obtained by small amplitude oscillatory shear tests and the viscoelastic behavior is characterized using the Lodge model. To account for enclosed gas volume, which inflates the thermoplastic composite membrane, a thermodynamic approach is used to express the external work in terms of a closed volume. Pressure load is deduced by thermodynamic law using the Redlich,Kwong gas equation. The Lagrangian method together with the assumption of membrane theory is used in the finite element implementation. In addition, the influence of air flow on thickness and stress and the energy required to form a thin polymeric part in the thermoforming process are analyzed for five different proportions of wood flour in the HDPE material. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source]

Effect of stereoregularity of polypropylene on flow instability in capillary extrusion

ADVANCES IN POLYMER TECHNOLOGY, Issue 3 2009
Makoto Suzuki
Abstract Rheological responses in capillary flow extrusion for syndiotactic polypropylene (sPP) are studied along with the linear viscoelastic properties. It is found that sPP produced by a metallocene catalyst shows a high level of the onset shear stress for flow instability as compared with conventional isotactic polypropylene. This should enable operation of extrusion processing at high output rates. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 28:185,191, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20159 [source]

Dispersion of multiwalled carbon nanotubes in thermoplastic elastomer gels: Morphological, rheological, and electrical properties

POLYMER COMPOSITES, Issue 2 2010
Marissa A. Paglicawan
An investigation was reported here with an aim to prepare nanocomposite thermoplastic elastomer gels by dissolving polystyrene- b -poly(ethylene/butylene)- b -polystyrene (SEBS) triblock copolymer in selective hydrocarbon oils with the presence of multiwalled carbon nanotubes (MWCNTs). The properties related to morphology, viscoelasticity, electrical and mechanical properties, and thermal stability were explored and discussed. Dynamic rheological measurements of the resultant nanocomposite thermoplastic elastomer gels (NCTPEGs) confirmed that addition of MWCNTs affects the linear viscoelastic properties in which dynamic storage and loss moduli increase to some extent. At a temperature between 30°C and 40°C below the gel point the NCTPEGs have dynamic storage modulus greater than loss modulus (G, and G,), thereby indicating that at room temperature a physical network is still present despite the addition of MWCNTs. The morphological properties revealed that MWCNTs were dispersed and exfoliated within the swollen TPE. The incorporation of small quantity of MWCNTs improved the thermal stability and mechanical properties of NCTPEGs. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers [source]

Properties of new nanocomposite triblock copolymer gels based on expandable graphite,

POLYMER ENGINEERING & SCIENCE, Issue 9 2008
Marissa A. Paglicawan
In this work, we investigated the effect of expandable graphite (EG) on the property of triblock copolymer prepared from a poly(styrene- b -(ethylene- co -butylene)- b -styrene) (SEBS) imbibed with an EB-compatible hydrocarbon oil. The rheological properties showed that at a temperature between 30 and 40°C below the gel point, the triblock copolymer gels had a dynamic storage modulus (G,) greater than loss modulus (G,), thereby indicating that at ambient temperature, a physical network is still present in spite of the addition of nanoparticles. Dynamic rheological measurements of the resultant nanocomposite triblock copolymer gels confirmed that the addition of EG affects the linear viscoelastic properties and maximum operating temperature of the parent triblock copolymer gels. The mechanical properties showed only marginal increase, which can be attributed to the poor dispersion that leads to agglomeration of particle into micrometer size stacks, and thus the particles behave only as inorganic fillers. The morphology and X-ray diffraction revealed that the EG used to generate nanocomposite triblock copolymer gels is dispersed generally within the swollen copolymer and/or solvent. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source]

Morphology and rheological properties of polypropylene/reactive elastomer blends

POLYMER ENGINEERING & SCIENCE, Issue 10 2002
Frédérique Marguerat
The relation of morphology to the linear viscoelastic properties for polymer blends consisting of an inert polypropylene and an elastomeric dispersed phase, made of two miscible copolymers, EVA and EMA, was investigated. The rheological properties of the elastomeric phase were modified by crosslinking in presence of an organometallic catalyst. The activation energy for the transesterification reaction taking place between EVA and EMA has been determined by following the increases of the complex viscosity with time and temperature. The Palierne model has been used to describe the linear viscoelastic behavior of the blends, and to estimate the interfacial tension between the immiscible components. The model was shown to describe relatively well the linear viscoelastic properties of reactive and nonreactive blends containing 30% or less elastomer. In parallel, the morphology of reactive and nonreactive blends (i.e. without catalyst in the elastomeric phase), before and after rheological experiments, has been determined using scanning electron microscopy. The size of the dispersed elastomeric particles for reactive blends prepared using an internal mixer was found to be, in most cases, much smaller than that for nonreactive blends. [source]

Effect of processing variables on the linear viscoelastic properties of SBS-oil blends

POLYMER ENGINEERING & SCIENCE, Issue 12 2001
F. J. Navarro
Block copolymers, especially styrene-butadiene-styrene three-block copolymers (SBS), are recognized as especially effective asphalt modifiers because of their thermoplastic elastomeric properties. The concentration of copolymer, its ability to swell by the maltenic oils, and the processing variables are essential in the development of a three-dimensional network in the polymer-rich phase that enhances the vis-coelastic properties of these modified binders. This swollen polymer phase may influence the mechanical properties of the modified bitumens and synthetic binders. This paper deals with the influences that processing variables exert on the linear viscoelastic properties of oil/SBS mixtures in a wide range of temperatures. From the experimental results obtained we may conclude that most of the oil/SBS blends studied are highly structured thermoplastic gels above a critical SBS concentration that depends upon temperature, time of processing and surrounding atmosphere. [source]

Solid-state linear viscoelastic properties of intercalated poly(L -lactide)/organo-modified montmorillonite hybrids

POLYMER INTERNATIONAL, Issue 8 2006
Pham Hoai Nam
Abstract Hybrids of poly(L -lactide)/organophilic clay (PLACHs) have been prepared by a melt-compounding process using poly(L -lactide) (PLLA) and different contents of surface-treated montmorillonite modified with a dimethyl dioctadecyl ammonium salt. The dispersion structures of clay particles in PLACHs were investigated using wide-angle X-ray diffraction and transmission electron microscopy. The solid-state linear viscoelastic properties for these PLACHs were examined as functions of temperature and frequency. The incorporation of organo-modified silicate into PLLA matrix enhanced significantly both storage moduli (E,) and loss moduli (E,). The strong enhancement observed in dynamic moduli of PLACHs could be attributed to uniformly dispersed state of the clay particles with high aspect ratio (= length/thickness of clay) and the intercalation of the PLLA chains between silicate layers. Copyright © 2006 Society of Chemical Industry [source]