Search results for "Elastic"

Thermal and viscoelastic properties of entangled supramolecular polymer networks as a powerful tool for prediction of their microstructure

2018

Abstract Thermal and viscoelastic properties of entangled supramolecular polymer networks, SPNs, depend strongly on binary and collective assembly of associative groups. The collective assemblies can phase separate from polymer matrix chains and form domains with different sizes and shapes, which have different melting point transitions. By increasing content of associative groups along the polymer chains, their high-order association leads to formation of domains, which have higher melting temperatures than other ones. We prepared a SPN system that contains three networks. All networks have similar precursor polymer backbone, but different content of ureidopyrimidinone, UPy, moiety as stro…

Modeling the non-linear deformation of a short-flax-fiber-reinforced polymer composite by orientation averaging

2013

Abstract The growing usage of short-flax-fiber-reinforced polymer composites in such applications as automotive industry necessitates the prediction of their mechanical response up to and beyond the limit of elasticity. Due to the imperfect, mechanical interlocking-dominated adhesion of natural fibers to most polymers, both fiber debonding and matrix yielding contribute to the non-linear deformation. In the present study, the deformation under an active loading of a short misaligned fiber composite is modeled by the orientation averaging approach, employing an analytical description of the behavior of a unit cell (UC), the parameters of which are determined using a FEM analysis of UC respon…

Model analysis of uniaxial and biaxial stretching of polymer melts

1976

The biaxial extension results byDenson et al. are compared with the predictions of a model of non-linear viscoelasticity. Date of uniaxial extension on the same material (a commercial polyisobutylene) are taken for extending the comparison. The model used seems to adequately describe both types of elongational flow with the same value of the single adjustable parameter.

Quasielastic neutron scattering study of dynamics at the crossover from dilute to semidilute behavior in polymer solutions

1982

On the Use of the Nanoindentation Unloading Curve to Measure the Young's Modulus of Polymers on a Nanometer Scale

2005

Summary: The nanoindentation test is a fundamental tool to assess the link between morphology and mechanical properties. The preliminary results of a more exhaustive study about the applicability to polymers of the most used procedure to determine elastic modulus by indentation are reported in this short communication. A departure of the experimental conditions from the theoretical assumptions and results that give rise to the Oliver and Pharr analysis is shown to occur under a wide range of experimental conditions, with applied loads and penetration depths covering several orders of magnitude and using different indenter geometries. Unloading curves with exponents significantly larger than…

EFFECT OF MOISTURE ON THE BULK PROPERTIES OF SALTED POLY(CAPROAMIDE).

1980

The glass-transition temperature (Tg) and the elastic modulus of nylon-6 and its mixtures with 4% w/w LiCl and with 2% LiCl+3% LiBr were investigated. In one set of experiments care was taken to avoid absorption of moisture during the measurements. In another set of experiments, samples were exposed to atmospheric humidity for different lengths of time. Both unoriented and oriented specimens were investigated. The presence of 4% LiCl almost doubles the amount of moisture absorbed at equilibrium by nylon-6. The Tg was found to be greatly affected by the moisture content and by salt type. When strict precautions to exclude moisture are taken, the addition of 4% LiCl raises the Tg of nylon-6 b…

Entanglement Transition in Hyperbranched Polyether-Polyols

2010

Are hyperbranched polymers capable of forming entanglements? This is the central issue of this contribution. Hyperbranched polyglycerol (hbPG) samples with different molecular weights (600-106 000 g · mol(-1) ), narrow polydispersities (1.2-1.8) and high degrees of branching (≈0.6) were prepared by anionic ring-opening polymerization. The viscoelastic properties of these polymers with respect to molecular architecture and molar mass were investigated. At low molecular weights "classical" scaling behavior between zero shear viscosity and molecular weight can be observed, whereas between 3 000 and 10 000 g · mol(-1) a plateau-like area is found. The results indicate entanglement dynamics when…

Enhancing the mechanical performance of polymer based nanocomposites by plasma-modification of nanoparticles

2012

Abstract The possibility of enhancing the mechanical performance of two different polymer-based nanocomposites using polyamide 6 (PA6) and poly[ethylene-co-(vinyl acetate)] (EVA) as matrices was investigated. The nanofillers used were, respectively, either carbon nanotubes (CNTs) or an organically modified montmorillonite (Cloisite 15A), both previously modified by plasma treatment to introduce polar moieties. The nanofillers were fully characterized by Raman spectroscopy, XPS, FT-IR and XRD, demonstrating their effective modification with oxygenated groups. The nanocomposites were prepared by melt processing in order to obtain films and fibres. The mechanical tests carried out on the nanoc…

EVA Copolymer Based Nanocomposites

2002

Nanocomposites are a new class of polymer material with an ultrafine phase dispersion of the order of a few nanometers that shows very interesting properties often very different from those of conventional filled polymers. In this work the mechanical and optical properties of Poly-[ethylene-co-(vinyl acetate)] (EVA copolymer) based nanocomposites have been investigated to evaluate its possible use in several applications. For example, films for covering greenhouse effect. Mechanical properties, and the rigidity in particular, are, on the contrary, quite low. Nanocomposites should avoid this shortcoming if optical properties and processability are not unfavorably effected. EVA copolymer base…

Ethylene-vinyl Acetate Thermoplastic Copolymers Filled with Multiwall Carbon Nanotubes: Effect of Hydrothermal Ageing on Mechanical, Thermal, and Ele…

2013

A range of properties of two commercial thermoplastic ethylene-vinyl acetate (EVA) copolymers, Elvax 420 and Elvax 450, neat and as melt-mixed composite filled with 15 wt.-% of multi-wall carbon nanotubes (MWCNTs), are studied in the “as produced” state and after hydrothermal ageing. Addition of MWCNTs into the neat copolymers introduces the functionality of electrical conductivity and significantly improves their mechanical properties, while thermal characteristics are slightly affected by the presence of carbon nanotubes. A remarkable increase of the elastic modulus (150%) and stress at failure (50%) in stress–strain experiments as well as creep resistance (40%) of the nanocomposites in c…