Search results for "Elastic Modulu"
showing 10 items of 189 documents
Processing and properties of blends with liquid crystal polymers
1990
Experimental data on the processing behavior and on the rheological and mechanical properties of blends with a liquid crystal polymer as one component are presented. The blends with low amounts of LCP show easier processability and lower viscosity than the thermoplastic matrix. The elastic modulus is also improved. The reduction of viscosity has been attributed to the lower pressure entry, due to the formation of fibrils and to the immiscibility of the two phases.
Nanoscale mechanical characterization of polymers by AFM nanoindentations: Critical approach to the elastic characterization
2006
AFM nanoindentations show a dependence of penetration, i.e., the relative motion between the sample and the tip (indenter), on material elastic properties when using the same load. This elationship becomes visible by using of samples being homogeneous down to the scale of nanoindentation. They were prepared from materials covering a broad range of mechanical behavior: from rubbery networks to glassy and semicrystalline polymers. The elastic modulus can be obtained applying Sneddon’s elastic contact mechanics approach. To do this, some calibrations and instrumental features have to be measured accurately. All the polymers tested show that the contact between the tip and the sample is dominat…
Morphology, rheology, and mechanical properties of a new nanobiocomposite
2015
Nanobiocomposites are a new class of biodegradable polymer materials with an ultrafine phase dispersion of the order of a few nanometers in a biodegradable polymer matrix that shows very interesting properties often very different from those of conventional filled polymers. In this work the morphology and the rheological and mechanical properties of a new nanobiocomposite made of a biodegradable copolyester based blend with an organomodified montmorillonite have been investigated to evaluate its possible use in several applications. SAXS diffractograms and TEM micrographs show that the in both the adopted processing conditions an hybrid intercalated/exfoliated morphology is observed. Rheolo…
Effects of filler type and mixing method on the physical properties of a reinforced semirigid liquid crystal polymer
1996
Semirigid liquid crystalline polymers (LCPs) show some advantages with respect to rigid LCP: in particular lower processing temperatures, better compatibility with flexible thermoplastics, but also some disadvantages. Thermal resistance of rigid LCPs is much better and the maximum working temperature is, in general, very high. The thermomechanical properties can be improved by adding inorganic fillers. In this work processing, mechanical and thermomechanical properties of a filled semirigid liquid crystal copolyester are reported. Several inorganic fillers have been used in order to put in evidence the influence of shape and dimensions of the particles on the properties of the filled materi…
Processing and characterization of blends of fluoroelastomers with semirigid liquid crystal polymers
1996
Fluoroelastomers (FEs) usually have working temperatures above 150°C and a great resistance to aggressive agents such as oils, fuels, aliphatic and aromatic solvents, steam, moderate acid, and basic environments. Liquid crystal polymers (LCPs) can be effective processing aids and reinforcing agents for elastomers. These characteristics are very attractive to lower melt viscosity and to stiffen and strengthen the final product through a simple blending. Among the LCPs, the semirigid LCPs seem the most appealing for blending with flexible thermoplastics (FTs) because their processing temperatures can be arranged to be in the same processing temperature range of FTs and because the presence of…
Kenaf-filled biodegradable composites: rheological and mechanical behaviour
2012
Biodegradable polymer composites, typically based on biodegradable polymer matrices and natural-organic fillers, are gaining rising interest and importance over the last few years. Several natural-organic fillers can be used but the most widespread so far is wood, in the form of fibres or flour. Alternative cellulosic fillers can ensure advantages in terms of resource utilization and properties of the final composite. In this work, Mater-Bi® based biodegradable composites were prepared with two kinds of wood flour, and directly compared with alternative composites containing kenaf fibres. The use of kenaf fibres allowed improved elastic modulus, tensile strength and interaction with the pol…
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…
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…