Search results for "natural rubber"

Effect of CTBN rubber inclusions on the curing kinetic of DGEBA–DGEBF epoxy resin

2003

Abstract The curing kinetics of an epoxy resin matrix, based on diglycil ether of bisphenol A and F (DGEBA–DGEBF), associated with an anhydride hardener, at different carboxyl-terminated copolymer of butadiene and acrylonitrile liquid rubber (CTBN) concentration (0–10 phr) are studied using a differential scanning calorimetry (DSC) and a stress-controlled rheometer in isothermal and dynamic conditions. The aim of this work is to correlate the presence of the rubber phase with the transition phenomena that occur during the curing process. The CTBN rubber induces a catalytic effect on the polymerization of the pure resin clearly observed by a significant enhancement of the curing rate. Calori…

Poisson's ratio and the incompressibility relation for various strain measures with the example of a silica-filled SBR rubber in uniaxial tension tes…

2010

Abstract The controversy in the definition of Poisson's ratio (PR) as a material constant is discussed in this study. PR of an isotropic material is usually defined as the ratio, taken with the opposite sign, between its lateral and longitudinal strains under the action of longitudinal stresses. However, if deformations of the material are large, the value of PR depends on the strain measure used. Five different measures of strain are considered, and a unified relation in terms of stretch ratios is obtained for calculating the PR. It is demonstrated that only for Hencky strains is the value of PR of an incompressible material constant and equal to 0.5 over its entire extension range. Other …

Modeling the influence of mineral content and porosity on ultrasound parameters in bone by using synthetic phantoms

1999

Model composite media − 10×15×80 mm3 bone tissue phantoms based on an epoxy resin with fillers—were made to study the influence of porosity and mineral content on ultrasound velocity and attenuation. The pores were simulated by ∼ 1 mm3 particles of a soft rubber, while the mineral content was imitated by a mineral residue of natural bone obtained by burning and grinding. The porosity and mineral content were varied in the range of 0–70% by volume with a step of 10%. The velocity, attenuation, and prevalent frequency of ultrasound were measured by the pulse transition method, using transducers with nominal frequencies 0.1, 0.2, 0.5, and 1.0 MHz. It was experimentally found that the ultrasoun…

Preparation and Characterization of Composites Materials with Rubber Matrix and with Polyvinyl Chloride Addition (PVC)

2020

An important problem that arises at present refers to the increase in performances in the exploitation of the conveyor belts. Additionally, it is pursued to use some materials, which can be obtained by recycling rubber and PVC waste, in their structure. Thus, the research aimed at creating conveyor belts using materials obtained from the recycling of rubber and PVC waste. Under these conditions, conveyor belts were made that had in their structure two types of rubber and PVC, which was obtained by adding in certain proportions of reclaimed rubber and powder obtained from grinding rubber waste. In order to study the effect of adding PVC on properties, four types of conveyor belts were made, …

BCD-01 JOINT INFLUENCE OF TRANSVERSE COMPRESSION AND SHEAR-FLEXURAL STIFFNESS ON RUBBER V-BELT MECHANICS(BELT AND CHAIN DRIVES)

2009

Solid State NMR Spectroscopy Investigation of the Molecular Structure of Epoxy Based Materials Cured in Different Conditions

2012

In this work two epoxy resin model systems, whose monomers are typically used in structural composites, were thermally cured in different cure conditions in order to obtain different cross-linking densities. Their molecular structures were investigated through solid state NMR spectroscopy in order to correlate them to the cure process conditions used and the results were discussed in the light of the dynamical mechanical thermal analysis (DMTA) performed.

Investigations on Load Capacity and stability of deformation of rubber cylindrical shells under internal pressure

1994

The paper presents a wide analysis of conditions under which a loss of deformation stability can be observed as well as local bulges form in axially-symmetric (rotational) shells of any length. Analytical relations of the theory of shells were used for the analysis. If the maximum pressure in the shell was exceeded, the deformation process was investigated too. In such a case, strains begin to develop more intensely in the central part of a long cylindrical shell and, owing to that, one or more superimposed bulges (blisters) form. Symmetry of the shell deformation in relation to the centre of its length can be disturbed. A set of algebraic equations was derived for determination of critical…

The influence of the rubber carboxyl functionality on the processability and properties of solid rubber modified epoxy mixtures

2005

A high molecular weight, carboxyl functionalised solid rubber was added to an epoxy resin-aromatic amino system developed for autoclave curing of honeycomb core composite structures. The achievement of an optimal balance of viscous flow and viscoelasticity of the resin, by controlling the nature and extent of cross-linking of the functionalised rubber, was proposed as a route to void-free honeycomb skins. The aim of the present investigation is to understand how the concentration of carboxylic groups of the rubber, prereacted with one of the epoxy monomers, affects the matrix resin flow properties. The concentration of carboxyl groups was changed by reacting them with a monofunctional epoxy…

Tyre rubber-modified bitumens development: the effect of varying processing conditions

2013

Tyre rubber-modified binders (TR-MBs), produced through McDonald’s wet process and used worldwide (e.g. asphalt rubber), have been demonstrated to provide various benefits to pavements and, moreover, they represent a good opportunity for recycling tyre rubber (TR). However, this technology is still struggling to be fully adopted in Europe, mainly because of their poor stability during high temperatures storage, which leads to high initial costs in modifying existing asphalt plants. Storage stable TR-MBs are proving to be a great option and their development could be the key to spread the recycling of TR within paving applications in Europe. This paper aims to enrich this field of research b…

Mechanical manipulation of molecular lattice parameters in smectic elastomers.

2006

Smectic liquid crystalline elastomers (SLCE) represent unique materials that combine a 1-D molecular lattice arrangement and orientational order with rubber-elasticity mediated by a polymer network. Such materials may exhibit large thermo-mechanical, opto-mechanical and electro-mechanical effects, due to the coupling of macroscopic sample geometry and microscopic structural features. It is shown that the molecular layer dimensions in the smectic phases can be influenced reversibly by macroscopic strain of the material. We present a microscopic model on the basis of experimental results obtained by mechanical dilatation measurements, optical interferometry, X-ray scattering, (13)C NMR, FTIR …