Predictive Continuum Constitutive Modeling of Unfilled and Filled Rubbers

The general CSE model fits Treloar’s uniaxial extension test and predicts unfitted uniaxial compression, equibiaxial extension, biaxial extension, pure shear, and simple shear tests. As a newly proposed method, the general CSE model, along with the stress-softening ratio, the residualstretch ratio, and the weighted piecewise two-point interpolation function, fits the Cheng–Chen’s test and the Diani–Fayolle–Gilormini’s test in cyclic uniaxial extension at different pre-stretches and predicts corresponding responses at untested pre-stretches. Physical mechanisms of the Mullins effect have also been predicted based on the evolution of constitutive parameters.

A Network Evolution Model for Recovery of the Mullins Effect in Filled Rubbers

The stress-softening phenomenon, named as the Mullins effect, can widely occur in filled rubbers after cyclic loading and unloading conditions. The reloading curve is typically below the initial loading curve unless the applied strain exceeds the previously applied maximum strain. Experimental observations have also shown that the Mullins effect can be recovered by annealing the pre-deformed filled rubbers at a high temperature while the recovery level strongly depends on the annealing time and temperature. In this work, we develop a theoretical model to describe the recovery of the Mullins effect by incorporating the dynamic scission and recovery of polymer chains into the eight-chain model. Experiments have also been performed on two types of filled rubbers to validate the theory. The results show that the model is able to capture the main features of the experimental observations including the Mullins effect of virgin specimens and the recovery of the Mullins effect of pre-deformed specimens subjected to different annealed conditions.

THE PROSPECT OF USING THE BICOMPONENT COAGULANT OF MOLLASES "SODIUM CHLORIDE" WNEN PRODUCTION OF OIL-FILLED RUBBERS

Currently, special attention is paid to improving the production technology of synthetic rubbers. Synthetic rubbers are in great demand in the tire and rubber industry, in the manufacture of composite materials for various purposes, etc. Every year, the requirements for both the quality of manufactured products and the environmental friendliness of their production are increasing. One of the problematic stages in the production of rubbers by emulsion polymerization is the stage of their separation from latex. The paper considers the possibility of using a bis-compound coagulant consisting of a by-product of beet sugar production of molasses and traditional sodium chloride in the process of obtaining oil-filled rubbers. It was found that the use of this bis-compound coagulant to reduce the agricul-ture stability of synthetic latexes reduces the consumption of coagulating agents by 3-4 times. It is shown that the main coagulating component of molasses is betaines, which are present in its composition. Sodium chloride contributes to the coagulation process by the concentration mechanism, and betaine – by the neutralization mechanism, based on the chemical interaction of surfactant anions with the positively charged ammonium group of the betaine molecule. The use of a bis-compound coagulant reduces environmental pollution by components of the emulsion system. The water phase remaining after the rubber is extracted from latex can be used to prepare a solution of molasses and sulfuric acid. Rubber mixtures prepared on the basis of experimental samples of rubber meet the requirements in terms of their parameters.

Elucidating the G″ overshoot in soft materials with a yield transition via a time-resolved experimental strain decomposition

Materials that exhibit yielding behavior are used in many applications, from spreadable foods and cosmetics to direct write three-dimensional printing inks and filled rubbers. Their key design feature is the ability to transition behaviorally from solid to fluid under sufficient load or deformation. Despite its widespread applications, little is known about the dynamics of yielding in real processes, as the nonequilibrium nature of the transition impedes understanding. We demonstrate an iteratively punctuated rheological protocol that combines strain-controlled oscillatory shear with stress-controlled recovery tests. This technique provides an experimental decomposition of recoverable and unrecoverable strains, allowing for solid-like and fluid-like contributions to a yield stress material’s behavior to be separated in a time-resolved manner. Using this protocol, we investigate the overshoot in loss modulus seen in materials that yield. We show that this phenomenon is caused by the transition from primarily solid-like, viscoelastic dissipation in the linear regime to primarily fluid-like, plastic flow at larger amplitudes. We compare and contrast this with a viscoelastic liquid with no yielding behavior, where the contribution to energy dissipation from viscous flow dominates over the entire range of amplitudes tested.

Effects of TESPT-Silane Coupling Agent on Torque Properties and Degree of Filler Dispersion of Silica Filled Natural Rubber and Epoxidized Natural Rubbers Compounds

The effect of the addition of a bis(triethoxysilylpropyl) tetra sulphide or TESPT-silane coupling agent on torque properties and degree of filler dispersion of silica-filled compounds of natural rubber (NR), epoxidized natural rubbers with 25% mole of epoxidation (ENR 25) and epoxidized natural rubbers with 50% mole of epoxidation (ENR 50) were investigated. All the rubbers were filled by silica filler at a fixed loading (30.0 parts per hundred rubber, phr) and the TESPT was added to each silica-filled rubbers compounds at 1.0phr. It was found that TESPT affected the torque properties of all the silica-filled rubbers compounds. The TESPT decreased the minimum torque of NR system but increased the minimum torque of ENRs systems and maximum and torque differences of the all rubbers systems. The minimum torque was decreased from 0.61 to 0.53 dN.m for NR; were increased from 0.23 to 0.49 dN.m for ENR 25 and from 0.07 to 0.34 dN.m for ENR 50.It was also found that the TESPT acted as an internal plasticizer for NR which improved the degree of silica dispersion. Presumably, for the ENRs, the TESPT acted as an additional cross linker with a more pronouncedly which poorer the degree of silica dispersion.

Multiphysics Coupling In Aging Process of Filled-Rubber

Filled rubbers are used popularly in damping parts which can be found in automobile sector or in building sector. However, the mechanical properties of material depend sensitively on temperature, chemical composition and environment conditions. In fact, the mechanical dissipation due to damping process leads to the increase of temperature considerably. Aging process can be activated sequentially by the heat which result in the change of damping properties during usage time. This paper presents a new behavior model that considers the simultaneous effects of temperature, mechanical loads on the behavior of materials along with the aging of materials. With the assumption of internal variables related to aging phenomenon and visco-plastic behavior, the model is built in the thermodynamical framework. A fully coupled finite element formulation is proposed to solve simultaneously thermo, chemical and mechanical phenomenon appeared in this material. An example illustrates the number of applicability of the model to predict the behavior of materials under the effect of cyclic loads in extremely working conditions