The Analysis of Stiffness for Rubbery Metallic Material Based on Mesoscopic Features

In this article, deformation and mechanical response of a rubbery metallic material were investigated. First, the mesoscopic structural properties of the material and its evolution during part producing were analyzed and described in detail. Then the inherence relationship between the macroscopic mechanical properties and mesoscopic structural characteristics were studied, in which the related mesoscopic structural characteristics were limited in the basic unit (mm) scale such as the radius of metal wire and unit coil, etc. Furthermore, according to the mesoscopic properties of the material, a curved beam unit based on the mesoscopic scale and shape factor was introduced to bridge the mechanical response and the mesoscopic parameters such as the beam orientation and spatial distribution. In the end, a mesoscopic stiffness model was proposed, from which the macroscopic mechanical properties of material could be deduced from the mesoscopic characteristic size, shape and the mechanical properties of base metallic material.

Rubbery neat carbon aerogels

Polymeric elastomers possess unique elastic mechanical properties that set them apart from other materials,and enable wide applications in a large variety of products such as elastic films,foams and tires.The polymer chains tend to be coil-like due to thermal fluctuation but can also be straightened by external forces,leading to large reversible deformations.

Review:Progress in Core-shell Rubber Particles for Efficiently Toughening Resins

Core-shell toughening particles are structured composite particles consisting of generally two different components, one at the center as a rubbery elastic core and surrounding by the second as a glassy inelastic shell. The design, preparation, and application of core-shell polymer particles have been briefly reviewed. Morphological characteristics of the core-shell particles by transmission electron microscopy(TEM) and scanning electron microscopy(SEM) are focused. The vital factors that are useful to control core-shell morphology and toughening properties including core-shell monomer species, polymerization conditions, cross-linking reagents, synthetic method, and post-processing techniques are analyzed. Distinguished properties are mainly considered as the most desirable features that endow core-shell polymer particles with various applicabilities, particularly as effectively toughening components in brittle epoxy resin and polylactide that are substrate of copper clad laminate widely used in the modern electronic world and environmentally friendly materials that are useful as packaging films, disposable tableware, biomedical equipment, and new energy vehicles.

VISCOELASTIC BEHAVIOR OF THE NON-HOOKE DEFORMATION BEFORE YIELDING IN UNIAXIAL DRAWING OF AMORPHOUS POLY(ETHYLENE TEREPHTHALATE)

Viscoelastic behavior of the non-Hooke deformation of amorphous PET film before yield was investigated in the temperature region 74-80.5 degreesC around the glass transition temperature. The film specimen was drawn to yield point followed by unloading to zero stress, then the residual deformation was held constant; while the subsequent evolution of the stress was recorded. An induction period was found in the course of stress evolution followed by a stress step-increase. The induction period decreases with increasing drawing temperature with an activation energy of 1.10 MJ/mol.K, which is attributed to the time needed for the relaxation of rubbery deformation through cooperative internal rotations. At temperatures lower than 74 degreesC, there is no stress increase or the induction period becomes too long to be observed. Thus the nature of anelasticity in the non-Hooke region before yielding is attributed to stress induced rubbery deformation. The experimental results are interpreted in terms of Perez' theological model of a series connected Hooks spring and a Voigt element consisting of a parallel connected elastic spring and a dashpot.

Preparation and Structure of Poly(ethylene-co-vinylacetate)/Montmorillonite Nanocomposites

Poly(ethylene-co-vinylacetate)/sodium montmorillonite(EVA/MMT)and Poly(ethylene-co-vinylacetate)/organophilic montmorillonite(EVA/o-MMT)nanocomposite were prepared by solid-state mixing.The morphology and structure of the composites were explored by scanning electron microscopy(SEM),wide-angle X-ray diffraction(WAXD),differential scanning calorimetry(DSC),and dynamic mechanical analysis(DMA).The results showed that the intercalated nanocomposite was successfully synthesized for EVA/o-MMT system,while in the EVA/MMT nanocomposite,MMT were poorly dispersed in the order of μm.An unexpected rubbery plateau modulus of EVA/o-MMT nanocomposite above melting point of EVA was explored by DMA.The possible origins of this high-temperature modulus were analyzed.