SbstractThe main objective of this work is the study of the influence of microwaves devulcanization of the elastomeric phase on dynamically revulcanized blends based on Ground Tire Rubber (GTR)/High Density Polyethylene (HDPE). The devulcanization of the GTR was performed in a system comprised of a conventional microwave oven adapted with a motorized stirring at a constant microwaves power and at various exposure times. The influence of the devulcanization process on the final properties of the blends was evaluated in terms of mechanical, viscoelastic, thermal and rheological properties. The morphology was also studied.

The dielectric properties of nanocomposites of polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS) triblock copolymers containing organically modified clay nanoparticles featuring controlled spatial orientation at the nanoscale: isotropic, totally oriented and partially oriented, have been investigated and correlated with the nanocomposite morphologies. A slow dielectric relaxation process attributed to elastomer chains with reduced mobility confined at nanoparticle/polymer interphase was observed in all the nanocomposites and was found to be dependent on the orientation of nanoclay and polystyrene (PS) domains, the location of clay tactoids as well as the PS block fraction. A dielectric "interfacial" glass transition temperature T gi assigned to this characteristic relaxation was estimated to occur at temperatures ranging between 6 °C and 35 °C depending on the nanocomposite, which is much higher than the bulk rubber phase glass transition temperature, normally lower than -40 °C for the studied block copolymers. Interestingly, the highest T gi were associated with the nanocomposites featuring random or partial orientation and/or selective location of nanoparticles in the rubber phase. I) IntroductionIn nanocomposite materials, controlled orientation of certain anisotropic nanoparticles such as nanoclay 1,2 , carbon nanotubes 3 and recently boron nitride nanotubes and nanosheets 4,5 is very beneficial for a wide spectrum of applications requiring excellent mechanical, electrical and/or thermal properties.For example, in the case of mechanical reinforcement, the alignment of nanoclay was reported in several publications to induce an improved mechanical strength in the alignment direction 6 . In the specific case of nanodielectrics, more efficient electron scattering and consequently higher breakdown strength perpendicular to the nanoparticles alignment direction were reported 2,7,8,9 . Simultaneously, nanoparticle alignment was shown to reduce dielectric losses in the direction perpendicular to the main plane of the M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT3 aligned nanoparticles 2 . This controlled orientation can be obtained using a wide range of techniques 3 although spatial alignment of nanoparticles according to 2D and 3D patterns is still a challenging field of study 10 .In applications requiring tuned spatial distribution of nanoparticles, the use of block copolymers can be really an asset due to the different nanoscale morphologies these materials present 11,12,13,14,15,16 . To probe the effect of tailored morphology and orientation of such designed nanocomposites on their polymer-filler interactions and implicitly on their final performance, techniques such as broadband dielectric spectroscopy (BDS) are often required 17 .In fact, the performance of polymer nanocomposites in general is governed by the interphase region 18,19 which consists mainly of a bound layer where the motion of macromolecular chains is strongly restricted affecting several properties including dielectric and m...

In this work, the effect of extensional flow on the morphology of polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS) triblock copolymers and their clay-containing nanocomposites was evaluated. Four types of SEBS copolymers with different block compositions and cylindrical morphology were chosen to understand the effects of cylinder orientation and state of clay dispersion on the evolution of morphology during extensional flow. The effect of clay concentration (ranging from 2.5 to 7.5 wt. %) was also studied. The samples were subjected to extensional flow using a Sentmanat extensional rheometer attached to a rotational rheometer at Hencky strain rates varying from 0.01 to 20 s À1 . Small angle X-ray scattering analysis was subsequently performed to evaluate the morphological changes caused by extensional flow. When preoriented block copolymers [SEBS-30% PS (polystyrene)] and their nanocomposites undergo elongation, the styrene cylinders and clay nanoparticles align themselves in the flow direction and their rheological behavior and morphological evolution are influenced by the stretching direction (longitudinal and transverse), strain rate magnitude, clay concentration, and dispersion state of the clay nanoparticles. When isotropic block copolymers (SEBS-13% PS) undergo elongation, it was observed that the PS cylinders only exhibit structural alignment in the stretching direction in the presence of clay. Block copolymer molecules can exhibit different relaxation times depending upon the volume fraction of PS domains (13% or 30%). The addition of clay, however, hinders complete relaxation, helping to promote a permanent domain alignment after flow cessation, especially in hard-to-align copolymers. V C 2016 The Society of Rheology.

Clay‐containing nanocomposites of polystyrene‐b‐poly(ethylene‐co‐butylene)‐b‐polystyrene (SEBS) copolymers having cylindrical domains were obtained by melt extrusion using a tape die. One type of sample (SEBS‐MA) had maleic anhydride attached to the middle block. Two types of organoclays were added, namely Cloisite 20A and Cloisite 30B. Small angle X‐ray scattering and transmission electron microscopy (TEM) analyses showed that the addition of 20A clay to SEBS and SEBS‐MA resulted in nanocomposites with intercalated and partially exfoliated structures, respectively. The addition of 30B clay to SEBS and SEBS‐MA promoted the formation of composites containing relatively large micron‐sized and partially exfoliated clay particles, respectively. Our TEM analysis revealed that clay particles embedded in SEBS are preferably in contact with the polystyrene cylindrical domains, while in SEBS‐MA they are in contact with the maleated matrix. The extrusion processing promoted alignment of the axes of the polystyrene cylinders along the extrusion direction in all samples, and the basal planes of the clay particles were mostly parallel to the main external surfaces of the extruded tapes. © 2013 Society of Chemical Industry

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In 2004, a single-crystalline graphite film of atomic thickness was isolated [1]. The researchers responsible for this revolutionary work, Novoselov and Geim, were shortly thereafter awarded the Nobel Prize in Physics for 'innovative experiments with graphene' in 2010. Several researchers have used graphene (Gr), graphene oxide (GO), and reduced graphene oxide (rGO) as mechanically reinforcing nanoparticles in polymeric matrices. The insertion of these two-dimensional (2D) materials considerably improves the mechanical properties of the polymers. They also increase the thermal and electrical conductivity and the dimensional stability of the composite when compared to the polymer matrix [2-7]. Important challenges still need to be overcome to produce polymer nanocomposites based on two-dimensional particles (graphene-based materials, molybdenum disulfide, hexagonal boron nitrite, and phosphorene among others) on a large scale. Essentially, there are three strategies for nanocomposites preparation: 1) solution mixing, 2) in situ polymerization, and 3) melt mixing. The first two options achieve excellent results in terms of particles dispersion, however,

SbstractThe main objective of this work is to study the influence of clay addition on dynamically revulcanized blends of Ground Tire Rubber (GTR)/High Density Polyethylene (HDPE). GTR was previously devulcanized in a system comprised of a conventional microwave oven adapted with a motorized stirring, with a fixed microwave power and at various exposure times. The influence of clay addition on the final properties of the blends was evaluated in terms of mechanical, viscoelastic, thermal and rheological properties, with morphology being also analyzed. The results depict that the clay can modify the rheological behavior of the GTR phase, in addition to the thermal and mechanical properties of some blends.