The effect of accumulated deformation and deformation routes in the course of equal-channel multiple angular extrusion (ECMAE) on physical and mechanical properties of polyethylene (PE) differed in molecular mass (MM) has been studied. As deformation routes, route C (shear planes are parallel, and the simple shear direction of every deformation zone is changed through 180 ) and route E (shear planes are turned through 645 around the extrusion axis and the normal to the axis, and simple shear direction is changed through 180 or 690 with respect to the deformation zone) were selected. It has been shown that ECMAE provides the increase of microhardness H, modulus of elasticity E, and tensile strength r T up to 4.5 times with strain at break e b staying practically at the level of e b of the initial material. The value of the effects achieved depends on MM, accumulated deformation and the selected deformation route. The best set of physical and mechanical characteristics was observed in the case of route E. The observed effects are related to the formation of a special orientation order and increased degree of crystallinity of extrudates. According to SEM data, route C results in mostly uniaxial orientation of macrofibrils at an angle of 35 to the direction of extrusion, and formation of a part of tie fibrils and macrofibrils oriented perpendicularly to the main orientation. The route E produces biaxial orientation of macrofibrils.
In this work we find that polyaniline (PANI), synthesized by aniline chemical polymerization at a surface of template polycarbonate (PC) particles, is significantly different in molecular weight, structural order, oxidation state, and conductivity from a neat PANI. Molecular weight of the PANI phase in the composite (Mw = 158,000) is 1.6 times higher than that of the neat PANI synthesized in the absence of the template particles. Moreover, XRD analysis shows that crystallinity of the PANI phase in the composite is three times higher than that of the neat PANI. Raman spectroscopy indicates that the oxidation level of PANI in the PC/PANI composite is lower than that of the neat PANI. These noticeable changes of the PANI phase properties suggest specific interactions of reagents in the polymerization medium and formed PANI with the template phase as well as an orientation effect of the latter surface. FTIR spectroscopy reveals that hydrogen bonding in the neat doped PANI is weaker than one between -NH- of PANI and C═O of PC at their interface. The discovered differences are supported by the fact that conductivity of the PANI phase in the composite is more than three times higher than that of the neat PANI.
Using a combination of the open circuit potential and pH profiles of aniline (An) polymerization and their mathematical treatment, we develop a new convenient semiquantitative approach to determine the influence of the dispersed nanoparticles (e.g., TiO nanoparticles) on the kinetic features of this process and molecular mass of the formed polyaniline (PANI). It is revealed that the reciprocal values of the polymerization stages, namely, the duration of the induction period, of homogeneous and heterogeneous pernigraniline (PN) accumulation, and of PN reduction with An, are linear functions of the weight fraction of the nanoparticles. We found that when nanoparticles are added the weight-averaged molecular weight of PANI initially increases from 56 000 to 79 000 and the polydispersity index drops from 3.9 to 1.7. However, at high TiO concentrations, the former dramatically decreases, whereas the latter increases. We use the relative proton concentration as a function of time and the different extents of acceleration of the consecutive stages of An polymerization to explain the changes in the molecular weight distribution of PANI with different contents of TiO nanoparticles in the polymerization medium.
Thermochemically partially devulcanized ground tire rubber (GTRD) was revulcanized in compositions with different virgin rubbers. Two different devulcanizing groups (mixture of softeners) with and without processing oil have been used for GTR treatment. As virgin rubbers methylstyrene/butadiene (SBR), isoprene (IR) and butadiene (BR) rubbers or their combinations were selected. They were cured by using sulfur, tetramethyl thiuram disulfide (TMTD) or peroxide based vulcanizing systems. The Rubber/GTRD (re)vulcanizates with the GTRD content from 20 to 80 wt. % have been prepared and studied. Vulcanization by sulfur system was found as preferable for IR/GTRD formulations. The best properties for BR/GTRD and SBR/GTRD vulcanizates were reached with the vulcanization system based on TMTD. The co-curing in the interphase between the GTRD particles and the surrounding rubber matrix improves the mechanical properties of (re)vulcanizates obtained. The reclaimed GTRD studied has been used successfully in standard formulations for tires instead of the part of virgin rubbers.
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