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.
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.
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.
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.
The characteristics of aniline polymerization in the absence and in the presence of a dispersion of polycarbonate powder in dependence on the nature of acid dopant and oxidant has been studied. By monitoring the polymerization in situ by electronic spectroscopy and redoxometry allows the determination of the stages of formation of shell of polyaniline on the surface of polymer particles and the influence of the latter on the rate of these stages and of the process as a whole.The steady growth in the number of studies linked with polyaniline (PAN) is evidently connected with its complex of practically important properties (electric, optical, catalytic, sensor, electrochemical, etc.) [1,2]. However the potentially wide use of pure PAN is limited by its low stability and poor workability. These problems may be avoided in particular by the creation of composite materials coupling the properties of industrial polymers and PAN [3]. The nature of the coupled polymers (the matrix) determines to a considerable extent the characteristics of the composite with PAN as a result of the physico-chemical and physical interactions of all components of the system [3]. Correspondingly, the choice of the matrix polymer is determined by the requirements of the composite. In particular, for applications in which good optical characteristics are required in addition of strength, it is necessary to use matrix polymers with such properties, for example, polycarbonates (PC) [4].A very important factor that influence the features of the composite with PAN is its formability, which determine the distribution of PAN in the dielectric matrix, in particular the quality of the conduction of the network. In particular, simple mixing of the components in a melt or solution does not always lead to high dispersion of PAN as a result of incomplete or poor compatibility of the components [3]. In this case it is more effective to carry out polymerization of aniline in the dispersed matrix polymer which permits the creation of a thin layer of PAN on the surface of particles. A composite powder formed in this way with a nucleus-shell structure on treatment gives a material with uniform distribution with the nanodimensional structure of PAN [3,5]. The quality of the composite depends on such factors as the conditions for the polymerization, the size and possibly the nature of the covering of the particles, which defines the size and structure of the PAN shell. In this connection, as the basic objective of this work was the determination of the characteristics of the polymerization of aniline in the absence and in the presence of dispersed polymer powder (using PC as example) depending on the nature of the dopant acid and oxidant. EXPERIMENTALAniline (Merck) was purified by vacuum distillation and was stored at 5°C. PC powder, obtained by repricipitation from PC granules based on bisphenol A (Lexan, General Electric), was used as the disperse phase. The dopants used were 54 0040-5760/08/4401-0054 camphorsulfonic acid (CSA, Merck) and p-toluenesulfonic a...
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