Monte Carlo computer simulations have been performed for model polymers containing randomly distributed spherical filler particles (20% in volume) with diameter between 4 times and 28 times the transverse diameter of the chains. By analyzing the results in conjunction with those of previous simulations, a few simple rules are deduced allowing to predict approximately the molecular arrangements in these complex systems.
Schematic two‐dimensional picture of the mutual arrangements of filler particles and chains predicted for system M12. 相似文献
There are number of important developments in the area of elastomeric polymers, including (i) network chains of controlled stiffness, (ii) model elastomers (including dangling-chain networks), (iii) fluorosiloxane elastomers, (iv) new thermoplastic elastomers, (v) other new elastomers, (v) bimodal network chain-length distributions, (vi) cross linking in solution or in a state of deformation, and (vii) gel collapse. Interesting elastomeric composites include those with (i) in-situ generated ceramic-like particles, (ii) ellipsoidal fillers, (iii) clay-like layered fillers, (iv) polyhedral oligomeric silsesquioxane (POSS) particles, (v) porous fillers, (vi) elastomeric domains modifying ceramics, and (vii) controlled interfaces. New characterization techniques are being developed for elastomers, and there have been new developments in elasticity theory and in elastomer processing. Some examples of societal aspects of relevance are (i) synthesis of elastomers in environmentally-friendly solvents, (ii) biosynthesis, (iii), recyclability, (iv) improved adhesion to tire cords, and (v) better barrier properties in anti-terrorism clothing. Educational topics include curriculum development, and mobile laboratories for elastomer experiments and demonstrations. 相似文献
Highly pure magnesium borate (Mg2B2O5) nanowires with an average diameter of - 30 nm, an average length of 15 μm, and a high aspect ratio of - 500 have been synthesized on a large scale via a two-step method. MgBO2(OH) nanowires with high aspect ratios were first prepared via a PVP-assisted hydrothermal technique. Using these nanowires as precursors, single crystalline Mg2B205 nanowires were synthesized by post-annealing treatment at a relatively low temperature of 700 ℃. The important effect of the MgBO2(OH)-Mg2B2O5 conversion process on the morphology of the Mg2B2O5 nanowires was investigated and it was indicated that the recrystallization process plays an important role in the protection of the one-dimensional (1D) nanostructure. Moreover, the rigidity and the toughness of the Mg2B2O5 nanowire- reinforced PHA composites were tremendously improved compared to those of the pure PHA. Our results demonstrate the effectiveness of Mg2B2O5 nanowires for reinforcement applications in polymer composites. 相似文献
This paper examines the combination of radial deformation with torsion for a circular cylindrical tube composed of a transversely
isotropic hyperelastic material subject to finite deformation swelling. The stored energy function involves separate matrix
and fiber contributions such that the fiber contribution is minimized when the fiber direction is at a natural length. This
natural length is not affected by the swelling. Hence swelling preferentially expands directions that are orthogonal to the
fiber. The swelling itself is described via a swelling field that prescribes the local free volume at each location in the
body. Such a treatment is a relatively simple generalization of the conventional incompressible theory. The direction of transverse
isotropy associated with the fiber reinforcement is described by a helical winding about the tube axis. The swelling induced
preferential expansion orthogonal to this direction induces the torsional aspect of the deformation. For a specific class
of strain energy functions we find that the twist increases with swelling and approaches a limiting asymptotic value as the
swelling becomes large. The fibers reorient such that fibers at the inner portion of the tube assume a more circumferential
orientation whereas, at least for small and moderate swelling, the fibers in the outer portion of the tube assume a more axial
orientation. For large swelling the fibers in the outer portion of the tube reorient beyond the axial orientation, and so
are described by helices with orientation in the opposite sense to that in the reference configuration.
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