1,721,006 research outputs found
Optimization of the sealing performance in transient conditions of rubber based hybrid nanocomposites by carbon nanotubes, as assessed by a tailored recovery test
No full textA key property of rubbers for sealing applications is their ability to rapidly recover the deformation
during a fast movement of the counterparts, occurring in a transient deformation phase. In this work, a
simple experimental test method (recovery test) is put forward to mimic the transient phase and to get
insight into the behavior of the material during such phase. The effect of the addition of small quantities
of carbon nanotubes (CNT) to a carbon black filled nitrile butadiene rubber on the sealing ability of the
material was studied. The recovery tests show that the overall recovery behavior is related mostly to the
material stress relaxation behavior, while the recovery behavior at very short times, which is indicative of
the performance during a transient deformation phase, is strongly influenced by the material elastic
modulus and, therefore, it is improved by the presence of CNT in the elastomeric composite
The role of silica in radiation induced grafting and crosslinking of silica/elastomer blends
No full textWhen silica/polybutadiene and silica/styrene-butadiene are submitted to g irradiation at 77 K a scavenging
of the silica radiolytic species by absorbed vinyl units takes place at the surface with concomitant
grafting and crosslinking of the polymers. Key intermediate in such reactions are SiO2-bonded radicals of
structure SiO2eC(CH3)CH(R)(R0). The role of silica is rationalized in terms of the following steps: a)
absorption of the radiation energy in the bulk of the silica particles followed by exciton migration at the
surface; b) reactions of excited groups (silanols) with absorbed vinyl units giving SiO2-bonded radicals; c)
crosslinking of the polymers initiated by grafted radicals
Influence of the silane modifiers on the surface thermodynamic characteristics and dispersion of the silica into elastomer compounds
No full textNatural rubber layered silicate nanocomposites: non linear dynamic behaviour and viscoelastic properties
No full textDresden (Germany
Polyacetylenes Bearing Mesogenic Side Groups: Synthesis ans Properties, 2.
No full textWe report on the synthesis of novel liquid crystalline polyacetylenes derived from monosubstituted acetylene monomers. In the monomers A1OBP-Acn obtained from 3-bromo-1-propyne, the acetylenic moiety is linked through a very short spacer to a biphenyl mesogenic core. Several linear acyl groups of different length are introduced as tail groups. Most of the monomers show liquid crystalline
behavior. Polymerizations are carried out in solution with typical metathesis catalysts based on Mo and W and yield polyacetylenes with fairly high molecular weight (MW), soluble in common organic solvents. Polymers PA1OBP-Acn are fully characterized in terms of molecular structure, by GPC, FT-IR, NMR and UV/VIS techniques, and of thermal and morphological behavior, by TGA, DSC, POM and X-ray
diffraction experiments. THF solutions of the polymers show a quite relevant photoluminescence with a broadened maximum located around 450 nm
Mechanical properties and morphology of NR vulcanizates reinforced by organo-modified layered silicates
No full textDynamic and viscoelastic behavior of natural rubber/layered silicate nanocomposites obtained by melt blending
No full textVulcanized natural rubber/layered silicate (montmorillonite)
nanocomposites prepared by melt blending with
different contents of organoclay (0, 5, 10, 20 wt%) were
investigated. The morphological characteristics of
the materials were studied by transmission electron
microscopy (TEM), wide angle X-ray diffraction, and
dynamic mechanical thermal analysis (DMTA). X-ray
spectra evidence some intercalation of the clay, while
TEM results show a good dispersion of the clay and
the occurrence of partial delamination. DMTA analysis
with varying temperature shows that the peak of the
loss modulus broadens by increasing the clay content
within the material, though the peak temperature is
scarcely affected. Mechanical reinforcement induced
by the presence of the clay is evidenced by static tensile
tests. At every clay content explored, dynamic
experiments show a nonlinear behavior (Payne effect),
which strongly increases with the amount of clay incorporated
and is considerably more pronounced than in
natural rubber filled with comparable amounts of conventional
fillers. The viscoelastic behavior of the materials
is investigated by recovery tests of low amplitude
storage modulus, carried out after the application of a
large strain perturbation, and by stress relaxation
experiments
Hybrid coatings containing silver nanoparticles generated in situ in a Thiol-Ene photocurable system
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