177 research outputs found
Hybrid coatings containing silver nanoparticles generated in situ in a Thiol-Ene photocurable system
No full text
The nanostructured morphology of linear polyurethanes observed by transmission electron microscopy
No full textDissertationes theologicae scholastico-dogmaticae ad mentem S.P. Hieronymi ... : in sex tractatus diuise ...
No full textNa portada consta relación de contenido dos seis tratadosSign.: *6, A-L
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
Correlating the morphology of poly(L-lactide)/poly(butylene succinate)/graphene oxide blends nanocomposites with their crystallization behavior
No full textBio-based blend nanocomposites of poly(L-lactic acid) (PLLA) and poly(butylene succinate) (PBS), with different concentrations (from 0.1 to 0.5 wt%) of graphene oxide (GO), are prepared via solution dispersion of PBS/GO followed by melt blending with PLLA in a 70/30 PLLA/PBS weight ratio. Scanning and Transmission Electron Microscopy reveals micron-sized droplets of PBS in the PLLA matrix with the GO nanofiller preferentially found in the PBS phase. The GO acts as nucleating agent for both semicrystalline polymers. The nanofiller nucleating effect is compared to the one of own selfnuclei for each polymer, to define a convenient nucleating efficiency (NE) scale. A value of around 80% is determined for GO towards PBS, among the highest NEs ever reported for this polymer. On the other hand, the efficiency in nucleating PLLA is equal to a modest 15%, also due to the uneven distribution of the nanofiller in the two polymers. A close relationship between the nanocomposite morphology and crystallization behavior of the two different polymers is thus established
Nanocomposites of Poly(1,4-cis-Isoprene) with Graphite Oxide Intercalation Compounds
No full textInnovative nanocomposites are obtained by melt blending poly(1,4- cis -isoprene) (PI) and graphite oxide intercalation compounds (GOICs) with dimethyl di(hydrogenated tallow) ammonium (2HT) cations ionically bonded to the graphite oxide layers. GOIC samples with different contents of 2HT are prepared and homogeneously dispersed in the PI matrix. The X-ray diffraction pattern of the GOIC shows an intense 100 refl ection due to the hexagonal rotator order of the methylene sequences of long alkyl chains. Said rotator order is present in the nanocomposites, in the absence of any evidence of stacked layers, suggesting the prevailing exfoliation of the GOICs. The cross-linking reaction promoted by sulfur is remarkably accelerated by the GOICs and the maximum modulus is enhanced. GOICs increase stresses at given elongations and the reinforcement under strai
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
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