Polyether from a biobased Janus molecule as surfactant for carbon nanotubes

A new polyether (PE) was prepared from a biobased Janus molecule, 2-(2,5-dimethyl-1H-pyrrol-1-yl)-1,3- propanediol (serinol pyrrole, SP). SP was synthesized with very high yield (about 96%) and high atom efficiency (about 80%) by reacting a biosourced molecule, such as serinol, with 2,5-hexanedione in the absence of solvent or catalyst. The reaction of SP with 1,6-dibromohexane led to PE oligomers, that were used as surfactants for multiwalled carbon nanotubes (MWCNT), in ecofriendly polar solvents such as acetone and ethyl acetate. The synergic interaction of aromatic rings and oxyalkylene sequences with the carbon allotrope led to dramatic improvement of surfactant efficiency: only 24% of SP based PE was extracted with ethyl acetate from the adduct with MWCNT, versus 98% of a typical pluronic surfactant. Suspensions of MWCNT-PE adducts in ethyl acetate were stable for months. High resolution transmission electron microscopy revealed a film of oligomers tightly adhered to MWCNT surface

Interactive effects between carbon allotrope fillers on the mechanical reinforcement of polyisoprene based nanocomposites

Interactive effects of carbon allotropes on the mechanical reinforcement of polymer nanocomposites were investigated. Carbon nanotubes (CNT) and nano-graphite with high shape anisotropy (nanoG) were melt blended with poly(1,4- cis-isoprene), as the only fillers or in combination with carbon black (CB), measuring the shear modulus at low strain amplitudes for peroxide crosslinked composites. The nanofiller was found to increase the low amplitude storage modulus of the matrix, with or without CB, by a factor depending on nanofiller type and content. This factor, fingerprint of the nanofiller, was higher for CNT than for nanoG. The filler-polymer interfacial area was able to correlate modulus data of composites with CNT, CB and with the hybrid filler system, leading to the construction of a common master curve. © BME-PT

Localizing the cross-links distribution in elastomeric composites by tailoring the morphology of the curing activator

The localization of the rubber vulcanization reaction close to the silica filler surface was investigated in isoprene rubber composites (IR NCs): the main goal was to highlight the role of curing agents’ dispersion and filler surface features on the spatial propagation of the rubber cross-links and the resulting mechanical behavior of the material. The study was realized by tailoring the morphology of the curing activator, i.e. by vulcanizing IR NCs with Zn@SiO2 double function filler, composed of Zn(II) single sites anchored on SiO2 filler, in comparison to silica filled IR NCs vulcanized with microcrystalline ZnO (m-ZnO). The microscopic cross-links distribution was measured by Transmission Electron Microscopy for network visualization (NVTEM) and Time Domain Nuclear Magnetic Resonance (TD-NMR). Besides the NCs mechanical behavior was characterized both at small strain and at fracture. In the presence of Zn@SiO2, higher cross-link density in proximity to SiO2 particles was evidenced, which gradually spreads from the filler surface to the bulk, induced by localization of the Zn(II) centers. IR NCs with Zn@SiO2 resulted stiffer (+45%) and with a lower fracture toughness (less than one third), compared to m-ZnO based NCs, which shows a quite homogeneous structure of the rubber cross-links network. The results highlighted the correlation between the composites structural features and their macroscopic behavior, paving the way to modulating the mechanical properties of elastomeric materials by tuning the nature of the curing agents

Rubber Clay Nanocomposites

The use of nanofillers allows the development of nanocomposites with improved properties and novel applications. The technological goal is possible due to the new compounding method that allows a particle dispersion in the nanometer scale increasing the specific surface area.Fil: Cova Sánchez, Mariajose. Instituto Nacional de Tecnología Industrial. Instituto Nacional de Tecnología Industrial - Caucho; Argentina. Universidad Nacional de San Martín. Instituto de Investigación e Ingeniería Ambiental. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigación e Ingeniería Ambiental; ArgentinaFil: Bacigalupe, Alejandro. Universidad Nacional de San Martín. Instituto de Investigación e Ingeniería Ambiental. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigación e Ingeniería Ambiental; Argentina. Instituto Nacional de Tecnología Industrial. Instituto Nacional de Tecnología Industrial - Caucho; ArgentinaFil: Escobar, Mariano Martin. Instituto Nacional de Tecnología Industrial. Instituto Nacional de Tecnología Industrial - Caucho; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Mansilla, Marcela Angela. Instituto Nacional de Tecnología Industrial. Instituto Nacional de Tecnología Industrial - Caucho; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Graphene layers functionalized with a janus pyrrole-based compound in natural rubber nanocomposites with improved ultimate and fracture properties

The ultimate properties and resistance to fracture of nanocomposites based on poly(1,4-cis-isoprene) from Hevea Brasiliensis (natural rubber, NR) and a high surface area nanosized graphite (HSAG) were improved by using HSAG functionalized with 2-(2,5-dimethyl-1H-pyrrol-1-yl)propane-1,3-diol (serinol pyrrole) (HSAG-SP). The functionalization reaction occurred through a domino process, by simply mixing HSAG and serinol pyrrole and heating at 180 °C. The polarity of HSAG-SP allowed its dispersion in NR latex and the isolation of NR/HSAG-SP masterbatches via coagulation. Nanocomposites, based either on pristine HSAG or on HSAG-SP, were prepared through traditional melt blending and cured with a sulphur-based system. The samples containing HSAG-SP revealed ultimate dispersion of the graphitic filler with smaller aggregates and higher amounts of few layers stacks and isolated layers, as revealed by transmission electron microscopy. With HSAG-SP, better stress and elongation at break and higher fracture resistance were obtained. Indeed, in the case of HSAG-SP-based composites, fracture occurred at larger deformation and with higher values of load and, at the highest filler content (24 phr), deviation of fracture propagation was observed. These results have been obtained with a moderate functionalization of the graphene layers (about 5%) and normal lab facilities. This work reveals a simple and scalable way to prepare tougher NR-based nanocomposites and indicates that the dispersion of a graphitic material in a rubber matrix can be improved without using an extra-amount of mechanical energy, just by modifying the chemical nature of the graphitic material through a sustainable process, avoiding the traditional complex approach, which implies oxidation to graphite oxide and subsequent partial reduction

Dynamic and viscoelastic behavior of natural rubber/layered silicate nanocomposites obtained by melt blending

Vulcanized 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