0000000000147360
AUTHOR
Andrés Nohales
Transparent thermoplastic polyurethanes based on aliphatic diisocyanates and polycarbonate diol
Segmented thermoplastic polyurethanes (PUs) were synthetized using polycarbonate diol as soft segment with a molar mass of 500 and as a hard segment 1,5-pentanediol with a combination of isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI). Differential scanning calorimetry, differential mechanical analysis, Fourier transform infrared-attenuated total reflection spectroscopy, haze, transmittance, hardness, tensile properties and retention of tensile properties tests were employed to characterize the different PUs. The results of this study show that IPDI/HDI relation has a significant impact on the phase mixing, crystallinity and therefore on the PU’s properties. The variati…
Morphology, flexural, and thermal properties of sepiolite modified epoxy resins with different curing agents
A bisphenol A-based epoxy resin was modified with 5 wt% organically modified sepiolite (Pangel B40) and thermally cured using two different curing agents: an aliphatic diamine (Jeffamine D230, D230) and a cycloaliphatic diamine (3DCM). The morphology of the cured materials was established by scanning and transmission electron microscopy analysis. The thermal stability, thermo-mechanical properties, and flexural behaviour of the sepiolite-modified matrices were evaluated and compared with the corresponding neat matrix. The initial thermal decomposition temperature did not change with the addition of sepiolite. The flexural modulus of the epoxy matrix slightly increases by the incorporation o…
Tunable Structure and Properties of Segmented Thermoplastic Polyurethanes as a Function of Flexible Segment
Segmented thermoplastic polyurethanes (PUs) were synthetized using macrodiols with different functional groups (carbonate, ester, and /or ether) as a segment with a molar mass of 1000 and 2000 g/mol, and 4,4&rsquo
Viscoelastic behavior of epoxy prepolymer/organophilic montmorillonite dispersions
Dispersions of a bisphenol A-based epoxy resin with an organophilic montmorillonite (Nanofil 919) were studied by X-ray diffraction and oscillatory shear rheometry. X-ray studies reveal that the clay is intercalated by the epoxy and forms stable dispersions. The viscoelastic behavior of the nanodispersions was measured as a function of the Nanofil concentration and temperature. An increase in both G′ and G″ moduli was detected as the concentration increases. Furthermore, a transition from a liquid-like behavior, at low temperatures, to a solid-like behavior, at higher temperatures, was observed for all the samples. This transition is accounted for the formation of a percolated structure of …
Rheological study of gel phenomena during epoxide network formation in the presence of sepiolite
The dynamic behaviour during the crosslinking of an epoxy polymer near the gel point was monitored using rheological multiple frequency experiments. The influence of a needle-shaped inorganic nanofiller, sepiolite, either non-modified or organically surface modified during the cure process in the presence of an aliphatic and an aromatic hardener was investigated. The validity of various criteria for determining the gel point was examined for the crosslinking of these filled thermosets. The Winter–Chambon criterion at the gel point is obeyed by the unfilled and by the non-modified sepiolite-filled epoxy matrix with either of the two hardeners. However, physical gels are formed in the presenc…
Enhanced polyurethanes based on different polycarbonatediols
Segmented thermoplastic polyurethanes (PUs) were prepared from 4,4′-diphenylmethane diisocyanate (MDI), 1,4-butanediol (BD) and different macrodiols with a molar mass of 1000. Properties of those PUs based on polycarbonatediol (PCD) were compared with their homologous based on polyesterdiol and polyetherdiol as macrodiols. The proportion used in this study was macrodiol:BD:MDI = 1:2:3, in mole ratio. The hard segment weight percentage is 48 wt% for different PUs. Thermogravimetric analysis, differential scanning calorimetry, differential mechanical analysis, Fourier transform infrared-attenuated total reflection spectroscopy, as well as mechanical properties and retention on flexural prope…
Structure-property relationships of polycarbonate diol-based polyurethanes as a function of soft segment content and molar mass
Segmented thermoplastic polyurethanes (PUs) have been synthesized with polycarbonate diol as soft segment and 4,4′-diphenylmethane diisocyanate and butanediol as hard segment. Two different series employing two different soft-segment molar mass, 1000 and 2000 g/mol, and by changing the hard-segment content from 32 to 67% have been investigated with the aim to elucidate the effect of the different content variations on the properties. Morphological, thermal, and mechanical properties have been studied by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), wide angle X-ray diffraction, atomic force microscopy, tensile and…
Sepiolite-reinforced epoxy nanocomposites: Thermal, mechanical, and morphological behavior
A bisphenol A-based epoxy resin was modified with pristine sepiolite and an organically surface-modified sepiolite and thermally cured using two different curing agents: an aliphatic and a cycloaromatic diamine. The nanocomposites were characterized by dynamic mechanical analysis (DMA), rheology, thermogravimetric analysis (TGA), and electron microscopy. The initial sepiolite–epoxy mixtures show a better dispersion for the sepiolite-modified system that forms a percolation network structure. Mechanical properties have also been determined. The flexural modulus of the epoxy matrix slightly increases by the incorporation of the organophilic sepiolite. The flexural strength of the sepiolite-mo…
Properties and structure of cyanate ester/polysulfone/organoclay nanocomposites
In this paper, a cyanate ester (CE) matrix has been modified with polysulfone and an organic montmorillonite (Nanofil 919). The blend was thermally cured in presence of copper acetylcetonate and nonylphenol. The morphology of the cured materials was investigated by wide angle X-ray, scanning and transmission electron microscopy techniques. An intercalate structure of silicate platelets in the cyanate matrix has been obtained. Furthermore, results of thermogravimetric analysis (TGA) suggest that CE/PSF/Nanofil 919 nanocomposites have higher thermal stability than the neat resin, increasing the onset decomposition temperature. Flexural strength distributions of modified and neat cyanate matri…