Garcia N.L.,Laboratorio Of Polimeros Y Materiales Compuestos |
Garcia N.L.,National University of San Martin of Argentina |
Ribba L.,Laboratorio Of Polimeros Y Materiales Compuestos |
Dufresne A.,Grenoble Institute of Technology |
And 2 more authors.
Carbohydrate Polymers | Year: 2011
Fully bio-based nanocomposites were prepared using starch nanoparticles obtained by acidic hydrolysis of waxy maize starch granules as reinforcement. The same type of starch, which contains 99 wt.% amylopectin, was used to prepare glycerol plasticized and unplasticized matrices. The X-ray diffraction pattern of the plasticized reinforced materials displays both A and B-type peaks, showing that the crystalline structure of the nanocrystals was not affected by processing. The storage modulus of the composite material increases, with respect to the unfilled film, by 470% at 50 °C, while the permeability increases by 70%. This is probably due to a good association of glycerol with the nanoparticles leading to a fibrillar structure, studied by scanning electron microscopy of plasticized and unplasticized composites. © 2010 Elsevier Ltd. All rights reserved.
Garcia N.L.,LPyMC |
Garcia N.L.,National University of San Martin of Argentina |
Lamanna M.,CONICET |
D'Accorso N.,CONICET |
And 3 more authors.
Polymer Degradation and Stability | Year: 2012
PLA was grafted onto starch nanoparticles using a novel synthetic strategy consisting of three reaction steps. The first step was aimed to protect the hydroxyl groups of PLA by benzoylation (PLABz), the second one involved the activation of carboxyl groups using thionyl chloride and the last reaction was the grafting of the modified PLA onto the starch nanoparticles (PLASTARCH). The thermal behavior of the composite obtained by this method was very different from that displayed by the physical mixture of PLA and the starch nanoparticles (PLA-NC blend). The benzoylation step that leads to PLABz produces an increase of the molecular mobility, resulting in lower glass transition temperature, Tg, than that of the original PLA; a change that was observed in the DSC thermograms of the samples. On the other hand, the Tg of the PLASTARCH was similar to that of the PLA as a consequence of two opposite effects acting simultaneously: a free volume increase due to the presence of benzoyl groups and a confinement of the polymer chain, originating from the grafting onto NC. The material obtained by chemical modification (PLASTARCH) has a degradation temperature slightly lower than that of PLA, which does not affect its potential use in the packaging industry. © 2012 Elsevier Ltd. All rights reserved.
Talou M.H.,Intema Inc. |
Villar M.A.,CONICET |
Camerucci M.A.,Intema Inc.
Ceramics International | Year: 2010
Starch is one of the agents used as both consolidator/binder of the ceramic suspension and pore former at temperature for porous ceramic processing. In this work, the thermogelling behaviour of aqueous suspensions of different starches (potato, cassava, and corn) was studied by dynamic rheological testing and optical microscopy in order to optimize the thermal consolidation of ceramic green bodies prepared by the starch consolidation method. Viscoelastic properties (G′, G″, tan δ) as a function of the temperature (30-95 °C) were determined by non-isothermal rheological measurements (temperature sweep tests). In these tests, the influence of experimental variables on viscoelastic properties, such as the amount of Dolapix CE-64 as dispersant (0, 3, 4.5, and 6 wt%), the heating rate (1, 2, 5, and 10 °C/min) and the starch concentration (14 and 40 vol%) was analyzed. Swelling capacity and the analysis of volume-weighted granule size distributions (median volume granule diameters, distribution widths and arithmetic mean diameters) in aqueous suspension, as a function of the temperature, was also evaluated. In addition, the degree of disintegration of starch granules and the rheological stability of the gels were also studied by dynamic time sweep test. The obtained results are useful in order to establish the experimental variables to be used in the thermal consolidation step for the production of porous ceramics with controlled microstructures. © 2009 Elsevier Ltd and Techna Group S.r.l.
Valcarce M.B.,Intema Inc. |
Vazquez M.,Intema Inc.
Corrosion Science | Year: 2010
Three dosages of PO4 3 - ions are evaluated as corrosion inhibitors of copper in artificial tap water by measuring the corrosion potential, polarization resistance, electrochemical impedance and reflectance spectra. The water is moderately hard, highly carbonated and chloride-rich. The results show that the surface film is composed by Cu2O. When the inhibiting agent is added, the film becomes thicker, denser and more compact. This behaviour is attributed to CuO incorporating into the passive layer. The optimal dosage of inhibitor is 10 mg l-1 P when the polarization resistance increases three times. The inhibitor retards the pit initiation, without hindering pit growth. © 2009 Elsevier Ltd. All rights reserved.
Yohai L.,Intema Inc. |
Schreiner W.H.,Federal University of Parana |
Vazquez M.,Intema Inc. |
Valcarce M.B.,Intema Inc.
Applied Surface Science | Year: 2011
The composition of the surface layers has been investigated on copper, zinc and brass in contact with moderately hard, highly carbonated and chloride rich artificial tap water (ATW). Cyclic voltammetry, reflectance spectroscopy, X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy have been used to identify the changes in composition that result from the incorporation of sodium orthophosphate to ATW. The results showed that when PO 4 3- is added, the film changes its composition and it also becomes thinner, denser and more compact. On copper, the presence of CuO in the passive film can be correlated to the improvement in the corrosion behavior in the presence of phosphate ions. In the case of brass, the development of a thinner, compact and less porous Zn3(PO4)2 layer hinders Cu(I) dissolution. A mechanism explaining the effect of this inhibitor is proposed, which accounts for the experimental results. © 2011 Elsevier B.V. All rights reserved.