FRLP - I+D+i - CENTROS - CITEMA - TRABAJOS DE INVESTIGACIÓN
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Item Starch Polyvinyl Alcohol blends containing Polyurethane as plasticizer(2016) González-Forte, Lucía del Sol; Pardini, Oscar; Amalvy, JavierStarch-based films containing 70wt% of starch and a combination of poly(vinyl alcohol) and a low glass transition temperature polyurethane as plasticizer were prepared. The effect of PVA/PU ratio content on the morphology and physical properties was investigated by infrared spectroscopy (FTIR), X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy and measurements of mechanical properties and water vapor permeability. A relative small amount of PU (less than 15 wt%), significantly changes the properties of the blend due to intermolecular hydrogen bonding interactions between the three components. FTIR and XRD results indicate that blends containing PU are more amorphous than the pure starch/PVA blend and SEM images show a homogeneous matrix due to the good compatibility between starch and PU. Incorporation of PU to the starch/PVA blend shifts the glass transition temperature to lower values and reduce the elastic modulus, indicating a successful plasticization effect. The resulting blends produce films with improved physical properties.Item Influence of dynamic crosslinking on the morphology, crystallization, and dynamic mechanical properties of PA6,12 EVA blends(2016) Bondan, Fabricio; Ernzen, Juliano; Amalvy, Javier; Machado, Ana; De Nardi Martins, Johnny; Bianchi, OtavioThis study investigated the effect of dynamic crosslinking of polyamide 6,12 and random copolymers of ethylene and vinyl acetate blends (PA6,12/EVA) on the morphology, crystallinity, and dynamic mechanical properties. The crosslinking agent was dicumyl peroxide (DCP), and the blends were processed in a torque rheometer. The morphology depended on the DCP content, and all blends exhibited the same crystallinity index. However, with increasing crosslinking degree, the interfacial tackiness (E) values increased from 1.8 to 2.7 nm. The lamellar structures of all blends started forming at approximately 160 8C, close to the temperature of pure polyamide. The crosslinked phase enhanced the pseudo-elastic behavior of the blends and increased their molecular mobility activation energy. Samples with higher crosslinking degree exhibited smaller permanent deformation (0.01%) than those with low crosslinking.Item Chitosan-graft-poly(n-butyl acrylate) copolymer Synthesis and characterization of a natural synthetic hybrid material(2016) Anbinder, Pablo; Macchi, Carlos; Amalvy, Javier; Somoza, AlbertoTwo chitosan polymers with different deacetylation degree and molecular weight were subjected to graft- ing reactions with the aim to enhance the properties of these bio-based materials. Specifically, n-butyl acrylate in different proportions was grafted onto two different deacetylation degree (DD%) chitosan using radical initiation in a surfactant free emulsion system. Infrared spectroscopy was used to confirm grafting and products grafting percentage and efficiency were evaluated against acrylate/chitosan ratio and DD%. Thermal and structural properties and the behavior against water of the raw and grafted biopolymers were studied using several experimental techniques: differential scanning calorimetry, transmission electron microscopy, dynamic light scattering, water swelling, contact angle and positron annihilation lifetime spectroscopy. The influence of the grafting process on the morphological and physicochemical properties of the prepared natural/synthetic hybrid materials is discussed.Item On the strategies for incorporating nanosilica aqueous dispersion in the synthesis of waterborne polyurethane silica nanocomposites, Effects on morphology and properties(2016) Peruzzo, Pablo; Anbinder, Pablo; Pardini, Francisco; Pardini, Oscar; Plivelic, Tomas; Amalvy, JavierIn this work the synthesis of waterborne polyurethane/nanosilica nanocomposites by using two differ- ent strategies is presented, starting from a vinyl terminated polyurethane prepolymer (PUP) based on isophorone diisocyanate and polypropylene glycol, and varying the nanosilica content. In one case, the PUP was dispersed in an aqueous solution containing glycerol-functionalized colloidal nanosilica parti- cles and the dispersion was further polymerized; in the other case, the PUP was dispersed in an aqueous media, then colloidal nanosilica was added to the dispersion and then polymerized. A physical mixture was also prepared for comparative purpose. Films were prepared by casting of the aqueous dispersion. The morphology of the dispersions and films depended on the incorporation route of nanoparticles as was observed by SAXS, SEM and TEM. While the blends had significantly less hydrogen bonding between the hard segments of the PU and nanosilica particles, samples prepared by the two different methods proposed in this work showed an strong interaction between both materials in agreement with FTIR and DSC results. Synthesis pathway plays an important role in order to obtain high performance waterborne polyurethane/nanosilica composites, since final properties of the films also depended on the nanoparticle incorporation strategy.Item Morphology and properties of neutralized chitosan-cellulosenanocrystals biocomposite films(2016) Corsello, Flavia Anahí; Bolla, Patricia Araceli; Anbinder, Pablo; Serradell, María de los Ángeles; Amalvy, Javier; Peruzzo, PabloChitosan/cellulose nanocrystals (CH-CN) films were obtained by casting of dispersions, and treated with NaOH for neutralization proposes. The composition of films was varied from 1 to 10 wt.% of CN. Changes in the morphology of the systems were correlated with the different properties studied. FTIR revealed the presence of a weak interaction between the polymer matrix and nanofiller, confirmed by a slightly increase in thermal stability. SEM images suggested that incorporating CN amounts higher than 3 wt.% generates phase-segregated systems, and SAXS showed that CH avoid the typical organization of CN at concentrations below 5 wt.%. Improved performance against water was obtained in composite materials comparing to the pure polymer matrix, as well as CH and CH-CN films did not show antibacterial activity demonstrating that remnant acetic acid, when no neutralization step is done, plays an important role in this property.Item Synthesis, characterization and swelling behavior of new pH-sensitive hydrogels derived from copolymers of 2-hydroxyethyl methacrylate and 2-(diisopropylamino) ethylmethacrylate(2012) Faccia, Paula; Amalvy, JavierThe aim of this work was to synthesize and to characterize new pH-sensitive hydrogels that can be used in the controlled release of drugs, useful for dermal treatments or ophthalmology’s therapies. Copolymers containing 2-hydroxyethyl methacrylate (HEMA) with different amounts of 2-(diisopropylamino)ethyl methacrylate (DPA) (10 and 30 wt %) and different amounts of cross- linker agent, ethylene glycol dimethacrylate (EGDMA) (1 and 3 wt %) were prepared by bulk photo-polymerization. The copolymers were fully characterized by using Fourier-transform infrared (FTIR) spectra, differential scanning calorimetry, thermogravimetric anal- ysis, UV–visible spectroscopy, and measuring water content and dynamic swelling degree. The results show that modifications in the amount of DPA and/or crosslinker in the hydrogel produce variations in the thermal properties. When adding of DPA, we observed an increase in the thermal stability and decomposition temperature, as well as a change in the mechanism of decomposition. Also a decrease in the glass transition temperature was observed with regard to the value for pure pHEMA, by the addition of DPA. The water content of the hydrogels depends on the DPA content and it is inversely proportional to both the pH value and the crosslinking degree. Pure poly-HEMA films did not show important changes over the pH range studied in this work. The dynamic swelling curves show the overshooting effect associated with the incorporation of DPA, the pH of the solution, and the crosslinking density. On the other hand, no important variations in the optical properties were observed. The synthesized hydrogels are useful as a drug delivery pH-sensitive matrix.Item Surface, thermal, and mechanical properties of composites and nanocomposites of polyurethane PTFE nanoparticles(2014) Anbinder, Pablo; Peruzzo, Pablo; de Siervo, A.; Amalvy, JavierFilms from blends of polyurethane and nano-polytetrafluoroethylene aqueous dispersions (PU/nanoPTFE) were prepared, and the effect of the addition of different amounts of PTFE nanoparticles (50 nm) was studied. The changes in the superficial properties of the films were studied by means of XPS, ATR/FTIR, and contact angle measurements. SEM and TEM results are also included. The contact angle values confirm the surface hydrophobicity of com- posite films. Even though nanoparticles are present in the bulk, higher concentrations of particles appear at the surface in samples with lower nanoPTFE content (up to 10 wt%), as revealed by XPS. Higher amounts of nanoPTFE particles cause aggregation. The mechanical and thermal properties of composites are also discussed.Item Synthesis and swelling behavior of pH-responsive polyurethane poly(2-(diethylamino)ethyl methacrylate) hybrid materials(2013) Pardini, Francisco; Amalvy, JavierPolyurethane (PU)/poly[2-(diethylamino)ethyl methacrylate] hybrids, having a chemical bond between the PU and acrylic moieties and with different compositions, were prepared by the dispersion polymerization of 2-(diethylamino)ethyl methacrylate (DEA) in the presence of preformed PU chains with polymerizable terminal vinyl groups. The PU dispersion was synthesized accord- ing to a prepolymer mixing process by the polyaddition of isophorone diisocyanate, poly(propylene glycol), 2-hydroxyethyl methacry- late, and dimethylol propionic acid (DMPA). Then, it was dispersed in water by the prior neutralization of the carboxylic acid groups of DMPA with triethylamine, chain-extended with ethylenediamine. The effect of the DEA content on the swelling properties (water uptake and dynamic swelling degree) at different pHs and at 37�����C was determined. The samples were also characterized by Fourier transform infrared spectroscopy and modulated differential scanning calorimetry. The experimental results indicate a higher water uptake when the DEA content was increased on the hybrid materials and a significant change in the kinetics of swelling at pH 4 com- pared to those at pH 7. The water content of the hydrogels depended on the DEA content, and it was inversely proportional to the pH value. The pure PU film did not show important changes over the pH range examined in this study. The synthesized hybrids were useful as drug-delivery, pH-sensitive matrices.Item The role of nanocrystalline cellulose on the microstructure of foamed castor-oil polyurethane nanocomposites(2015) Cordero, Andrés Ignacio; Amalvy, Javier; Fortunati, Elena; Kenny, José María; Chiacchiarelli, Leonel MatíasNanocrystalline cellulose (CNC), obtained by sulphuric acid hydrolysis, was used to synthesize polyurethane foams (PUFs) based on a functionalized castor oil polyol and a Methylene diphenyl diiso- cyanate (MDI). Formulations with varying isocyanate index (FI) and NCO number were prepared. At 0.5 wt.%, SEM’s of the fractured surface underlined that the CNC acted both as a nucleation agent and as a particulate surfactant with cell geometries and apparent density changing selectively. The chemical structure of the PUF (FTIR) changed after the incorporation of CNC by a relative change of the amount of urea, urethane and isocyanurate groups. A low NCO number and isocyanate index contributed to the migration of the CNC to the Hard Segment (HS), acting as reinforcement and improving substantially the compressive mechanical properties (Ec and �����c improvements of 63 and 50%, respectively). For a high NCO number or isocyanate index, the CNC migrated to the Soft Segment (SS), without causing a reinforcement effect. The migration of the CNC was also detected with DSC, TGA and DMA, furtherly supporting the hypothesis that a low NCO number and index contributed both to the formation of a microstructure with a higher content of urethane groups.Item Polyurethane Poly(2-(Diethyl Amino)Ethyl Methacrylate) blend for drug delivery applications(2015) Echeverría, María Gabriela; Pardini, Oscar; Debandi, María Valeria; François, Nora; Daraio, Marta; Amalvy, JavierA pH-sensitive blend of polyurethane (PU) and poly(2-(diethyl amino)ethyl methacrylate (PDEA) with good film-forming capacity was prepared from the corresponding aqueous dispersions. The polymer matrix was first characterized by using FTIR, DSC, water vapor transmission and water swelling capacity at different pHs. The drug release profile of films was evaluated using a vertical Franz Cell and theophylline as model drug. The water swelling degree increases from 54 to 180% when the pH of the medium is changed from 6 to 2, demonstrating the pH-responsive behavior of the film. The in-vitro release studies indicate that an anomalous transport mechanism governs the theophylline release.