FRLP - I+D+i - CENTROS - CITEMA - TRABAJOS DE INVESTIGACIÓNhttp://hdl.handle.net/20.500.12272/17502024-03-29T04:46:40Z2024-03-29T04:46:40ZStarch Polyvinyl Alcohol blends containing Polyurethane as plasticizerhttp://hdl.handle.net/20.500.12272/34262019-02-19T00:05:14Z2016-01-01T00:00:00ZStarch Polyvinyl Alcohol blends containing Polyurethane as plasticizer
Starch-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.
2016-01-01T00:00:00ZInfluence of dynamic crosslinking on the morphology, crystallization, and dynamic mechanical properties of PA6,12 EVA blendshttp://hdl.handle.net/20.500.12272/34252019-02-19T00:04:56Z2016-01-01T00:00:00ZInfluence of dynamic crosslinking on the morphology, crystallization, and dynamic mechanical properties of PA6,12 EVA blends
This 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.
2016-01-01T00:00:00ZChitosan-graft-poly(n-butyl acrylate) copolymer Synthesis and characterization of a natural synthetic hybrid materialhttp://hdl.handle.net/20.500.12272/34242019-02-19T00:04:43Z2016-01-01T00:00:00ZChitosan-graft-poly(n-butyl acrylate) copolymer Synthesis and characterization of a natural synthetic hybrid material
Two 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.
2016-01-01T00:00:00ZOn the strategies for incorporating nanosilica aqueous dispersion in the synthesis of waterborne polyurethane silica nanocomposites, Effects on morphology and propertieshttp://hdl.handle.net/20.500.12272/34232019-02-19T00:04:26Z2016-01-01T00:00:00ZOn the strategies for incorporating nanosilica aqueous dispersion in the synthesis of waterborne polyurethane silica nanocomposites, Effects on morphology and properties
In 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.
2016-01-01T00:00:00Z