Showing papers by "María José Abad published in 2005"
TL;DR: In this article, the authors studied the crystalline morphology of biaxially oriented polypropylene (BOPP) films, by tenter-frame technology in its different steps, and found that the stretchings lead to a strong alignment of the crystals, producing fibers oriented in the stretching direction.
Abstract: The production of biaxially oriented polypropylene (BOPP) films, by tenter-frame technology in its different steps, was studied to find the crystalline morphology of these films. DMA, DSC, and WAXD measurements and tensile tests were carried out for the cast film, the MDO film (the produced film in the machine direction orienter unit) and BOPP film. The obtained results suggest that the stretchings lead to a strong alignment of the crystals, producing fibers oriented in the stretching direction. This fact can be proved by WAXD, DMA, and tensile tests, moreover the DSC technique is not sensitive to detect these changes.
30 citations
TL;DR: In this article, thermal and mechanical properties and morphologies of blends of poly(propylene) (PP) and an ethylene-vinyl alcohol copolymer (EVOH) and blends of PP/EVOH/ethylene-methacrylic acid)-Zn2+ ionomer were studied to establish the influence of the ionomer addition on the compatibilization of PP and EVOH blends and on their properties.
Abstract: The thermal and mechanical properties and the morphologies of blends of poly(propylene) (PP) and an ethylene–(vinyl alcohol) copolymer (EVOH) and of blends of PP/EVOH/ethylene–(methacrylic acid)–Zn2+ ionomer were studied to establish the influence of the ionomer addition on the compatibilization of PP/EVOH blends and on their properties. The oxygen transmission rate (O2TR) values of the blends were measured as well. PP and EVOH are initially incompatible as was determined by tensile tests and scanning electronic microscopy. Addition of the ionomer Zn2+ led to good compatibility and mechanical behaviour was improved in all blends. The mechanical properties on extruded films were studied for 90/10 and 80/20 w/w PP/EVOH blends compatibilized with 10 % of ionomer Zn2+. These experiments have shown that the tensile properties are better than in the injection-moulded samples. The stretching during the extrusion improved the compatibility of the blends, diminishing the size of EVOH domains and enhancing their distribution in the PP matrix. As was to be expected, the EVOH improved the oxygen permeation of the films, even in compatibilized blends. Copyright © 2004 Society of Chemical Industry
18 citations
TL;DR: In this article, the phase separation process of an epoxy prepolymer based on diglycidyl ether of bisphenol A (DGEBA) with a thermoplastic polystyrene (PS) was thermodynamically studied in the frame of the Flory-Huggins theory.
14 citations
TL;DR: In this article, the deformation and fracture behavior of polypropylene-ethylene vinyl alcohol (PP/EVOH) blends compatibilized with ionomer Zn2+ were investigated.
Abstract: This work investigated the deformation and fracture behavior of polypropylene–ethylene vinyl alcohol (PP/EVOH) blends compatibilized with ionomer Zn2+. Uniaxial tensile tests and quasistatic fracture experiments were performed for neat PP and for 10 and 20 wt % EVOH blends with different ionomer contents. The addition of EVOH copolymer to PP led to an increase in the Young's modulus whereas the yield strength was decreased with the EVOH content as a consequence of the higher stiffness of EVOH and the poor interfacial adhesion between PP and EVOH, respectively. Furthermore, the incorporation of EVOH into PP promoted stable crack growth. Neat PP displayed nonlinear load-displacement behavior with some amount of slow crack growth preceding unstable brittle fracture, whereas most PP/EVOH blends exhibited “pseudostable” fracture characterized by slow crack growth that could not be externally controlled. All blends exhibited lower resistance to crack initiation than PP but the fracture propagation resistance was significantly improved. For 10 wt % EVOH blends, the resistance to crack initiation was roughly constant with the ionomer content up to 5%, then it increased with the further addition of compatibilizer. Conversely, for 20 wt % EVOH blends, the resistance to crack initiation appeared to be independent of the ionomer content. The better resistance to crack initiation exhibited by the 10 wt % EVOH blends could be attributed to a higher level of compatibilization in these blends. By contrast, 20 wt % EVOH blends with ≤2% ionomer content showed completely stable crack growth. In addition, J–R curves and valid plane strain fracture toughness values for these blends could also be determined. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1271–1279, 2005
10 citations