Depth sensing indentation of organic-inorganic hybrid coatings deposited onto a polymeric substrate

PEO-Si/SiO2 hybrid coatings deposited onto a PVC substrate were micromechanically characterized using depth sensing indentation. The effect of curing time and coating thickness was investigated. Elastic moduli of coated systems determined by the Oliver–Pharr approach displayed a continuous decreasing trend with increasing indentation depth, reflecting that the hybrids are stiffer than the substrate. Aiming to extract coating-only elastic modulus a simple method based on FE simulations was developed. The method was applied to evaluate the moduli of the hybrid coatings and the values were compared with those obtained by applying different approaches available in literature. The elastic modulus of PEO-Si/SiO2 hybrids was proven to be practically independent of curing time after 24 h. However, large curing times resulted in coatings being more prone to failure.Fil: Fasce, Laura Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Seltzer, Rocío. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Frontini, Patricia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Mechanical and fracture behavior of gelatin gels

Hydrogels were prepared from bovine and porcine gelatin powders of different Bloom values. Gelatin concentration and pH were selected to obtain self-supporting gels with stiffness in the range of those employed in structural applications in foodstuff, ballistic and pharmacy. Glycerol and sorbitol were also added in gel formulations. Deformation and fracture behaviors were assessed by means of gel strength measurements, uniaxial compression tests and wire cutting experiments. All gels showed non-linear elastic deformation with strain hardening and brittle fracture. Large deformation was described with a first order Ogden constitutive model. Strain hardening was attributed to protein chains renaturation capability under stress. It was found that neat porcine gelatin gels displayed higher gel strength, shear modulus, failure strain and stress, fracture toughness and water retention than bovine gelatin gels. The addition of sorbitol and glycerol caused an increase in water retention capability and a marked enhancement in gels´ fracture toughness. The major content of hydrophilic amino acids in the gelatin, the stronger the effect of glycerol and sorbitol on gelatin network morphology. The correlation between large deformation and fracture toughness parameters with the technological gel strength values was also investigated.Fil: Czerner, Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación en Ciencia y Tecnología de Materiales (i); ArgentinaFil: Martucci, Josefa Fabiana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); ArgentinaFil: Fasce, Laura Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); ArgentinaFil: Ruseckaite, Roxana Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); ArgentinaFil: Frontini, Patricia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentin

Poly(acrylic acid) surface grafted polypropylene films: Near surface and bulk mechanical response

Radical photo-grafting polymerization constitutes a promising technique for introducing functional groups onto surfaces of polypropylene films. According to their final use, surface grafting should be done without affecting overall mechanical properties. In this work the tensile drawing, fracture and biaxial impact response of biaxially oriented polypropylene commercial films grafted with poly(acrylic acid) (PAA) were investigated in terms of film orientation and surface modification. The variations of surface roughness, elastic modulus, hardness and resistance to permanent deformation induced by the chemical treatment were assessed by depth sensing indentation. As a consequence of chemical modification the optical, transport and wettability properties of the films were successfully varied. The introduced chains generated a PAA-grafted layer, which is stiffer and harder than the neat polypropylene surface. Regardless of the surface changes, it was proven that this kind of grafting procedure does not detriment bulk mechanical properties of the PP film.Fil: Fasce, Laura Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Costamagna, Vanina. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Química Orgánica; ArgentinaFil: Pettarin, Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Strumia, Miriam Cristina. Universidad Nacional de Córdoba. Facultad de Cs.agropecuarias. Departamento de Fundamentación Biológica. Cátedra de Química Organica; ArgentinaFil: Frontini, Patricia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Mechanical and fracture characterization of 50:50 HDPE/PET blends presenting different phase morphologies

Uncompatibilized and compatibilized blends of poly(ethytene terephthalate) (PET) and high-density polyethylene (HDPE) (50:50 PET/HDPE) have been prepared and characterized. A commercial grade of ethylene/methacrylic acid copolymer was used as compatibilizing agent and added to the blends in two different proportions, 1 % and 7%. Compounded blends were processed following three different procedures: compression molding, extrusion, and extrusion followed by annealing. In every case, there is evidence that suggests that HDPE constitutes the matrix and PET is the dispersed phase. The PET phase shape was related to the processing procedure of the blends. PET adopted a globular morphology in the compression molded samples but it took the form of microfibers (microfibrillar-like reinforced composites) in extruded samples, which were flattened during the postextrusion annealing process. According to the results obtained in tensile and fracture tests, extruded blends having 7% of ethylene/methacrylic acid copolymer appeared as the optimum combination of processing method and compatibilizer content.Fil: Fasce, Laura Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Seltzer, Rocío. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Frontini, Patricia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Pita, V.J. Rodriguez. Universidade Federal do Rio de Janeiro; BrasilFil: Pacheco, E.B.A.V.. Universidade Federal do Rio de Janeiro; BrasilFil: Dias, M.L.. Universidade Federal do Rio de Janeiro; Brasi

Effect of nitrogen ion irradiation on the nano-tribological and surface mechanical properties of ultra-high molecular weight polyethylene

Generation of wear debris is the principal obstacle limiting the durability of ultra-high molecular weight polyethylene (UHMWPE) in biomedical applications. Aiming to enhance UHMWPE wear resistance, surface modification with swift heavy ion irradiation (SHI) appears as a potential and attractive methodology. Contrary to ion implantation techniques, the swift heavy ions range can reach tens to hundreds microns and its extremely high linear energy is able to induce effective chemical modifications using low fluence values. Nano-wear performance and surface mechanical properties of samples of pristine and SHI irradiated (using N2+ ions at 33MeV and a fluence of 1×1012ions/cm2) were characterized by depth sensing indentation (DSI) and scanning probe microscopy (SPM). It turned out that modifications induced by irradiation at the surface layers were successful to reduce nano-wear volume and creep deformation. These improvements were related to beneficial changes in hardness, elastic modulus, hardness to elastic modulus ratio and friction coefficient.Fil: Fasce, Laura Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Cura, Josefina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: del Grosso, Mariela Fernanda. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Garcia Bermudez, Gerardo Jose. Comisión Nacional de Energía Atómica; Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Frontini, Patricia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Mechanical behaviour of polypropylene modified with an elastomeric polyolefin

En este trabajo se estudia ampliamente la respuesta mecánica de mezclas novedosas basadas en PP y un 10, 20, y 30% en peso de una poliolefina elastomérica (POEs). La morfología de las mezclas consiste en un patrón continuo de partículas elastoméricas dispersos en la matriz de PP. El módulo elástico resulta el máximo obtenible para una mezcla bifásica. El criterio de Von Mises modificado resulta adecuado para describir los límites de aplicación de las mezclas bajo estados biaxiales. La tenacidad a la fractura a baja temperatura y en condiciones de impacto, determinada aplicando metodologías de la mecánica de fractura, queda representada por una distribución de Weibull. El valor umbral de tenacidad a la fractura del PP se ve notablemente incrementada por la presencia de la POEs, asimismo la modificación incrementa la tendencia a la propagación estable de fisura. Esto es resultado del acrecentamiento de la capacidad inherente de la matriz a deformar por crazing y/o por el desgarramiento dúctil (corte) de los ligamentos entre partículas.In this work the mechanical behavior of novel blends based on PP modified with 10, 20 and 30% weight of an elastomeric polyolefin (POEs) is deeply investigated. Blend’s morphology results a continuous pattern of globular POEs particles dispersed in the PP matrix. Elastic modulus agrees with the maximum value that can be achieved in binary blends. Modified Von Mises Yield Criteria well represents the confidence limits of these blends under biaxial stress states. Low temperature and high impact fracture toughness assessed by the application of different fracture mechanics methodologies are described by a Weibull type distribution model. PP thresholds toughness parameters are notably enlarged by the elastomer modification. The presence of POEs also increases the tendency towards stable crack propagation. Both effects are due to the enhancement of the matrix capability to deform via multiple crazing and to the shear deformation of the PP ligaments between particles.Fil: Fasce, Laura Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Assessment of impact fracture toughness of PP-elastomeric polyolefin blends

The present investigation is concerned with evaluation of the impact fracture toughness of novel blends based on commercial polypropylene homopolymer (PPH) and elastomeric polyolefin (POEs). At room temperature and high load rate, PPH behaves in a brittle manner while the blends exhibited semi-brittle behavior as judged from the nonlinearity in load deflection curves and fracture surface appearance. The challenge of determining reliable toughness values was faced by applying different approaches available in the literature based on fracture mechanics concepts, including corrected linear elastic fracture mechanics (LEFM), equivalent energy concept, and non-LEFM. The fracture toughness data of the blends appeared to be widely scattered in accord with the samples being in the ductile-brittle transition region. In order to provide a consistent description of the entire range of sample behavior, the statistical weakest link model was also applied to the data.Fil: Fasce, Laura Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Frontini, Patricia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Non linear fracture mechanics of polymers: Load Separation and Normalization methods

Fracture toughness of ductile polymers can be measured by the incremental crack growth resistance curve, where J-Integral value is plotted as a function of crack extension. The determination of the resistance curve, J-R, is generally performed through the so-called multiple-specimen technique. In this procedure, several identical specimens are loaded to obtain different amounts of crack growth, thus involving a large number of tests and large quantity of test material. It is also hard to apply in situations such as under high-loading rate conditions, elevated temperatures and/or aggressive environments where it is difficult to stop the test to measure crack extension. Consequently, alternative single specimen techniques appear attractive. The theoretical basis for the single specimen J form used in the incremental J-R curves is given by the Load Separation Principle. It is based on the assumption that the load can be represented as the multiplication of two separate functions: a crack geometry function and a material deformation function. This principle allows the introduction of the so-called η parameter which greatly simplifies J calculation. The crack geometry function is general represented as a power law function which exponent coincides with η factor. By analyzing load line displacement records of several blunt notched specimens differing in their initial crack length before the starting of crack propagation it is possible to evaluate η factor and verify Load Separation Principle assumption. Based on the validity of this principle two methodologies have been developed: Load Separation method, S pb, and Normalization Data Reduction technique. These methodologies have the inherent advantage of developing J-R curves directly from a single load versus load-line displacement record without using any sophisticated automated crack length monitoring system. Load Separation method infers the growing crack length from the load ratio of two load-displacement records: one growing crack and other stationary crack. Normalization method utilizes the Material Key Curve, calibrated using one individual normalized load-displacement record, to infer the instantaneous crack length. Variants of both methodologies have been already successfully used in ductile fracture characterization of polymers by several authors.Innovatively here, the Load Separation Principle and the deformation function are expressed in terms of total displacement without distinguishing between elastic and plastic displacement components. Hence, calculations are simply made using the J-Integral formula based on total energy. The performance of the proposed methods is evaluated and compared with the standard multiple-specimen technique for a broad spectrum of ductile polymers. Several features of the approaches are discussed like: suitability of functional forms, influence of blunting assumption, calibration points and general limitations to their application. The results demonstrate the ease and the accurate of the Normalization method based on total displacement for ductile polymer J-R curve determination. Conversely, the great potentiality of Load Separation method relies on the special fracture cases in which the actual final crack length cannot be easily determined. © 2011 Elsevier Ltd.Fil: Frontini, Patricia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Fasce, Laura Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Rueda, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Assessment of multiaxial mechanical response of rigid polyurethane foams

Multiaxial deformation behavior and failure surface of rigid polyurethane foams were determined using standard experimental facilities. Two Commercial foams of different densities were assayed under uniaxial, biaxial and triaxial stress states. These different stress states were reached in a uniaxial universal testing machine using suitable testing configurations which imply the use of special grips and lateral restricted samples. Actual strains were monitored with a video extensometer. Polyurethane foams exhibited typical isotropic brittle behavior, except under compressive loads where the response turned out to be ductile. A general failure surface in the stress space which accounts for density effects could be successfully generated. All of failure data, determined at the loss of linear elasticity point, collapsed in a single locus defined as the combination of a brittle crushing of closed-cell cellular materials criterion capped by an elastic buckling criterion.Fil: Pettarin, Valeria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Fasce, Laura Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); ArgentinaFil: Frontini, Patricia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; Argentin

Wire cutting method to assess fracture toughness of gelatin gels: Phenomenological analysis and limitations of methodology

In this work the performance of the wire cutting method for determining the fracture toughness, Gc, of gelatin hydrogels is assessed. In this method, wires of different diameters are pushed into a sample while the force and displacement are continuously recorded. The cutting action reaches a steady state, in which fracture propagation, deformation, and friction occur simultaneously. The method implies a linear relationship between the steady-state cutting force per unit sample width and the wire diameter, of which the y-intercept is Gc. Several gel samples differing in gelatin concentration, source (bovine or porcine), solvent (water or water–glycerol mixture), and crosslink type (physical or chemical induced by glutaraldehyde) were tested at different rates. Post-mortem fracture surfaces examined via optical microscopy displayed four different morphologies depending on the gel formulation, cutting rate, and wire diameter: I, striated; II, with one or two oblique straight lines; III, with rhombus-like figures; and IV, with material pull-out. A direct relationship between the developed fracture surface morphology and the method performance existed. One necessary condition for obtaining the linear relationship is a unique fracture surface morphology remaining for all of the wires utilized in the determination. The method is invalid if the fracture surface morphology changes with changing wire diameter, abnormal crack path deflection takes place, or material pull-out occurs as a result of adhesion effects. The applicability of the method seems to be not constrained to physical gels. An appropriate cutting rate and wire diameter have to be selected in order for a unique fracture surface morphology to be achieved. In such cases, reasonable Gc values were obtained from the y-intercept of the best linear fit of experimental data. Gc increased with increasing gelatin concentration, Bloom number, and solvent viscosity. Moreover, Gc was greater when a rhombus-like pattern was induced rather than other morphology due to greater crack path tortuosity.Fil: Czerner, Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Fasce, Laura Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Frontini, Patricia Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; Argentin