Sandro Campos Amico

Pull-out and other evaluations in sisal-reinforced polyester biocomposites

Although sisal fibers have been used by several authors, the Brazilian variety has not yet been thoroughly characterized. In this work the surface of sisal fibers was modified by treatment with NaOH or N-isopropyl-acrylamide solutions. Lignin content and density of fibers are reduced with the chemical treatment and the N-isopropyl-acrylamide treatment causes a significant reduction in moisture absorption. Tensile tests of NaOH (0.25, 0.5, 1, 2, 5, and 10% w/w) and N-isopropyl-acrylamide (1, 2, and 3% w/w) treated fibers were carried out and a reinforcement effect of the sisal treated with 2% solutions was observed. TGA measurements showed that with the NaOH treatment the fiber becomes more thermally resistant. SEM micrographs and crystallinity index of sisal indicated how different treatments alter the fiber surface. Pull-out tests in polyester resin were performed, evidencing that all treatments were effective in improving interfacial adhesion. The best results were obtained with the 2% N-isopropyl-acrylamide treatment. The main advantages of pull-out tests is that without considering composite processing variables, good performance sisal/polyester composites may be selected before their laborious and material-consuming preparation step.

Desempenho de filmes multicamadas em embalagens termoformadas

Flexible multilayer plastic films may be used for the thermoforming of packages for meat products. In this case, the packages must meet the technical requirements of medium or high barrier to oxygen, depending on the characteristics of the food product, in order to avoid contamination during its shelf-life and consequently risk to human health. However, the thermoforming process alters the original characteristics of the plain films, which could render them inadequate to use, especially in the deepest corners of the packages, which are the critical points. This work addressed the thermoforming effects on the properties of two multi-layered plastic films, called medium barrier (MB), comprising PP/tie/PA6/tie/PA6/tie/LDPE, and high barrier (HB), where the central adhesive (tie) layer was replaced by a layer of ethylene vinyl alcohol copolymer (EVOH). The characterization of the films included investigations of thickness, oxygen permeability, and mechanical and optical properties.

A Methodology for the Evaluation of Mechanical Properties of Sausage Based on Tensile and Compression Tests

The food product called sausage is a meat emulsion in which the fat drops are dispersed in an aqueous matrix containing soluble proteins, other muscle components and conjunctive tissue. The rheological behavior of sausage needs to be known in order to monitor the quality and acceptance of this product and the evaluation of its response, for instance, to different packaging situations, which is a result of their stress-strain behavior when subjected to a particular static or dynamic stress. A methodology for the assessment of mechanical properties of sausage has been developed. A universal testing machine was used and tests were carried out in sausage available in the market to validate the methodology. Tensile and compression tests were carried out and test conditions were varied, including strain rate and specimen shape and temperature. The influence of the skin on the determinations was also assessed. The need to control cross-section shape was identified, and a dumb-bell and a cylinder specimen shape were proposed for tensile and compression tests, respectively. Temperature is critical and higher temperatures decrease tensile and compressive strengths. Sausage resistance is also sensitive to the strain rate, especially at low values. A travel speed of 50 mm/min seems to be appropriate since variations around this value did not affect tensile or compressive strength determinations. The presented methodology was found adequate to the intended objectives, producing reliable and reproductive results.