Sebastião V. Canevarolo

Bio: Sebastião V. Canevarolo is an academic researcher from Federal University of São Carlos. The author has contributed to research in topics: Birefringence & Polypropylene. The author has an hindex of 17, co-authored 67 publications receiving 965 citations.

Evolution of peroxide-induced thermomechanical degradation of polypropylene along the extruder

Abstract: An experimental study of the peroxide-in-duced degradation of polypropylene in a corotating twin-screw extruder, operating under various conditions, wasreported. Runs were performed without and with peroxidein different concentrations. The evolution of the chemicalreactions along the extruder was characterized by on-linerheological measurements and by determination of the mo-lecular weight of samples collected at the same locations.The results evidenced the relationships between peroxideconcentration and processing conditions with rheologicalproperties and molecular structure of the modified materi-als. The concept of chain-scission distribution function elu-cidated the mechanisms involved in the thermomechanicaldegradation of PP, which is by chain scission and is depen-dent on the level of stress imposed by the screw elements,temperature, and concentration of hydrogen-abstractingagents. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91:2711–2720, 2004 Key words: processing; degradation; molecular weight dis-tribution; polypropylene (PP); rheology

Mechanical and morphological characterization of polypropylene toughened with olefinic elastomer

Abstract: The effect of incorporating (C2-C8) ethylene-octene elastomer on the mechanical properties and morphology of polypropylene copolymers has been investigated employing two types of PP copolymer, with and without nucleating agent. The results were compared to the ones presented by a commercial PP heterophase (reactor impact modified PP/EPR). The addition of the elastomer increases the toughness of the blends but reduces their stiffness. PP blends in the low elastomer content region (< 20%) show low values of the Izod impact strength and both, elastomer content and impact strength, are directly proportional to the area under the b damping peak or its maximum intensity of the elastomer. The morphology is a continuous pattern of segregate elastomeric particles with average particle size in the range of 0.27 mm to 0.39 mm. The average particle size and particle size distribution plotted in log-normal distribution curves, increases slightly with the increase in the elastomer content. The reactor modified PP heterophase has a broader particle size distribution and an average particle size of 0.56 mm, at the lower limit but inside the range for good impact performance, as observed.

Mechanical Recycling of Packaging Plastics: A Review.

Abstract: The current global plastics economy is highly linear, with the exceptional performance and low carbon footprint of polymeric materials at odds with dramatic increases in plastic waste. Transitioning to a circular economy that retains plastic in its highest value condition is essential to reduce environmental impacts, promoting reduction, reuse, and recycling. Mechanical recycling is an essential tool in an environmentally and economically sustainable economy of plastics, but current mechanical recycling processes are limited by cost, degradation of mechanical properties, and inconsistent quality products. This review covers the current methods and challenges for the mechanical recycling of the five main packaging plastics: poly(ethylene terephthalate), polyethylene, polypropylene, polystyrene, and poly(vinyl chloride) through the lens of a circular economy. Their reprocessing induced degradation mechanisms are introduced and strategies to improve their recycling are discussed. Additionally, this review briefly examines approaches to improve polymer blending in mixed plastic waste streams and applications of lower quality recyclate.

Mechanism of Degradation of Starch, a Highly Branched Polymer, during Extrusion

Abstract: An investigation of the mechanisms of degradation of a branched polymer in extrusion was performed using starch as substrate. Starch has the advantage that the distribution of degree of polymerization of individual branches can be readily obtained using a debranching enzyme and also that it does not undergo any reaction except scission during extrusion, thereby aiding mechanistic interpretation. Various starches, containing a range of the highly branched amylopectin component and the much less branched amylose component, were extruded in the presence of water and glycerol as plasticizers with extruder barrel temperatures ranging from 50 °C at the hopper zone through to 140 °C near the die exit. Analysis by size-exclusion chromatography of both whole and debranched samples subject to various levels of extrusion showed that the extrusion degradation process involved preferential cleaving of larger molecules, while causing the size distribution to narrow and converge toward a maximum stable size. This is ana...