Clodoaldo Saron

Chain extension of poly (ethylene terephthalate) by reactive extrusion with secondary stabilizer

Poly(ethylene tereftalate) (PET) is a polymer highly susceptible to the hydrolytic reactions that occur during applications and mainly in thermomechanical processing. These reactions lead to the decrease of molecular weight of the polymer, limiting the recycling number of the material. The reactive extrusion of the PET in presence of chain extenders is an alternative to recover mechanical and rheological properties that were depreciated by the polymer degradation. In this study, PET wastes from nonwoven fabrics production were extruded in presence of the secondary stabilizer Irgafos 126 (IRG) on variable concentrations. The results showed that Irgafos 126 increased molecular weight, decreased crystallinity and changed processing behavior of the PET, similarly to the effects produced by the well-known chain extender pyromellitic dianhydride (PMDA), showing that the secondary stabilizer Irgafos 126 can also act as a chain extender for the PET.

Characterisation of recycled acrylonitrile-butadiene-styrene and high-impact polystyrene from waste computer equipment in Brazil.

Polymeric materials constitute a considerable fraction of waste computer equipment and polymers acrylonitrile-butadiene-styrene and high-impact polystyrene are the main thermoplastic polymeric components found in waste computer equipment. Identification, separation and characterisation of additives present in acrylonitrile-butadiene-styrene and high-impact polystyrene are fundamental procedures to mechanical recycling of these polymers. The aim of this study was to evaluate the methods for identification of acrylonitrile-butadiene-styrene and high-impact polystyrene from waste computer equipment in Brazil, as well as their potential for mechanical recycling. The imprecise utilisation of symbols for identification of the polymers and the presence of additives containing toxic elements in determinate computer devices are some of the difficulties found for recycling of acrylonitrile-butadiene-styrene and high-impact polystyrene from waste computer equipment. However, the considerable performance of mechanical properties of the recycled acrylonitrile-butadiene-styrene and high-impact polystyrene when compared with the virgin materials confirms the potential for mechanical recycling of these polymers.

Reciclagem de rejeitos de poli(tereftalato de etileno) (PET) e de poliamida (PA) por meio de extrusão reativa para a preparação de blendas

The increasing use of polymeric materials in several applications leads to the production of a high amount of post consume and post industrial wastes with expressive pollutant potential. Mechanical recycling is an important way to decrease the problems caused by these wastes because it allows one to associate economic viability with environmental benefits. In this paper a study was carried out on the recycling of poly(ethylene tereftalate) (PET) wastes from the production of nonwoven fabrics (NWF) and of polyamide (PA) wastes from old tires for production of polymeric blends via reactive extrusion in the presence of trans-reaction catalysts. The results from thermal and chemical characterization indicated trans-reactions between segments of polymeric chains of the two polymers, promoting the system compatibilization. The production of PET/PA blends is an interesting alternative for recycling PET and PA wastes.

Microwave Devulcanization of Waste Rubber with Inorganic Salts and Nitric Acid

Rubber wastes cause severe damages for the environment when unsuitably disposed in the environment and represent a challenger for mechanical recycling, because the vulcanized rubber is formed by a tridimensional network with intermolecular sulfur crosslinks. Microwave radiation can lead to the breaking of sulfur crosslinks and so enable the recycling of vulcanized rubbers. The aim of this work was to study the SBR devulcanization by microwave using inorganic salts and nitric acid. Soxhlet extraction and FTIR analyzes were carried out to evaluate the devulcanization degree and chemical modifications in the rubber structure. The results showed that the presence of carbon black in the rubber is an important factor for devulcanization and some metallic ions decrease the sulfur crosslink content. On the other hand, these ions promote the oxidation in the rubber.

Microwaves Devulcanization of SBR Containing Carbon Black

Polymer recycling has been the most suitable alternative for management of plastics waste that are responsible by serious environmental damages. However, the recycling of some polymer materials, such as vulcanized elastomers, is not a trivial process. The recycling of elastomers is a process more complex than the recycling of thermoplastic polymers because the elastomers cannot be remolded by simple heating after vulcanization. Methods for rubber devulcanization has been developed as an interesting alternative for recover flow properties of elastomers, allowing other molding cycle. The aim of this work was to evaluate the effect of the presence of carbon black on devulcanization of styrene-butadiene rubber (SBR) by microwaves and analyze properties of recycled material. The devulcanization by microwaves showed efficiency for rubber compositions with higher content of carbon black incorporated as well as the properties of recycled material showed satisfactory performance for reuse in other products. Microwaves devulcanization of SBR is an important alternative for reuse of rubber waste and decrease of the environmental problem generated with discard of these materials.

Low-density polyethylene/sugarcane fiber composites from recycled polymer and treated fiber by steam explosion

ABSTRACT Low-density polyethylene (LDPE) has caused serious environmental damages, and it has been a challenge for waste management in large cities. The LDPE recycling as composites with natural fibers such as sugarcane fibers (SCF) has been an interesting alternative to conciliate economic aspects with environmental benefits. In this study, SCF has been treated by steam explosion and incorporated to low-density polyethylene waste (LDPEW) to generate LDPEW/SCF composites with higher fiber/polymer interaction and improved mechanical properties. LDPEW/SCF composites with fibers content until 20 wt% showed mechanical properties with performance adequate for nobler applications when compared to the isolated recycled LDPEW.

Mechanical Recycling of PET Waste from Non-Woven Fabrics by Reactive Extrusion with Chain Extenders

Mechanical recycling of poly (ethylene terephthalate) (PET) is an important industrial activity with direct effect for environmental saving. However, recycled PET (R-PET) undergoes progressive degradation during each recycling process, leading to considerable loss of properties such as mechanical, thermal and melting strength. Chain extenders have been successfully used to increase molecular weight of R-PET, improving process ability and mechanical performance of the material. The aims of this work was to evaluate the performance of the compounds polymeric methylene diphenyldiisocyanate (PMDI) and bis-(2,4-di-t-butylphenol) pentaerythritoldiphosphite (Irgafos ® 126) for potential use as chain extenders when compared to the traditional chain extender pyromelliticdianhydride (PMDA). Tensile testing, differential exploratory calorimetry, viscometry and dynamic rheometry were used to evaluate changes in mechanical properties, crystallinity, molecular weight and rheological properties of R-PET. PMDI showed effective action on increase in molecular weight and improvements in mechanical and rheological properties of R-PET, while Irgafos 126 causes depreciation of properties of the R-PET after initially to increase the molecular weight of the polymer. Thus, the use of PDMI as chain extension can represent an important alternative for mechanical recycling of highly degraded PET.