Márcia A. S. Spinacé

A tecnologia da reciclagem de polímeros

Solid municipal waste contains a large volume of polymers and its final disposal is a serious environmental problem. Consequently, the recycling of the principal polymers present in the solid waste is an alternative. In this review we describe the mechanical and chemical recycling of polymers and the energy recovery from plastic wastes. Polymer recycling involves not only the development of processing technologies, but also the solution of many chemical and analytical problems. The technological, economical and social aspects of polymer recycling are also considered.Solid municipal waste contains a large volume of polymers and its final disposal is a serious environmental problem. Consequently, the recycling of the principal polymers present in the solid waste is an alternative. In this review we describe the mechanical and chemical recycling of polymers and the energy recovery from plastic wastes. Polymer recycling involves not only the development of processing technologies, but also the solution of many chemical and analytical problems. The technological, economical and social aspects of polymer recycling are also considered.

Poly(ethylene oxide-co-epichlorohydrin)/NaI: a promising polymer electrolyte for photoelectrochemical cells

We have investigated the thermal and ionic conductivity properties of the elastomer poly(ethylene oxide-co-epichlorohydrin) filled with NaI and I2. The reason for using this composition is its potential application as electrolyte in photoelectrochemical cells. This copolymer was characterized as a function of NaI concentration, temperature and relative humidity. According to the data obtained, the Na+ ion interacts with the ethylene oxide repeating units by means of Lewis type acid–base interactions. The empirical Vogel–Tamman–Fulcher equation was used to model the conductivity and temperature relationships, indicating that the conduction occurs in the amorphous phase of the copolymer. The sample with 9.0% (w/w) of NaI presents a conductivity of 1.5×10−5 S cm−1 in a dry atmosphere (30°C, [H2O]<1 ppm) and 2.0×10−4 S cm−1 at 86% relative humidity (22°C).

Polymer electrolytes based on ethylene oxide–epichlorohydrin copolymers

In this work we studied the ionic conductivity for three copolymers of the title co-monomers as a function of LiClO4 content, temperature and ambient relative humidity. We also investigated the interactions between the salt and the co-monomer blocks in the copolymers and its effect on the morphology and thermal properties of the copolymer/salt complexes. Our data indicate that the Li+ ion predominantly interacts with the ethylene oxide repeating units of the copolymers. The copolymer with the highest ionic conductivity was obtained with an ethylene oxide/epichlorohydrin ratio of 84/16 containing 5.5% (w/w) of LiClO4. It showed a conductivity of 4.1×10−5 S cm−1 (30°C, humidity< 1 ppm) and 2.6×10−4 S cm−1 at 84% relative humidity (24°C). The potential stability window of the copolymer/salt complex is 4.0 V, as measured by cyclic voltammetry. For comparison, we also prepared a blend of the corresponding homopolymers containing LiClO4; it showed higher crystallinity and lower ionic conductivity.

Efeito da forma de processamento e do tratamento da fibra de curauá nas propriedades de compósitos com poliamida-6

The interest for the use of vegetal fibers as polymer reinforcement has recently increased because of their unique environmental and technological advantages. This work evaluated the use of Curaua fibers in polyamide-6 composites, aiming at glass fiber replacement. Fiber contents of 0, 20, 30 and 40 wt% and fiber lengths of 0.1 or 10 mm were analyzed. Part of short fibers were treated with N2 plasma, or washed with NaOH solution, to improve their adhesion to the PA-6 matrix. Samples with 20 wt% of short or long fiber, with or without pre-treatment, were compounded in an internal mixer and in two different co-rotating inter-meshing twin-screw extruders. Test specimens molded from these samples were submitted to mechanical (tensile, flexural and impact) and thermal (HDT) tests. In summary, for the samples with non-treated fiber compounded in the extruder, moist raw materials improved fiber/matrix interfacial adhesion. Tensile and flexural properties of this composite are better than unfilled PA-6, but lower than glass fiber reinforced PA-6. However, its impact resistance and heat deflection temperature, similar to the glass fiber reinforced PA-6, and its lower density, enable it to replace the latter in specific, non-critical applications.

Biocomposite of a multilayer film scrap and curauá fibers: Preparation and environmental degradation

An important material for making composites is the scrap of multilayer films. Using plant fibers in these composites can further contribute to reduce their environmental impact. We prepared, by extrusion and injection molding, composites of this scrap reinforced with 20 wt% of curauá fibers. These were characterized using scanning electron microscopy (SEM); optical microscopy; tensile, flexural, and notched impact strength tests; differential scanning calorimetry; carbonyl index (CI) by Fourier transform infrared spectroscopy; reflectance ultraviolet–visible spectroscopy; and water absorption measurements. The fiber promoted an increase in the flexural and tensile moduli strengths. SEM showed good fiber/matrix adhesion, dispersion of the fibers in the matrix and their fibrillation. Weathering of the surface of the composite during environmental aging was evidenced by CI, degree of crystallinity, melting temperature, and the formation of cracks caused by chemi-crystallization. Despite the environmental degradation of the exposed composite surface, the mechanical properties and interfacial adhesion did not change significantly.