Ademir José Zattera

Caracterização de resíduos de copolímeros de etileno-acetato de vinila - EVA

Poly((ethylene)-co-(vinyl acetate)) (EVA) has large application in the shoes industries, especially as expanded sheets, in order to produce insoles and innersoles. Studies carried out in the south region of Brazil in 2001 have demonstrated that the residues generated by shoes industries were higher than 200 ton/month, the major part of which is composed by EVA expanded sheets. With this in mind, the objective of this work was to characterize the residues of expanded EVA and also to analyze the milling cost in order to make the recycling possible. The EVA residues presented originally a microcellular structure, which was destroyed after milling, according to SEM analysis. The EVA powder was found to be composed by two phases: a crosslinked phase (75wt%) and a soluble one (25wt%). The VAc content in EVA residues was found to be around 20wt% and it is believed that the EVA had originally ca. 28wt% of VAc before the crosslinking process, according to the TG analysis. Besides, it was found that the crosslinked structure of EVA residues make them stiffer than virgin EVA used for comparison, according to mechanical tests. The milling cost was estimated to be less than 5% compared to the virgin EVA.

Obtenção e Caracterização de Compósitos Utilizando Poliestireno como Matriz e Resíduos de Fibras de Algodão da Indústria Têxtil como Reforço

The aim of this work is to use cotton fibers as reinforcement in polymeric composites materials using polystyrene as matrix and poly(styrene-co-maleic anhydride) coupling agent. The composites were developed by first mixing in a single screw extruder and a co-rotation parallel twin screw extruder and injection molded. The composites were characterized by analysis mechanical, thermal, dynamic mechanical thermal and morphology. The results from the flexural and tensile strength demonstrate that the addition of 20% cotton fibers tends to increase in these properties; however there is increase when using a coupling agent. The impact resistance increased with the increase of load; however the results of the composites with coupling agent were lower than those without. The temperature of thermal deflection increased for all composites, but the increase for the composites with 20% cotton fiber was approximately 7 oC. The results show that the addition of cotton fibers changes the initial temperature of wheight loss for the composites to temperatures close to 200 oC. The DMTA analysis showed increasing in stiffness and the storage modulus with cotton addition. The micrographs showed a reduction in the pull-out fibers, due to a greater adhesion fiber / matrix with the use of compatibilizer.

Desvulcanização do resíduo de terpolímero de etileno-propileno-dieno (EPDM-r) por micro-ondas

Vulcanized elastomers are materials commonly used in several applications, such as automotive and footwear industries. In this study, scraps of ethylene-propylene-diene terpolymer (EPDM-r) from the automotive industry were exposed to microwaves during different periods (2-5 min). After devulcanization, the samples were characterized by gel content, differential scanning calorimetry (DSC) and activation energy of degradation (Ea) determined by thermogravimetric analysis (TGA). The degradation behavior of EPDM-r was consistent with the literature. The gel content analysis showed that the EPDM-r was devulcanized only at 5 minutes of exposure to the microwaves. DSC analysis demonstrated no significant changes in the samples, and the Ea results confirmed that the additives found in the composition of the EPDM-r affect the efficiency of the regeneration method.

Efeito da concentração de segmentos rígidos nas propriedades físico-mecânicas, químicas e na morfologia de elastômeros microcelulares de poliuretano

In this study, three different microcellular polyurethane elastomers (MPUE) based on 4,4-diphenylmethane diisocyanate (MDI) with different rigid segment contents were prepared (Formulations 1, 2 and 3 with 32, 35 and 42% of rigid segment content, respectively). The MPUE were obtained through a two-step method using the prepolymer system. The samples were analyzed to determine their physical, mechanical, morphological and chemical properties. The results showed that a greater rigid segment content gave higher tensile, compressive and tear strength values. The deformation at break did not show significant changes with a variation in the rigid segment content. The MPUE had a low swelling index in common industrial solvents. However, in acetone a high swelling index was observed. The SEM micrographs indicated a large number of closed cells, and that a higher rigid segment content gave a better cell homogeneity of the samples.

Compósitos de HDPE com resíduos de fibras têxteis. Parte I: caracterização mecânica

In this work, results of mechanical properties of new composites based on textile fiber residues from clothing industry and commodity polymers are discussed. Natural fibers offer some advantages over synthetic ones, regarding mechanical and thermal properties. The composites were produced by mixing high density polyethylene with the textile fibers (50% cotton /50% acrylic) in increasing contents, from 10 to 40% in a thermokinetic mixer, using Surlyn 2601, Polybond 3009 and Polybond 1009 as coupling agents. The tensile, flexural and impact samples were produced by cutting sheets obtained in a hydraulic press. The composites with coupling agents showed good results of tensile and flexural strength, mainly with 5% of Polybond 3009 and 20-40% of textile fiber residues.

Thermal and Rheological Properties of Poly(ethylene-co-vinyl acetate) (EVA) Nanoclay

Poly(ethylene-co-vinyl acetate) (EVA) is a copolymer of utmost importance in nanocomposite applications. Clay dispersed in an EVA matrix was tested using different types of clays with hydrated silicate layers. Several observations have led to the unexpected physical point of view of (clay/polymer) interaction. Due to the polar nature of the acetate group, a strong interaction would be expected when using a polar group-bearing surfactant such as organophilic modified montmorillonite (OMMT – 30B). Through research using techniques that explore the rheology in the molten state, it was evident that a stronger interaction is possible for nonpolar group-modified organophilic clays. This strong interaction is the result of a complex environment of physical entanglements that show a pseudo-solid behavior among the nanoclay dispersed in the EVA matrix. In this chapter, we will emphasize the influence of processing and type of organic modifier in natural organophobic clay (Cloisite® Na+) dispersed in an EVA matrix. The characterization techniques will be discussed by the study of melt state rheology and thermal behavior of these materials. The relaxation phenomena and creep compliance behavior as well as a correlation between the processing and final properties are detailed for EVA and OMMT nanocomposites.

Efeito de EPDM modificado nas propriedades mecânicas e no processamento de composições de EPDM contendo resíduo de EPDMR

This work was aimed at examining the effect from three agents in the recycling of waste rubber, namely copolymer ethylene-propylene-diene (EPDMR) containing carbon black. Three agents were prepared: EPDM modified by 1-dodecanotiol (EPDMSDD), EPDM modified by stearic acid (EPDMAE) and EPDM modified by fatty linolenic acid (EPDMAG). For the mechanical properties, the better tensile and tear strength associated with manufacturing extrusion were obtained using EPDMSDD. EPDMAE and EPDMAG improved the processing by extrusion, while keeping the mechanical properties. These results indicate that EPDMAE and EPDMAG act as auxiliary agents for processability.

Estudo do reprocessamento de polietileno de baixa densidade (PEBD) reciclado do processamento de extrusão de filmes tubulares

The recycling market of thermoplastic polymers is currently in a sharp increase. Recycled materials are regarded as having inferior properties compared to the virgin material. Here we investigated the viscoelastic and thermal properties of the recycled low density polyethylene (LDPE). The samples were reprocessed up to ten times under extreme processing conditions (300 °C/80 rpm) in a single screw extruder in order to evaluate structural changes in their properties. Analyses were performed in an oscillatory rheometer with parallel plates and in a differential scanning calorimeter (DSC). From the analysis of the oscillatory rheometry, relaxation and retardation spectra were obtained upon applying a non-linear adjustment using a computational program (NLREG), while the kinetics parameters were estimated from the results of the first DSC heating using the Avrami and Freeman-Carroll methods. From the rheological study we inferred that the samples reprocessed more than four times had an increase in complex viscosity, storage and loss moduli, also displaying wider relaxation and retardation phenomena. However, the DSC thermograms and the melt kinetic parameters showed that the LDPE studied maintained their thermal stability, regardless of the modification in their viscoelastic properties.

INFLUENCE OF SILANE TREATMENTS ON THE PROPERTIES OF GRAPHITE NANOPLATELET/EPOXY NANOCOMPOSITES

Epoxy resins are used in composite applications due to their good mechanical properties. To further enhance their performance, the use of nanofillers such as graphite nanoplatelets (GrNP) has been proposed, which can be surface treated for extra improvement. This study aims to evaluate the influence of GrNP content and treatment on the mechanical and dynamic-mechanical properties of GrNP/epoxy composites. GrNP was treated with (3glycidyloxypropyl)trimethoxysilane and (3-aminopropyl)triethoxysilane, and later dispersed in epoxy resin aided by sonication. Composites reinforced with 0.25 wt% GrNP displayed increased tensile strength compared to the neat resin. Silane treated fillers showed an improvement in tensile strength and dynamic-mechanical properties compared to both neat resin and GrNP/epoxy composites at the same wt% of reinforcement, evidencing that the silane treatment was advantageous.