Ticiane Sanches Valera

Modification of a Brazilian smectite clay with different quaternary ammonium salts

In this work, a smectite clay from the State of Paraiba, Brazil, was treated with six different types of ammonium salts, which is an usual method to enhance the affinity between the clay and polymer for the preparation of nanocomposites. The clays, before and after modification, were characterized by X ray diffraction. The conformation of the salts within the platelets of the clay depended on the number of long alkyl chains of the salt. The thermal stability of the clays was also studied. The ammonium salts thermal decomposition was explained in light of their position within the organoclays.

Blends of ground tire rubber devulcanized by microwaves/HDPE - Part A: influence of devulcanization process

The main objective of this work is the study of the influence of microwaves devulcanization of the elastomeric phase on dynamically revulcanized blends based on Ground Tire Rubber (GTR)/High Density Polyethylene (HDPE). The devulcanization of the GTR was performed in a system comprised of a conventional microwave oven adapted with a motorized stirring at a constant microwaves power and at various exposure times. The influence of the devulcanization process on the final properties of the blends was evaluated in terms of mechanical, viscoelastic, thermal and rheological properties. The morphology was also studied.

Blends of ground tire rubber devulcanized by microwaves/HDPE - Part B: influence of clay addition

The main objective of this work is to study the influence of clay addition on dynamically revulcanized blends of Ground Tire Rubber (GTR)/High Density Polyethylene (HDPE). GTR was previously devulcanized in a system comprised of a conventional microwave oven adapted with a motorized stirring, with a fixed microwave power and at various exposure times. The influence of clay addition on the final properties of the blends was evaluated in terms of mechanical, viscoelastic, thermal and rheological properties, with morphology being also analyzed. The results depict that the clay can modify the rheological behavior of the GTR phase, in addition to the thermal and mechanical properties of some blends.

Effect of filling factor on the determination of shear rate and viscosity from batch mixer

In this work, the effect of filling factor on torque data obtained with a torque rheometer was studied. Torque data were obtained for polypropylene (PP), high density polyethylene (HDPE), and polystyrene (PS), for filling degrees ranging from 60 to 90%. The processing temperature used for HDPE was 160°C and the other polymers were processed at 200°C. The torque data obtained were used to calculate the shear rate in the batch mixer and corresponding viscosity of the polymer using Bousminas model [Journal of Rheology 43, 415 (1999)], which provides a quantitative correlation between torque data and viscosimetric properties of a polymer. Bousminas model considers the mixer chamber and rotor blades as concentric cylinders of internal and external radii R; and R e , respectively. The model was used making different assumptions for the rheological nature of the polymers. The polymers were considered either Newtonian or power law fluids. The calculated values of viscosity versus shear rate were compared to results obtained by rotational and capillary rheometry. The experimental results showed that the torque increases exponentially with increasing filling factor. The results of the comparison indicated that in order to evaluate viscosity versus shear rate from torque rheometer data, the experimental chamber should be calibrated to obtain R iPC (internal radius for calibration polymer) using a first polymer. This value of R iPC should fulfill Ripe / R e > 0.9, otherwise the calibration should be made with another polymer. This value of R iPC can then be used together with torque data obtained with a filling degree of 90% or more for a second polymer assuming the polymer as a Newtonian fluid. If the torque data are obtained with a filling degree less than 90%, the Newtonian hypothesis is not valid any more and Bousminas model and an emulsion model should be used sequentially to infer viscosimetric data from torque data obtained using a partially filled mixing chamber.

Synthesis and Characterization of Organophilic Clay from Cuban Chiqui Gomez Bentonite

Smectites are clay mineral with a layered structure and nanometric thickness, high specific area and a huge variety of uses. Consisting on stacked layers of about 1nm thickness, including two silica tetrahedral and one octahedral sheet. Properties of natural Smectites can be enhanced by organic modification, due to the substitution of the exchangeable cations in the interlayer area. In fact, the properties of the modified smectite (organophilic clay) are related to its modified chemical composition and structural parameters. The interaction of smectite clays with surfactants has an important interest in the fields of drilling fluids, paints, cosmetic, ceramic industries and others. Recent applications are: remediation of contaminated areas and polymer/clay nanocomposites. The aim of this paper is to obtain organophilic clays using a bentonite from the Chiqui Gómez deposit in Central Cuba. The raw and organophilic clays were analyzed by DRX, SEM, swelling capacity in organic solvents and others.

Characterization of the Non-Polymeric Fraction of Post-Consumer LCD Monitor Housings

This work aims to characterize the non-polymeric components, usually present as additives to perform different functions, present in the polymer housing of post-consumer computer monitors, in order to help finding the most adequate recycling destination for such material. The non-polymeric fraction was characterized by thermogravimetry (TG), loss on ignition (LOI), chemical analysis by X-ray fluorescence (XRF), and atomic absorption spectroscopy, scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS), and X-ray diffraction (XRD). TG analysis indicated that the polymer has about 4 wt% of inorganic materials (performed in N2 atmosphere), whereas LOI (performed in ambient atmosphere) indicated just 0.07 wt%. The XRF, SEM/EDS analyses, and atomic absorption spectroscopy of the post-fired material confirmed the presence of many elements. Nonetheless, toxicological relevant elements showed acceptable concentration levels, below 0.01 ppm. The XRD analysis indicated the presence of crystalline phases based on CaCO3, SiO2 and TiO2.

Estudo de sistemas retardantes de Chama sem Bromo para ABS

This work presents a study on alternative systems to substitute brominated flame retardants used in ABS. Combinations of flame retardants without bromine were studied: Ammonium polyphosphate, Melamine, Titanium dioxide Nanoparticles and phosphonium salt modified Organoclay. The composites obtained were characterized by mechanical tests (Izod Impact and Tensile strength), thermal analyses, scanning electron microscopy and Flame Retardancy tests. The results indicated that the Linear Burning Rate of ABS was reduced ca. 48% when the APP/MEL/OMMT/TiO2 system was used.

Effect of the Addition of a Brazilian Sodium Smectite Clay in Toughened Nylon-6

In this work, the effect of the incorporation of a sodium smectite clay (Brasgel) in Nylon-6 toughened with Poly (vinyl butyral) film (PVB film) was evaluated. The composites contain 60 wt.% of Nylon-6, 40 wt.% of PVB film and 5 wt.% of clay, relative to the total weight of the mixture. The clay was previously purified by sedimentation, and dried in a spray-dryer at 150°C. The composites were obtained by extrusion, in two steps: step 1 - mixture of nylon-6 with clay (called master of nylon-6) and step 2 - mixture of master of nylon-6 with PVB film. The clay was characterized by X-ray diffraction and X-rayfluorescence. The composites were characterized by mechanical tests (tensile and notched Izod impact strength), X-ray diffraction and scanning electron microscopy (SEM). The composites showed significant increase in the values of the notched Izod impact strength, when compared to the ones for pure nylon-6, and kept the stiffness of the matrix phase.

Evaluation of the Influence of a Smectite Clay in PP Composites

In this work, the effect of the addition of an organophilic smectite clay on the properties of polypropylene (PP) was evaluated. The clay was a commercial natural montmorillonite treated with ammonium quaternary salt (Cloisite 20A®). The composites were prepared by extrusion, and contain 5 wt.% of clay. The materials were characterized by: tensile and impact strength, oxygen permeability tests, optical microscopy, thermal analysis and X-ray diffraction analysis. The mechanical properties of the PP were decreased due to the clay addition. The composites presented a microstructure predominantly intercaleted, with fine and homogeneous dispersion of the clay layers within the matrix. The composite showed an increase of about 30% in the oxygen barrier property of the PP, which is an interesting result when considering the application of the composite as a packaging material.

Use of Glass Particles from Recovered LCD Screen Components as Fillers for Polyamide-6

Glass from computers’ LCD monitor screens were recovered, ground and used as filler for Polyamide-6. The composites contained 10 wt% of glass particles. Two particle sizes were tested: glass particles smaller than 106 μm (ABNT#150 sieve) and smaller than 53 μm (ABNT#270 sieve). The filler was evaluated by loss on ignition and the composites by tensile strength and Izod impact strength. The morphology was characterized by scanning electron microscopy (SEM). The value of Young’s modulus of composites processed with glass particles smaller than 53 μm was higher than the one for PA-6. The properties of impact strength, tensile strength, and elongation of PA-6 were reduced with the addition of filler, and the composite containing glass particles smaller than 53 μm showed the lowest reduction in mechanical properties (about 6% in the tensile strength and about 48% in impact strength). The micrographs of fracture surfaces of tensile strength specimens showed weak adhesion particle/matrix and uniform distribution of the particles in the matrix, especially in the composite with finest particle sizes.