Samuel Marcio Toffoli

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.

Evaluation of Industrial Rejects of Mineral and Metallurgical Processing as Ceramic Synthetic Proppants

Hydraulic fracturing is a very important technique to increase the productivity and recovery of oil reservoirs with low pressure or high depth. The hydraulic fracturing technique is a method of well stimulation in which liquid under high pressure is pumped down a well to fracture the reservoir rock adjacent to the wellbore. Propping agents are used to keep the fractures/cracks open. They can be made from the reject of mineral extraction processes when they present specifics characteristic. The aim of this paper is the evaluation of the use of industrial rejects to the development of ceramic synthetic proppants that are resistant to chemical corrosion and high mechanical strength in aqueous acid and salt water environment. In this study, industrial rejects from nickel sulfide ore flotation (grey mud - GM), red mud (RM) from Bayer process and black mud (BM) from Caron processing of nickel was used as raw material for the production of ceramic synthetic proppants. The material processing was performed through drying, milling, pressing, sintering and characterizing raw material. Several characterization techniques such as X-ray powder diffraction (XRD), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), high temperature dilatometry and compression strength test were performed after sintering to evaluate the technological potential of recycling these metallurgical and mineral rejects. Mechanical properties were improved after sample sintering. The results show that it is possible to manufacture ceramics of high strength and resistance to acidic/salt water environment as a result of processing minerals reject.

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.

Characterization of Selenium Doped Silica Gels Synthesized by Sol-Gel Method

Selenium is a rare element in nature. It is used in the food, pharmaceutical, and glass industries. In commercial glasses, selenium is the element responsible for most of the pink or light red color, but its effect is primarily dependent on the oxidation state of the element in the glassy matrix. Besides, selenium is highly volatile, and as high as 80 wt% may be lost in the furnace during the industrial glass elaboration. The sol–gel method yields synthesized materials of high purity and homogeneity, and uses low processing temperatures. Samples of silica gels were obtained by sol-gel method, incorporating precursors of selenium, with the main objective of reducing selenium losses during its heating. The results of optical absorption, XRD and thermal analysis (TGA, DSC) of the gels are presented and discussed.

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.

Design of a Ceramic Slip for Electrical Porcelain Insulators, Using Clay Dispersed in a Ball Mill

An electrical insulator is a piece or structure of an insulating material, which aims to rigidly or flexibly support electrical conductors or equipments, insulating them of the ground [1]. The insulators have distinct styles or types, offering a wide choice of components for overhead distribution design. The first and oldest series is the standard line post insulator for upright mounting on crossarms or structures [2]. An outline of the design can be seen in the Figure 1. These components have an integral head manufactured in porcelain for tie top attachment, and a base cemented on the lower end, for stud mounting to a flat surface.

Use of Calcined Tannery Sludge Containing Chromium Compounds in Soda-Lime Glass Fabrication

Tanning industries generates large quantities of solid wastes containing chromium compounds with characteristics of high-polluting and hazardous conditions. However, these wastes are a potential source of chromium which could be used by the glass and ceramic enamels industries. In this study the properties of a calcined tannery sludge containing chromium compounds was investigated in order to evaluate the potential of using this powder as a suitable and cheap green colorant for the glass manufacturing. X-ray diffraction (XRD), chemical (XRF) and thermal (DTA/TG) analyses were used to determine the physical and chemical characteristics of tannery sludge. Colorimetric method using diphenylcarbazide were conducted to determinate the Cr (VI) concentration in the samples. Soda-lime glass containing calcined tannery sludge was prepared by melting at 1550°C. The results showed that the calcined tannery sludge has a favorable behavior to be used as an alternative source of chromium for the glass manufacturing.

Rheological Studies of Brazilian Clays in Water-Alcohol Suspensions

In this paper, the rheological behaviors of dispersions of two types of clays a kaolin and a smectitic clay from Paraíba State, Northeastern Brazil, were investigated. Both clays are mainly employed by ceramics industries in the Southern States of São Paulo and Santa Catarina. Viscosity measurements of dispersions in water and three types of alcohols (methanol, ethanol, and propanol) were carried out in a concentric cylinder geometry viscometer. The concentration of the dispersions was 20 wt.% of clay in water-alcohol suspensions containing up to 75 wt.% of each one of the three alcohols. The results are compared and discussed.

Brazilian bentonites for geosynthetic clay liners (GCL)

Bentonites have been used for several purposes, due to their excellent physical, chemical, and structural properties. The main applications of bentonites in Brazil are, among others, as agglomerants for foundry molds, in iron ore pelletizing, as drilling mud in oil and water wells, as wine clarifiers, in catalysis, at the chemical and pharmaceutical industries, for pollutants removal in water treatment plants, and in cosmetics. Since the 1980’s, bentonites have been used as barriers in landfills, thanks to the attractive characteristics of the montmorillonite, the principal clay mineral in the smectitic clays (popularly called bentonites). The inadequate accumulation of residues in soils and waters is identified as one of the most serious current problems. Nowadays, geosynthetic clay liners, or GCL’s, have been used as a geo-synthetic hydraulic barrier. They are constituted by a sodium or calcium bentonite layer encapsulated in geo-textiles or attached to geo-membranes, which are secured together by physical or chemical methods. This paper discusses GCL’s, their uses, the influences of the type of clay, the working principles, the related aspects to landfills projects, and also the main Brazil’s bentonite exploitation areas.

Study Aiming the Use of Powder Waste Reject from the Sanitary Ware Production in Mass for Red Ceramics

A procedure that comes being studied for the exploitation of powder waste rejected from the sanitary ware production is the incorporation in mass for red ceramics. Objective of this work is to present the results gotten in the incorporation of this rejects. The used clay was from ceramics industries of the Jundiai region, SP. Spherical bodies test samples had been conformed incorporating 1%, 5%, 10%, 20% and 30% of the powder waste in mass. These bodies had been evaluated on compression resistance after dried to 110°C and to color after burns to 950°C. The composition that presented better results had been conformed by extrusion in prismatic bodies test samples. Again, the dried to 110°C and burnt to 950°C bodies test samples had been evaluated on flexion resistance but to linear retraction too. It was measured the ceramic properties of the burnt bodies test samples. Results indicate that there is a great potential in the formula with 30% incorporation of powder waste in mass. Comparative assays were made being used a mixture without incorporation of the denominated white reject.