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Rheological and morphological studies were performed on polymer blends of ethylene-octene copolymer [polyethylene elastomer (PEE)] and polypropylene (PP). The viscosities of PEE, PP, and PEE/PP blends were analyzed using an Instron capillary rheometer and a Rheometrics Dynamic Stress Rheometer, SR 200. A non-Newtonian flow behavior was observed in all samples in the shear rate range from 27 to 2700 s Ϫ1 , whereas at shear rates in the range from 0.01 to 0.04 s Ϫ1 , a Newtonian flow behavior was verified. The scanning electron micrographs showed that dual-phase continuity may occur between 50 and 60 (wt %) of PEE. This result is consistent with the Sperling's model. The mechanical analysis showed that PEE/PP, with 5 wt % of PEE, presented an increase on the mechanical properties and as the PEE content increased, a negative deviation in relation to an empirical equation was observed. Thermal analysis showed that there were no change in the crystallization behavior of the matrix when different elastomer contents were added. Dynamic mechanical thermal analysis showed that samples with low PEE contents presented only one peak, indicating a certain degree of miscibility between the components of these blends.

Clays of different composition have been used in the development of polymer nanocomposites. The utilization of bentonite clays of the State of Paraíba, Brazil, has been emphasized mainly due to their availability. However, these bentonite deposits are becoming exhausted after several years of exploitation. Thus, the aim of this work was to characterize bentonite clays recently discovered in the municipality of Cubati, Paraíba. The samples underwent a particle size classification step and were characterized by granulometric analysis by laser diffraction, X-ray fluorescence, X-ray diffraction, infrared spectroscopy, thermogravimetric analysis and cation exchange capacity. The results of particle size distribution showed that the clay samples have similar physical characteristics to bentonite clays of Boa Vista, Paraíba. Results of X-ray diffraction indicated that the mineralogical composition of the samples consisted of montmorillonite, kaolinite and quartz. The characterization of the samples by FTIR confirmed these results. Results of chemical analysis showed that the samples are polycationic bentonite clays and have predominantly different exchangeable cations similar to those seen in South American bentonites.

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Characterization studies of clays are often performed to identify possible markets for these materials. Bearing this in mind, two samples of natural clays from the Southeast region of Brazil were studied. Conventional techniques of characterization were used. Granulometric analysis and determination of cationic exchange capacity of these clays were also performed. Nitrogen adsorptiondesorption measurements were used to determine the Brunauer-Emmett-Teller specific surface area, and Barrett-Joyner-Halenda and t-plot pore size analysis were carried out. The results obtained were similar for the two clays. Both present high clay fraction (above 80 wt%) composed of illite, kaolinite and quartz minerals. Stratified illite-smectite structures were also observed. Traces of calcite were detected in one of the clay samples, while traces of montmorillonite were observed in the other sample. These results were corroborated by the low cationic exchange capacity values obtained for both clays. These clays showed good adsorptive properties, evidenced by their specific surface areas, with predominantly mesoporous structures and slit-like pores. According to their features, these clays have potential use as adsorbents to replace more expensive materials due to their easy availability and low cost. Keywords: characterization techniques, clay minerals, natural clays. Resumo

Blends of PHB and LDPE were prepared by melt mixing in a twin screw extruder. Castor oil cake (CC) was used as filler for the blends. The design of experiments (DOE) technique was used to evaluate the effect of the components proportion on the materials properties. The mechanical properties and morphology of the materials were evaluated. The LDPE Young's modulus increases but the other tensile properties and impact resistance deteriorate with the addition of PHB or CC. The tensile strength values of binary mixtures of LDPE lie in the range from 8.9 to 10 MPa. As some commercial grades of LDPE have mechanical strength in this range, it may be inferred that the addition of a certain amount of PHB or CC to LDPE may be considered as a possibility for obtaining LDPE based materials with increased susceptibility to biodegradation. The poor interfacial adhesion between the phases became visible in all samples.

Blends of linear low density polyethylene (LLDPE) ethylene-1-octene copolymers (EOC), with different 1-octene (OC) content, and ground rubber tire (GRT) were prepared by melt mixing in a twin screw extruder. Five different compositions of LLDPE/EOC/GRT blends were processed in the extruder to evaluate the effect of EOC addition to the LLDPE/GRT blends. The addition of EOC to LLDPE/GRT blends improves the mechanical properties. Besides, the replacement of 5% of GRT by EOC grades (OC = 20 or 30 wt %) in the 50/50 LLDPE/GRT blend, leads to a significant increase of ultimate tensile properties. The EOC comonomer content affects the properties of LLDPE/EOC and LLDPE/EOC/GRT blends. Dynamical-mechanical analyses showed that, with the addition of EOC to LLDPE/GRT blends, the Tg of GRT and the Tg of EOC are closer. This effect is more pronounced when the EOC with the highest content of comonomer (30 wt %) is added to LLDPE/GRT blend. In this case, only one peak related to the Tg of the rubber phase can be visualized in the amorphous region. These findings indicate that EOC may act as compatibilizer agent for LLDPE/GRT blends.