Polypropylene (PP) blends with acrylonitrile‐butadiene‐styrene (ABS) were prepared using the styrene‐ethylene‐butylene‐styrene copolymer (SEBS) as a compatibilizing agent. The blends were prepared in a co‐rotational twin‐screw extruder and injection molded. Torque rheometry, Izod impact strength, tensile strength, heat deflection temperature (HDT), differential scanning calorimetry, thermogravimetry, and scanning electron microscopy properties were investigated. The results showed that there was an increase in the torque of PA6/ABS blends with SEBS addition. The PP/ABS/SEBS (60/25/15%) blend showed significant improvement in impact strength, elongation at break, thermal stability, and HDT compared with neat PP. The elastic modulus and tensile strength have not been significantly reduced. The degree of crystallinity and the crystalline melting temperature increased, indicating a nucleating effect of ABS. The PP/ABS blends compatibilized with 12.5% and 15% SEBS presented morphology with well‐distributed fine ABS particles with good interfacial adhesion. As a result, thermal stability has been improved over pure PP and the mechanical properties have been increased, especially impact strength. In general, the addition of the SEBS copolymer as the PP/ABS blend compatibilizer has the advantage of refining the blend's morphology, increasing its toughness and thermal stability, without jeopardizing other PP properties.

Testes de dureza; Esmalte dentário; Bebidas isotônicas. Hardness tests; Dental enamel; Foods for persons engaged in physical acti viti es. Objecti ve: To evaluate the microhardness of dental enamel aft er exposure to isotonic beverages. Method: Twenty-fi ve specimens were prepared and allocated to fi ve groups: G1: control (disti lled water), G2: Gatorade® tangerine at room temperature, G3: Gatorade® tangerine at 9 0 C, G4: Gatorade® lemon at room temperature, and G5: Gatorade® lemon at 9 0 C. Vickers microhardness was measured before (T1) and aft er (T2) immersion of the specimens in these soluti ons, by the applicati on of a load of 100 g during 15 seconds. The acid challenge had the durati on of 1 minute followed by 3 minutes in arti fi cial saliva. This cycle was repeated 5 ti mes, totalizing 20 minutes, and was performed twice a day, during 3 consecuti ve days with a 12-hour interval between them. At the end of the sixth acid challenge, new microhardness measurements (100 g/15 seconds) were made. Data were presented by descripti ve stati sti cs (maximum, minimum, mean and standard deviati on) using ANOVA and paired t-test. A signifi cance level of 0.05 and 95% confi dence interval were used. Database and stati sti cal analyses were done using the SPSS 13.0 soft ware. Results: The analysis of Vickers microhardness in T1 and T2 showed stati sti cally signifi cant diff erence before and aft er immersion of the specimens in the isotonic beverages (t =10.49; p =0.000). All experimental groups presented a decrease of the microhardness values aft er the acid challenge (T2). There was stati sti cally signifi cant diff erence between G3 and G5 in T2 (p<0.05). Conclusion: The beverages evaluated in this study caused permanent dental enamel demineralizati on with signifi cant diff erence between the initi al and the fi nal microhardness values in the groups subjected to the acid challenge.

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Objective: To investigate the in vitro effect of four pediatric liquid medicines on the microhardness and morphology of the enamel of permanent teeth after different exposure times. Material and Methods: Claritin, Celestone, Amplictil and Vick syrup honey flavor were tested. Seventy tooth fragments were obtained, 50 embedded in acrylic resin and submitted to Knoop Hardness test (50 gf, 15 s, and 5 indentations) before and after immersion in drugs. The specimens were randomly divided into five groups (n = 10), four experimental and one control group (distilled water). The immersion cycle consisted of a single exposure in times of 5 and 15 minutes. Other 20 dental specimens were divided between groups and analyzed by Scanning Electron Microscopy. The level of statistical significance was set at 5% with a confidence interval of 95%. Results: The microhardness analysis showed no statistically significant difference between experimental groups (p > 0.05), although there was statistically significant difference within each group at different times (p < 0.05). The SEM micrographs showed distinct changes in the enamel morphology. Conclusion: The decreased in microhardness was dependent on the time of the immersion cycle and morphological changes were influenced by the type of drug and by the exposure time.

The development of new ecological materials to promote sustainability is being encouraged. Crosslinked biopolyethylene (BioPE)/noni flour (Morinda citrifolia) biocomposites were prepared using maleic anhydride-grafted polyethylene (PE-g-MA) and dicumyl peroxide (DCP). The biocomposites were processed in an internal mixer and injection molded. Torque rheometry, Izod impact strength, tensile strength, heat deflection temperature (HDT), differential scanning calorimetry (DSC), thermogravimetry (TG), and scanning electron microscopy (SEM) properties were investigated. Torque rheometry curves suggest that the biocomposites did crosslink due to the DCP attack on the BioPE chain. The BioPE/noni flour/PE-g-MA formulation with 0.5% and 1% DCP produced a higher level of crosslinking. As a result, the mechanical properties (impact strength, elastic modulus, and tensile strength) were improved. SEM showed fractured noni flour particles in the BioPE matrix with the formation of a tubular structure. The HDT increased, suggesting that the biocomposites exhibit enhanced thermomechanical strength. Furthermore, the biocomposites thermal properties obtained by DSC underwent few modifications. The TG results showed that the crosslinked biocomposites have better thermal stability than the noncrosslinked biocomposites. The crosslinking process of BioPE/noni flour biocomposites with the PE-g-MA/DCP hybrid is an effective way to improve the performance of these materials.

This work investigated the effect of thermo-oxidation aging in blends of copolymer polypropylene (PPc)/recycled copolymer polypropylene (PPcr) from industrial container waste, coded as PPc/PPcr blends. All compounds were melt extruded, and the injection molded specimens were characterized by mechanical properties (tensile and impact), Fourier-transform infrared spectroscopy (FTIR), melt flow index (MFI), contact angle, heat deflection temperature (HDT), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). FTIR spectra presented bands related to the hydroperoxides and carbonyl groups, as resulted from thermo-oxidation aging. The contact angle decreased upon a thermo-oxidation aging influence, corroborating the FTIR spectra. PPcr presented higher MFI as a consequence of reprocessing. Impact strength and elongation at break were quite sensible to the thermo-oxidation aging influence and were progressively reduced upon increased time, whereas tensile strength, elastic modulus, and HDT only slightly changed. SEM images of PPc presented a higher quantity of pulled-out particles, resulted from a lower interaction between phases, i.e., polypropylene and ethylene/propylene. From the impact strength and toughness data, proper dissipation energy mechanisms were found in PPc/PPcr blends. Summing up, using PPcr contributed to minimize properties’ losses, which may be related to the stabilizer agents, whereas the described results presented great potential for the PP market, while contributing to the sustainable environment.

The reactivity of different polyethylene modifiers based on acrylic acid (AA) and maleic anhydride (MA) with polyamide 6 (PA6) is investigated, using several degrees of functionalization. The polymer blends are processed in an internal mixer and injection molded. Mechanical, rheological, infrared spectroscopy, thermal, thermomechanical properties, and morphology are evaluated. The torque rheometry results show that higher functionalization degrees favored a high reactivity with PA6. As a consequence, there is an increase in the viscosity of the polymer blends, which is reflected in the reduction of the melt flow index (MFI), compared to PA6. High impact strength and elongation at break properties confirm the blends' compatibility. The elastic modulus and the tensile strength maintain high values, suggesting a balance of mechanical properties. In addition, the polymer blends' heat deflection temperature (HDT) and thermal stability properties are comparable to neat PA6. The morphology obtained by scanning electron microscopy show dispersed and refined particles in the PA6 matrix, indicating stabilization at the interface. Incorporating only 10% of high‐density polyethylene grafted with acrylic‐acid (HDPE‐g‐AA) is very efficient in optimizing the properties of PA6, contributing to broadening the range of applications for the processing industry.