ABSTRACT Despite the increasing use of plaster as a construction material, due to its numerous advantages when compared to cement, its use is still restricted, because of its low mechanical resistance and high solubility in water. In this context, research has been carried out related to the addition of nanomaterials to improve the mechanical and physical properties of plaster in civil construction. A highly available, low-cost nanomaterial with excellent properties is nanotalc. In this work, nanocomposites with dimensions of 40 × 40 × 160 mm were produced with ultrafine micronized nanotalc replacing plaster in proportions of 0%; 0.5%; 1%; 1.5% and 2%. The physical and mechanical properties of the nanocomposites were evaluated according to standards. The nanocomposites produced with 1% nanotalc showed satisfactory results for physical and mechanical properties, with an increase of 1.8% in apparent density and 24.12% in compressive strength, and a decrease in water absorption of 6.23%, compared to the composite without the incorporation of nanotalc. The production of nanocomposites with the incorporation of 1% nanotalc is viable and shown to be promising, presenting potential for application as linings and internal partitions, since they showed low water absorption due to the hydrophobicity of nanotalc.

ABSTRACT The concentration of carbonate-rich phosphate ores through conventional flotation is difficult due to the similarities in their surface properties. Thus, the reactive flotation based on the retention of carbon dioxide produced by carbonates in an acid medium arises. Given the current demands of new concentration techniques, this work investigated the reactive flotation of silica-carbonated phosphate ore. For that, samples from the granulometric ranges, –10# +20# (–1.70 mm +0.84 mm) and –20# +65# (–0.84 mm +0.210 mm) were used during the process. Through factorial design tests, the reagents employed were sulfuric and phosphoric acids and polymer polyvinyl alcohol (PVA). Phosphoric acid favored the reduction of the CaO/P2O5 ratio and the increase of the P2O5 grade. The best result was the one that provided an increase of about 30% in the P2O5 grade (12.3 to 16%) in the range –20# +65#, when using 10% (v/v) phosphoric acid and 0.5% (m/v) PVA. Although it was possible to reach, in some tests, the industrial parameter for the CaO/P2O5 ratio (less than 1.6), the same did not occur for the MgO contents (less than 1%). The results are promising however, new studies with more sustainable alternatives are extremely necessary nowadays.

RESUMO A concentração de minérios fosfáticos ricos em carbonatos através de flotação convencional é dificultada devido às similaridades de suas propriedades superficiais. Assim, surge a flotação reativa baseada na retenção de dióxido de carbono produzido pelos carbonatos em meio ácido. Diante das atuais demandas de novas técnicas de concentração, este trabalho investigou a flotação reativa do minério fosfático sílico-carbonatado. Para tanto, amostras das faixas granulométricas, –10# +20# (–1,70 mm +0,84 mm) e –20# +65# (–0,84 mm +0,210 mm) foram empregadas durante o processo. Os ácidos, sulfúrico e fosfórico, bem como o polímero álcool polivinílico (PVA) foram avaliados por intermédio de ensaios de planejamento fatorial. O ácido fosfórico favoreceu a redução da relação CaO/P2O5, bem como a elevação do teor de P2O5, sendo o melhor resultado, aquele que proporcionou aumento de cerca de 30% no teor de P2O5 (12,3 para 16%) na faixa –20# +65#, ao utilizar 10% (v/v) de ácido fosfórico e 0,5% (m/v) de PVA. Embora tenha-se conseguido atingir, em alguns testes, o parâmetro industrial para a relação CaO/P2O5 (inferior a 1,6), o mesmo não ocorreu para os teores de MgO (inferior a 1%). Os resultados são promissores, entretanto, novos estudos com alternativas mais sustentáveis são extremamente necessários atualmente.

RESUMO O interesse em nanocristais de celulose obtidos a partir de recursos naturais tem crescido principalmente devido a características que esses materiais fornecem quando inseridos em matrizes poliméricas. O presente estudo teve como objetivo avaliar o efeito da adição de nanocristais de celulose nas propriedades mecânicas dos biofilmes feitos a partir de hipromelose (ou hidroxipropil metilcelulose - HPMC) e misturas com amido de mandioca (CS). Os nanocristais de celulose foram produzidos por hidrólise ácida e caracterizados por microscopia óptica (OM), microscopia eletrônica de transmissão (TEM), difração de raios X (XRD) e termogravimetria (TG). Os filmes foram feitos por fundição (ou “casting”) com CS puro, hipromelose pura e também com misturas de CS e hipromelose. Em seguida, os nanocristais de celulose foram adicionados às misturas nas concentrações de 1, 3 e 10% (m/m). As avaliações dos filmes incluíram a resistência a tração e a superfície da fratura por microscopia eletrônica de varredura (SEM). Observou-se que o reforço com nanocristais de celulose melhorou as propriedades mecânicas, e as observações da superfície de fratura dos filmes testados mostraram que os nanocristais promoveram uma melhora na coesão da hipromelose e do amido na mistura e promoveram uma superfície mais homogênea.

ABSTRACT Interest in cellulose nanocrystals obtained from natural resources has grown mainly because of features that such materials provide when inserted into polymeric matrices. The present study aimed to evaluate the effect of cellulose nanocrystals addition on mechanical properties of biofilms made from hypromellose (or hydroxypropyl methylcellulose - HPMC) and cassava starch blends (CS). The cellulose nanocrystals were produced by acid hydrolysis and characterized by optical microscopy (OM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and thermogravimetry (TG). Films were made with pure CS, pure hypromellose and also with blends of CS and hypromellose by casting. Then cellulose nanocrystals were added to the blends in the concentrations of 1, 3 and 10% (m/m). Evaluations of the films included tensile performance and fracture surface by scanning electron microscopy (SEM). It was observed that the reinforcement with nanocrystals improved the mechanical properties of the films, and their fracture surface showed that cellulose nanocrystals promoted an improvement in the cohesion of the hypromellose and starch molecules in the blend, and created a more homogeneous surface.