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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The aim of this study is to evaluate the effect of some experimental variables such as the content of styrene–ethylene–butylene–styrene (SEBS) and talc, processing conditions and mixing protocol on the properties of polypropylene (PP). To achieve this objective, PP/SEBS blends and PP/SEBS/talc composites were processed in a corotating twin-screw extruder. A masterbatch of PP/talc was prepared before the extrusion of PP/SEBS/talc composites. The morphology of blends and composites was evaluated by scanning electron microscopy, which revealed the dispersion of small rubber droplets in the PP matrix. Moreover, the micrographs also showed that SEBS and talc particles were uniformly dispersed and distributed in the polymer matrix. Results of thermal properties showed that talc had a nucleating effect, which promoted the increase of both PP crystallization temperature and crystallinity degree. The incorporation of talc in PP/SEBS blends led to an expressive increase in the impact resistance by 70% as compared with the reference blend: PP/SEBS 80/20% (w/w). This result reveals that although the PP/SEBS/talc composites showed a separated morphology, the good dispersion and distribution of this mineral filler in the polymers contributed to avoid crack propagation and increase the impact properties. The tensile properties in the elastic region were not significantly affected.

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Chitinase is produced by a wide variety of plants as a defense against peste attacks. In this study, grape chitinases were purified 16 times by fractionation in 80% ammonium sulfate followed by dialysis and filtration. Purified chitinases exhibited enzymatic activity toward chitin azure. The yield of purified chitinase was 229 mg/L with chitinase activity of 563 U/g. Chitinases had molecular masses of 24 and 30 kDa, as evaluated by SDS-PAGE 12.5%. Two pH optima were determined 3.0 and 6.0. The optimal temperature was 42 o C. Pre hydrolysis of crystalline shrimp chitin by chitinases caused in an increase in the deacetylation ratio triggered by chitin deacetylase producing chitooligosaccharides with DA (degree acetylation) of 58.8%.Keywords: grape chitinases; purification and characterization; chitin deacetylation. INTRODUÇÃOOs monossacarídeos formam uma grande variedade de estruturas poliméricas (oligossacarídeos e polissacarídeos), diferenciadas pelo tipo de monômero constituinte e pela forma como eles estão ligados ao longo do polímero, que desempenham funções como componentes estruturais, compostos de reserva e de reconhecimento e sinalização celular, por exemplo. As ligações glicosídicas presentes nestes polímeros podem ser clivadas por um grande número de enzimas pertencentes à superfamília de glicosil-hidrolases, composta por 115 famílias de hidrolases que atuam tanto sobre as ligações glicosídicas que unem monossacarídeos, quanto sobre as que unem carboidratos a outras biomoléculas. 1,2As quitinases (E.C. 3.2.1.14) são endoglicosil-hidrolases que clivam de forma específica as ligações glicosídicas da quitina, um homopolissacarídeo linear formado por unidades de 2-acetamida-2-desoxi-D-glicose (N-acetil-D-glucosamina) unidas por ligações do tipo β-[1-4], encontradas principalmente nas carapaças de crustáceos, cutículas de insetos e na parede celular de fungos, sendo, depois da celulose, o biopolímero mais abundante na natureza.3 As quitinases estão distribuídas por entre duas númerosas famílias de glicosil-hidrolases (famílias 18 e 19), que diferem em relação às suas estruturas primárias e terciárias 1 e ao mecanismo de catálise. 4As quitinases da família 18 formam produtos β-anoméricos, através de um mecanismo de retenção, enquanto as enzimas da família 19 formam produtos α-anoméricos, por um mecanismo de inversão. 5,6As quitinases (Chase) de planta são independentemente classificadas, com base na presença de um domínio de ligação à quitina e na homologia de suas sequências de aminoácidos, em sete classes, nomeadas de I a VII.7 A maioria destas quitinases pertence à família 19, (classes I, II IV, VI e VII), com um pequeno número pertencente à família 18 (classes III e V), junto como as quitinases de fungos, animais e bactérias. 8 As quitinases são expressas constitutivamente em níveis relativamente baixos em todos os órgãos e tecidos das plantas, compartimentalizadas no vacúolo e apoplasto. 9 As quitinases de plantas fazem parte do grupo de proteínas denominadas PR (proteínas relacionadas à patogenesis), ca...

Summary: Polystyrene/cornstarch blends were prepared by melt‐processing in the presence of maleic anhydride (MA), using an internal mixer as reactor. Scanning electron microscopy (SEM) was used to visualize the blends morphology. Addition of MA contributed to improve interfacial adhesion between the two phases. Soil burial tests were used to investigate biodegradability. Results from samples weight loss, as a function of incubation time, revealed that the increase in the content of starch contributed to increase biodegradability. The results showed that the microbial activity inside the specimens was accelerated in the first 15 days of evaluation. Photographs of the films showed significant differences after 30 days of incubation in soil. SEM was also used to evaluate biodegradation, and revealed fractured surfaces covered with a heterogeneous microorganism community.