Poly(vinyl chloride) (PVC) is considered one of the most versatile polymers due to its interaction with different additives. On the other hand, binary sulfides have wide applications as zinc sulfide (ZnS), one of the first discovered semiconductors. This study aims to synthesize a nanocomposite material containing nano ZnS in the PVC matrix with a surfactant as a compatibilizer agent to evaluate its optical and electrical properties when exposed to gamma radiation. Our results showed that adding ZnS at 0.5 wt% concentration in the PVC matrix promoted the system from insulating to the semiconductor material. Therefore, gamma radiation has played an important role in nanocomposites' optical and electrical properties with changes in electrical and electrical conductivity, constant dielectric parts, refraction index, optical band gap, and Urbach energy. Thus, our study points to the development of nanocomposite material, semiconductors, and features useful for applications in flexible electronics or optical-electronic devices.

Poly(methyl methacrylate) (PMMA) is a polymer with applications in the medical and aerospace industries that require resistance to gamma radiation. However, the effects caused by gamma radiation on PMMA properties may make its application in situations of exposure to gamma radiation unfeasible. In this study, the impact of commercial additives on the radiolytic stabilization of PMMA will be studied through viscosimetric assays. In a preliminary trial, additives with different mechanisms of action were tested, and the efficacy of two additives (Tinuvin 770 and Tinuvin 622) hindered amine stabilizers (HAS) types were registered. PMMA films with the additives at different concentrations were exposed to gamma radiation and studied through viscosimetric molar mass and G-value. The Tinuvin 622 at 0.3 wt% showed the best performance in the radiolytic stabilization of p PMMA films at the 20-50 kGy range. Antagonism was observed when Tinuvin 700 and Tinuvin 622 mixture was studied in different proportions. These results show the potential of commercial additives, initially produced for other purposes, in the radiolytic stabilization of PMMA.

Abstract Bioequivalence (BE) assessment of topical drug products is a long-standing challenge. Agencies such as the Food and Drug Administration (FDA) and the European Medicines Agency (EMA) have published several drafts in recent years suggesting different approaches as alternative to evaluate the BE. A proposed Topical Classification System (TCS) has even been discussed. Given the above, the objective of this research was to use in vitro and in vivo BE approaches to evaluate Brazilian marketed mupirocin (MPC) ointments, previously classified as TCS class The in vitro permeation test (IVPT) was performed by applying formulations to pig skin by Franz cells. The in vivo methodology was dermatopharmacokinetic (DPK). These approaches (in vivo tape stripping and IVPT) demonstrated capability of distinguishing among different formulations, thus making them useful methodologies for BE evaluation.

Chitosan is a biopolymer derived from chitin and the most abundant polysaccharide in nature after cellulose. This biopolymer has been applied in different areas due its biodegradability and biocompatibility properties. Modifications of chitosan structure by cross-linking chemical agents can alter its physical, chemical, and morphological characteristics. The present work aimed at studying the structural characteristics of chitosan/polyvinyl alcohol (PVA) spheres cross-linked with glutaraldehyde submitted to oven-drying and freeze-drying processes. The thermal-treated of spheres and chitosan (control sample) were analyzed by XRD, SEM and FTIR techniques. Multivariate statistical analysis, PCA, was applied to samples IR spectra. According to results, the freeze-dried spheres showed a smaller crystal size (6.032 nm), while the oven-dried spheres presented a smaller crystalline phase (3.49%). MEV images have encompassed the different surfaces of the manufactured spheres as a result of drying methods. Slight chemical changes were observed in the IR spectra from the cross-linked spheres. In addition, PCA has revealed different clusters referred to the structural modifications. Therefore, the increasing of openness and receptivity for chemical reactions, as well as the adsorption capacity, could enable different applications of the chitosan, mainly the adsorption properties to remove residues and for water treatment.

Resumo O ensino de química muitas vezes é guiado pela utilização de fórmulas e esquemas, dada a natureza dos símbolos que permeiam tal disciplina. Nesse cenário, são poucos os estudos que tratam de aspectos ligados ao processo de reflexão usando temas na área de ciências exatas. Assim, fazer parte da formação de indivíduos críticos e reflexivos em relação ao conhecimento, a eles mesmos e ao ambiente social e natural em que vivem tem sido preocupação de educadores e psicólogos e está na base do movimento CTS – Ciência, Tecnologia e Sociedade. Este estudo, apoiando-se no potencial metacognitivo da argumentação na educação, amplia essa discussão ao investigar se a utilização desse tipo de discurso propicia aos alunos a reflexão sobre seus próprios pensamentos, mostrando um funcionamento ao nível metacognitivo necessário ao enfoque CTS em sala de aula. Foram analisadas produções textuais de três alunos em aulas de química no ensino médio, nas quais se solicitava o posicionamento destes diante da pergunta “Radioatividade: vida ou morte?”, após serem realizados debates sobre esse tema. As análises mostraram que a argumentação, por sua organização discursiva peculiar, se constitui em interessante alternativa para fazer emergir formas de pensamento sofisticadas, como as que definem um pensamento crítico e reflexivo.

Abstract The teaching of chemistry is often guided by the use of formulae and schemes, given the nature of the symbols pervading this discipline. In this scenario, few studies deal with aspects associated with the process of reflection involving themes of exact sciences. Thus, being part of the education of critical, reflective individuals with regard to knowledge, to themselves and the social and natural environment they live in has been a concern of educators and psychologists and is in the basis of the STS (Science, Technology and Society) movement. Building on the metacognitive potential of argumentation in education, this study widens this discussion by investigating whether the use of this type of discourse allows students to reflect about their own thoughts, showing a functioning at the metacognitive level that is necessary to an STS approach in classroom. We analyzed the texts written by three students in chemistry classes in secondary education during which they were required to express their opinion on the question “Radiation: life or death?”, after debates had been conducted about this subject. Our analyses showed that argumentation, due to its peculiar discursive organization, is an interesting alternative to promote the emergence of sophisticated forms of thought, such as the ones that define critical and reflective thinking.

The poly (vinyl chloride), PVC, undergoes changes in its physicochemical properties when it is exposed to gamma radiation. Thus, the radiolytic stabilization of PVC is one way for obtain a material with radiation resistance. In this work, we studied the coffee grounds oil as PVC radiolytic protection in two systems forms: PVC film and PVC specimen. The systems were irradiated at sterilization dose of medical devices and viscosity measurements were performed. According to viscosity assays of PVC films, there was a 67% protection in polymer matrix promoted by the oil. On the other hand, the mean viscosity molar mass (Mv) of PVC specimens increased about 13%, indicating predominance of crosslinking effect, however samples containing the oil showed no Mv significant changes. Therefore, the oil can be considered a PVC radio stabilizing substance and open a way for use of sustainable additive in PVC industry.

Zinc sulfide (ZnS) was synthesized by sonochemical method and nanoparticles with crystallite size around 2 nm were obtained. PVC containing ZnS nanoparticles at concentrations of 0.10; 0.30; 0.50; 0.7 and 1.00 wt% were gamma irradiated (60Co) at room temperature in air. No appreciable decrease in PVC Viscosity-Average Molar Mass (Mv) was observed for samples containing 0.7 wt% of ZnS nanocrystals. It was demonstrated that the addition of ZnS nanocrystals imparted molecular protection to the polymer matrix while improving flexibility, by decreasing the Young Modulus of PVC films. These results suggest the use of sonochemically synthesized ZnS nanocrystals as a new additive for radiation-grade PVC materials.

AbstractPoly (methyl methacrylate), PMMA, may be used in manufacturing of devices, which are exposed to gamma irradiation. However, the polymer undergoes significant changes in its properties during process and the use of additives is a common form to stabilize the PMMA matrix. In this way, stibnite was synthesized by sonochemical method and the amorphous powder constituted of nanospheres was obtained and investigated as additive. Commercial PMMA containing stibnite nanoparticles (ST-NP) was investigated and the samples were irradiated with gamma radiation (60Co). Our results showed that the addition of ST-NP at 0.3 wt% into the PMMA decreased the number of main chain scissions caused by the irradiation process, resulting in radiolytic stabilization of the polymer matrix. Analyses of mechanical properties showed influence of the ST-NP in the physical behavior of PMMA. Our findings suggest that stibnite nanoparticles are an effective additive for PMMA used in application of radiation resistance.

Lead (II) sulfide (PbS) were synthesized by sonochemical method and crystals with cubic structure exhibit aggregated nanoparticles with size in the range of 50-100 nm. Commercial Poly(methyl methacrylate) (PMMA) containing the PbS nanoparticles (PbS-NP) exposed to gamma irradiation were investigated and both the viscosity-average molar mass (Mv) and degradation index (DI) values were measured. Ours results showed decreases in molar mass when the systems were gamma irradiated, i. e., random scission effects that take place in the main chain. On the other hand, DI results showed that the addition of PbS-NP at 0.3 wt% into the PMMA matrix decreased 100% the number of main chain scissions. Results about the free radical scavenger action of the PbS-NP were obtained by use of 2,2-diphenyl-1-(2,4,6-trinitrophenyl)-hydrazyl radical (DPPH) and are discussed in this study. Analysis of infrared spectra, refraction index, mechanical, and thermal properties showed influence of the PbS-NP in the physical behavior of PMMA.