This work aimed to synthesize bacterial cellulose (BC) membranes functionalized with Ce(NO3)3 and silver nanoparticles (AgNPs) heat-treated in oven and autoclave. The AgNPs were characterized by TEM and the membranes were characterized by their rehydration capacity, Thermogravimetric Analysis (TGA), Scanning Electron Microscopy with Dispersive Energy Spectroscopy (SEM/EDS), Wide-angle X-ray Diffractometry (XRD), Atomic Absorption Spectroscopy (AAS), antimicrobial activity and cytotoxicity. The BC membranes were white to light yellow or brown indicating functionalization with AgNps with 20 nm. XRD detected a decrease in the degree of crystallinity in functionalized membranes. The autoclaved samples exhibited the largest porosity and good rehydration capacity. AAS showed Ag presence in all samples. The best antibacterial activity was achieved for the membrane’s oven treated with 40 ppm of AgNPs. Among the functionalized membranes, the most recommended to be used as burn dressing is the Ag40A and Ag20CN1.1A since they showed good porosity, good antimicrobial activity, and better suitable cell viability.

RESUMO Em polímeros autorregeneráveis faz-se uso de cápsulas preenchidas com agentes cicatrizantes, cuja parede rompe em função de estímulo externo, liberando e selando as trincas nos materiais. Assim, esse trabalho teve como objetivo avaliar as possíveis mudanças na morfologia e diâmetro de microcápsulas (MC) de poli(ureia-formaldeído) (PUF) pela variação da concentração de octanol. Medidas de microscopia ótica (MO) e microscopia eletrônica de varredura com efeito de campo (FEGSEM) mostraram que o diâmetro das MC e a rugosidade da parede, associada com a formação de nanocápsulas na emulsão, aumentaram conforme a quantidade de octanol adicionada na síntese aumentou. As curvas termogravimétricas (TG) mostraram que as microcápsulas são mais estáveis termicamente comparadas a trabalhos da literatura. Concluiu-se que o uso do octanol contribui para a obtenção de MC de tamanho mais uniforme e com superfície mais lisa.

ABSTRACT In self-healing polymers, capsules filled with healing agents are used, whose walls rupture as a response to external stimulation, releasing and sealing the cracks in the materials. Thus, this work had as objective to evaluate the possible changes in the morphology and diameter of microcapsules (MC) of poly(urea-formaldehyde) (PUF) by variation of the octanol concentration used in the synthesis. Through the measurements with optical microscopy (OM) and scanning electron microscopy with field effect (FEGSEM), it was verified that the MC diameter and the wall roughness associated with the formation of nanocapsules in the emulsion increased as the amount of octanol added in the synthesis increased. Thermal analysis showed that the microcapsules synthesized this way are more thermally stable compared to those reported in the literature. It was concluded that the use of octanol contributes to obtaining MCs with a more uniform size and smoother surface.

ABSTRACT Epoxy resin is one of the most important polymeric matrixes for diverse uses, such as aeronautical, mobile, electronics and others. Providing a material capable of self-healing microcracks will allow it to have a more reliable and longer use. In order to study this new property of self-healing to an epoxy resin, a Differential Scanning Calorimetry (DSC) study was carried out to measure physical chemical properties such as activation energy, enthalpy of polymerization, order of reaction and pre-exponential factor based on an Arrhenius equation modelling. The materials used are diglycidyl ether of bisphenol A (DGBA) as the core material, triethylenetetramine (TETA) and an aminated polydimethylsiloxane (ADM), as curing agent and poly(urea-formaldehyde) (PUF) as microcapsule wall. Tests were done by dynamic and isothermal DSC of systems containing the resin and microencapsulated curing agent and also the resin with the free curing agent. The results showed the necessity of heating for the cure and the self-healing to be initiated.

Resumo Avaliar o efeito da incorporação de vidro niobofosfato bioativo (NbG, 40% em peso) em dois sistemas adesivos simplificados convencionais (One Step [OS] e Prime & Bond {PB}) com e sem silano, no grau de conversão (%) e resistência de união (RU) após 6 meses. Os seguintes grupos foram testados: Controle OS: sem adição de partículas; OS e adição de NbG sem silano (OSNbG); OS e adição de partículas silanizadas NbG (OSNbGS); Controle PB: sem adição de partículas; PB e adição de partículas de NbG sem silano (PBNbG); PB e adição de partículas silanizadas NbG (PBNbGS). O grau de conversão (GC) foi determinado utilizando espectroscopia de Fourier (FTIR/ATR). Para RU, 48 terceiros molares humanos (n=8) foram restaurados e cortados para obter corpos-de-prova (0,8 mm2) e, em seguida, testados em dois momentos: imediato e após seis meses. O padrão de fratura foi avaliado com lupa estereoscópica (40×) e microscópio eletrônico de varredura (MEV). Os dados foram submetidos à análise de variância e Tukey (a=0,05). NbG não comprometeu valores de GC dos sistemas adesivos (p>0,05). Além disso, a adição de NbG aos sistemas adesivos não afetou os valores de RU (p>0,05). O padrão de fratura ocorreu predominantemente na interface dentina-adesivo. NbG não afetou os resultados de GC e RU.

Abstract To evaluate the effect of incorporating niobium phosphate bioactive glass (NbG) into commercial etch-and-rinse adhesive systems, with and without silane, on their degree of conversion (DC) (%) and microtensile bond strength (μTBS). The NbG micro-filler was added to two etch-and-rinse adhesive systems: One Step (OS) and Prime & Bond (PB) at 40% concentration. The following groups were formed: control without glass addition OS; addition of unsilanized NbG (OSNbG); addition of silanized NbG (OSNbGS); control without glass PB; addition of unsilanized NbG (PBNbG); addition of silanized NbG (PBNbGS). The DC was determined using total Fourier spectroscopy reflection (FTIR/ATR). For μTBS testing, 48 human third molars (n=8) were restored and sliced to obtain specimens (0.8 mm2) and they were tested at two different time intervals: immediately and after 6 months. The fracture mode was evaluated with a stereoscopic loupe (40×) and by scanning electron microscopy (SEM). The data were subjected to ANOVA and Tukey tests (a=0.05). NbG addition did not compromise the adhesive system DC values (p>0.05). Furthermore, the NbG added to the adhesive systems did not affect μTBS values (p>0.05). Fracture occurred predominantly at the dentin-adhesive interface. NbG bioactive glass did not affect the DC or microtensile bond strength results.

Resumo A aplicação de polímeros biodegradáveis para encapsular pesticidas é uma estratégia que permite, a partir de diferentes proporções entre os polímeros, modificar o perfil de liberação do agente. Este trabalho avaliou a liberação controlada do pesticida cipermetrina encapsulado em microesferas de blendas de P(3HB)/PCL (100/0, 0/100, 97/03, 95/05, 90/10, 80/20 e 70/30) obtidas pelo método de emulsificação-evaporação do solvente. As imagens de microscopia eletrônica de varredura revelam a forte influência da PCL na porosidade das microesferas. As análises de infravermelho mostraram a presença do pesticida em todas as composições de polímeros avaliadas. O ensaio de liberação de cipermetrina sugere que, no intervalo de 4 horas, o teor de cipermetrina liberada é dependente da composição das blendas utilizadas. As microesferas de PHB e blendas com menores teores de PCL, 97/03 e 95/05 liberaram 75% a 85% enquanto a composição 70/30 liberou 100% de cipermetrina.

Abstract This work evaluated the controlled release of cypermethrin pesticide loaded in microspheres of P(3HB)/PCL blends obtained by emulsion-evaporation method. SEM analysis revealed a strong influence of PCL on the porosity of the microspheres. The infrared spectra showed the presence of pesticide in all polymer compositon evaluated. DSC curves showed that with higher content of PCL, decreased the crystallinity degree of polymers, resulting in a faster release of the pesticide. The release assay of cypermethrin suggests that within an interval of four hours the amount of pesticide released varies depending on the composition of the blends.

This study investigated the influence of silane concentration and filler size distribution on the chemical-mechanical properties of experimental composites. Experimental composites with silane contents of 0%, 1% and 3% (in relation to filler mass) and composites with mixtures of barium glass particles (median size = 0.4, 1 and 2 μm) and nanometric silica were prepared for silane and filler analyses, respectively. The degree of conversion (DC) was analyzed by FTIR. Biaxial flexural strength (BFS) was tested after 24-h or 90-d storage in water, and fracture toughness, after 24 h. The data were subjected to ANOVA and Tukey’s test (p = 0.05). The DC was not significantly affected by the silane content or filler distribution. The 0% silane group had the lowest immediate BFS, and the 90-d storage time reduced the strength of the 0% and 3% groups. BFS was not affected by filler distribution, and aging decreased the BFS of all the groups. Silanization increased the fracture toughness of both the 1% and 3% groups, similarly. Significantly higher fracture toughness was observed for mixtures with 2 μm glass particles. Based on the results, 3% silane content boosted the initial strength, but was more prone to degradation after water storage. Variations in the filler distribution did not affect BFS, but fracture toughness was significantly improved by increasing the filler size.

As microcápsulas que contêm agentes de cura têm sido utilizadas para desenvolver compósitos poliméricos com propriedades auto regenerativas. Este trabalho tem como objetivo a produção e caracterização de microcápsulas de poli (uréia-formaldeído), PUF, contendo diciclopentadieno, que satisfaz os requisitos para um material de auto cura para resinas epoxídicas. Uma série de microcápsulas de PUF foram sintetizadas utilizando diferentes parâmetros do processo, incluindo o tipo e concentração de surfactante, o método e a velocidade de agitação. As microcápsulas foram caracterizadas por microscopia eletrônica, análise térmica (DSC, TG) e espectroscopia no infravermelho (FTIR). A distribuição do tamanho e o diâmetro médio das microcápsulas foram determinados por difração a laser. Os resultados mostram que os parâmetros do processo afetam diretamente o tamanho e a morfologia das microcápsulas. Pela seleção da taxa de agitação, foi possível produzir microcápsulas com diâmetros entre 1 e 100 µm.

Microcapsules containing curing agents have been used to develop polymer composites with self-healing properties. This work aims the production and characterization of microcapsules of poly (urea-formaldehyde), PUF, containing dicyclopentadiene, which satisfies the requirements for the self-healing of epoxy resins. A series of PUF microcapsules was synthesized using different process parameters, including the type and concentration of surfactant, and the stirring method and speed. The microcapsules were characterized by scanning electron microscopy, thermal analysis (DSC, TG) and infrared spectroscopy (FTIR). The size distribution and the average diameter was determined in a particle size analyzer by laser diffraction. The results show that the process parameters directly affect the size and morphology of the microcapsules. By the selection of the stirring rate, microcapsules were produced in the diameter range of 1-100 µm.

AIM: To evaluate the radiopacity and microhardness (KHN) of experimental dental adhesives (EX). The experimental adhesive resins of the present study were formulated based on the simplified adhesive system Ambar (FGM). METHODS: Five EX with different concentrations of zirconia nanoparticles [0(EX0), 15(EX15), 25(EX25), 30(EX30) e 50%(EX50)] were incorporated in a UDMA/HEMA adhesive (control). Adper Single BondTM 2 (SB, 3M ESPE) was used as a commercial reference. For the radiopacity (n=5), KHN (n=5), adhesive specimens were fabricated using a stainless steel mold. Data were submitted to one-way ANOVA and Tukey's test (α=0.05). RESULTS: The filler addition on the EX showed radiopacity similar to enamel and higher than SB. The EX25, EX35 and EX50 showed higher KHN values when compared to the commercial SB. EX25, EX35 and EX50 showed higher KHN values when compared to the commercial SB. CONCLUSIONS: The results of the present investigation suggest that the addition of zirconia nanoparticles seems to be a good alternative to produce radiopaque adhesives with increased microhardness.