Resumo em Inglês:

Abstract One of the most widespread applications of poly(lactic acid) (PLA) is as a raw material in the form of filaments for 3D printing. To improve final disposal alternatives and minimize their effects on the environment, the aim of this study is to determine the biodegradability of 3D-printed PLA waste composted in a landfill with leachate soil and garden soil for 90 days and 180 days. The soil characteristics and material properties were evaluated by laboratory analyses. Changes in soil chemical composition and the loss of microorganisms were recorded. The thermal and mechanical properties of PLA did not change significantly, but fungal colonies, encrustation, and changes in the original colour were found, indicating the onset of surface biodegradation of the samples. Controlled conditions or longer periods would be needed to maintain an ecosystem favourable to biodegradation; otherwise, PLA could accumulate in the environment, causing future pollution problems.

Resumo em Inglês:

Abstract Scaffolds with osteoconductivity, biocompatibility and good mechanical properties are promising for local drug release of sodium alendronate (ALN), a first-choice drug for treatment of bone tissue diseases, with low bioavailability. The viability to manufacture poly (L-lactic acid) (PLLA)/poly (methyl methacrylate) (PMMA) filaments containing ALN in different proportions, through extrusion, followed by scaffolds using 3D printing by fusion deposition modelling (FDM) and to investigate the influence of processes in mixtures drove this study. Differential scanning calorimetry (DSC), spectroscopy in the infrared region with Fourier transform (FTIR/ATR), and X-ray diffractometry (XRD) analysis indicated that PMMA decelerates crystallinity and confers malleability to PLLA/ALN mixture, besides its good processability and miscibility with PLLA and no relevant changes in physicochemical properties of components. Field emission scanning electron microscopy (SEM/FEG) showed good interfacial compatibility between PLLA/PMMA and homogeneously dispersed drug crystals in matrix. PLLA-PMMA-ALN scaffolds were manufactured by accurate with interesting properties for bone tissue engineering.

Resumo em Inglês:

Abstract Waterborne polyurethane (WPU) coatings used for moisture protection of surfaces have been used broadly. They have been considered environmentally friendly because their synthesis releases less or no volatile organic compounds (VOCs) to the atmosphere. With the Covid-19 pandemic concerns, cleaning protocols of these surfaces have been applied and scientific knowledge about the effects of these liquids on WPU surfaces is necessary. In this work, diffusion experiments were performed using four liquids, in pure WPU and WPU filled with graphene oxide (GO). Detergent had the most severe effect on polyurethane films, causing severe cracks and weight loss. Diffusion parameters of HCl 5% and HCl 10% were greater in WPU/GO nanocomposites than in pure WPU. Mechanical tests under chemical aging showed that alcohol reduced most the tensile strength and Young modulus. Overall, GO protected the films for all liquid exposures, increasing their tensile strength and Young modulus.

Resumo em Inglês:

Abstract This study examines the effect of processing parameters and reactive extrusion on the mechanical, thermal, morphological, and rheological properties of low-density polyethylene (LDPE) and sepiolite composites (LDPE/sepiolite: 95/5 wt/wt) produced by in situ reactive extrusion in a twin-screw extruder. Using a design of experiments, the contribution of the factors reverse mixing elements (RE), maleic anhydride (MA), and dicumyl peroxide (DCP) was determined. The results showed that a better interaction between LDPE and sepiolite phases occurred when reactive extrusion was carried out, leading to a satisfactory balance between mechanical properties and thermal stability behavior. The rheology analysis revealed that a more pronounced solid-like behavior was achieved in the composite prepared by reactive extrusion and in the presence of the filler. The SEM micrographs showed the appearance of a network-like morphology in the composite processed in the presence of additives and sepiolite filler.

Resumo em Inglês:

Abstract This paper investigates evidence regarding the influence of a CaSt2 residual additive in the optical properties of a commercial polystyrene. This work proposes an in-line optical detector operating by illuminating the polymer with a red monochromatic light in order to evaluate its thermal behavior during a heat cycling. The detection system was bench validated by measuring the light absorption of aqueous solutions of organic acid dyes. The system showed great sensitivity in detecting the contamination’s effect on the polymer, as a great impact on the polymer’s behavior was observed due to the presence of the additive during different thermal cycles. The detector system showed that the salt’s presence elevates absorbance by five times when the temperature is higher than its fusion temperature. The in-line optical detector has proved to be suitable to quantify the presence of additives that affects the polymer’s optical properties.

Resumo em Inglês:

Abstract In this work, moringa leaf extract was encapsulated in gum arabic by lyophilisation, using different extract:gum arabic ratios (1:10, 1:6 and 1:4). The physicochemical characteristics, total phenolic content and antioxidant potential of the microcapsules were evaluated at time 0 and after 10 months of storage at 25 °C. The moisture content, hygroscopicity and solubility of the microcapsules decreased, and the water activity increased after storage. The total phenolic content increased from 28 to 36%, with the highest increase in the microcapsule formulation with less gum arabic. The antioxidant activity also increased significantly, to values between 140 and 307%, with activity being higher in the 1:4 (extract: gum arabic) ratio microcapsules. The microcapsules of moringa leaf extract encapsulated with gum arabic showed good antioxidant potential in vitro, especially after storage, and could be a promising alternative for the future applications in the food, pharmaceutical and cosmetic sectors as additives or preservatives.

Resumo em Inglês:

Abstract Coconut mesocarp fiber (CMF) is a by-product of the coconut industry; it was milled to produce coconut mesocarp particles (CMP). The main elements identified in CMP samples were C and O, which represent 96.75%. The CMP were mixed with a polylactic acid (PLA) matrix by extrusion. The mechanical, thermal, structural, and morphological properties of four biocomposites with 0, 2, 5, and 8 wt% CMP (CMP0, CMP2, CMP5, and CMP8, respectively) were determined. The biocomposites showed a decrease in tensile strength, elongation at break, and elastic modulus values as the CMP content increased, except for CMP5, which showed a higher elastic modulus than the PLA matrix. The thermal analysis showed that the biocomposites presented better thermal stability than the PLA matrix. CMP2 and CMP5 had rough surfaces, while CMP8 had weaker fracture zones.

Resumo em Inglês:

Abstract Bacterial cellulose (BC) is a biopolymer produced by several microorganisms and has attracted attention due to its unique characteristics, replacing cellulose extracted from nature. This work aimed to compare different BC production methods and the possible interference of these methods on the characteristics of the BC produced, seeking low-cost and large-scale production. BC membranes were produced by K. hansenii and a microbial consortium using different culture media. Rehydration percentage, water-holding capacity, TGA, and FTIR characterized the membranes. The production from the microbial consortium was highlighted for having a higher dry mass yield (0.289 ± 0.199 g), more than triple the amount produced by pure strain. Both samples showed similar chemical structures, as pointed out by FTIR. However, the BC produced by the microbial consortium showed superior thermal stability (357 °C). Moreover, using the microbial consortium, it was possible to obtain BC with a reduction in production cost of 92%.

Resumo em Inglês:

Abstract This paper investigates mold materials for polypropylene (PP) injection molding, including CuBe alloy (high thermal conductivity), AISI P20 mold steel (the conventional material for injection molds), and polyurethane resin (rapid tooling). Characterization of molded parts involved microstructural analysis, tensile tests, warping, and degree of crystallinity assessments. The results show that the higher thermal conductivity of the mold’s inserts reduced the injection molding cycle time and produced thicker skins, which resulted in smaller spherulite sizes in the core of the samples, reduced the crystallinity degree, and consequently reduced the maximum strain property. The thermal conductivity of the molds’ inserts was shown to be more significative than the skin thickness and mold temperature for the size of the spherulites when they are formed. In addition, CuBe alloys showed to be a strong competitor with additive manufacturing-produced molds with conformal cooling channels to reduce injection molding cycle time.

Resumo em Inglês:

Abstract Thermoactive binders are the most widely used form of polymer matrix materials in modern composites. In the production of composites, thermoactive binders are the basis of the matrix structure formation process with different properties. Various thermoactive binders based on epoxy, polyester and other resins compatible with corresponding polymer matrices were examined in the article. The influence of binders on the pre-molding process, various properties of the products, including density, stability and water permeability, as well as the main characteristics of composite materials obtained by various methods, was considered. The most optimal thermoactive binder (epoxy resin) were determined. The influence of thermoactive binders was shown and the advantage of using thermoactive binders in the production of composites was proved on the example of bitumen asphalt.

Resumo em Inglês:

Abstract This study aimed to develop a pyriproxyfen-based Rumino-Reticulum Device (RRD) consisting of films of poly(vinyl)alcohol (PVA) and sodium carboxymethylcellulose (NaCMC) to control the horn fly in cattle, one of the major pests of livestock. Films were obtained by the solvent casting method by PVA/NaCMC crosslinking and presented satisfactory homogeneity, drug content (104.8%) and pH (6.5), besides great absorptive capacity with swelling degree of 331.40% after 1 hour and diffusion-controlled release kinetics (Higuchi). FTIR and SEM analyzes clarify the characteristic bands of PVA, NaCMC and pyriproxyfen. The XRD and thermal analysis shows an increase in crystallinity due to pyriproxyfen (Xc:36.59%) and the active delivery alters the chain packing (Tg:74ºC). The pyriproxyfen-based RRD developed, in addition to fulfilling the characteristics of prolonged release, allows it to be rolled up (compressed form) facilitating swallowing and subsequent conversion to an expanded form that is retained in the rumen throughout the treatment period.