Resumo em Inglês:

Abstract Plasticulture improves crop quality and yield through polymeric films, but their improper disposal harms the environment due to humidity and contamination. This study aimed to develop biodegradable mulch films using soybean and peanut hulls and poly (butylene-adipate-co-terephthalate) (PBAT). The residues were characterized by thermogravimetric analysis and mulch films were evaluated by water absorption, contact angle and mechanical properties. The thermal behavior of the residues indicated stability below 200ºC. The agro-waste improved hydrophobicity but increased the water absorption values of the films by up to 18.5x (PBAT/SH5 after 14 days). Micrographs obtained by scanning electron microscopy indicated an important distribution of residue particles and formation of agglomerates, leading to lower mechanical performance. The study found that agro-industrial residues in powder form can be added to the polymeric matrix to produce biodegradable mulch films through traditional processing techniques. This approach has the potential to contribute to a more sustainable production system.

Resumo em Inglês:

Abstract Polymeric composite materials, presenting a practical solution for sealing non-metallic expansion joints under extreme conditions such as high temperatures and harsh chemical and physical abrasion, were investigated in this scientific study to discern the impact of welding parameters on their degradation and properties. The study entailed the bonding of polymeric composite blankets through hot plate pressing with a PTFE film, encompassing variations in temperature, duration, and load application. The findings elucidated that lower temperatures and shorter processing times failed to achieve optimal blanket adhesion, while higher temperatures led to material degradation, subsequently diminishing the mechanical strength of the welded joint. In contrast, extended processing times and the application of load during welding demonstrated a positive correlation, enhancing the mechanical strength of the joint by ameliorating interfacial adhesion. This research underscores the critical significance of carefully selecting welding parameters to ensure the peak performance and durability of polymeric composite structures.

Resumo em Inglês:

Abstract This work consisted of studying polyglycerols in an acidic and micellar environment. The effects on surface tension, micellisation, and the Gibbs free energy of interface liquid-liquid (w/o) for directing the etherification of monomer glycerol with n-hexanol, n-octanol, n-decanol, n-dodecanol, and micellar solutions of sodium dodecylsulfate and dodecylbenzenesulfonic acid were studied at 70, 90 and 130°C . Polyglycerols with low weights and prepolymers were obtained. Theoretical methods such as density functional theory and molecular dynamics simulations were used to examine the effects of surface tension, the conformations of glycerol, and the position of the hydroxyl group of alcohols. A theoretical analysis (DFT/B3LYP) of the potential energy surface of glycerol and alcohols allowed finding stable conformations of the molecule, differing in the relative arrangement of hydroxyl groups. Our results helped achieve a better understanding of the interaction complex process of surfactant/catalyst of glycerol reactions in biphasic systems.

Resumo em Inglês:

Abstract The objective of this study was to characterize the physicochemical-mechanical properties of corn and cassava starch films reinforced with CNF via Tape-Casting. There were differences in size and shape of the starch granules. Corn starch nanocomposites (NCO) showed a significant increase in tensile strength (5.14 to 25.58 MPa) and significant decrease in strain (24.81 to 2.76%) as the CNF concentration increased. Among the cassava starch nanocomposites (NCA), only the cassava starch sample with 1% CNF (NCA-1) showed significant difference both in the maximum stress (4.94 MPa) and strain (15.17%). The corn starch sample with 2% of CNF (NCO-2) presented a lower roughness and NCA-1 a smooth surface. There was no difference in chemical composition between the samples. The CNF-free starch films showed more transparency than other films. The NCA showed more transparency than NCO. Tape-casting technique unveils enhanced mechanical properties of cellulose nanofiber-reinforced starch films. Starch nanocomposites exhibit improved tensile strength and surface characteristics.

Resumo em Inglês:

Abstract In this study, thyme essential oil was added to poly (butylene adipate-co-terephthalate) (PBAT) films in a variety of compositions (0, 1, 2, 5, 10, 15, and 20% w/w), and the effect of the essential oil on the PBAT's characteristics was evaluated. The films were produced using the casting technique. Thyme essential oil (EO) was evaluated by mid-infrared, gas chromatography-mass spectrometer, and antimicrobial activity. The films were evaluated by mid-infrared, mechanical, and thermal tests. The results demonstrated that EO has a higher concentration of o-cymene and antimicrobial activity against the bacteria Escherichia coli and Staphylococcus aureus. The films were analyzed for their mechanical and thermal properties according to the compositions tested. The films have shown promise for use as active packaging.

Resumo em Inglês:

Abstract Polymer blends, derived from the combination of two or more polymers, yield novel materials with properties distinct from that of the original polymers. These materials have garnered interest in the medical field. However, for such applications the biocompatibility of the material must be evaluated. In this study, we prepared polymer blends from poly(ε-caprolactone) (PCL) and polypyrrole-block-poly(caprolactone) (PPy-b-PCL) using the casting method. The observed compatibility resulted from specific interactions between the carboxylic group of PCL and the amine group of PPy-b-PCL, as well as between the pyrrole ring of PPy-b-PCL and the CH2 group of PCL. Micro-Raman imaging revealed homogeneity in surface morphology, whereas thermogravimetric analysis indicated that the formation of polymer blends enhances the material’s thermal stability. Importantly, the results demonstrated that the addition of PPy-b-PCL does not affect the cytotoxicity to bovine fibroblasts, suggesting their biocompatibility and potential application in cattle veterinary devices.

Resumo em Inglês:

Abstract The polymer transition temperature is a crucial parameter in the industry for knowing raw materials before starting the manufacturing process. The current work reports a novel low-cost prototype instrument to measure the transition temperature with reliable accuracy. The equipment was built using commercial load cells composed of strain gauges in combination with an Arduino® microcontroller. The prototype measurement quality was validated by measuring the transition temperatures of most commercial polymers. The obtained values were compared with values obtained by conventional thermal analysis known as differential scanning calorimetric and thermo-mechanical analysis (DSC and TMA), which results in identical values.

Resumo em Inglês:

Abstract Amburana cearensis tree is used in various applications, from artisanal to pharmaceutical use. However, the gum extracted from its exudate has not yet been investigated. This study aimed to the physicochemical and structural characterization of Amburana cearensis Gum (AcG) by elemental, rheological, and thermal analyses, X-ray diffraction (XRD), high-Performance Liquid Chromatography (HPLC), Gel Permeation Chromatography (GPC), Infrared Spectroscopy (FTIR), UV-Vis spectroscopy and nuclear magnetic resonance (NMR). Additionally, a hemolytic assay was performed to evaluate the biocompatibility of AcG using human erythrocytes. The results showed that AcG consists of β-D-Galactopyranose monomers linked by glycosidic bonds (1→3). At the same time, the side chains exhibit β-Galactopyranose (1→6) and α-L-Arabinofuranoside (1→3,6) monomers as non-reducing terminals, whose biocompatibility was excellent in the model used. AcG was described for the first time as a biopolymer that could have broad applications in the pharmaceutical and cosmetic industries, justifying the interest in further studies about AcG applications.

Resumo em Inglês:

Abstract The objective of this manuscript was to investigate the influence of different Babassu Mesocarp Flour (BMF) contents (3, 5, 8, and 10% by weight) on the physical and surface properties of the Poly(Lactic Acid) (PLA) matrix. For this purpose, composite films were produced through flat-die extrusion processing. Visual analysis showed that the films were successfully produced by this processing method and exhibited good handling. The physical properties of the films varied as follows: width (16.41‒20.38 cm), thickness (0.14‒0.24 mm), apparent density (0.78‒1.07 g/cm3), and grammage (168.34‒255.31 g/m2). Through optical microscopy, good distribution and dispersion of the particles were observed despite the presence of some agglomerates. The film surface became rough due to the incorporated flour content, which influenced the contact angle result. The combination of PLA/BMF for producing composite films has technological potential, enabling the valorization of an industrial by-product and preserving the environment.

Resumo em Inglês:

Abstract Bio-high density polyethylene (BHDPE) films with organoclay and antimicrobial additives (zinc pyrithione) were evaluated. The composites were prepared in a single-screw extruder using the melt intercalation technique, and the films were obtained by flat extrusion. The diffractograms indicated the formation of an intercalated nanocomposite (BHDPE/6 wt% of clay). Infrared spectra suggested that the polymer predominates over the antimicrobial agent bands. Thermal stability was slightly reduced by up to 3°C. The clay and antimicrobial agent reduced the melting point and crystallinity of BHDPE by up to 12 °C and 13.3%, respectively. In addition, the presence of clay and antimicrobial agent significantly (p < 0.05) affected all mechanical properties. Proliferation of Staphylococcus aureus demonstrated that both evaluated additives did not significantly (p > 0.05) inhibit microbial growth. The results emphasize a promising application of the films for packaging that does not require antimicrobial control, with films highlighted by 6 wt% of clay.

Resumo em Inglês:

Abstract The inlet velocity of thermoplastic in injection molds plays a crucial role in obtaining high-quality polymer parts and the final performance of the product. It is known that the way the polymer is injected into the mold can directly affect important properties, such as the distribution of internal stresses, the cooling rate and the formation of surface defects. However, there are injection molding machines that only control injection pressure and dosage, making it difficult to obtain the gate inlet velocity into the mold cavity. Besides, some molds have many injection channels as well as complex inlet geometries, which make a challenging task to identify the inlet velocity. This study presents numerical and experimental approaches on how to determine the entry velocity in thermoplastic injection molds. The main results showed that these methods are highly efficient and contribute to identifying the gate inlet velocity with good accuracy.

Resumo em Inglês:

Abstract This paper investigates the electrical, morphological, and mechanical behavior of ultrathin layer-by-layer polyaniline/poly(vinyl sulfonic acid) (PANI/PVS) ultrathin films for ammonia gas sensing. Atomic force microscopy shows that the PANI/PVS surface's roughness increases almost linearly with the number of PANI/PVS bilayers, while the surface morphology varies from a rod-like structure to a film-like architecture. Impedance measurements and their representation by a Cole-Cole model confirm this transition at ~15 bilayers. The designed sensor shows low response time (< 1 min), an optimal operating frequency range (1–100 Hz), high stability and sensibility to ammonia (~ 98 kΩ/ppm), and low sensibility to strain (~ 3.6 kΩ/%). This study suggests that hopping carriers' concentration remains constant, and hopping carriers' mobility changes with the number of bilayers. The simultaneous analysis of morphology with complex impedance measurements is a strategy for enhancing the electrical performance of low-cost and flexible organic sensing devices.