Resumo em Inglês:

Abstract In this work, a study was undertaken to explore the possibility of using leftover tamarind fruit fibres as reinforcement in PLA and HDPE matrix. PLA and HDPE polymers form minimum 75% of the total polymers used in the composites. PLA and HDPE was mixed with natural fibres (5 wt.%, 10 wt.%, 15 wt.%, 20 wt.% and 25 wt.%,) individually and also as a hybrid filler to enhance its mechanical properties. Characterizations, mechanical behaviour and microscopic investigation were performed to understand the excellent mechanical properties and good chemical resistance of the prepared composites, which demonstrated potential suitability for semi-structural applications.

Resumo em Inglês:

Abstract Using ternary blends is a technological solution to combine the best characteristics of different elastomers. Quantifying rubbers in a blend, in which each content influences the result, is a task complex and usually requires the coupling of techniques. Therefore, it is necessary to develop simple, fast and accurate methodologies for this purpose. This study presents the analysis of polychloroprene, poly-cis-isoprene and polybutadiene (CR/NR/BR) rubber, with the selection of bands A1116 (CR), A2960 (NR) and A738 (BR), by universal attenuated total reflection (UATR) infrared spectroscopy performed on the sample as received. The error found was 2%, with 98 to 99% of the data explained by the methodology. The methodology responds more adequately to CR and BR cis, but has the ability to detect up to 5% of NR and 10% of CR and BR. Acid-resistance data are used quantitatively in the determination of BR rubber, satisfactorily confirming the spectral data found.

Resumo em Inglês:

Abstract Single-use plastics represent almost a fifth of the global plastics market, leading to high residual accumulation. The study aimed to evaluate the biodegradability, under anaerobic conditions, of additivated polyethylene terephthalate (PET-ad), marketed by a company in Brazil. The polymeric films were submerged in digesters in sludge from sewage treatment plants. Films were characterized throughout time, as were the biogas and microorganisms in the medium. The results indicated weight and microscopic differences attributed to sludge components and microbial colonization on films’ surfaces. The thermal properties did not show changes. Moreover, at the end of the research, the microorganisms still had considerable concentration – 106 and 109 NMP/ml, anaerobic and aerobic, respectively. The production of methane (60% v/v) and carbon dioxide (30% v/v) gases peaked in the first month and decreased subsequently. At eighteen months, PET-ad has been proven to undergo the initial degradation process faster than negative control.

Resumo em Inglês:

Abstract We report an efficient protocol to synthesize rod-coil diblock copolymers of an α-helical polypeptide and poly(4-vinyl pyridine) via a combination of “living” ring-opening polymerization of α-amino acid N-carboxyanhydrides at 0 °C, polymer end-group modification and atom transfer radical polymerization (ATRP) of 4-vinyl pyridine (4-VP). Due to the competent effect of the pyridine groups with the ATRP ligand and the low initiation efficacy of the rigid polypeptide macroinitiator at mild temperatures, the challenge on ATRP of 4-VP was overcome by performing the ATRP process at 100 °C. Relatively well-defined poly(γ-benzyl L-glutamate)-b-poly(4-vinyl pyridine) diblock copolymers were successfully synthesized and characterized. Upon solvent vapor annealing, thin films of the diblock copolymers showed micro-phase separation behavior.

Resumo em Inglês:

Abstract Green composites are sustainable alternatives to conventional materials. This study developed composites based on bio-polyethylene (Bio-PE) and babassu mesocarp (BM) (1.5 and 3 phr), using PE-grafted maleic anhydride (PE-g-MA) (3 phr) as a compatibilizer. Materials were processed by extrusion and injection molding. BM exhibited starch-rich structure with a maximum degradation peak at 306 °C. PE-g-MA improved dispersion and surface finish, increasing the contact angle by up to 9.06%. Compared to neat Bio-PE, composites with PE-g-MA showed a 44.33% increase in yield stress and a 50.49% rise in ultimate tensile strength. Izod impact strength remained unchanged. Water absorption increased with BM, but was reduced up to 33.57% with PE-g-MA. This work introduces a novel use of BM in Bio-PE matrices, highlighting its potential as a Brazilian, renewable filler for sustainable composites.

Resumo em Inglês:

Abstract This study assessed films of different formulations produced from whey protein and gelatin by casting. The results were compared with synthetic polycrystalline wool (PCW) polymer. Citric acid was used as a crosslinker at 10 wt.% - 40 wt.% relative to whey mass. Adding citric acid increased the films’ thickness and solubility. Only the formulations with the highest concentration of citric acid were hydrophilic. The morphological analysis showed that all films have uniform and dense structures. The films had lower thermal stability concerning the standard, and the increase in the citric acid concentration decreased the mass loss in the films. The characterization revealed that the films produced with 10 wt.% and 20 wt.% citric acid have the potential to be used as packaging for feminine pads. The study of the proposed application for films produced based on whey and gelatin is promising since there is little literature regarding the suggested application.

Resumo em Inglês:

Abstract This investigation presents a deep examination on the behavior of radiation effects on pristine (IIR) and halogenated butyl (IIR-Cl, IIR-Br) rubbers. The retrieving these materials is appropriately achieved by the radiolysis fragmentation of main chains that initiates the structural modifications based on the radiation susceptibilities of studied rubbers. The γ-irradiation process causes oxidation under air atmosphere and the effects are revealed by chemiluminescence and FTIR characterizations. The radiolysis on butyl rubbers is conducted onto a specific fragmentation, which allows the two antagonistic processes: oxidation and recombination. During the γ-radiolysis in rubbers is revealed the influence of the electronegativity possesed by the halogen atoms presented in polymer structures, determining the values of activation energy for their oxidative degradation. The γ-processing suggests an ecological procedure for an appropriate preparation of blends or for the recycling as composite products. The calculated activation energies place the polymers in the following stability order of IIR<IIR-Cl<IIR-Br.

Resumo em Inglês:

Abstract Polymer materials (plastics and elastomers) are widely used in applications involving ionizing radiation environmental exposure. Such rush in service conditions might promote significant material degradation. Here, we investigated gamma irradiation effects on poly(ethylene-co-vinyl acetate) (EVA) (25 and 40 wt% vinyl acetate - VA) in the dose range of 5 – 30 kGy. This range is suitable for applications in food preservation and matches expected absorbed doses for nuclear power plants electrical cables and wires. EVA copolymers with 40 or 25 wt% VA predominantly underwent crosslinking effects promoted by gamma irradiation at dose of 10 kGy. Additional irradiation of EVA (25% VA) up to 30 kGy did not promote further alterations. Refractive index or thermal degradation under nitrogen atmosphere remained practically unaltered after gamma irradiation. Our findings suggest that EVA is a suitable material for irradiated food packaging films, and in electrical cable jacketing materials exposed to gamma radiation.

Resumo em Inglês:

Abstract Gold nanoparticles (AuNPs) were prepared by green synthesis using the gum extracted from Amburana cearensis (GAmb) exudate. The influence of polysaccharide concentration, precursor salt (HAuCl4), temperature, pH, and reaction time on the final properties of the AuNPs-GAmb was evaluated. The UV-VIS spectrum of the AuNPs-GAmb showed an absorption band in the region of 524 nm, characteristic of spherical nanostructures, and the synthesis conditions strongly influenced the average diameter of these nanoparticles. The optimized AuNPs-GAmb presented a high colloidal stability and spherical shape with an average diameter of 13.22 ± 1.86 nm (when measured by Atomic Force Microscopy -AFM). Later, the catalytic activity of AuNPs-GAmb was evaluated in the degradation of toxic dyes such as toluidine blue (TB), methylene blue (MB), and methyl orange (MO), which were degraded in less than 11 minutes. Thus, the AuNPs-GAmb obtained in this work are eco-friendly and have a high potential for applications in biotechnology.

Resumo em Inglês:

Abstract Antistatic packaging prevents electrostatic discharge (ESD) damage, protecting electronic components during storage and transport, ensuring reliability in industries like electronics and aerospace. This study develops heterophasic ethylene-propylene copolymer (HEPC) composites reinforced with recycled aircraft graphite for antistatic applications. HEPC composites with 1, 5, and 10 wt% recycled graphite were prepared via twin-screw extrusion and injection molding. Morphological, thermal, rheological, mechanical, and electrical properties were analyzed. Adding 5 wt% graphite increased the elastic modulus by 21.3% and Shore D hardness by 6.1%. Electrical conductivity improved significantly, with a nine-order magnitude increase for 5 wt% graphite, enabling effective electrostatic dissipation. This sustainable approach enhances material performance while promoting circular economy practices by upcycling aerospace waste into high-value functional materials.

Resumo em Inglês:

Abstract Superparamagnetic microspheres of poly(glycidyl methacrylate-co-divinylbenzene) were produced via suspension polymerization and were functionalized with ethylenediamine, diethylenetriamine and triethylenetetramine. The results of Cr(VI) adsorption showed better removal at pH 2. The adsorptive process was best described by the pseudo-second order model, and an equilibrium isotherm study indicated the best suitability of the Langmuir model. The microspheres modified with ethylenediamine had greater adsorption capacity and the highest ΔH value at pH=2 and 318 K. The choice among EDA, DETA, and TETA as substituent groups depends on balancing adsorption efficiency, selectivity and process kinetics. In these studies, R14-DETA showed better performance than the others. The adsorbents had ΔH around 40-45 kJ/mol and ΔS between 148-159 J/mol.K. The results indicated an endothermic process, of chemical nature, with negative ΔG values. This study indicates the potential for applications in Cr(VI) removal.

Resumo em Inglês:

Abstract This study examines the impact of three surface treatment methods on sisal fibers used as reinforcement in styrene-butadiene rubber (SBR) composites: washing with water, alkaline treatment (mercerization), and silanization, with each composite containing 5 wt% of fibers. The preparation process involved using an internal mixer and rubber mixing mill to shape the composites, followed by vulcanization in an automated system press. The effectiveness of the treatments was evaluated using scanning electron microscopy, along with tensile tests, rheometer analysis, and measurements of hardness and density. The treatments enhanced fiber modification by increasing surface roughness through the grafting of silanol groups, thereby improving their interaction with the elastomeric matrix. Notably, composites reinforced with silanized fibers exhibited the highest performance and interaction among the various treatment methods, showing a higher modulus at 100%. Alkaline and silanization treatments reduced vulcanization time. Sisal fibers combined with SBR waste can promote sustainability in the footwear industry.