Abstract In this work, a bio-based adhesive is prepared from Protium heptaphyllum resin. The resin is first characterized by 1H and 13C nuclear magnetic resonance spectroscopy and the bioadhesive is then prepared using a simple mixture of the resin with linseed oil, catalyzed by cobalt octanoate, to induce crosslinking. The precursors and bioadhesive obtained are characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The NMR analysis shows the presence of groups of triterpenes, such as α- and β-amyrins, and diols, such as brein and maniladiol. Thermogravimetric analysis reveals that the resin has less thermal stability than the bioadhesive. Mechanical tests indicate that the bioadhesive has greater adhesion strength compared to the commercial adhesive, reaching an average stress at break of 7.66 and 0.113 MPa for the wood and carbon steel substrates, respectively. In conclusion, the bioadhesive can be used for the production of composites.
ABSTRACT The use of polymeric residues in the civil construction has been the target of many studies aiming to reduce the volume of post-consumer plastics in the environment. This work focuses on the viability to use polyethylene terephthalate (PET) and polypropylene (PP) as partial replacement to sand in concrete. PET and PP flakes from post-consumer packings were used as light aggregate to partially replace, individually, 10% in volume of sand. The effect of adding these polymers was investigated in terms of physical, mechanical, durability and morphological properties of the concrete. Physical properties were measured in terms of water absorption, voids content and specific mass. Mechanical properties were measured in terms of compressive strength and elasticity modulus. Durability properties were measured in terms of capillarity water absorption and electrical indication of the concrete to resist to chloride ion penetration. MEV and EDS were used to carry out morphological analysis. DSC curves were carried out to evaluate thermal properties of the polymeric flakes. Contact anlge test was also performed. The partial addition of PET and PP polymers reduced the compressive strength by 20%, whilst the reduction of the elasticity modulus was 16% for PET samples, and almost insignificant for PP samples. The durability results show that the polymers contributed to increase the resistance of the samples to chloride penetration by 15% and 57%, for PET and PP samples, respectively; however, there was an increase in the voids content and water absorption. In the morphological test it is possible to observe a lower interfacial adhesion between PP and the cementions paste in comparison to PET.
RESUMO O uso de resíduos poliméricos na construção civil tem sido alvo de muitos estudos com o objetivo de reduzir o volume de plásticos pós-consumo no meio ambiente. Este trabalho concentra-se na viabilidade do uso de politereftalato de etileno (PET) e polipropileno (PP) como substituição parcial da areia no concreto. Os flocos de PET e PP pós-consumo foram utilizados como agregado leve para substituir parcialmente em 10% o volume de areia. O efeito da adição desses polímeros foi investigado em termos de propriedades físicas, mecânicas, de durabilidade e morfológicas do concreto. As propriedades físicas foram a absorção de água, teor de vazios e massa específica. As propriedades mecânicas das amostras foram medidas em termos de resistência à compressão e módulo de elasticidade. A durabilidade foi avaliada em termos de absorção de água por capilaridade e indicação elétrica do concreto para resistir à penetração de íons cloretos. A análise morfológica foi realizada pelo MEV e EDS. Curvas de DSC foram utilizadas para avaliar as propriedades térmicas dos flocos. O-teste de ângulo de contato também foi realizado. A adição parcial de polímeros de PET e PP reduziu a resistência à compressão em 20%, enquanto a redução do módulo de elasticidade foi de 16% para as amostras de PET e quase insignificante para as amostras de PP. Os resultados de durabilidade mostram que os polímeros contribuíram para aumentar a resistência das amostras à penetração de cloretos em 15% e 57%, para amostras de PET e PP, respectivamente, no entanto, houve um aumento no teor de vazios e na absorção de água. No ensaio de morfologia é possível observar uma menor adesão interfacial entre o PP e a massa cimenticia em comparação ao PET.
Abstract This work investigated the effect of thermal treatment in an autoclave on the chemical, physical, and morphological properties of lignocellulosic fibers from açaí (Euterpe oleracea Mart), and the behavior of this treated fiber in polypropylene (PP) matrix composites with polypropylene-graft-maleic anhydride (PPgMA) as the coupling agent. The treated and untreated fibers were characterized by chemical composition, x-ray diffraction, FTIR spectroscopy, and thermogravimetry, scanning electron microscopy and tensile tests were carried out for the composites. The results showed that the thermal treatment modified the hemicellulose and lignin content and increased the fiber surface roughness, without compromising the thermal stability. The composite prepared with thermally treated fibers and PPgMA exhibited an increase in tensile strength but a reduction in tensile modulus. In conclusion, the thermal treatment of vegetable fiber is a promising technique for improving the performance of composites.
ABSTRACT Fused Filament Fabrication (FFF) is an Additive Manufacturing process popularized in the last decade due to its easiness of use and lower costs. However, despite its increasing popularity, the process itself has several gaps in knowledge, hindering further uses on more advanced objects. Also, the freedom of design allows significant variances in the printed parts, many influencing production and mechanical properties. This work studies the influences of the infill patterns in the mechanical response of printed parts. Using poly (lactic acid) (PLA), a widely used polymer in FFF process, the mechanical responses of parts printed with different infill patterns were analyzed. Rectilinear, Honeycomb, Triangle and Grid patterns were tested on impact resistance and tensile strength. Additionally, samples masses were measured and compared to the mechanical response. Results shown significant differences in the on tested properties. Tensile strength varied from 2.4 to 1.1 MPa, and impact resistance from 3.8 to 1.5 kJ/m2 Also, measured mass was found to be significantly higher on the Honeycomb pattern. Considering mechanical response from both tensile and impact tests along with printed mass, Rectilinear pattern can be considered the most advantageous from the economic point of view.
The production of a material with rigid, multifunctional three-dimensional porous structure at a low cost is still challenging to date. In this work, a light and rigid carbon foam was prepared using rice husk as the basic element through a simple fermentation process followed by carbonization. For the fermentation process, the amount of biological yeast (7.5 g for the carbon foam CA-1P and 5 g for the carbon foam CA-2P) was used to evaluate its influence on the morphology of the foams. In order to prove that the heat treatment made in the foam alters the hydrophilic character of the rice husk foam, a chemical treatment with steam deposition was carried out. The foams were characterized by the following analyzes: apparent density, micrograph, thermogravimetry, contact angle, water sorption capacity and thermal conductivity. Visually, the CA-1P foams presented a structure with larger pores due to the greater amount of yeast used in its formulation. The heat treatment of rice potato foams proved to be as efficient as the chemical treatment for water contact angle above 90º, proving the ability of the foams to repel water/moisture. The thermal conductivity of the foams (0.029 and 0.026 W m-1 K-1 for CA-1P and CA-2P, respectively) was close to the conductivity of polyurethane foams (0.032 W m-1 K-1). Thus, the method used in the production of the carbon foams produced from the rice husk proved to be effective. In addition, the foams produced have the potential to be used for thermal insulation.
Abstract Ballistic armor has been manufactured primarily based on polyaramide (Kevlar and Twaron) or Dyneema but the lifespan warranty in Brazil is only 5 years and after this time period they are incinerated or comminuted and ground up. This study aims to evaluate the changes on the physical, mechanical and morphological properties of polyaramide fibers of ballistic armor after natural aging. These samples with different fabrication (2005 and 2010) and usage time were exposed to natural weathering in the city of Porto Alegre, southern Brazil, during the period of one year. Morphology fiber results surfaced after ageing, it showed fiber swelling, stress cracking and defibrillation, and the results of the mechanical tensile testing of the polyaramide fibers showed a pronounced decrease (80%) in tensile strength. It can be concluded that the weight, the dtex of the fiber and the kind of fabric can influence the degradation degree under natural exposure.
ABSTRACT The growth of oil exploration and transport in marine environments brings concern over potential environmental disasters caused by oil spills. Thus, various materials are being developed and studied in order to minimize environmental impacts caused by these oil spills. Among these materials, the use of sorbents has appeared as a great potential technique for the treatment of effluents, by separating and collecting oil in the aqueous medium. This work describes the development of a sorbent system based on acetylated microfibrillated cellulose. Initially, cellulose fibers were modified by an acetylation reaction and thereafter, by a mechanical process using a wheel mill grinding. To produce the sorbent system, fibers were coated by three different types of envelopes to prevent leakage during the sorption experiment. Main results indicate a higher oil sorption by sorbents with higher oil viscosity and higher grammage of the envelope. Acetylated microfibrillated cellulose showed low water adsorption and high selectivity to oil and greater oil sorption values than commercially sorbent currently used, based on polypropylene fibers.
ABSTRACT The footwear industry uses in its products various raw materials derived from the plastics sector. One of the most used is the synthetic PVC laminate, used in the construction of leather because of the great versatility of colors, prints and thicknesses. The laminate is composed of PVC and textile fiber, usually in the mass ratio of 60/40. Cutting of parts generates a large amount of shavings that are normally discarded or deposited in landfills or ARIPs (Hazardous Industrial Waste Landfills). The present work evaluates the feasibility of incorporating these residues in the form of powder in virgin PVC matrix for use in soils in proportions of 0, 5, 15, 25, 35 pcr (parts per cent of resin), as well as their mechanical performance. Physical-mechanical properties with traction, shore A hardness and bonding, scanning electron microscopy (SEM) and infrared spectroscopy (FTIR) were evaluated. The results of the hardness and tensile tests showed a decrease in performance as the concentration of residue in the composite increased. The bond strength also showed a decrease in the final resistance obtained by the pull out effect, confirmed by fracture surface micrographs. Mixtures with powdered laminate residues may be said to have acceptable characteristics, in accordance with the standards indicated and the standards specified for use as flooring material. In addition, the incorporation of this residue reduces the amount of material discarded reducing the environmental impact.
RESUMO A indústria de calçados emprega em seus produtos diversas matérias primas derivadas do setor de plásticos. Um dos mais utilizados é o laminado sintético de PVC, utilizado na construção de cabedais devido à grande versatilidade de cores, estampas e espessuras. O laminado é composto de PVC e de fibra têxtil, normalmente na proporção mássica de 60/40. O corte das peças gera uma grande quantidade de aparas que normalmente são descartadas ou depositadas em aterros sanitários ou ARIPs (Aterros de Resíduos industriais Perigosos). O presente trabalho avalia a viabilidade de incorporação destes resíduos em forma de pó em matriz de PVC virgem para uso em solados nas proporções de 0, 5, 15, 25, 35 pcr (partes por cento de resina), bem como seu desempenho mecânico. Foram avaliadas propriedades físico-mecânicas com tração, dureza shore A e colagem, microscopia eletrônica de varredura (MEV) e espectroscopia no infravermelho (FTIR). Os resultados dos ensaios de dureza e tração demonstraram um decréscimo no desempenho na medida em que a concentração de resíduo no compósito aumentou. A força de colagem também apresentou queda na resistência final obtida pelo efeito pull out, confirmado pelas micrografias da superfície de fratura. Pode-se dizer que as misturas com resíduos de laminados em pó apresentam características aceitáveis, segundo as normas indicadas e os padrões especificados para a utilização como material para solado. Além disso, a incorporação deste resíduo diminui a quantidade de material descartado reduzindo o impacto ambiental.
ABSTRACT The fouling formation in the EVA production leads to an increase in the residence time of the material. This result is a favorable condition to generation of the crosslinks during the polymerization. The crosslinking allows raising the molar mass of the polymer, which after the polymerization reaction are characterized as gels, thus generating problems in the product quality during production due to contamination of the resin. This paper describes the fouling process in the reactor, the defouling mechanism, the crosslinking, the scission of chain and presents a study on the influence of the reaction temperature in relation to the formation of gels by quantitative analysis by Optical Controller System -OCS. The average temperature rise of the reaction at 10 ºC, helped to reduce the generation of gels due to the viscosity reduction over the reactor, which reduces the polymer residence time in the walls of the tube and consequently the formation of fouling.
ABSTRACT The increasing concern over the spread of diseases has lead to a high consumption of antimicrobial additives in the medical and industrial fields. Since these particles can lixiviate from loaded materials, the contact between this additive and mammalian cells can occur during manufacture, use and disposal of the products. Silver on fumed silica (AgNP_SiO2) and titanium dioxide (TiO2) can be used as antimicrobial additives that are applied in polymeric formulation. While these additives can inhibit bacteria, fungus and virus proliferation; they may also be harmful to humans. Standard toxicological studies were undertaken using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide), CBPI (cytokinesis-block proliferation index) and micronucleus assay using different sets of additive concentrations. The nanosize of the samples evaluated was confirmed by transmission electronic microscopy. No significant micronucleus frequency increase or cell viability reduction were observed with the exposure of L-929 murine fibroblast cells to AgNP_SiO2 and TiO2 particles at any of the tested concentrations. The non toxic effect of the analyzed particles can be explained by considering its agglomeration tendency, composition, and crystalline form. Further investigations should be done to understand the interference of agglomeration and how it affects the toxicological study.
The purpose of the present study was to evaluate the antimicrobial potential of styrene-ethylene/butylene-styrene based thermoplastic elastomers (TPE) incorporated with zinc pyrithione (ZnPT) and silver nanoparticles (AgNano). Japan Industrial Standard was applied to evaluate the antimicrobial potential of incorporated TPE compounds against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Antifungal action was evaluated against Aspergillus niger, Candida albicans and Cladosporium cladosporioides. Samples prepared with ZnPT eliminated 99.9% of the E. coli and 99.7 % of the S. aureus population, and presented an inhibition zone in the fungal assay. Samples prepared with AgNano eliminated 99.7% of the E. coli and 95.5 % of the S. aureus population. There was no inhibition zone in samples containing AgNano; however, these samples did not present fungal growth on their surfaces. TPE samples containing ZnPT showed biocidal activity against the microorganisms tested and can be used to develop antimicrobial products.
ABSTRACT Wood flour composites main applications are represented by outdoor furnishing. Therefore, it is important to evaluate their behavior under natural ageing conditions. This work aims to investigate the natural ageing impact on the mechanical, physical, thermal e morphological properties of recycled polypropylene/ethylene vinyl acetate/wood flour composites (PP/EVA/ITA). Samples were exposed to natural ageing for 12 months in Porto Alegre (BR). Mezilaurus itauba (ITA) wood flour was used at 30 % w/w. Results showed that PP filled wood flour retained a higher fraction of the original mechanical properties after natural ageing. Crystallinity degree for composites increased from 30.9 up to 37.5% Climatic conditions affected the colorimetric and morphological characteristics of composites, indicating that there was not only photo-degradation but also thermo-oxidative and hydrolytic degradation. In this way, the use of antioxidant additives and UV photo-absorbers is recommended to avoid stress-cracking, discoloration and loss the mechanical properties.
The final destination of PET packaging is creating economic and environmental concerns. One of the alternatives to minimize this problem would be making use of chemical recycling of this material through glycolysis with the aim to produce bis(hydroxiethyl) terephthalate, BHET monomer. This reaction is well known, but it still presents problems as BHET purity since it makes necessary the development of new catalysts highly selective. In this context, the present work studied the catalytic activity of a nanostructured material, titanate nanotubes (TNT), and compared it to a commercial catalyst (zinc acetate), which is the most used for this glycolysis reaction according to literature researches, and analyzed the influence of PET type (virgin and post-consumer) in the depolymerization for reaction times of 2, 3 and 4 hours. Using TNT as catalyst, BHET production yield and values of turnover number for the evaluated reaction times were higher than the results using Zn(OAc)2 for virgin PET, proving itself as a promising catalyst.
Styrene-ethylene/butylene-styrene (SEBS) copolymer- based thermoplastic elastomers (TPE) are applied in the production of household items used in places with conditions for microbial development. Metal oxides like zinc oxide (ZnO) and others can be added to the TPE composition to prevent microbial growth. The aim of this study is to evaluate the effect of thermal accelerated ageing on mechanical, chemical and antibacterial properties of SEBS-based TPE containing 0%, 1%, 3%, and 5% zinc oxide. Zinc oxide was characterized by laser diffraction, X-ray diffraction, superficial area, porosity and scanning electron microscopy. Both aged and unaged samples were analyzed by infrared spectroscopy, tensile at rupture, elongation at rupture, hardness and antimicrobial activity against Escherichia coli and Staphylococcus aureus. Following thermal exposure, a reduction of antimicrobial activity was observed. No significant difference was observed in the chemical and mechanical characteristics between aged and unaged samples.
Two polyethylene-based on single-site metallocene catalyst (mLLDPE) were selected to characterize the effect of long chain branching (LCB) on blown film processability, optical and mechanical properties. 13C NMR and parallel plate rheology were used to identify LCB presence on LLDPEs. Blown films were produced from 100% LLDPEs using three different machine direction (MD) stretch ratios. When the same processing conditions for the two LLDPEs grades were used, better processability was observed for LLDPE with LCB. In relation to mechanical and physical properties, Elmendorf tear and optical properties were highly influenced by the presence of LCB. Tear resistance is affected by film orientation and is inversely proportional to the level of LCB in the polymer. It was observed a reduction of 50% in the MD tear strength when comparing with the polymer without LCB. However, haze decreases significantly with the presence of LCB, about 40%.