Derval dos Santos Rosa
UFABC - Federal University of ABC, CECS, Faculty Member
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Effects of the compatibilizer PE‐g‐GMA on the mechanical, thermal and morphological properties of virgin and reprocessed LDPE/corn starch blends
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The inappropriate storage of solid wastes, particularly those containing polymeric materials, is a serious cause of environmental pollution and has led to much investigation on the use of biodegradable polymers. In this work, we examined... more
The inappropriate storage of solid wastes, particularly those containing polymeric materials, is a serious cause of environmental pollution and has led to much investigation on the use of biodegradable polymers. In this work, we examined the biodegradation properties of different blends of the binary system poly(?-caprolactone) (PCL) and cellulose acetate (CA). The parameters assessed included the change in mass during aging in simulated soil, the occurrence of morphological alterations and the tensile strength at break. The incorporation of PCL improved the biodegradation rates of the blends, with those that had the highest phase separations also showing the greatest morphological alterations, probably because of polymer chain hydrolysis.
The storage of post-consumer unsaturated polyester/glass fibre composites impacts negatively on the environment due to its persistence (long lifetime of both the glass fibre and the resin) as well as the high volume/weight ratio of the... more
The storage of post-consumer unsaturated polyester/glass fibre composites impacts negatively on the environment due to its persistence (long lifetime of both the glass fibre and the resin) as well as the high volume/weight ratio of the residues. In this work we introduce a new approach for the recycling process of artefacts made of these polyester/glass fibre composites that involves the dispersion of the ground, not powdered, composite in raw polyester resin. Room temperature resin curing was employed. Flexural and impact tests were performed to optimize the processing conditions and the manufacturing process. Significant improvement in texture, flexural strength and impact resistance of sheets were achieved by pressing and heating the sheets at 40∞C and 50∞C during curing. The artefacts utilized in our work were post-consumer public telephone weather protector caps, which, in Brazil, are manufactured with a composite of unsaturated polyester/glass fibre. Although we used this spec...
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Cerâmicas porosas têm sido utilizadas em diversas aplicações tecnológicas como coletores de partículas sólidas, isolantes térmicos e acústicos. As áreas de biotecnologia e biomedicina utilizam cerâmicas porosas como reatores em processos... more
Cerâmicas porosas têm sido utilizadas em diversas aplicações tecnológicas como coletores de partículas sólidas, isolantes térmicos e acústicos. As áreas de biotecnologia e biomedicina utilizam cerâmicas porosas como reatores em processos de fermentação e em implantes, respectivamente. Adicionalmente, estes materiais apresentam grande aplicação na área de microfiltração de líquidos e emulsões, como a purificação de combustíveis através da separação da água e óleo, e na separação das proteínas do leite. O objetivo deste trabalho é o de produzir tubos de cerâmicas porosas para microfiltração de combustíveis. A primeira etapa compreendeu a produção de tubos cerâmicos porosos por colagem de suspensões e avaliação de suas propriedades físicas, fluidodinâmicas e mecânicas finais. Já a segunda etapa consistiu na análise do desempenho destes tubos durante a microfiltração de combustíveis. As propriedades finais das cerâmicas porosas foram avaliadas em função das variações na composição da su...
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The storage of post-consumer unsaturated polyester/glass fibre composites impacts negatively on the environment due to its persistence (long lifetime of both the glass fibre and the resin) as well as the high volume/weight ratio of the... more
The storage of post-consumer unsaturated polyester/glass fibre composites impacts negatively on the environment due to its persistence (long lifetime of both the glass fibre and the resin) as well as the high volume/weight ratio of the residues. In this work we introduce a new approach for the recycling process of artefacts made of these polyester/glass fibre composites that involves the dispersion of the ground, not powdered, composite in raw polyester resin. Room temperature resin curing was employed. Flexural and impact tests were performed to optimize the processing conditions and the manufacturing process. Significant improvement in texture, flexural strength and impact resistance of sheets were achieved by pressing and heating the sheets at 40∞C and 50∞C during curing. The artefacts utilized in our work were post-consumer public telephone weather protector caps, which, in Brazil, are manufactured with a composite of unsaturated polyester/glass fibre. Although we used this specific artefact, the methodology can be extended to different types of post-consumer materials or industrial scraps.
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Cardanol–formaldehyde thermoset resin was reinforced with raw and chemically modified fibers of bamboo ( Bambusoideae). Modified fibers were treated with alkali solutions of NaOH (5% and 10%) and bleached with sodium hypochlorite... more
Cardanol–formaldehyde thermoset resin was reinforced with raw and chemically modified fibers of bamboo ( Bambusoideae). Modified fibers were treated with alkali solutions of NaOH (5% and 10%) and bleached with sodium hypochlorite NaClO/H2O (1:1) at 60℃–75℃. The biocomposites were fabricated with a hand lay-up technique. This study investigated the fibers microstructure before and after alkali treatment, as the interaction between matrix and reinforce by scanning electron microscopy. The Fourier transform infrared spectra allowed the identification of characteristic stretching frequencies attributed to the methyl groups of lignin. A considerable increase in thermal stability was observed in the materials studied, which was verified by thermogravimetric analysis and confirmed by X-ray diffraction. The tensile tests showed that the mechanical properties (tensile modulus, tensile strength, and elongation at break) of bamboo fibers improved after alkali treatment, as well as the increase...
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ABSTRACT Despite poly(vinyl chloride) (PVC) being one of the most useful materials available to the fabricator, its inadequate disposal has contributed to strong noneconomic issues based on the allegedly evil effects of chlorine. In this... more
ABSTRACT Despite poly(vinyl chloride) (PVC) being one of the most useful materials available to the fabricator, its inadequate disposal has contributed to strong noneconomic issues based on the allegedly evil effects of chlorine. In this study, we examined the influence of adding starch, a biodegradable bioplastics, to mixtures of PVC plasticized with di(2-ethylhexyl) adipate (which is susceptible to fungal attack). PVC and its mixtures were assessed by mechanical properties, differential scanning calorimetry, Fourier-transform infrared spectroscopy, low-field nuclear magnetic resonance, thermogravimetric analysis, optical microscopy, and degradation in simulated soil. Increasing the amount of starch in the mixtures resulted in greater material stiffness, with a reduction in tensile strength at break (σ) and elongation at break (ɛ). Fourier-transform infrared spectroscopy and nuclear magnetic resonance showed that there was limited interfacial interaction between components of the PVC mixtures, which agreed with slight phase separation (breakage of the interfaces) and the decrease in the values of σ and ɛ for the mixtures. Samples containing a larger content of starch showed little weight loss after 2, 4, and 6 months in simulated soil, possibly because the starch was encapsulated by the PVC resin. J. VINYL ADDIT. TECHNOL., 2015. © 2015 Society of Plastics Engineers
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Biodegradable polymers represent a promising solution to the environmental problem of plastic waste disposal. Among the candidate polymers, starch, a low-cost natural polymer, can be processed as a thermoplastic. In this work,... more
Biodegradable polymers represent a promising solution to the environmental problem of plastic waste disposal. Among the candidate polymers, starch, a low-cost natural polymer, can be processed as a thermoplastic. In this work, thermoplastic starch containing glycerol (20, 30 or 40wt%) was prepared by extrusion. The mechanical properties of the blends were assessed by tensile stress at break, elongation at break
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RESUMO Polímeros sintéticos são largamente utilizados em diversos produtos devido às suas propriedades físicas, químicas e facilidade de transformação. O poli (cloreto de vinila), conhecido como PVC, é um dos polímeros mais versáteis... more
RESUMO Polímeros sintéticos são largamente utilizados em diversos produtos devido às suas propriedades físicas, químicas e facilidade de transformação. O poli (cloreto de vinila), conhecido como PVC, é um dos polímeros mais versáteis desenvolvidos pelo homem, de ...
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ABSTRACT The effect of ultraviolet exposure on the biodegration of poly(propylene) without (PP) and with 0.3 (wt/wt) (PPOx) pro-oxidant additives, produced by extrusion was studied. After UV exposure the samples were submitted to... more
ABSTRACT The effect of ultraviolet exposure on the biodegration of poly(propylene) without (PP) and with 0.3 (wt/wt) (PPOx) pro-oxidant additives, produced by extrusion was studied. After UV exposure the samples were submitted to biodegradation (weight loss) in prepared soils. The samples before and after UV exposure were analyzed using differential scanning calorimetry, Fourier transform infrared spectroscopy, size exclusion chromatography, and optical microscopy. The exposure to UV radiation lead to more intense degradation of PPOx than of PP; the amount of carbonyl groups was larger for the PPOx samples than for PP, as well as the decrease in the Tm and in the molecular weight. The samples exposed to UV radiation showed some level of fragmentation after 56 days when placed in the prepared soil; the samples which were exposed to UV for 480 h presented just a small weight loss. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers
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Materials Engineering, Chemical Engineering, POlymer degradation and stability, Differential scanning calorimetry, Thermal Stability, and 8 morePoly Ethylene Glycol, Thermogravimetric Analysis, Chemical Properties, Thermal Properties, Light microscopy, Tensile Strength, Water Vapor, and Tensile Properties
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ABSTRACT Poly(3-hydroxybutyrate) (PHB) was evaluated in blends with poly(ethyleneglycol) (PEG) of different weight average molecular weight (Mw = 300, 600, 1,000 and 6,000). Irradiation of the PHB/PEG films was carried out to different... more
ABSTRACT Poly(3-hydroxybutyrate) (PHB) was evaluated in blends with poly(ethyleneglycol) (PEG) of different weight average molecular weight (Mw = 300, 600, 1,000 and 6,000). Irradiation of the PHB/PEG films was carried out to different levels of irradiation doses (5 and 10 kGy) and the effects were investigated talking into consideration: thermal properties by differential scanning calorimetry (DSC), perforation resistance, water vapor transmission rate and biodegradation in simulated soil. The addition of plasticizer alters thermal stability and crystallinity of the blends. The improvement in perforation resistance due to irradiation was regarded to be a result of the crosslinking effect. Also, biodegradation assays resulted in mass retention improvements with increases in PEG molar masses, PEG concentration and irradiation dose. The irradiation process was shown to hamper the biodegradation mechanism.
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... Oxford University Press, New York, p 551 7. Carioca JOB, Arora HL, Selvam PVP, Tavares FCA, Kennedy JF (1996) Starch/Stärke 48:322 8. Matzinos P, Tserki V, Gianikouris C, Pavlidou E, Panayiotou C (2002) Eur ... Gan Z, Abe H, Doi Y... more
... Oxford University Press, New York, p 551 7. Carioca JOB, Arora HL, Selvam PVP, Tavares FCA, Kennedy JF (1996) Starch/Stärke 48:322 8. Matzinos P, Tserki V, Gianikouris C, Pavlidou E, Panayiotou C (2002) Eur ... Gan Z, Abe H, Doi Y (1997) Polym Degrad Stab 56:209 24. ...
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The dwarf-green coir fibers treated with sodium hydroxide 10% produced the best set of properties of the biocomposites generated: greater roughness and exposure of intrafibrillar cavities, providing better adhesion with the matrix, higher... more
The dwarf-green coir fibers treated with sodium hydroxide 10% produced the best set of properties of the biocomposites generated: greater roughness and exposure of intrafibrillar cavities, providing better adhesion with the matrix, higher rigidity, increased resistance to traction and better interface properties, making them better as structural materials. The best results reported in the thermal behavior of biocomposite fibers were found in fibers treated with sodium hydroxide 10%. These showed a single stage of decomposition, which occurs at a higher temperature (300°C). It was observed that the natural fibers were more resistant to the action of the microorganisms due to the presence of more lignin and hemicellulose, while fibers treated with 5 and 10% sodium hydroxide showed different degradation degree.
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ABSTRACT
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... Oxford University Press, New York, p 551 7. Carioca JOB, Arora HL, Selvam PVP, Tavares FCA, Kennedy JF (1996) Starch/Stärke 48:322 8. Matzinos P, Tserki V, Gianikouris C, Pavlidou E, Panayiotou C (2002) Eur ... Gan Z, Abe H, Doi Y... more
... Oxford University Press, New York, p 551 7. Carioca JOB, Arora HL, Selvam PVP, Tavares FCA, Kennedy JF (1996) Starch/Stärke 48:322 8. Matzinos P, Tserki V, Gianikouris C, Pavlidou E, Panayiotou C (2002) Eur ... Gan Z, Abe H, Doi Y (1997) Polym Degrad Stab 56:209 24. ...
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This work analyses the different conceptions of science presented in schools, questioning the scientific education and the several conceptions of science in various instances, as they influence actions and thoughts in many contexts.
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Traditional cancer treatments, such as surgery, radiotherapy, and chemotherapy, are still the most effective clinical practice options. However, these treatments may display moderate to severe side effects caused by their low temporal or... more
Traditional cancer treatments, such as surgery, radiotherapy, and chemotherapy, are still the most effective clinical practice options. However, these treatments may display moderate to severe side effects caused by their low temporal or spatial resolution. In this sense, photonic nanomedicine therapies have been arising as an alternative to traditional cancer treatments since they display more control of temporal and spatial resolution, thereby yielding fewer side effects. In this work, we reviewed the challenge of current cancer treatments, using the PubMed and Web of Science database, focusing on the advances of three prominent therapies approached by photonic nanomedicine: (i) photothermal therapy; (ii) photodynamic therapy; (iii) photoresponsive drug delivery systems. These photonic nanomedicines act on the cancer cells through different mechanisms, such as hyperthermic effect and delivery of chemotherapeutics and species that cause oxidative stress. Furthermore, we covered the...
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The application of cellulose nanowhiskers in polymeric composites is growing due to its good properties, which expands the applicability in the industrial sector, although many studies are still in the laboratory stage. Silva, R. et al.... more
The application of cellulose nanowhiskers in polymeric composites is growing due to its good properties, which expands the applicability in the industrial sector, although many studies are still in the laboratory stage. Silva, R. et al. cites many segments for application of natural cellulosic fibers, wide applicability detaching, from textile industry to some studies for the use of fibers such as heavy metals absorbent in industrial waste treatment.[1]
Due to verification of problems caused by scientific technology development. we crossed a historical moment in that Chemistry is seen as villanous and the Man as Epimeteus, stupid and idiot, that fell in love with Pandora, seductive... more
Due to verification of problems caused by scientific technology development. we crossed a historical moment in that Chemistry is seen as villanous and the Man as Epimeteus, stupid and idiot, that fell in love with Pandora, seductive possessor of the power of humanity's destruction. These illustrations of Greek mythology send us to a necessary reflection about the positions that Chemistry Teachers can assume in teaching relationships looking for to overcome this vision. To focus this discussion, this work relates some experiences developed in General Chemistry Discipline in University.
O trabalho objetivou avaliar a resistencia dos isolados de Staphylococcus spp. de ruminantes (caprinos, bubalinos e bovinos) com mastite a alguns antibioticos -lactâmicos pela presenca do gene Bla-Z e producao de biofilme. O perfil de... more
O trabalho objetivou avaliar a resistencia dos isolados de Staphylococcus spp. de ruminantes (caprinos, bubalinos e bovinos) com mastite a alguns antibioticos -lactâmicos pela presenca do gene Bla-Z e producao de biofilme. O perfil de resistencia dessas bacterias aos antibioticos ampicilina, penicilina G e oxacilina foi realizado pelo metodo de Kirby-Bauer. A producao do biofilme foi avaliada pela aderencia em microplaca, e a presenca do gene blaZ por PCR. Isolados de caprinos nao foram resistentes a oxacilina, mas, 25% foram resistentes a penicilina e 25% a ampicilina. Nos isolados de bovinos, 23% apresentaram resistencia a oxacilina, 67% a ampicilina e 64% a penicilina G. Em 46% dos isolados de bubalinos, observou- 1Estudante de
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The growing trend in biodegradable and renewable materials has generated a demand for new food packaging applications. This study aimed to produce active cellulose-based papers incorporated with two different essential oil isolated active... more
The growing trend in biodegradable and renewable materials has generated a demand for new food packaging applications. This study aimed to produce active cellulose-based papers incorporated with two different essential oil isolated active compounds, eugenol, and linalool, to promote the inhibition of pathogenic bacteria's growth. Cellulose was extracted from eucalyptus sawdust by receiving chemical and mechanical treatment and incorporating the active compounds by microwave. FTIR, SEM, TGA, DSC, and antibacterial activity against E. coli, Salmonella, S. aureus, and L. monocytogenes characterized active papers prepared by casting. Cellulose–eugenol papers showed chemical interactions by hydrogen bonding, in concern to linalool paper bands, identified by FTIR results. Highlighting that after the active compound's addition, the hydrogen energy bond values decreased from 22.5 to 22.3 kJ mol−1, confirming the cellulose fibers' swelling with the oils, which slightly amorphized the papers. The active compounds changed the paper's morphology, increasing porosity and roughness, as seen in the SEM images. Besides, TGA indicated that the active compounds increased the papers' thermal resistance. The active papers exhibited excellent antimicrobial activity against all the microorganisms; the cellulose–eugenol papers demonstrated a more significant antibacterial effect (24 mm), with a larger inhibition zone than linalool paper (12 mm). These results revealed that cellulose-based papers containing eugenol or linalool have good potential to prepare antimicrobial edible papers or coatings for various types of food packaging applications.
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This work aimed to prepare nanocellulose-based Pickering emulsions using cinnamon essential oil. Different formulations were investigated by varying the preparation time, homogenization speed, oil and nanocellulose concentration, and... more
This work aimed to prepare nanocellulose-based Pickering emulsions using cinnamon essential oil. Different formulations were investigated by varying the preparation time, homogenization speed, oil and nanocellulose concentration, and morphology. The emulsions were first characterized by droplet size, morphologies, and storage stability. The Design of Experiments (DoE) was used to evaluate the parameter’s effects on the emulsions’ stability, and the emulsions with optimum particle size and stability were evaluated by antimicrobial activity. The more stable emulsions required higher energy in the system to obtain efficient emulsification. The cellulose nanocrystal (CNC) emulsions showed a 30% oil volume as a constant to obtain a low creaming index (34.4% and 42.8%) and zeta potential values around −29 mV, indicating an electrostatic stabilization. The cellulose nanofiber (CNF) emulsions showed 100% stability after a month using a 20% oil volume as a constant and Zeta potential values ...
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Abstract In recent year, the interest in environmentally friendly materials, like cellulose nanostructures (CNSs) has increased. Nanoscale dimensions, high surface area, low density, and high mechanical strength are examples of CNSs... more
Abstract In recent year, the interest in environmentally friendly materials, like cellulose nanostructures (CNSs) has increased. Nanoscale dimensions, high surface area, low density, and high mechanical strength are examples of CNSs properties that attract researchers' attention. CNSs stability and dispersity are the main limitations that prevent its application as nanofiller in polymeric matrices. In this work, the surface modification of CNSs was investigated. To overcome CNSs limitation, they were modified with polyethylene glycol (PEG), in aqueous solution, in different proportions: 2, 5 and 10 wt%. FTIR, elemental analysis, NMR, and XPS were carried out to verify the adsorption efficiency. The results showed an excellent adsorption of PEG chains on the CNSs surface, with particle size increase of 50–90 nm and a considerable increase in thermal stability. XRD and AFM analysis observed no significant variation in crystallinity and morphology in modified CNSs. Thus, modification of CNSs with PEG is an environmentally friendly process and showed positive results regarding improving CNSs stability, in aqueous media.
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The influence of the different contents of organo-modified montmorillonite clay (1 and 3%wt.) and two essential oils (Carvacrol and Eugenol - 2 and 6%wt.) when incorporated into low-density polyethylene films (LDPE) was characterized by... more
The influence of the different contents of organo-modified montmorillonite clay (1 and 3%wt.) and two essential oils (Carvacrol and Eugenol - 2 and 6%wt.) when incorporated into low-density polyethylene films (LDPE) was characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). This study shows the potential of montmorillonite clay as a carrier of carvacrol and eugenol essential oils, ClayC and ClayE, respectively, into LDPE nanocomposites. To prepare the nanocomposites, oils and clay hybrid were mixed and added to polyethylene using a homogenizer. The clay increased the thermal stability of the essential oils. PE/ClayC and PE/ClayE nanocomposites showed increased crystallinity as a function of the amount of hybrid; this was more significant for the PE/ClayC system. Increased crystallinity suggests that clay acts as nucleating agent, due its intercalated/exfoliated configuration. The results contribute to obtaining a more efficient nanocomposite system for subsequent applications, such as active packaging. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers