Abstract Graphene and reduced graphene oxide are promising materials that are increasingly used in the field of polymer materials. In this study, reduced graphene oxide was prepared by chemical exfoliation of graphite, and subsequently, used in different amounts of 0.05, 0.2 and 2.0 wt.% in poly(ethylene-co-vinyl acetate) - EVA nanocomposites and foams. The approach used to prepare the reduced graphene oxide showed good efficiency with nanometer-scale particles and an average number of eight layers. Reduced graphene oxide in water suspension was introduced into the EVA by thermofusion using a closed mixer. Subsequently, sheets and foams were prepared by thermocompression molding using chemical expansion and crosslinking agents. The leading results suggest that the presence of reduced graphene oxide could change the cell morphology of the foam by increasing the cell density and decreasing its size. The sample containing 2 phr of reduced graphene oxide exhibited lower density and higher resistance to compression compared to pure EVA. study graphite subsequently 005 0 05 0.05 02 0. 20 2. wt wt. polyethylenecovinyl poly ethylene co vinyl acetate nanometerscale nanometer scale layers mixer Subsequently agents size 00 0.0

RESUMO Neste trabalho foram utilizados resíduos de Medium Density Fiberboard (MDF) e madeira como cargas de reforço em compósitos de estrutura sanduiche. O MDF foi utilizado em diferentes proporções em espumas rígidas de poliuretano (PU) bem como em diferentes granulometrias; as placas externas foram produzidas com um compósito de polietileno de baixa densidade (PEBD) e copolímero de etileno acetato de vinila (EVA) (80:20) reforçadas com pó de madeira Pinus elliottii (20%). As espumas foram avaliadas quanto a resistência à compressão, densidade e morfologia. Já os compósitos com estrutura sanduíche foram avaliados quanto a resistência à flexão e isolamento térmico. Observou-se aumento na densidade das espumas com aumento do teor de cargas e redução de até 0,05 MPa na resistência à compressão quando adicionado cargas de MDF. A inserção de cargas nas espumas de PU gera colapso das células, levando a maior contração da espuma durante o processo de expansão. Nas análises realizadas no compósito com estrutura sanduíche, observou-se uma variação na resistência a flexão, com resistências superiores à espuma de PU puro para os compósitos com o núcleo de PU10A e PU10B, e valores de resistência menores nas demais amostras com carga. (MDF sanduiche (PU granulometrias PEBD (PEBD EVA (EVA 8020 80 20 (80:20 20%. 20% . (20%) morfologia térmico Observouse Observou se 005 0 05 0,0 células expansão observouse observou PUA PU10B PUB B carga 802 8 2 (80:2 (20% 00 0, (80: (20 (80 (2 (8 (

ABSTRACT In this work, waste Medium Density Fiberboard (MDF) and wood were used as reinforcing fillers in sandwich composites. MDF powder was used in different proportions in rigid polyurethane (PU) foams as well as in different grain sizes; the outer boards were produced with a composite of low-density polyethylene (LDPE) and ethylene vinyl acetate copolymer (EVA) (80:20) reinforced with Pinus elliottii wood powder (20%). The foams were assessed for compressive strength, density and morphology. The composites with a sandwich structure were evaluated for flexural strength and thermal insulation. An increase in the density of the foams was observed with an increase in the content and a reduction of up to 0.05 MPa in compressive strength when MDF fillers were added. The insertion of fillers in PU foams causes the cells to collapse, leading to greater contraction of the foam during the expansion process. In the analyses carried out on the composite with a sandwich structure, a variation in flexural strength was observed, with higher strengths at pure PU foam compared to the composites with the PU10A and PU10B core, and lower strength values in the other loaded samples. work (MDF (PU sizes lowdensity low LDPE (LDPE EVA (EVA 8020 80 20 (80:20 20%. 20% . (20%) morphology insulation 005 0 05 0.0 added collapse process PUA A PUB B core samples 802 8 2 (80:2 (20% 00 0. (80: (20 (80 (2 (8 (

Abstract A thermosetting epoxy polymer composed of diglycidyl ether of bisphenol A and triethylenetetramine (DGEBA/TETA) was modified by incorporating flexographic photopolymer plate residues (rubber microparticles). The photopolymer plate residues were processed in two ways: (a) by grinding and performing particle size classification (where the resulting samples were denoted PP) and (b) by polyester layer separation and grinding the elastomeric fraction by cryogenic grinding (where the resulting samples were denoted ER). Both residual particles were incorporated into the epoxy at concentrations of 2.5, 5 and 7.5 wt%. The main results indicate that PP was not efficient as a modifier of the epoxy system. A reduction in mechanical properties (maximum tensile strength and deformation) was observed in the samples produced with PP in different concentrations. But, when the ER is incorporated, an increase in tensile property and in the deformation capacity, as well as impact resistance was observed in samples produced with ER. Scanning electron microscopy analysis showed a greater presence of voids in formulations produced with PP, which corroborates the decrease in the tensile strength of these samples. DGEBA/TETA DGEBATETA DGEBA TETA (DGEBA/TETA rubber microparticles. microparticles . microparticles) ways (a where b (b ER) 25 2 2.5 75 7 7. wt wt% system maximum But capacity 2.

In this study, the effects of incorporating recycled photopolymer-plate residues from a packaging flexography process into polyester-glass fiber composites were examined. Ternary composites with an unsaturated polyester matrix with elastomer particles from recycled photopolymer-plate residues were evaluated using two types of glass fibers: in the forms of a fabric with bidirectional fibers and a blanket with multidirectional fibers. The composites were prepared by hand lay-up lamination using different rubber contents (0, 2.5, 5, and 10 wt% based on the polyester resin mass fraction), and were characterized for their void content, flexural and impact strengths, and dynamic mechanical properties. Primary results indicated that the incorporation of the rubber particles increased the difficulty of lamination, while promoting greater void formation with higher filler content. The rubber particles decreased the impact resistance properties but did not reduce the flexural strength or storage modulus, indicating that despite the elastomeric composition, this residue from the photopolymer plates showed a reinforcing rather than toughening character.

Abstract Oil spills into water have been an environmental concern since the beginning of large-scale oil extraction. In this study, flexible open-cell polyurethane (PU) foams with added microcrystalline cellulose (MCC) were formulated and chemically modified with organosilane for use as an absorbent system for oil spill cleanup in water. The influence of cellulose concentration on mechanical properties and chemical treatment with organosilane was evaluated. The primary findings indicate that the surface treatment of the solid fraction of the foams was effective, as indicated by the contact angle, increasing the hydrophobicity of the samples. Because of the increased roughness of the PU solid fraction and the cellulose reactivity, the mechanical compressive strength and thickness of the organosilane layer increased with increasing MCC content. However, the higher the MCC content in the composition, the higher was the density, which reduced the sorption capacity of the samples. largescale large scale extraction study opencell open cell (PU (MCC evaluated effective angle samples reactivity However composition density

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 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.

The objective of this study is to develop expanded composites of poly(ethylene-co-vinyl acetate) (EVA) filled with two vegetable reinforcements (banana fiber or wood flour) as well as to evaluate the influence of the type, size and concentration of these reinforcements on the cell growth and their morphological, mechanical, thermal and physical properties. The results indicated that the natural fibers act as nucleating agents and affect the cells stability during the formation of the cellular structure in the expanded composites. The mechanical properties of the expanded composites are directly related to the composite expansion degree. Comparative results of the use of vegetable residues indicate that wood flour reinforcement provides more homogeneous cells, while banana fibers restrict the expandability of the composite and its density.