Ionized-air-treated curaua fibers as reinforcement for phenolic matrices

Curaua fibers were treated with ionized air to improve the fiber/phenolic matrix adhesion.The treatment with ionized air did not change the thermal stability of the fibers. The impact strength increased with increase in the fiber treatment time. SEM micrographs of the fibers showed that the ionized air treatment led to separation of the fiber bundles. Treatment for 12 h also caused a partial degradation of the fibers, which prompted the matrix to transfer the load to a poorer reinforcing agent during impact, thereby decreasing the impact strength of the related composite. The composites reinforced with fibers treated with ionized air absorbed less water than those reinforced with untreated fibers.

Surface esterification of cellulose fibres: Processing and characterisation of low-density polyethylene/cellulose fibres composites

Low-density polyethylene was filled with cellulose fibres from sugar cane bagasse obtained from organosolv/supercritical carbon dioxide pulping process. The fibres were also used after chemical modification with octadecanoyl and dodecanoyl chloride acids. The morphology, thermal properties, mechanical properties in both the linear and nonlinear range, and the water absorption behaviour of ensuing composites were tested. The evidence of occurrence of the chemical modification was checked by X-ray photoelectron spectrometry. The degree of polymerisation of the fibres and their intrinsic properties (zero tensile strength) were determined. It clearly appeared that the surface chemical modification of cellulose fibres resulted in improved interfacial adhesion with the matrix and higher dispersion level. However, composites did not show improved mechanical performances when compared to unmodified fibres. This surprising result was ascribed to the strong lowering of the degree of polymerisation of cellulose fibres (as confirmed by the drastic decrease of their zero tensile strength) after chemical treatment despite the mild conditions used. (c) 2007 Elsevier Ltd. All rights reserved.

Biobased composites from tannin-phenolic polymers reinforced with coir fibers

Tannin-phenolic polymers prepared using tannin, a macromolecule obtained from natural sources, were used in the preparation of composites reinforced with coir fibers. The composites based on tannin-phenolic polymers (50% (w/w) of tannin as substitute of the phenol) were prepared using the coir fibers as reinforcement (30-70% (w/w), 3.0-6.0 cm, randomly distributed). The Izod impact strength of the composites showed an improvement in this property due to the incorporation of coir fibers in the tannin-phenolic matrices. The SEM images showed excellent adhesion at the fiber/matrix interface. The coir fiber had bundles regularly spaced, which enhanced the diffusion of the resin into the fiber. In addition, the high lignin content of this fiber results in a high concentration of aromatic rings, which increased the compatibility with the matrix. The values of the diffusion coefficient of water, determined using Fick`s laws, show that there was no correlation between the fiber percentage and the water diffusion. The DMTA curves showed that the storage moduli of the composites reinforced with coir fibers were considerably higher than that of the thermoset, and the increase in the proportion of fibers led to a proportional increase in the storage moduli of these materials. The biobased composites obtained have potential for non-structural applications, such as in the internal parts of automotives vehicles. To our knowledge, this is the first study on this kind of biobased composites. (C) 2010 Elsevier B.V. All rights reserved.

Biobased composites from glyoxal-phenolic resins and sisal fibers

Lignocellulosic materials can significantly contribute to the development of biobased composites. In this work, glyoxal-phenolic resins for composites were prepared using glyoxal, which is a dialdehyde obtained from several natural resources. The resins were characterized by (1)H, (13)C, (2)D, and (31)P NMR spectroscopies. Resorcinol (10%) was used as an accelerator for curing the glyoxal-phenol resins in order to obtain the thermosets. The impact-strength measurement showed that regardless of the cure cycle used, the reinforcement of thermosets by 30% (w/w) sisal fibers improved the impact strength by one order of magnitude. Curing with cycle 1 (150 degrees C) induced a high diffusion coefficient for water absorption in composites, due to less interaction between the sisal fibers and water. The composites cured with cycle 2 (180 degrees C) had less glyoxal resin coverage of the cellulosic fibers, as observed by images of the fractured interface observed by SEM. This study shows that biobased composites with good properties can be prepared using a high proportion of materials obtained from natural resources. (C) 2009 Elsevier Ltd. All rights reserved.

Pineapple Leaf Fibers for Composites and Cellulose

Pineapple leaf fiber (PALF) which is rich in cellulose, abundantly available, relatively inexpensive, low density, nonabrasive nature, high filling level possible, low energy consumption, high specific properties, biodegradability and has the potential for polymer reinforcement. The utilization of pineapple leaf fiber (PALF) as reinforcements in thermoplastic and thermosetting resins in micro and nano form for developing low cost and lightweight composites is an emerging field of research in polymer science and technology. In this paper we examines the industrial applicabiliy of PALF, mainly for production of composite materials and special papers, chemical feedstocks (bromelin enzyme) and fabrics.

Phenolic matrices and sisal fibers modified with hydroxy terminated polybutadiene rubber: Impact strength, water absorption, and morphological aspects of thermosets and composites

The aim of the present work was to investigate the toughening of phenolic thermoset and its composites reinforced with sisal fibers, using hydroxyl-terminated polybutadiene rubber (HTPB) as both impact modifier and coupling agent. Substantial increase in the impact strength of the thermoset was achieved by the addition 10% of HTPB. Scanning electron microscopy (SEM) images of the material with 15% HTPB content revealed the formation of some rubber aggregates that reduced the efficiency of the toughening mechanism. In composites, the toughening effect was observed only when 2.5% of HTPB was added. The rubber aggregates were found located mainly at the matrix-fiber interface suggesting that HTPB could be used as coupling agent between the sisal fibers and the phenolic matrix. A composite reinforced with sisal fibers pre-impregnated with HTPB was then prepared; its SEM images showed the formation of a thin coating of HTPB on the surface of the fibers. The ability of HTBP as coupling agent between sisal fibers and phenolic matrix was then investigated by preparing a composite reinforced with sisal fibers pre-treated with HTPB. As revealed by its SEM images, the HTPB pre-treatment of the fibers resulted on the formation of a thin coating of HTPB on the surface of the fibers, which provided better compatibility between the fibers and the matrix at their interface, resulting in a material with low water absorption capacity and no loss of impact strength. (C) 2009 Elsevier B.V. All rights reserved.

Cassava bagasse cellulose nanofibrils reinforced thermoplastic cassava starch

Cellulose cassava bagasse nanofibrils (CBN) were directly extracted from a by-product of the cassava starch (CS) industry, viz. the cassava bagasse (CB), The morphological structure of the ensuing nanoparticles was investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), presence of other components such as sugars by high performance liquid chromatography (HPLC), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) experiments. The resulting nanofibrils display a relatively low crystallinity and were found to be around 2-11 nm thick and 360-1700 nm long. These nanofibrils were used as reinforcing nanoparticles in a thermoplastic cassava starch matrix plasticized using either glycerol or a mixture of glycerol/sorbitol (1:1) as plasticizer. Nanocomposite films were prepared by a melting process. The reinforcing effect of the filler evaluated by dynamical mechanical tests (DMA) and tensile tests was found to depend on the nature of the plasticizer employed. Thus, for the glycerol-plasticized matrix-based composites, it was limited especially due to additional plasticization by sugars originating from starch hydrolysis during the acid extraction. This effect was evidenced by the reduction of glass vitreous temperature of starch after the incorporation of nanofibrils in TPSG and by the increase of elongation at break in tensile test. On the other hand, for glycerol/sorbitol plasticized nanocomposites the transcrystallization of amylopectin in nanofibrils surface hindered good performances of CBN as reinforcing agent for thermoplastic cassava starch. The incorporation of cassava bagasse cellulose nanofibrils in the thermoplastic starch matrices has resulted in a decrease of its hydrophilic character especially for glycerol plasticized sample. (C) 2009 Elsevier Ltd. All rights reserved.

Extrusion and characterization of functionalized cellulose whiskers reinforced polyethylene nanocomposites

The surface of ramie cellulose whiskers has been chemically modified by grafting organic acid chlorides presenting different lengths of the aliphatic chain by an esterification reaction. The occurrence of the chemical modification was evaluated by FTIR and X-ray photoelectron spectroscopies, elemental analysis and contact angle measurements. The crystallinity of the particles was not altered by the chain grafting, but it was shown that covalently grafted chains were able to crystallize at the cellulose surface when using C18. Both unmodified and functionalized nanoparticles were extruded with low density polyethylene to prepare nanocomposite materials. The homogeneity of the ensuing nanocomposites was found to increase with the length of the grafted chains. The thermomechanical properties of processed nanocomposites were studied by differential scanning calorimetry (DSC), dynamical mechanical analysis (DMA) and tensile tests. A significant improvement in terms of elongation at break was observed when sufficiently long chains were grafted on the surface of the nanoparticles. It was ascribed to improved dispersion of the nanoparticles within the LDPE matrix. (C) 2009 Elsevier Ltd. All rights reserved.

O efeito do tratamento da atapulgita no desenvolvimento de compósito com o polietileno reciclado

The study aimed at the treatment of attapulgite for the development and characterization of composite recycled low density polyethylene - PEBD_rec embedded with natural attapulgite - ATP_NAT, sifted - ATP_PN and attapulgite treated with sulfuric acid - ATP_TR in different compositions (1, 3 and 5%) and compared with the PEBD_rec. The atapulgitas, natural, screened and treated, were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), particle size analysis, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and determining the area specific surface (BET). The composites were characterized by thermogravimetry (TG), differential scanning calorimetry (DSC), Xray diffraction (XRD), torque rheometry, scanning electron microscopy (SEM) and traction. The composite PEBD_rec / ATP (natural, sieved and treated) were produced by mixing in the molten state in a single screw extruder matrix wire with subsequent reprocessing matrix tape. It was found that the screening of attapulgite not reduce the quantity of quartz and the acid treatment completely extracted dolomite aggregate impurities of the channels attapulgite, and increase their surface area. The addition of attapulgite in PEBD_rec acts as a catalyst, reducing the thermal stability of the polymer. The increased concentration of attapulgite, increases resistance and reduces the elongation at break and modulus of elasticity of the composite PEBD_rec / attapulgite

Tratamentos de fibras de carnaúba [copernicia prunífera (miller) h. e. moore] para o desenvolvimento de compósito biodegradável com matriz de polihidroxibutirato

The use of raw materials from renewable sources for production of materials has been the subject of several studies and researches, because of its potential to substitute petrochemical-based materials. The addition of natural fibers to polymers represents an alternative in the partial or total replacement of glass fibers in composites. In this work, carnauba leaf fibers were used in the production of biodegradable composites with polyhydroxybutyrate (PHB) matrix. To improve the interfacial properties fiber / matrix were studied four chemical treatments to the fibers..The effect of the different chemical treatments on the morphological, physical, chemical and mechanical properties of the fibers and composites were investigated by scanning electron microscopy (SEM), infrared spectroscopy, X-ray diffraction, tensile and flexural tests, dynamic mechanical analysis (DMA), thermogravimetry (TGA) and diferential scanning calorimetry (DSC). The results of tensile tests indicated an increase in tensile strength of the composites after the chemical treatment of the fibers, with best results for the hydrogen peroxide treated fibers, even though the tensile strength of fibers was slightly reduced. This suggests a better interaction fiber/matrix which was also observed by SEM fractographs. The glass transition temperature (Tg) was reduced for all composites compared to the pure polymer which can be attributed to the absorption of solvents, moisture and other low molecular weight molecules by the fibers

Efeito da adição do poli(etileno acrilato de metila) (ema) e da fibra de linter de algodão nas propriedades do poli(tereftalato de etileno) reciclado (petrec)

The development of new materials to fill the demand of technological advances is a challenge for many researchers around the world. Strategies such as making blends and composites are promising alternatives to produce materials with different properties from those found in conventional polymers. The objective of this study is to evaluate the effect of adding the copolymer poly(ethylene methyl acrylate) (EMA) and cotton linter fibers (LB) on the properties of recycled poly(ethylene terephthalate) (PETrec) by the development of PETrec/EMA blend and PETrec/EMA/LB blend composite. In order to improve the properties of these materials were added as compatibilizers: Ethylene - methyl acrylate - glycidyl methacrylate terpolymer (EMA-GMA) and maleic anhydride grafted polyethylene (PE-g-MA). The samples were produced using a single screw extruder and then injection molded. The obtained materials were characterized by thermogravimetry (TG), melt flow index (MFI) mensurements, torque rheometry, pycnometry to determinate the density, tensile testing and scanning electron microscopy (SEM). The rheological results showed that the addition of the EMA copolymer increased the viscosity of the blend and LB reduces the viscosity of the blend composite. SEM analysis of the binary blend showed poor interfacial adhesion between the PETrec matrix and the EMA dispersed phase, as well as the blend composite of PETrec/EMA/LB also observed low adhesion with the LB fiber. The tensile tests showed that the increase of EMA percentage decreased the tensile strength and the Young s modulus, also lower EMA percentage samples had increased the elongation at break. The blend composite showed an increase in the tensile strength and in the Young`s modulus, and a decrease in the elongation at break. The blend formulations with lower EMA percentages showed better mechanical properties that agree with the particle size analysis which showed that these formulations presented a smaller diameter of the dispersed phase. The blend composite mechanical tests showed that this material is stronger and stiffer than the blend PETrec/EMA, whose properties have been reduced due to the presence of EMA rubbery phase. The use of EMA-GMA was effective in reducing the particle size of the EMA dispersed phase in the PETrec/EMA blend and PE-g-MA showed evidences of reaction with LB and physical mixture with the EMA

Plásticos reforçados a base de tecidos híbridos: efeitos da anisotropia e geometria normativa na caracterização mecânica e da fratura

As most current studies, reinforced plastics have been, in recent years, a viable alternative in building structural elements of medium and large, since the lightness accompanied by high performance possible. The design of hybrid polymer composites (combination of different types of reinforcements) may enable structural applications thereof, facing the most severe service conditions. Within this class of composite materials, reinforced the underlying tissues hybrid high performance are taking space when your application requires high load bearing and high rigidity. The objective of this research work is to study the challenges in designing these fabrics bring these materials as to its mechanical characterization and fracture mechanisms involved. Some parameters associated with the process and / or form of hybridization stand out as influential factors in the final performance of the material such as the presence of anisotropy, so the fabric weave, the process of making the same, normative geometry of the specimens, among others. This sense, four laminates were developed based hybrid reinforcement fabrics involving AS4 carbon fiber, kevlar and glass 49-E as the matrix epoxy vinyl ester resin (DERAKANE 411-350). All laminates were formed each with four layers of reinforcements. Depending on the hybrid fabric, all the influencing factors mentioned above have been studied for laminates. All laminates were manufactured industrially used being the lamination process manual (hand-lay-up). All mechanical characterization and study of the mechanism of fracture (fracture mechanics) was developed for laminates subjected to uniaxial tensile test, bending in three and uniaxial compression. The analysis of fracture mechanisms were held involving the macroscopic, optical microscopy and scanning electron microscopy

Production of reinforced composites with natural fibers for industrial applications - Extrusion and injection WPC

The aim of this work is to study the replacement of currently used thermoplastics by composites reinforced with vegetable fibers with several advantages, mainly better mechanical properties, low weight and competitive cost compared to its counterparts. Extrusion and injection molding processes were studied using polypropylene (PP) matrix. The raw materials used were sugar cane bagasse, elephant grass, wood, milk cartons and recycled polypropylene. The composites were tested for bending, tension, hardness and impact resistance, following ASTM standards. The results obtained were extremely positive since they proved that natural fibers as reinforcement can be an important alternative to replace talc and other fillers.

Obtenção de compósitos cerâmicos baseados em Al2O3/TiC através dos precursores poliméricos

The obtaining of ceramic materials from polymeric precursors is subject of numerous studies due to lower energy costs compared to conventional processing. The aim of this study is to investigate and improve the mechanism for obtaining ceramic matrix composite (CMC) based on SiOC/Al2O3/TiC by pyrolysis of polysiloxane in the presence of an active filler and inert filler in the pyrolysis temperature lower than the usually adopted for this technique, with greater strength. It also investigates the influence of pyrolysis temperature, the content of Alas active filler, the presence of infiltrating agents (Al, glass and polymer) after pyrolysis, temperature and infiltration time on some physical and mechanical properties. Alumina is used as inert filler and Al and Ti as active filler in the pyrolysis. Aluminum, glass and polysiloxane are used as agents infiltrating the post-pyrolysis. The results are analyzed with respect to porosity and bulk density by the Archimedes method, the presence of crystalline phases by X-ray diffraction (XRD) and microstructure by scanning electron microscopy (SEM). The ceramic pyrolyzed between 850 °C 1400 °C contain porosity 15% to 33%, density 2.34 g/cm3 and flexural strength at 4 points from 30 to 42 MPa. The microstructure features are porous, with an array of Al2O3 reinforced by TiC particles and AlTi3. The infiltration post-pyrolysis reveals decrease in porosity and increase density and strength. The composites have potential applications where thermal stability is the main requirement

Avaliação da estrutura de tecidos técnicos como elemento reforçante em compósitos poliméricos sistema poliéster isoftálico

Materials known as technical textiles can be defined as structures designed and developed to meet specific functional requirements of various industry sectors, which is the case in automotive and aerospace industries, and other specific applications. Therefore, the purpose of this work presents the development and manufacture of polymer composite with isophthalic polyester resin. The reinforcement of the composite structure is a technical textile fabric made from high performance fibers, aramid (Kevlar 49) and glass fiber E. The fabrics are manufactured by the same method, with the aim of improving the tensile strength of the resulting polymer composite material. The fabrics, we developed some low grammage technical textile structures in laboratory scale and differentiated-composition type aramid (100%), hybrid 1 aramid fiber / glass (65/35%) and hybrid 2 aramid fiber / glass (85/15% ) for use as a reinforcing element in composite materials with unsaturated isophthalic polyester matrix. The polymer composites produced were tested in uniaxial tensile fracture surface and it´s evaluated by SEM. The purpose of this work characterize the performance of polymer composites prepared, identifying changes and based on resistance to strain corresponding to the mechanical behavior. The objectives are to verify the capability of using this reinforcement structure, along with the use of high performance fibers and resin in terms of workability and mechanical strength; verify the adherence of the fiber to the matrix and the fracture surface by electron microscopy scanning and determination of tensile strength by tensile test. The results indicate that, in a comparative study to the response of uniaxial tensile test for tensile strength of the composites and the efficiency of the low percentage of reinforcement element, being a technical textile fabric structure that features characteristic of lightness and low weight added in polymer composites