Advanced Materials Research Vols. 123-125

Abstract: The search for materials from renewable sources such as vegetable oil-based polymers, polyurethane based on castor oil represents a promising alternative in researches. Using castor oil polyurethane as matrix for composites reinforced with lignin and cellulose from sugarcane straw is in tune with economical and environmental interests. The objective of this work was the evaluation of the changes on the structure and thermal behavior of castor oil polyurethane composites reinforced with lignin and cellulose from sugarcane straw. The cellulose and lignin were extracted from the straw by acid hydrolysis and then they were milled. For the production of the polyurethane, the mass reason between polyol (castor oil) and diisocyanate was 1.5:1.0. Reinforcement of the matrix was done changing the concentration of cellulose and lignin. SEM micrographs of fractured surfaces of the obtained composites and thermal analysis (TGA) were done. No lignin could be seen in SEM micrographs, what suggests a blend material behavior. The addition of cellulose fibers (30%) and lignin (40%) to the polyurethane matrix has caused an increase of the stiffness in the resulting composite when compared with the pure matrix. Above these rates, stiffness decreases. The presence of lignin or cellulose fibers in polyurethane matrix seems to increase mechanical properties of the composite, and also introduce better thermal stability than the pure matrix. Its presence might also bring other significant synergetic properties to the final composite, what has currently been studied. At the same time, the blend behavior of Polyurethane-Lignin composites has been investigated.

Abstract: Development of composite materials requires reinforcement and matrix in which fiber is finest suitable material for reinforcement which improves properties of materials. The use of high strength fiber leads to birth of advanced composites, which are mainly used, for high strength application or aerospace application. However, the use of medium strength and low strength fiber available in nature are also having enough potential for other application where high strength are not critical but it can provide a feasible range of alternative materials to suitable conventional material. Several billion tons of fillers and reinforcements are used annually in the plastics industry, and there is a huge potential market for recyclable, energy efficient and more environmentally friendly composite materials. The present work examines the different types of natural fiber available for the development potential composites. The attempts are already made for jute, flax and sisal natural fibers provides data from literature but there is lack of experimental data availability for unidirectional natural fiber composite like cotton, pineapple, banana fiber reinforced unidirectional composite. It is decided to carry out the systematic experimental study for the effect of volume fraction of reinforcement on longitudinal strength as well as elastic modulus using developed mould-punch set up and testing aids. The testing is carried out as per ASTM D3039/3039M-08. Specimen failure inspection was carried out through Scanning Electron Microscope (Model: Hitachi S-3400N). The comparative assessment of obtained experimental results with predictive models forms an equally important constituent of present work.

Abstract: In this research, short jute fiber reinforced polylactide composite, unidirectional long fiber reinforced polylactide composite and a sandwich structure polylactide composite were fabricated and the mechanical properties were tested. The mechanical properties of the fabricated composites were compared with those of a prototype spare tyre compartment cover of a passenger car. Tensile strength and flexural strength of all the composites are higher than those of the spare tyre compartment cover. The results show that the polylactide composites are applicable to car interior plates.

Abstract: In order to improve the interfacial bonding with polylactic acid, Lyocell fabric’s surfaces were treated with various silanes. The silanes applied were aminoethylaminopropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane, respectively. Silane was chosen since hydroxyl group (-OH) in silane always reacts with -OH in Lyocell fabric. As received fabric’s sizing was with a solution containing polyvinyl alcohol (PVA), poly acrylic acid (PAA) and water at the ratio of 3 : 1 : 96. Highest peel test results was obtained with 3wt% silane concentration (3-methacryloxypropyltrimethoxysilane). Highest tensile strength was obtained with 2wt% silane concentration (3-methacryloxypropyltrimethoxysilane). Tensile tests were carried out before analyzing the fracture surface of the composites by scanning electron microscope. FT-IR run confirmed the silane on the surface of fabric.

Abstract: Composites with polypropylene (PP) and lyocell fibers were manufactured by compression molding technique. In order to improve the interfacial adhesion between the natural fibers and thermoplastic matrix during manufacturing, maleic anhydride grafted polypropylene (MAPP) as a coupling agent has been employed. Physical properties such as void contents and water absorption rate were studied. Tensile and flexural tests were carried out to evaluate the composite mechanical properties. Tensile test results showed the higher strength and modulus of composite than pure polypropylene (PP). In addition, strength and modulus were found to be influenced by the variation of MAPP contents (1%, 2%). Unlike tensile properties, flexural properties were not improved. However, between 1 and 2 wt% MAPP content, the composites containing 2 wt % MAPP showed better flexural properties than 1 wt % MAPP.

Abstract: This paper deals with the characterization of high strength and functional natural fiber reinforced composite materials which are fabricated using starch-based biodegradable resin and Manila hemp fiber. Hemp fiber reinforced cross-ply composites were prepared by a conventional hot-pressing method. Their mechanical characterization was carried out by evaluating tensile strength as a function of fiber content. It can be seen that the tensile strength of the cross-ply composites was saturated over 50 wt% due to the interaction between warp and weft during the hot-pressing. However in the case of flexible weft; such as cotton thread or resin fiber, the tensile strength of the cross-ply composites almost linearly increased with increasing fiber content. The biodegradation behavior of the hemp fiber reinforced unidirectional composites was also examined by burying them into compost media. The changes in surface morphology of the specimen and in specimen weight loss were monitored for 30 days. It is apparent that the natural fiber reinforced composites showed an enhanced biodegradation speed. This enhanced biodegradation behavior seems to be derived from increased apparent surface area of the composite specimen due to the preferential biodegradation at interface between hemp fiber and biodegradable resin as well as the preferential water transportation through internal cavity in hemp fiber.

Abstract: Polylactic acid (PLA) and natural rubber (NR) were melt blended with vetiver grass fiber using an internal mixer. Heat treatment at the temperature of 180°C was done to obtain heat treated vetiver grass fiber. Glycidyl methacrylate grafted natural rubber (NR-g-GMA) was used as a compatibilizer of PLA/vetiver/NR composites. The injection molding and compression molding were used to prepare the specimens. Molecular weight determination of PLA before and after processing was done by Gel Permeable Chromatography (GPC).Comparisons between the mechanical properties of the composites prepared from injection molding and compression molding were made.

Abstract: Sisal fiber/natural rubber (NR) composites were prepared by the incorporation of sisal fiber into NR at various content (10, 20, 30 phr) using a two-roll mill. Natural rubber grafted with maleic anhydride (NR-g-MA) prepared in house was used to improve interfacial adhesion between sisal fiber and NR matrix. NR-g-MA contents were varied. Mechanical properties, morphologies, and cure characteristics of the composites were studied. Maximum torque, modulus at 100% strain (M100), modulus at 300% strain (M300), and hardness of the composites increased with increasing fiber content while scorch time, cure time, tensile strength, and elongation at break decreased. The addition of NR-g-MA into the composites gave a positive impact on M100, M300, tensile strength, and hardness. Moreover, increasing NR-g-MA content resulted in increased scorch time, cure time, maximum torque, M100, M300, tensile strength, and hardness of the composites. SEM micrographs of the composites revealed that the addition of NR-g-MA into the composites improved the interfacial interaction between sisal fiber and NR matrix. In addition, the compatibilized NR composites exhibited higher specific tensile strength and modulus than the carbon black/NR composites.

Abstract: The present study deals with the preparation of natural fiber reinforced polystyrene composites by compression molding technique in which good interfacial adhesion is generated by fiber surface modification. The fiber surface was modified through graft copolymerization of methyl methacrylate onto the fiber surface. The short grafted fibers were then spread between the alternate layers of polystyrene resin by hand lay up method to obtain the composites. The samples of the composites thus prepared were characterized by FTIR spectroscopy, scanning electron microscopy and thermogravimetric analysis. The composites were then evaluated for mechanical properties like tensile strength, compressive strength, flexural strength and wear resistance etc.

Abstract: Electrophoretic deposition (EPD) technique was applied to deposit carbon nanotubes on a carbon fabric. Optimization of EPD conditions was investigated to improve electrical conductivity for CNTs/carbon fiber hybrid multiscale composites by Taguchi method. Based on design of experiment, a L9(3)4 orthogonal array was chosen to conduct experiments. Due to the electrical conductivity of composites increased with the increasing content of CNTs in composites, it was selected as the response on the analysis of the means (ANOM) and the signal to noise (S/N) ratio. In addition, scanning electron microscopy (SEM) was utilized to examine the distribution of CNTs on the surface of a carbon fabric. The statistical software MINITAB 14 was utilized to determine the optimal deposition conditions.