Effect of coir fiber content and compatibilizer on the properties of unidirectional coir fiber/polypropylene composites

The main objective of this research was to study the effect of fiber content variation and stearic acid (SA) treatment on the fundamental properties of unidirectional coir fiber (CF) reinforced polypropylene (PP) composites. Several percentages of filler contents were used (10–40 wt %) in order to gain insights into the effect of filler content on the properties of the composites. Coir/PP composites were fabricated by compression molding, and the properties of composites were studied by physico-mechanical and thermal properties. The results from mechanical properties such as tensile strength (TS), tensile modulus (TM) and impact strength (IS) of the CF/PP composites were found to be increased with increasing fiber content, reached an optimum and thereafter decreased with further increase in fiber content. Treatment of the coir with SA as the coupling agent enhanced the mechanical properties, crystallization temperature and crystallinity of virgin PP and water desorption of the resulting composites, resulting from the improved adhesion between the CF and PP matrix. Scanning electron micrographs (SEM) of the tensile fractured samples showed improved adhesion between fiber and matrix upon treatment with SA. Interfacial shear strength (IFSS) of the composites was measured by single fiber fragmentation test (SFFT).     

Effect of fiber length on mechanical behavior of coir fiber reinforced epoxy composites

Fiber reinforced polymer composites have played a dominant role for a long time in a variety of applications for their high specific strength and modulus. The fiber which serves as a reinforcement in reinforced plastics may be synthetic or natural. To this end, an investigation has been carried out to make use of coir, a natural fiber abundantly available in India. Natural fibers are not only strong and lightweight but also relatively very cheap. The present work describes the development and characterization of a new set of natural fiber based polymer composites consisting of coconut coir as reinforcement and epoxy resin as matrix material. The developed composites are characterized with respect to their mechanical characteristics. Experiments are carried out to study the effect of fiber length on mechanical behavior of these epoxy based polymer composites. Finally, the scanning electron microscope (SEM) of fractured surfaces has been done to study their surface morphology.     

Physical and mechanical properties of jute, bamboo and coir natural fiber

A systematic study has been carried out to investigate the mechanical and physical properties of jute, bamboo and coir (brown and white) single fibers. The tensile properties (tensile strength, Young’s modulus and strain to failure) were determined by varying span length. Scanning electron microscopic analysis was also carried out to determine the physical properties of fibers in order to correlate with its strength, Young’s modulus and strain to failure. The Young’s modulus and strain to failure were corrected using newly developed equations. The study revealed that with increasing test span length the Young’s modulus increased and tensile strength as well as strain to failure decreased. This is because no extensometer could be used in this test set-up and machine displacement (denoted by α) was used for the modulus determination. It is also attributed that larger span length helps to minimize the machine displacement compared to smaller ones due to the reduced relative effect of slippage in the clamps. Among all fibers, the Young’s modulus of bamboo fiber was the highest. Jute fiber had smoother surface compared to other three examined fibers.     

Effect of chemical modifications on the performance of biodegradable photocured coir fiber

Coir fibers (Cocos nucifera) were treated with 1-ethyl-2-pyrrolidone (1-E-2-P) mixed with methanol (MeOH) under UV radiation. A series of solutions of different concentrations of 1-E-2-P in methanol along with a photoinitiator, Darocur-1173, were prepared. Monomer concentration, soaking time, and radiation dose were optimized in terms of grafting and mechanical properties. Ten percent 1-E-2-P, 6 min soaking time, and a 15th pass of radiation produced higher tensile strength (53 %) and elongation at break (230 %) than those of virgin fiber, as well as the highest grafting value (4.9 %). The effect of additives (1 %), such as urea and silane (3-trimethoxysilyl propyl methacrylate) on the properties of coir fiber was studied. Among the additives used, silane showed the best performance. For further improvement of the properties, the fibers were treated with alkali (potassium hydroxide) solution of different temperatures (0–60 °C). A 10 % alkali-treated fiber showed the best properties such as grafting (6.2 %), tensile strength (72 %) and elongation at break (330 %) over virgin fiber. The silane-treated fiber produced the minimum loss of the properties, as well as a lower water uptake than those of the untreated one. The effect of simulating weathering on the degradation properties of samples was also performed.     

Flexural characteristics of coir fiber reinforced cementitious composites

This study has examined the flexural properties of natural and chemically modified coir fiber reinforced cementitious composites (CFRCC). Coir fibers of two different average lengths were used, and the longer coir fibers were also treated with a 1 % NaOH solution for comparison. The fibers were combined with cementitious materials and chemical agents (dispersant, defoamer or wetting agent) to form CFRCC. The flexural properties of the composites, including elastic stress, flexural strength, toughness and toughness index, were measured. The effects of fiber treatments, addition of chemical agents and accelerated ageing of composites on the composites’ flexural properties were examined. The results showed that the CFRCC samples were 5–12 % lighter than the conventional mortar, and that the addition of coir fibers improved the flexural strength of the CFRCC materials. Toughness and toughness index, which were associated with the work of fracture, were increased more than ten times. For the alkalized long coir fiber composites, a higher immediate and long-term toughness index was achieved. SEM microstructure images revealed improved physicochemical bonding in the treated CFRCC.     

Effect of temperature and durations of heating on coir fibers

Biocomposites derived from polymeric resin and lignocellulosic fibers may be processed at temperatures ranging from 100 °C to 230 °C for durations of up to 30 min. These processing parameters normally lead to the degradation of the fiber's mechanical properties such as Young's modulus (E), ultimate tensile strength (UTS) and percentage elongation at break (%EB). In this study, the effect of processing temperature and duration of heating on the mechanical properties of coir fibers were examined by heating the fibers in an oven at 150 °C and 200 °C for 10, 20 and 30 min to simulate processing conditions. Degradation of mechanical properties was evaluated based on the tensile properties. It was observed that the UTS and %EB of heat treated fibers decreased by 1.17-44.00% and 15.28-81.93%, respectively, compared to untreated fibers. However, the stiffness or E of the fibers increased by 6.3-25.0%. Infra red spectroscopy (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) were used to elucidate further the influence of chemical, thermal and microstructural degradation on the resulting tensile properties of the fibers. The main chemical changes observed at 2922, 2851, 1733, 1651, 1460, 1421 and1370 cm⁻¹ absorption bands were attributed to oxidation, dehydration and depolymerization as well as volatization of the fiber components. These phenomena were also attributed to in the TGA, and in addition the TGA showed increased thermal stability of the heat treated coir fibers with reference to the untreated counterparts which was most probably due to increased recrystallization and cross linking. The microstructural features including microcracks, micropores, collapsed microfibrils and sort of cooled molten liquid observed on the surface of heat treated coir fibers from the scanning electron microscope (SEM) could not directly be linked to the effect of temperature and durations of heating although such features may have largely account for the lower tensile properties of heat treated coir fibers with reference to untreated ones.     

Effect of peroxide and softness modification on properties of ramie fiber

Ramie fiber is one of the natural cellulose fibers that have undergone rapid development due to its good performance. This study confirmed that hydrogen peroxide and isopropyl alcohol can be used as very efficient agents for simultaneous removal of non-cellulosic substances and improvement of ramie fiber properties. The factors influencing the properties of modified fiber with combined chemicals were investigated. Optimum treatment conditions were achieved at 85 °C, 60 min, pH 11.0, hydrogen peroxide concentration 7 %, and isopropyl alcohol concentration 4 %. SEM, XRD, and FT-IR were used to elucidate the effects of preparation and modification. Results showed that fiber preparation and chemical modification process in the same bath solution could successfully remove most of the gummy materials. The treated fibers demonstrated improved softness, elongation, and fineness properties as compared to the alkali or peroxide method.     

Effect of wheat bran addition on in vitro starch digestibility,physico-mechanical and sensory properties of biscuits

Biscuits contain high amount of fat and sugar thus having high calorie but low nutrient density. Wheat bran is a good source of dietary fibre (DF) and protein and is thus a good candidate for nutritional enrichment of cereal foods. The aim of this study was to understand the effect of bran incorporation and particle size reduction on biscuit microstructure, texture and in vitro starch digestibility. Five different biscuits containing 5–15% DF were produced. Two different particle sized wheat brans were used: coarse (450 μm) and fine (68 μm). Bran particle size reduction increased the elastic modulus and hardness of biscuits. Biscuits containing fine bran had visually more compact structure without any surface or internal defects than those with coarse bran. Fine bran containing sample had the highest hardness value. Sensory evaluation showed that roughness and breakdown of biscuits in the mouth was significant for the coarse bran with highest level of bran addition. The instrumental elastic modulus, stress and hardness were closely related to sensory hardness and strength to break. Increasing DF content from 5 to 15% increased hydrolysis index by 16%, from 32 to 37.     

Banana fiber-reinforced polypropylene composites: A study of the physico-mechanical properties

Banana fiber-reinforced polypropylene (PP) matrix composites were prepared by compression molding and their mechanical properties were evaluated. Banana fibers and matrices were irradiated with UV radiation at different intensities. Mechanical properties of irradiated banana fibers and matrices based composites were found to increase significantly compared to untreated counterparts. Optimized banana fibers were treated with 2-hydroxyethyl methacrylate (HEMA) solution and were cured in an oven at different temperatures for different curing times and then composites were fabricated. Monomer concentration, curing temperature and curing time were optimized with the extent of polymer loading and mechanical properties and showed better mechanical properties over untreated composites. Water uptake and simulating weathering test of the composites were also investigated.     

Effect of water and fiber length on the mechanical properties of polypropylene matrix composites

This paper presents the results of a current study on polypropylene matrix composites processed by injection, with two different glass fiber lengths and five different volume fractions. Physical and mechanical properties were obtained, namely flexural strength, stiffness modulus and fracture toughness. The mechanical properties of the composites increased significantly with the increase of the fibers volume fraction in agreement with the Counto model. The effect of water immersion time was also analysed. Immersion in water promotes a marked decrease in mechanical properties in the early seven-ten days, and afterwards tends to stabilize. Water causes a decrease of the relative strength which increases with fiber volume fraction and reaches about 29 % and 32 % for 20 % of 4.5 mm fiber length and for 25 % of 12 mm fiber length respectively, after 28 days immersion in water. Fracture toughness increases with fiber volume fraction and is always higher for 12 mm fiber length composites than for 4.5 mm fiber length composites.     

Macro-micro structure,antibacterial activity,and physico-mechanical properties of the mulberry bast fibers

In this paper, the mulberry fibers were successfully obtained by a new pretreatment named alkali-assisted microwave plus biological enzymatic technique (AMBET). The morphology, microstructure, physico-mechanical and antibacterial properties of the mulberry bast fibers were investigated by means of scanning electron microscope (SEM), Fourier Transform-Infrared (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), instron tensile tester and antibacterial testing. The results showed that impurities of the bast fibers could be removed by AMBET treatment. AMBET treated mulberry fiber was even, smooth and fine, and typical cellulose I in the mulberry fibers was confirmed by FTIR and XRD analysis. The crystallinity of the AMBET treated fibers was higher than that of the raw mulberry and chemical treated mulberry fibers. Thermal analysis indicated that the mulberry fibers had a good thermal stability. Moreover, the AMBET treated mulberry fibers showed excellent antimicrobial activities against S.aureus. The physical properties of the mulberry fibers indicated the AMBET treated mulberry fibers were ideal candidates for new textile materials.     

Effect of kenaf and EFB fiber hybridization on physical and thermo-mechanical properties of PLA biocomposites

Kenaf/empty fruit bunch/polylactic acid (kenaf/EFB/PLA) hybrid biocomposites were prepared using hot press technique. The ratio of fiber to polylactic acid was set at 60:40 with 1:1 ratio between kenaf and empty fruit bunch fibers. Physical, mechanical and thermal properties of hybrid biocomposites were subsequently characterized using Fourier transform infrared spectroscopy, scanning electron microscope, X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, tensile and water absorption tests. Test results indicated that mechanically stronger fiber was able to support the weaker fiber. Hybrid fiber biocomposite had higher crystallinity as compared to single fiber biocomposite. Water absorption of hybrid composite was higher as compared to single fiber composite. Thermal result revealed that hybridization of fiber was not significantly influence the thermal properties of composites. However, the presence of two different fibers proposed good wettability properties, which could reduce the formation of voids at the fibers-polymer interface and produce composites with high stiffness and strength.     

Mechanical properties of fragrant screwpine fiber reinforced unsaturated polyester composite: Effect of fiber length,fiber treatment and water absorption

Fragrant screwpine fiber reinforced unsaturated polyester composites (FSFRUPC) were subjected to water immersion tests in order to examine the effect of water absorption on the mechanical properties. FSFRUP composite specimen containing 30 % fiber volume fraction with fiber length of 3 mm and 9 mm was considered in this study. Water absorption test was performed by immersing specimen in sea, distilled and well water at room temperature under different time durations (24, 48, 72, 96, 120, 144, 168, 192, 216, 240 hours). The tensile, flexural and impact properties of the water absorption specimen were appraised and compared with those of the dry composite specimen as per the ASTM standard. The tensile, flexural and impact properties of FSFRUPC specimen were found to decrease with the increase in the percentage of moisture uptake. The percentage of moisture uptake of composite was reduced after alkali treatment with 3 % NaoH for 3 hours. In moisture absorption test, the lowest diffusion coefficient, D (6.62513×10^-13 m²/s) and swelling rate parameter, K _sr (6.341×10^-3 h^-1) were obtained through the specimen immersed in sea water. The chemical composition, elemental composition of fiber and surface morphology of the FSFRUPC were analysed by using Fourier transform infrared spectroscopy (FTIR), Energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM) respectively.     

Effect of impact force on tensile properties and fiber splitting of splittable bicomponent hydroentangled fabrics

The effect of impact force when using inclined water jets on splittable bicomponents hydroentangled fabrics are investigated focusing on changes in tensile properties and fiber splitting. The results indicated that with increase of impact force, the tensile strength was increased in both machine direction (MD) and crosswise direction (CD). On changing of water jet inclination angle, the tensile strength was the highest at 10 degree followed by 20 degree and the last 0 degree. The highest fiber splitting were observed in pie segment (PA6/PET) followed by island in sea (PA6/COPET) fiber but no fiber splitting was observed for island in sea (PET/COPET) fiber. The impact force in inclined mode of impact, played a great role in improving fiber splitting and tensile properties of hydroentangled nonwoven fabrics. The Scanning Electron Microscope (SEM) photos were used for investigation of fiber splitting by comparing fiber diameter before and after hydroentanglement.     

Effect of temperature and time on mechanical and electrical properties of HDPE/glass fiber composites

In recent years, composites based on glass fiber reinforced polymer have been widely used in order to meet increasing durability and safety regulations, particularly in the power cable, automotive and plane industry. In this paper, mechanical and electrical properties of high density polyethylene (HDPE) and HDPE containing glass fiber polymer composites were investigated and compared at different temperatures. Composite materials were prepared with the hot pressing method. Tensile strength, % elongation and the modulus of elasticity (or Young’s modulus) were determined for each sample at different temperatures. In addition to this, at different temperatures τ _σ and τ _E have mechanical and electrical lifetime respectively, corresponding to mechanical tension (σ) and electrical strength (E), and this was investigated for each sample. As compared to the mechanical and electrical properties of neat HDPE, HDPE/0.5 % glass fiber composites have been found to have better mechanical and electrical durability.     

Effect of polypropylene fiber cross sectional shapes on some structural/mechanical fiber properties and compressibility behaviour of plain knitted fabrics

Synthetic fibers are generally produced with circular cross sectional shapes. Other cross sectional shaped fibers such as trilobal, triangular, hollow and pentagonal fibers are also produced to improve some properties of fibers and fabrics such as lustre, handle, wicking rate, strength, stiffness and bulkiness. In this research we aimed to investigate compressional behaviours of fabrics knitted from polypropylene fibers having three different cross sectional shapes; namely circular, trilobal and triangular. Morphological, structural and mechanical properties of produced fibers were evaluated by using scanning electron microscopy, X-ray diffractometry, differential scanning calorimetry and tensile tester, respectively. In terms of structural and mechanical properties, no significant differences were found related to fiber cross sectional shapes. Then, plain knitted farbrics were produced and compressional properties of these fabrics were investigated. Fabrics knitted from trilobal fibers showed the highest compressibility properties and it is followed by fabrics which are produced from triangular and circular fibers.     

Effect of soaking corrosion on flexural properties of carbon fiber reinforced epoxy syntactic foams

The fiber-reinforced syntactic foam is a type of lightweight materials. In this paper, hollow glass microspheres/epoxy syntactic foams reinforced by carbon fibers are prepared. Carbon fibers of five mass fractions are used to obtain five types of reinforced syntactic foams. The effect of the fiber content and soaking corrosion on the flexural properties of syntactic foams are investigated. The results of soaking test show that the moisture rate in distilled water is greater than that in seawater. The flexural test results show that the flexural strength of syntactic foams increases obviously by adding fibers. The maximum value increases 25.5 % than that of composites without adding fibers when fiber-mass fraction is 5 %. Soaking corrosion reduces the flexural properties of the syntactic foams. The flexural strengths of syntactic foams immersed in water and seawater with 5 % fiber-mass fraction decrease 34.4 % and 37.5 % respectively. The main reasons of the flexural strength reduction of syntactic foams with soaking corrosion are discussed.     

Effect of the low and radio frequency oxygen plasma treatment of jute fiber on mechanical properties of jute fiber/polyester composite

We investigated the surface modification of jute fiber by oxygen plasma treatments. Jute fibers were treated in different plasma reactors (radio frequency “RF” and low frequency “LF” plasma reactors) using O₂ for different plasma powers to increase the interface adhesion between jute fiber and polyester matrix. The influence of various plasma reactors on mechanical properties of jute fiber-reinforced polyester composites was reported. Tensile, flexure, short beam shear tests were used to determine the mechanical properties of the composites. The interlaminar shear strength increased from 11.5 MPa for the untreated jute fiber/polyester composite to 19.8 and 26.3 MPa for LF and RF oxygen plasma treated jute fiber/polyester composites, respectively. O₂ plasma treatment also improved the tensile and flexural strengths of jute fiber/ polyester composites for both plasma systems. It is clear that O₂ plasma treatment of jute fibers by using RF plasma system instead of using LF plasma system brings about greater improvement on the mechanical properties of jute/polyester composites.     

Effect of cross-sectional morphology and composite structure of glass fiber felts on their corresponding acoustic properties

This paper presents the effect of cross-sectional morphologies and composite structures of glass fiber felts on their corresponding acoustic properties. Glass fiber felts with random and layered cross-sectional structure are produced by centrifugal-spinneret-blow system. Acoustic properties are determined by a B&K impedance tube. The results show that sound transmission loss (STL) of glass fiber felts with layered cross-sectional structure exhibit greater than that with random cross-sectional structure. However, there is a little difference between the absorption coefficient values for random and layered cross-section. It means that glass fiber felts with layered cross-section are better to improve the sound insulation. With the increase of thickness, STLs of glass fiber felts with the same areal density do not increase monotonically due to the changing of porosity and characteristic impedances. Different glass fiber felts with layered cross-sectional structure are combined to form a variety of composite structures. It finds that assembly order of glass fiber felts have an effect on the total sound insulation. The large mismatch between the acoustic impedances causes multiple reflections leading to the best STL.     

Effect of chemically modified date palm leaf fiber on mechanical,thermal and rheological properties of polyvinylpyrrolidone

Polyvinylpyrrolidone/date palm leaf fiber (PVP/DPL) biocomposites were prepared by melt mixing fabrication technique with different weight percentage of fibers. DPL fibers were chemically modified by acrylic acid in order to have better dispersion and compatibility with PVP matrix. The interaction of DPL fibers with PVP matrix was studied by Fourier transforms infrared spectroscopy (FTIR). Field emission scanning electron microscope (FESEM) was used for the study the morphology of chemically modified DPL fibers and PVP/DPL biocomposites. Mechanical properties were improved with fiber loading due to strong interfacial adhesion between PVP and DPL fibers. The storage modulus, loss modulus and tan delta values of PVA/DPL biocomposites were measured by DMTA. The rheological properties were investigated to study the shearing storage and loss modulii along with complex viscosity of biocomposites. The thermal and conducting properties of biocomposites were measured and compared with that of virgin PVP.