Transport studies of peanut shell powder reinforced natural rubber composites in chlorinated solvents

Composites of Natural rubber (NR) Peanut shell powder (PSP) were prepared and their morphology, transport behavior at different temperatures in chlorinated solvent were studied. The PSP used in compounding the natural rubber was processed in two particle sizes. The effect of modification by alkali treatment of PSP on polymer properties was also investigated. The computed solvent properties were discussed in terms of PSP content, particle size, nature of solvent, and temperature. All the NR-PSP composites were found to decrease with the uptake of chlorinated solvents than NR, but the effect was more significant in the case of alkali treated PSP composites. Furthermore, the uptake of solvent decreased with increase in penetrant size; being the highest for dichloromethane, and the lowest for carbon tetrachloride. Activation energy was found to be maximum for highest in dichloromethane at the filler contents investigated. The thermodynamic parameters of the sorption process were also evaluated. The results showed that PSP filler acts as functional additives capable of manipulating and tailoring the transport of chlorinated solvents through elastomeric membranes even at concentrations as low as 10 parts per hundred (phr). The relationship between the transport behaviour and the morphology of the system was also examined.     

Oil palm fiber (OPF) and its composites: A review

Twenty first century has witnessed remarkable achievements in green technology in material science through the development of biocomposites. Oil palm fiber (OPF) extracted from the empty fruit bunches is proven as a good raw material for biocomposites. The cellulose content of OPF is in the range of 43%–65% and lignin content is in the range of 13%–25%. A compilation of the morphology, chemical constituents and properties of OPF as reported by various researchers are collected and presented in this paper. The suitability of OPF in various polymeric matrices such as natural rubber, polypropylene, polyvinyl chloride, phenol formaldehyde, polyurethane, epoxy, polyester, etc. to form biocomposites as reported by various researchers in the recent past is compiled. The properties of these composites viz., physical, mechanical, water sorption, thermal, degradation, electrical properties, etc. are summerised. Oil palm fiber loading in some polymeric matrices improved the strength of the resulting composites whereas less strength was observed in some cases. The composites became more hydrophilic upon addition of OPF. However treatments on fiber surface improved the composite properties. Alkali treatment on OPF is preferred for improving the fiber–matrix adhesion compared to other treatments. The effect of various treatments on the properties of OPF and that of resulting composites reported by various researchers is compiled in this paper. The thermal stability, dielectric constant, electrical conductivity, etc. of the composites improved upon incorporation of OPF. The strength properties reduced upon weathering/degradation. Sisal fiber was reported as a good combination with OPF in hybrid composites.     

Mechanical properties of denim fabric reinforced poly(lactic acid)

Denim, a twilled cotton fabric, was used to enhance the mechanical and thermal properties of poly(lactic acid) (PLA). The denim fabric reinforced composites with different numbers of denim layers were fabricated by using a hand layup method. The impact, tensile, and dynamic mechanical properties of the composites were observed with increasing denim layers to examine the reinforcing effect of denim fabrics. Numerical analysis was carried out to model the elastic modulus of the composite by using a commercial software. Three-dimensional geometry of the denim fabric reinforced PLA composite was generated through a CAD program, and the elastic modulus was calculated by applying uniform deformation on one surface. The impact strength, tensile strength, and thermal properties of the composites were improved by piling denim fabrics. The denim fabric reinforced composites exhibited outstanding impact strength due to the retarded crack propagation as well as large energy dissipation. The 3 layer denim reinforced composite showed best results among all specimens, and its impact strength, tensile strength, and tensile modulus were measured to be 82 J/m, 75.76 MPa, and 4.65 GPa, respectively. The PLA/denim composites have good mechanical properties and can substitute traditional composites such as glass fiber or carbon fiber reinforced composites.     

Functionalized multi-walled carbon nanotubes with hyperbranched aromatic polyamide for poly(methyl methacrylate) composites

Multi-walled carbon nanotubes (MWCNTs) were functionalized with hyperbranched aromatic polyamide (HAP) by in situ polymerization and by the AB ₂ approach to enhance the mechanical properties of poly(methylmethacrylate) (PMMA) composites. Various concentrations of HAP-functionalized MWCNTs (HAP-f-MWCNTs) were used to prepare HAP-f-MWCNT-reinforced PMMA composite films. The covalent attachment of HAP to the MWCNTs, as achieved by in situ functionalization, resulted in effective dispersion of the MWCNTs in the PMMA matrix, thus enhancing the mechanical and thermal properties of the composite films. The breaking stress of the composites increased largely with the HAP-f-MWCNT loading.     

Grain of high digestible,high lysine (HDHL) sorghum contains kafirins which enhance the protein network of composite dough and bread

The aim of this study was to determine whether protein body-free kafirins in high digestibility, high-lysine (HDHL) sorghum flour can participate as viscoelastic proteins in sorghum-wheat composite dough and bread. Dough extensibility tests revealed that maximum resistance to extension (g) and time to dough breakage (sec) at 35 °C for HDHL sorghum-wheat composite doughs were substantially greater (p < 0.01) than for normal sorghum-wheat composite doughs at 30 and 60% substitution levels. Functional changes in HDHL kafirin occurred upon exceeding its T_g. Normal sorghum showed a clear decrease in strain hardening at 60% substitution, whereas HDHL sorghum maintained a level similar to wheat dough. Significantly higher loaf volumes resulted for HDHL sorghum-wheat composites compared to normal sorghum-wheat composites at substitution levels above 30% and up to 56%, with the largest difference at 42%. HDHL sorghum-wheat composite bread exhibited lower hardness values, lower compressibility and higher springiness than normal sorghum-wheat composite bread. Finally, HDHL sorghum flour mixed with 18% vital wheat gluten produced viscoelastic dough while normal sorghum did not. These results clearly show that kafirin in HDHL sorghum flour contributes to the formation of an improved protein network with viscoelastic properties that leads to better quality composite doughs and breads.     

The preparation and characterization of conductive poly(ethylene terephthalate)/polyaniline composite fibers using benzoyl peroxide

Conductive polyaniline (PAn)/poly(ethylene terephthalate) (PET) composite fibers were prepared by chemical polymerization of aniline in the presence of PET fibers using benzoyl peroxide (Bz₂O₂) in organic solvent/aqueous hydrochloric acid mixtures. The effects of polymerization conditions such as organic solvent/water ratio, oxidant, aniline and hydrochloric acid concentrations and temperature were investigated on the amount of PAn deposited on PET fiber and the electrical surface resistance of composite fibers. The maximum PAn content and the lowest electrical surface resistance of composite fibers were observed at HCl concentrations of 0.5 mol L⁻¹. The properties of PAn/PET composite fibers such as density, diameter, tensile strength and breaking elongation were also investigated in comparison with those of pure PET. Characterization of conductive composite fibers was carried out by FTIR, TGA, SEM techniques, surface resistance measurements, and cross section images taken by optical microscope.     

Effect of mercerization on mechanical, thermal and degradation characteristics of jute fabric-reinforced polypropylene composites

Jute fabric reinforced polypropylene composites were fabricated by compression molding technique. Fiber content in the composites was optimized at 45 % by weight of fiber by evaluating the mechanical parameters such as tensile strength, tensile modulus, bending strength, bending modulus. Surface treatment of jute fabrics was carried out by mercerizing jute fabrics with aqueous solutions of NaOH (5, 10 and 20 %) at different soaking times (30, 60 and 90 mins) and temperatures (0, 30 and 70 °C). The effect of mercerization on weight and dimension of jute fabrics was studied. Mechanical properties of mercerized jute-PP composites were measured and found highest at 20 % NaOH at 0 °C for 60 min soaking time. Thermal analytical data from thermogravimetric and differential thermal analysis showed that mercerized jute-PP composite achieved higher thermal stability compared to PP, jute fabrics and control composite. Degradation characteristics of the composites were studied in soil, water and simulated weathering conditions. Water uptake of the composites was also investigated.     

Enhanced thermal transport performance for poly(vinylidene fluoride) composites with superfullerene

High thermal conductive polymer composites have recently attracted much attention, along with the quick development to the electronic devices toward higher speed. The addition of high thermal conductive fillers is an efficient method to solve this problem. Here, we introduced superfullerene (SF), a novel zero-dimensional carbon-based filler, and incorporated into PVDF by a solution method. The effects of SF filler on the thermal conductivity of PVDF composites were systematically investigated. It was found that PVDF composites exhibited an improvement in thermal conductivity at a low SF loading. PVDF composites with only 5 wt% SF filler present the thermal conductivity value of 0.365 Wm^-1K^-1, which is as much as 121 % enhancement in comparison with that of neat PVDF. In view of the excellent thermal transport performance, the composites may enable some applications in thermal management in the future.     

Preparation and properties of pineapple leaf fiber reinforced poly(lactic acid) green composites

Green composites from Pattawia pineapple leaf fiber (PALF) and poly(lactic acid) (PLA) were prepared. The mechanical method was chosen to extract PALF from fresh leaves due to this method gave high yield of fiber, short extraction time, and environmental friendly. Tensile and thermal properties, together with morphology of the fibers were disclosed. The fibers were conducted into a specified length of 1–3 mm and blended with PLA, using a twin screw extruder, with the PALF content of 10–50 wt%. Tensile testing, morphology investigation and thermogravimetric analysis were applied. Preliminary results showed that tensile modulus of the composites depended on PALF content. The tensile modulus and elongation at break of the composite containing 40 % PALF was about 48 %, and 111 % increase, respectively, compared with that of PLA. With addition of maleic anhydride coupling agent, such the composite showed the tensile modulus of 5.1 GPa, which was 34 % higher than that of the non-coupling agent composite, and about 104 % higher than that of PLA. Although the elongation at break of the composite containing 40 % PALF was found to dramatically increase by 111 %, the introduction of maleic anhydride in such the composite caused only 57 % increase in the elongation at break compared with that of PLA. Finally, a pilot product of square boxes was produced successfully from the proposed composite, by conventional injection molding process.     

Shear modeling of fiber reinforced soil composite on the base of fiber pull-out test

The concept of reinforcing soil with natural fibers was originated in ancient times. However, short natural and synthetic fiber soil composites have recently attracted increasing attention in geotechnical engineering for the second time. Consequently in this work, shear behavior of fiber reinforced soil composite was modeled by using force-equilibrium method. The proposed model indicated that fiber percentage, fiber diameter, fiber aspect ratio, Elastic Modulus of fiber, coefficient of friction between fiber and matrix, the thickness of shearing zone and vertical compressive stress determine the shear resistance of a fiber reinforced soil composite. In the next step, a set of laboratory direct shear tests was performed on different samples including both neat soil and fiber reinforced treatments. In order to compare model outputs and experimental results, it was necessary to measure the coefficient of friction between fiber and soil. Therefore, a novel apparatus based on fiber pull-out test was designed to determine the interfacial shear stress between fiber and soil. Since, soil considers as a soft material and its mechanical properties depend on vertical stress, therefore, the Instron Tensile Tester was modified to provide fiber pull-out test through the soil matrix. Consequently, the proposed model adequately predicted shear behavior of fiber reinforced soil composite based on fiber pull-out test results.     

Green composites. II. Environment-friendly, biodegradable composites using ramie fibers and soy protein concentrate (SPC) resin

Fully biodegradable and environment-friendly green composite specimens were made using ramie fibers and soy protein concentrate (SPC) resin. SPC was used as continuous phase resin in green composites. The SPC resin was plasticized with glycerin. Precuring and curing processes for the resin were optimized to obtain required mechanical properties. Unidirectional green composites were prepared by combining 65 % (on weight basis) ramie fibers and SPC resin. The tensile strength and Young’s modulus of these composites were significantly higher compared to those of pure SPC resin. Tensile and flexural properties of the composite in the longitudinal direction were moderate and found to be significantly higher than those of three common wood varieties. In the transverse direction, however, their properties were comparable with those of wood specimens. Scanning electron microscope (SEM) micrographs of the tensile fracture surfaces of the green composite indicated good interfacial bonding between ramie fibers and SPC resin. Theoretical values for tensile strength and Young’s modulus, calculated using simple rule of mixture were higher than the experimentally obtained values. The main reasons for this discrepancy are loss of fiber alignment, voids and fiber compression due to resin shrinking during curing.     

A Statistical Framework for Selecting Natural Fibre Reinforced Polymer Composites Based on Regression Model

Material selection is an important stage in the development of products from composites process of automotive component application. Numerious different Multi-Criteria Decision-Making tools have their own strenghts and limitations. This paper presents a framework for material selection of natural fibre reinforced polymer composites by using statistical approach. The framework is developed using statistical methods which are simple, multiple and stepwise regression for the material selection process. The performance of potential material is investigated by a statistical analysis such as coefficient of correlation, coefficient of determination and analysis of variance. A case study to select the best composite of parking brake lever is applied to this framework. End results revealed that kenaf reinforced polypropylene is the best candidate for construction of automotive parking brake lever component. The best possible of statistical model for material selection of the composite can be referred by design engineer in composite industry for a multiple application. Moreover, the proposed framework is an aid to help engineers and designers to choose most suitable material.     

Characterization and electrochemical properties of poly(aniline-co-o-methoxyaniline)/multi-walled carbon nanotubes composites synthesized by solid-state method

The composites of copolymers of aniline (An) and o-methoxyaniline (OMA) with multi-walled carbon nanotubes, named as copolymers/MWNT, (poly(An-co-OMA)/MWNT) were prepared by solid-state synthesis method at room temperature. The homopolymers/MWNT composites were synthesized for comparison. The structure and morphology of these composites were characterized by FT-IR spectroscopy, UV-Vis absorption spectroscopy, X-ray diffraction (XRD) and TEM. The electrochemical performances of the composites were investigated by galvanostatic charge-discharge, cyclic voltammetry (CV) and cycle life measurements. The results from FT-IR and UV-Vis spectra showed that different molar ratio of [An]/[OMA] in reaction system has great influence on the oxidation degree, conjugation length and doping level of the copolymers in these composites. The presence of MWNT in the composites was confirmed from the characteristic peaks of MWNT in XRD patterns and the enwrapped MWNT in TEM images. The TEM images further indicates that the MWNT uniformly distributed and enwrapped with polymer in the case of composite from molar ratio of [An]/[OMA]=1:1. The results also showed that the morphology, crystallinity and solubility of composites were highly affected by the incorporation of OMA unit copolymer chain. The results from electrochemical performances suggested that the molar ratio of [An]/[OMA]=3:1 in reaction system can make the obtained composites displayed a higher specific capacitance, good rate ability and cycling stability.     

An Investigation on Wear and Dynamic Mechanical behavior of Jute/Hemp/Flax Reinforced Composites and Its Hybrids for Tribological Applications

Bio-materials have ignited a quest among research fraternity to be used in every possible field of applications like automobile, sports, medical, civil and textile industry. Application spectrum of natural fiber reinforced polymer composites is spreading globally in every field of engineering having structural and tribological applications. The present work investigates the tribological performance of regionally available inexpensive plant based natural fiber reinforced polymer composites. In this work, three different types of natural fibers (jute, hemp, and flax) were reinforced with epoxy matrix to fabricate natural fiber reinforced polymer composites (NFRP) and their hybrid composites (jute/hemp/Epoxy, hemp/flax/epoxy and jute/ hemp/flax/epoxy) using hand-layup technique. Tribological performance of the developed bio-composites were evaluated in terms of frictional characteristics and sliding wear under dry contact condition at different process parameters, such as applied load (10-50 N), sliding speed (1-5 m/s) and sliding distance (1000-2000 m). Experimental results of wear analysis confirmed that incorporation of natural fibers into epoxy polymer matrix significantly improved the wear behavior of the developed NFRP composites in comparison to neat epoxy polymer. Among all the developed composites, jute/epoxy composite achieved the highest coefficient of friction, frictional force and specific wear rate. Dynamic mechanical analysis (DMA) was also analyzed to evaluate the viscoelastic behavior of the developed composites. The surface morphology of samples after wear test was examined by scanning electron microscopy to investigate and propose the possible wear mechanism of the developed composites.     

Synthesis and characterization of electrically conductive composite films of polypyrrole/poly(acrylonitrile-co-styrene)

Homogeneus Polypyrrole (PPy)/poly(acrylonitrile-co-styrene) (SAN) composite thin films were prepared by chemical polymerization of pyrrole on poly(acrylonitrile-co-styrene) matrix. Ce (IV) is used as an oxidant for in-situ polymerizion of pyrrole on SAN matrix, having an advantageous over the impregnation method. The formation and incorporation of PPy in the copolymer matrix were confirmed by FTIR-ATR and UV-Visible spectrophotometric measurements. Thermal analyses showed that after polymerization of Py in copolymer matrix, thermal behavior of SAN was changed and derivative of weight loss at this temperature was increased by increasing of PPy content. XPS and FTIR-ATR analysis of composite films indicated cerium salt with nitrate ion acted as a dopant. The increase in the AC electrical conductivity of the PPy/SAN composites over pure SAN was observed. At lower frequency up to 10⁵ Hz, conductivity was shown an independent behavior from frequency; but at high frequencies (10⁵–10⁷ Hz), dependence on frequency was explained by polaron and bipolaron formations of PPy. The dispersion of PPy particles in copolymer matrix was proven by SEM, AFM and digital camera. By the increase of PPy content in the composite films, increase in AC conductivities, and decrease in dielectric constants and loss were observed.     

Optimization of extraction techniques and quantification of Betulinic Acid (BA) by RP-HPLC method from Ancistrocladus heyneanus Wall. Ex Grah.

Simple, cost effective, quick and sustainable technique was investigated for determining Betulinic acid (BA) from samples of Ancistrocladus heyneanus. The methods comprised of continuous shaking, Soxhlet, ultra sonication and microwave assisted extraction techniques. RP-HPLC technique was used to quantify BA from varied samples and confirmation of the samples was done using TLC, FT-IR and FT-Raman methods. The study also evaluated productivity of operational parameters such as solvent composition and extraction time for three distinctive parts of the plant (green leaves, brown leaves and stem). Brown leaves showed response to continuous shaking extraction and ultrasonic extraction techniques with 95% Aq. MeOH as a good extraction solvent. BA was detected and quantified in continuous shaking method with 15, 30 and 45 min of exposure time. Comparison of 6 min with 12 min of ultra sonication, showed longer sonication diminished extraction efficiencies. Concluding, brown leaves in 95% MeOH and ultrasonic extraction technique to be the fastest, easiest and best method for detection and screening of BA from A. heyneanus.     

Facile fabrication of carbon nanotubes/polystyrene composite nanofibers for high-performance electromagnetic interference shielding

Polystyrene (PS) composites with nanofibrous structure consisting of multi-walled carbon nanotubes (MWCNTs) with 0-10 wt.% of nanofiller have been fabricated via electrospinning technique. The surface morphology and thermal properties of the composites were evaluated by scanning electron microscopy (SEM) and thermo-gravimetric analysis (TGA). The SEM analysis of the composite nanofibers samples revealed that the average diameter of the nanofibers increases with increasing MWCNTs content. The resultant MWCNTs/PS composite nanofibers diameters were in the range of 391±63 to 586±132 nm. The thermal stability of composites was increased after addition of MWCNTs to PS matrix. The electrical conductivity of the composites with different weight percentage of MWCNTs was investigated at room temperature. Electrical conductivity of MWCNTs/PS composite nanofiber followed percolation theory having a percolation threshold V _c= 0.45 vol% (~0.75 wt. %) and critical exponent q=1.21. The electrical conductivity and thermal properties confirmed the presence of good dispersion and alignment MWCNTs encapsulated within the electrospun nanofibers. The electromagnetic interference (EMI) shielding effectiveness of the MWCNTs/PS composites was examined in the measurement frequency range of 8.2-12.4 GHz (X-band). The total EMI shielding efficiency of MWCNTs/PS composite nanofibers increased up to 32 dB. The EMI shielding results for MWCNTs/PS composite nanofibers showed that absorption loss was the major shielding mechanism and reflection was the secondary mechanism. The present study has shown the possibility of utilizing MWCNTs/PS composite nanofibers as EMI shielding/absorption materials.     

Porous Laponite/Poly(L-lactic acid) Membrane with Controlled Release of TCH and Efficient Antibacterial Performance

Fabrication of porous polymer membrane with controlled drug release and efficient antibacterial performances is of great interest in biomedical fields. In this study, Laponite (LAP) nanodisks were first used to encapsulate a model antibiotic drug, tetracycline hydrochloride (TCH). Then, drug-loaded LAP nanodisks with an optimized loading efficiency (85.3 %) were mixed with poly(L-lactic acid) (PLLA) polymer to form drug-loaded composite porous membrane via solvent coasting. The structure, morphology and swelling property of the porous membranes formed with varied solvent ratio of methylene dichloride (DCM) and dimethyl formamide (DMF) in the mixture solvent were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy and swelling test. In vitro drug release behavior, the cytotoxicity and the antibacterial activity of drug-loaded composite membranes were evaluated. Results showed that the TCH release was dependent on the physical structure of PLLA membrane and the presence of LAP nanodisks effectively weakened the initial burst release of TCH, and improved the sustained release property of porous PLLA membrane. The released TCH of TCH/LAP/PLLA_3:1 and TCH/LAP/PLLA_4:1 was 10.0 % and 5.3 % within initial 1 h, respectively. More importantly, the porous TCH/LAP/PLLA membrane was cytocompatible and displayed considerable antibacterial activity, solely associated with the loaded TCH drug, confirming its potential utility in wound dressings and tissue engineering.     

Preparation and use of amine-functionalized glycidyl methacrylate-g-poly(ethylene terephthalate) fibers for removal of chromium(VI) from aqueous solution

Poly(ethylene terephthalate) (PET) fibers were grafted with glycidyl methacrylate (GMA) using benzoyl peroxide as initiator. 1,6-diaminohexane (HMDA) was then covalently attached to this GMA grafted PET fibers. Variations of time, temperature, initiator and monomer concentrations were investigated. HMDA-GMA-g-PET fibers were used as a new sorbent for removal of Cr(VI) ions from aqueous solutions through batch adsorption method. Effects of various parameters such as pH, treatment time, and initial ions concentration on the adsorption amount of ions onto reactive fibers were investigated. The adsorption rates of Cr(VI) ions were much higher on the HMDA-GMA-g-PET fiber than on GMA-g-PET and ungrafted PET fiber. Within 60 min, at pH 3, Cr(VI) was removed by 98 % while the initial concentration of ions was at 25 mg/l and by 94 % at 400 mg/l. The Cr(VI) ions adsorbed were easily desorbed by treating with 1M KOH within 10 min.     

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.