Fiber Biocomposites Research Articles

Electrospun PLGA–silk fibroin–collagen nanofibrous scaffolds for nerve tissue engineering

Electrospun nanofibrous scaffolds varying different materials are fabricated for tissue engineering. PLGA, silk fibroin, and collagen-derived scaffolds have been proved on good biocompatibility with neurons. However, no systematic studies have been performed to examine the PLGA-silk fibroin-collagen (PLGA-SF-COL) biocomposite fiber matrices for nerve tissue engineering. In this study, different weight ratio PLGA-SF-COL (50:25:25, 30:35:35) scaffolds were produced via electrospinning. The physical and mechanical properties were tested. The average fiber diameter ranged from 280 + 26 to 168 + 21 nm with high porosity and hydrophilicity; the tensile strength was 1.76 ± 0.32 and 1.25 ± 0.20 Mpa, respectively. The results demonstrated that electrospinning polymer blending is a simple and effective approach for fabricating novel biocomposite nanofibrous scaffolds. The properties of the scaffolds can be strongly influenced by the concentration of collagen and silk fibroin in the biocomposite. To assay the cytocompatibility, Schwann cells were seeded on the scaffolds; cell attachment, growth morphology, and proliferation were studied. SEM and MTT results confirmed that PLGA-SF-COL scaffolds particularly the one that contains 50% PLGA, 25% silk fibroin, and 25% collagen is more suitable for nerve tissue engineering compared to PLGA nanofibrous scaffolds.

Mechanical and fracture behavior of banana fiber reinforced Polylactic acid biocomposites

Polylactic acid (PLA)/banana fiber (BF) biocomposites were fabricated using melt compounding technique. The effect of variable fiber composition, mercerization of fiber as well as incorporation of Maleic anhydride (MA) as compatibilizer and Glycerol triacetate ester (GTA) on the properties of PLA/BF composites was studied. MA compatibilized biocomposites exhibited improved tensile modulus to the tune of 62% whereas GTA plasticized composites showed improvement in impact strength by 143%. Thermogravimetric analysis (TGA) revealed an increase in the stability of MA incorporated systems and differential scanning calorimetry (DSC) showed increase in Tc with the incorporation of BF and compatibilizer. Increase in storage modulus of the composites as determined from Dynamic mechanical analysis (DMA) also confirmed effective stress transfer from the matrix to banana fiber. The morphological investigations using Scanning electron microscopy (SEM) indicated improved interfacial adhesion in compatibilized and plasticized systems.

Preparation and physical properties of the biocomposite, cellulose diacetate/kenaf fiber sized with poly(vinyl alcohol)

Cellulose diacetate (CDA)/kenaf fiber biocomposites were prepared using a melting process. In order to increase the fiber density and compatibilize the kenaf fiber with CDA, the fiber was sized with poly(vinyl alcohol)(PVA). The sized kenaf fiber was compounded with the plasticized CDA using a twin screw extruder, and the optimal processing conditions were determined. The incorporated kenaf fiber improved the mechanical and thermal properties of CDA. In the case of the composites containing 30 wt% kenaf fibers, the tensile strength and modulus increased almost 2 and 3 fold, which were 85.6 MPa and 4831 MPa, respectively. The PVA treated kenaf fiber showed better adhesion to the CDA matrix.

Ultra-Violet Radiation-Cured Biofiber Composites from Kenaf: The Effect of Montmorillonite on the Flexural and Impact Properties

Biofiber composites, cured by ultra-violet (UV) radiation were produced using kenaf fibers as the reinforcing agent and unsaturated polyester as the matrix. This research work focused on the effects of the incorporation of kenaf fiber, montmorillonite (MMT), and cetyl trimethyl ammonium bromide-modified MMT (CTAB-MMT) in the unsaturated polyester composite. Overall, the incorporation of kenaf fibers in the form of mat had improved the flexural and impact properties of the composites. Addition of MMT into the kenaf fiber-polyester system showed an improvement up to 1% MMT after which it decreased. The increase was attributed to better stress transfer mechanism in the matrix. However, further increase in the MMT loading had resulted in the decrease in the properties, which was believed to be due to agglomeration. Modification of MMT with CTAB had produced composites with higher flexural and impact properties as compared to those without modification. This was attributed to a combination of effective dispersion of MMT in the matrix, availability of effective high aspect ratio MMT, and enhanced compatibility between CTAB-MMT with the matrix.

Biocomposites Electrospun with Poly(ε-caprolactone) and Silk Fibroin Powder for Biomedical Applications

Biomedical synthetic polymers have been used in soft and hard tissue regeneration because of their good processability and biodegradability. However, biomaterials such as poly(ε-caprolactone) (PCL) have various shortcomings, including intrinsic hydrophobicity and lack of bioactive functional groups. The material must be reinforced with natural biomaterials to achieve good cellular and mechanical performance as biomedical material. We fabricated a biocomposite using PCL and silk fibroin (SF) powder, which has good biocompatibility and mechanical properties. The hydrophilicity, mechanical properties and cellular behavior of the PCL/SF fibers were analyzed. In addition, we obtained a highly oriented conduit of electrospun biocomposite fibers by modifying the rolling collector of the electrospinning system. As the alignment of micro/nanofibers increased, the orthotropic mechanical properties were improved. The biocompatibility of the biocomposite was evaluated in a culture of bone-marrow-derived rat mesenchymal stem cells. The cellular result demonstrated the potential usefulness of electrospun biocomposites for various biomedical conduit systems.

The effect of glycidyl methacrylate treatment of empty fruit bunch (EFB) on the properties of ultra‐violet radiation cured EFB‐unsaturated polyester composite

AbstractIn this study, biofiber composites cured by ultra‐violet, were produced using pulp made from empty fruit bunch (EFB) as the reinforcing agent and unsaturated polyester as the matrix. The conversion of EFB fibers into pulp was carried out using organosolv pulping process. The EFB pulp was then chemically treated with glycidyl methacrylate (GMA) to different percentage of weight percent gain and the composites were made with different percentages of pulp loading. Results showed that the Kappa number of EFB decreased as the NaOH concentration in organosolv pulping increased. Composites which were made from GMA‐treated EFB showed better mechanical properties (tensile, flexural, and impact strength) than those of the unmodified. Fourier transform infrared spectroscopy showed peaks that proved the occurrence of grafting between GMA and OH from EFB pulp. Scanning electron microscope analysis showed the evidence of the enhancement of the compatibility between EFB and matrix. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Thermal properties and spectral characterization of wood pulp reinforced bio-composite fibers

Bio-composite fibers were developed from wood pulp and polypropylene (PP) by an extrusion process. The thermo-physical and mechanical properties of wood pulp-PP composite fibers, neat PP and wood pulp were studied using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). The thermal stability of bio-composite fibers was found to be significantly higher than pure wood pulp. An understanding into the melting behaviour of the composite system was obtained which would assist in selecting a suitable temperature profile for the extruder during processing. The visco-elastic properties of bio-composite fibers were also revealed from the study. The generated bio-composite fibers were also characterized using Fourier transform infrared spectroscopy (FTIR) to understand the nature of chemical interaction between wood pulp reinforcement and PP matrix. The use of maleated polypropylene (MAPP) as a compatibilizer was investigated in relation to the fiber microstructure. Changes in absorption peaks were observed in FTIR spectra of bio-composite fibers as compared to the pure wood pulp which indicated possible chemical linkages between the fiber and polymer matrix.

Development and morphological characterization of wood pulp reinforced biocomposite fibers

Biocomposite fiber has been developed from wood pulp and polypropylene (PP) by an extrusion process and the generated biocomposite fibers were characterized to understand the nature of interaction between wood pulp reinforcement and PP matrix. The use of maleated polypropylene (MAPP) as a compatibilizer was investigated in relation to the fiber microstructure. Fiber length analysis showed that most of the fiber lengths lie within the range of 0.2–1.0 mm. Changes in absorption peaks were observed in Fourier transform infrared spectroscopy of biocomposite fibers as compared to the virgin wood pulp, which indicated possible chemical linkages between the fiber and polymer matrix. SEM study was carried out to observe fiber–matrix adhesion at the interface within the composite and MAPP treatment was found to be effective in increasing reinforcing fibers–matrix compatibility. X-ray computed tomography was conducted to understand the internal architecture of the biocomposite fiber and the results showed that with incorporation of additional wood pulp content, the fiber becomes more aligned along length axis possibly due to compression and die geometry of the extruder.

Characterization of castor oil/polycaprolactone polyurethane biocomposites reinforced with hemp fibers

The thermal and mechanical properties of castor oil/polycaprolactone-based polyurethane (CPU) films and polyurethane biocomposites reinforced with hemp fibers (HCPU) were investigated. Although similar films can be synthesized from petroleum, the main interest in studying these biomass-based composites is based on the fact that both fiber and matrix are derived from renewable resources. In this study, castor oil was used as a polyol for polyurethane films and hemp fiber was used to reinforce the biocomposites. To control the mechanical properties of CPU and HCPU, polycaprolactone diol (PCL) was added to the polyol mixture. Varying the mixing ratio of castor oil and PCL, the thermal and mechanical properties of the CPU and HCPU samples were investigated by using FT-IR, DSC, DMTA, Minimat, and SEM. In an attempt to improve interfacial adhesion between the fiber and matrix biocomposites, hemp fiber was reacted with MDI. FE-SEM micrographs showed that the surface of the hemp fiber became smoother after reaction with MDI. Urethane bonding formation was confirmed by FT-IR.

Fabrication, property characterization and toughening mechanism of HA-ZrO2(CaO)/316L fibre composite biomaterials

HA-ZrO2(CaO)/316L fibre composites were successfully fabricated with vacuum sintering method and their properties and toughening mechanism were studied. The results showed that HA-ZrO2(CaO)/316L fibre biocomposite having 20 vol% fibres had optimal comprehensive properties with bending strength, Young’s modulus, fracture toughness and relative density equal to 140.1 MPa, 117.8 GPa, 5.81 MPa·m1/2 and 87.1%, respectively. The research also addressed that different volume ratios of the composites led to different metallographic microstructures, and that metallographic morphologies change regularly with volume ratios of the composites. 316L fibres were distributed randomly and evenly in the composites and the integration circumstance of the two phases was very well since there were no obvious flaws or pores in the composites. Two toughening mechanisms including ZrO2 phase transformation toughening mechanism and fibre pulling-out toughening mechanism existed in the compsites with the latter being the main toughening mechanism.

A Preliminary Study on Ultraviolet Radiation–Cured Biofiber Composites from Oil Palm Empty Fruit Bunch

Biofiber composites, cured by ultraviolet (UV) radiation were produced using pulp made from empty fruit bunch (EFB) as the reinforcing agent and unsaturated polyester as the matrix. The EFB fibers were treated with sodium hydroxide (NaOH) solutions. The kappa number of the EFB decreased as the NaOH concentration increased. The flexural and tensile strength of the composites made from 22% NaOH-treated EFB increased as the percentage of EFB increased. Composites with 28% NaOH treated EFB had lower strength as the percentage of EFB increased. Generally, those with EFB fibers treated with 22% 15 NaOH displayed higher flexural, tensile, and impact strength and tensile modulus than those with 28% NaOH-treated fibers. No significant difference was observed for both types of composite with respect to flexural modulus and elongation at break.

Effect of mercerization of flax fibers on wheat flour/flax fiber biocomposite with respect to thermal and tensile properties

New composites materials, 100% ecofriendly based on modified wheat flour as matrix and flax fiber as fillers have been obtained by means of an extrusion process. The wheat flour matrix contains non-toxic plasticizers and is mixed well with natural fibers. One sample series without specific fiber surface treatment and a second series with a mercerization surface treatment have been prepared. The content of fillers varies from 0% w/w to 20% w/w. In this work the performances of these new composites in term of thermal stability, mechanical behaviours are compared and discussed in regard to the fiber treatment efficiency and composition. We observe an interesting behaviour: the efficiency is found the best for a fiber composition close to 10% w/w.

Effect of MAPP and TMPTA as compatibilizer on the mechanical properties of cellulose and oil palm fiber empty fruit bunch–polypropylene biocomposites

The effect of compatibilizers, namely, maleic anhydride grafted polypropylene (MAPP GR-205) and trimethylolpropane triacrylate (TMPTA), on the mechanical and morphological properties of the PP-cellulose (derived from oil palm empty fruit bunch fiber) and PP-oil palm empty fruit bunch fiber (EFBF) biocomposites has been studied. The ratio of PP : cellulose and PP : EFBF is fixed to 70 : 30 (wt/wt%) while the concentration of the compatibilizer is varied from 2.0 to 7.0 wt%. Results reveal that at 2.0 wt% of MAPP concentration, tensile strength of PP-EFBF biocomposite is significantly improved. This is due to the enhanced EFBF matrix adhesion resulting in an improvement in EFBF biocomposite performance. There are no significant changes observed in the PP-cellulose biocomposite properties upon the addition of MAPP. In contrast to the tensile strength, flexural modulus and impact strength are significantly improved with the addition of 2.0 wt% TMPTA to PP-cellulose biocomposite. The enhancement of mechanical properties in the presence of TMPTA is believed to be attributed to crosslinking of multifunctional monomer with the hydroxyl groups of cellulose.

Micromechanical Simulations on Hygro-Mechanical Properties of Bio-fiber Plastic Composites

AbstractThe hygro-mechanical properties of bio-fiber composites comprise two aspects: the coupling between moisture diffusion and mechanical deformations and the coupling of moisture contents and the constitutive behaviors. Bio-fiber is hydrophilic, which absorbs water promptly when environmental moisture content increases; as the moisture content in the fiber increases, its mechanical properties decrease. This paper presents a series of micromechanical simulations to predict the hygro-mechanical behaviors of woodfiber-reinforced plastic composites considering the effects of fiber arrangements on the stress-strain relations and moisture-expansions on three progressively constructed constitutive configurations: 1) the fiber is elastic orthotropic and expandable under moisture variations; the plastic matrix is elastic isotropic and insensitive to environmental moisture variations, and the interface between fiber and matrix is perfectly bounded; 2) the plastic matrix is hyperelastic and expresses a certain degree of damage as deformation progresses; and 3) the interface has a pseudo adhesive layer that obeys Smith and Ferrante's universal binding law implemented as a cohesive zone model in the micromechanical simulation. In configuration II, micromechanical simulations demonstrate significant reductions in the nominal elastic modulus of composites when a nonlinear elastic model for the polymer matrix is assumed. The prediction for stress-strain relationship is found to be comparable to the experimental measurements. A cohesive model in configuration III is introduced to evaluate the possible moisture degradation to the fiber-matrix interface, which results in a reduction in elastic modulus and failure strength of the composite s, as observed in experiments. The cohesive zone model parameters as a function of moisture content in the composites requires more attention in model correlation and guarantee more direct experimental observations.

Effect of chemical modification on properties of hybrid fiber biocomposites

The effects of chemical modification of fiber surface in sisal–oil palm reinforced natural rubber green composites have been studied. Composites were prepared using fibers treated with varying concentrations of sodium hydroxide solution and different silane coupling agents. The vulcanisation parameters, processability conditions and tensile properties and swelling characteristics of these composites were analysed. The fiber reinforcing efficiency of the chemically treated biocomposites was compared with that of untreated composites. The extent of fiber alignment and strength of fiber–rubber interfacial adhesion was analysed from the swelling measurements. Composites containing chemically treated fibers were found to possess enhanced mechanical properties. The hardness and abrasion resistance of the untreated and treated composites were also analyzed. Surface characterization of treated and untreated sisal fibers by XPS showed the presence of numerous elements on the surface of the fiber. The fracture mechanism of treated and untreated fiber reinforced rubber biocomposites was investigated from SEM studies.

Nanostructured Biocomposite Scaffolds Based on Collagen Coelectrospun with Nanohydroxyapatite

Nanofibrous biocomposite scaffolds of type I collagen and nanohydroxyapatite (nanoHA) of varying compositions (wt %) were prepared by electrostatic cospinning. The scaffolds were characterized for structure and morphology by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD) techniques. The scaffolds have a porous nanofibrous morphology with random fibers in the range of 500-700 nm diameters, depending on the composition. FT-IR and XRD showed the presence of nanoHA in the fibers. The surface roughness and diameter of the fibers increased with the presence of nanoHA in biocomposite fiber as evident from AFM images. Tensile testing and nanoindendation were used for the mechanical characterization. The pure collagen fibrous matrix (without nanoHA) showed a tensile strength of 1.68 +/- 0.10 MPa and a modulus of 6.21 +/- 0.8 MPa with a strain to failure value of 55 +/- 10%. As the nanoHA content in the randomly oriented collagen nanofibers increased to 10%, the ultimate strength increased to 5 +/- 0.5 MPa and the modulus increased to 230 +/- 30 MPa. The increase in tensile modulus may be attributed to an increase in rigidity over the pure polymer when the hydroxyapatite is added and/or the resulting strong adhesion between the two materials. The vapor phase chemical crosslinking of collagens using glutaraldehyde further increased the mechanical properties as evident from nanoindentation results. A combination of nanofibrous collagen and nanohydroxyapatite that mimics the nanoscale features of the extra cellular matrix could be promising for application as scaffolds for hard tissue regeneration, especially in low or nonload bearing areas.

Hybrid Thermoplastic Pre-preg Oil Palm Frond Fibers (OPF) Reinforced in Polyester Composites

This paper presents a novel approach to toughen the otherwise brittle unsaturated polyester resin (USP) in the polymer matrix biofiber composites. In contrast to the conventional method of incorporating the toughening agent in the matrix resin, the method used in the present investigation consisted in treating the biofiber (OPF) with the toughening resin before impregnating with USP resin. Accordingly biofiber was first impregnated with toughening resin, acrylonitrile-butadienne-styrene (ABS) to produce a pre-preg. The pre-preg was then impregnated with USP resin containing free radical initiator. The ABS content in the biofiber pre-preg was varied from 5 to 25%. Unsaturated polyester was reinforced with the pre-preg and cured in presence of MEKP to produce “hybrid composite”. The physical and mechanical properties of the composites were determined.

A Solvent Free Graft Copolymerization of Maleic Anhydride onto Cellulose Acetate Butyrate Bioplastic by Reactive Extrusion

AbstractSummary: Interfacial adhesion between fibers and matrix is a crucial factor for effective stress transfer from matrix to fiber; especially in short fiber reinforced composite systems. The use of a chemical compatibilizer is an efficient means to achieve such adhesion. Maleic anhydride‐grafted‐cellulose acetate butyrate (CAB‐g‐MA) is one such compatibilizer which can be used in biocomposite fabrication, and this has been synthesized in our laboratory by utilizing a twin‐screw reactive extrusion process in the presence of a free radical initiator (2,5‐dimethyl‐2,5‐di(tert‐butylperoxy)hexane). The unique feature of this process is its solvent‐free approach for grafting of maleic anhydride onto CAB, without hydroxyl group protection. CAB‐g‐MA was characterized using FTIR as well as by a non‐aqueous titration method. The effects of initiator and monomer concentrations and various processing conditions on the graft content were also investigated. The preliminary results show that by adding approximately 10 wt.‐% of CAB‐g‐MA into a plasticized cellulose acetate butyrate (TEB)‐industrial hemp fiber biocomposites system, an improvement in tensile strength (20%) and in tensile modulus (45%) were obtained. These results are promising in that they pave the way for future studies involving the use of CAB‐g‐MA as a suitable compatibilizer for cellulose ester‐natural fiber biocomposites. magnified image

Biodegradable polymers/bamboo fiber biocomposite with bio-based coupling agent

Abstract Effects of lysine-based diisocyanate (LDI) as a coupling agent on the properties of biocomposite from poly (lactic acid) (PLA), poly (butylene succinate) (PBS) and bamboo fiber (BF) were investigated. Tensile properties, water resistance, and interfacial adhesion of both PLA/BF and PBS/BF composites were improved by the addition of LDI, whereas thermal flow became somewhat difficult due to cross-linking between polymer matrix and BF. Crystallization temperature and enthalpy in both composites were increased and decreased with increasing LDI content, respectively. The heat of fusion in both composites was decreased by addition of LDI, whereas there was no significant change in melting temperature. Thermal degradation temperature of both composites was lower than those of pure polymer matrix, but the composites with LDI showed higher degradation temperature than those without LDI. Enzymatic biodegradability of PLA/BF and PBS/BF composites was investigated by Proteinase K and Lipase PS, respectively. Both composites could be quickly decomposed by enzyme and the addition of LDI delayed the degradation.

Photofabrication of biofiber‐based polymer matrix composites

AbstractThe novel development of a photofabrication process of biofiber composites, based on oil palm empty fruit bunch fibers, is reported. The process consists of the following steps: (1) the preparation by a wet process of nonwoven mat of biofiber, either alone or in combination with glass and nylon; (2) drying the mat; (3) preparation of photocurable resin matrix, consisting of vinyl ester and photoinitiator; (4) impregnation of the mat by photocurable resin; and (5) irradiation of the impregnated mat by UV radiation to effect the cure of the composite. The nonwoven mat was formed in a “headbox” into which was poured a slurry of fibers. A wet mat was formed by after dewatering of the slurry. Biofiber, glass, and nylon fibers were mixed in different proportions. A “mixture experimental design” was used to generate experimental compositions of the reinforcing fibers and to model dependency of the response variables on the components through mathematical relationships. These relationships were meant to (1) determine the effect of composition of the reinforcing fibers on the physical and mechanical properties, (2) predict the response for any unknown composition of fibers, and (3) determine the optimum values of any identified properties. Because the product was characterized by multiple responses, simultaneous maximization of all properties was not feasible. The product must be considered in the definition of the trade‐off or compromise of properties to obtain overall satisfactory performance. Such an optimization was carried out and the results are reported. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1493–1499, 2005