Despite substantial progress being made relating to 2D-nanofiller-based composite nanolaminates, the fabrication of composite nanolaminates with enhanced ductility and toughness is still challenging. In this study, layered structure graphene oxide (GO)/gelatin powder (GP) composites nanolaminates with enhanced ductility and toughness have been achieved by a simple vacuum filtration of aqueous dispersion of GO/GP composite solution containing 5 wt% of GO. The composite film containing 5 wt% GO shows outstanding improvement of 200% in the stress at break value, with simultaneous enhancement of 52% of the strain at break value compared to GP film. A significant improvement in toughness from 2.2 MJ m(-3) to 9.5 MJ m(-3) is observed in the composite film containing 5 wt% GO. These significant enhancements of the mechanical properties of the composite film are obtained via the formation of an intercalated nanolaminate structure, H-bonding interactions, and the tailoring of the crystal structure of GP in the composite film, as proved via field-emission scanning electron microscopy, Fourier-transform infrared spectroscopy, and wide-angle X-ray diffraction studies. The growing of fibroblast cells on the composite films signifies that they are not cytotoxic. These GO/GP composites with significant mechanical properties and biocompatibility are very promising for various biomedical applications.
Large amounts of cotton/PET textiles are wasted every year due to economically unfeasible separation of cotton and PET from waste textiles. These waste textiles were reused to form composites for technical applications and their properties were studied in this project. The waste textile, bed linen, used in this project comes from local hospital. The aim of this study is to produce composites from cotton/PET waste textiles and characterize by mechanical and thermal analysis. The effect of orientation of the fibers was studied and the processing parameters such as temperature, pressure and time of compression were optimized.
This paper presents the melt spinning and characterisation of polymer actuator fibres; fibres that reversibly contract along the fibre axis in response to heat. Recently, Haines et al (1) showed that low-cost filaments, e.g. fishing lines, can be relevant precursors for artificial muscles. They demonstrated a reversible fibre-direction thermal contraction, which was significantly amplified when the fibres were twisted and coiled. The effect was explained to result from an increase in the conformational entropy of the amorphous phase. In earlier studies on negative thermal expansion in anisotropic polymer structures, it has been shown that the negative thermal expansion in oriented highly crystalline polymers approaches values typical of polymer crystals (2).
To further investigate the mechanisms behind these seemingly simple artificial muscles, we have melt spun fibres from poly(vinylidene fluoride) (PVDF) – Solef 1006 and 1008 kindly provided by Solvay (Milan, Italy) – and compared their properties to a commercially available PVDF-fishing line. The fibres were characterised with respect to their thermal actuation properties, crystal morphology and degree of orientation along the spin-line axis.
We have further done modelling on the molecular and macroscopic levels examining the possible mechanisms of negative thermal expansion in semi-crystalline PVDF. We believe that tie molecules (a polymer chain linking two crystalline regions) are the predominant factor influencing actuation. Two mechanisms are considered: an entropic effect and a conformational change effect. The entropic effect causes an increase in the elastic stiffness with an increase in temperature, effectively resulting in a contraction of a strained fibre. The conformational change effect is also expected to contribute to contraction as tie molecules, under strain, revert to their unloaded preferred conformation when heated.
Novel composite films constituted of poly(lactic acid) (PLA), hydroxyapatite (HAp), and two types of regenerated cellulose fillers—particulate and fibrous type—were produced by melt extrusion in a twin-screw micro-compounder. The effect of the film composition on the tensile and dynamic mechanical behavior and the HAp dispersion in the PLA matrix were investigated thoroughly. Appearance of crazed regions and prevention of HAp aggregation in the PLA matrix were elucidated in the composites with up to 15 wt % particulate cellulose content, which was the main reason for only slight reduction in the tensile properties, and consequently trivial degradation of their pre-failure energy absorption as compared to neat PLA films. Superior dynamical energy storage capacities were obtained for the particulate cellulose modified composites, while their fibrous counterparts had not as good properties. Additionally, the anisotropic mechanical behavior obtained for the extruded composites should be favorable for use as biomaterials aimed at bone tissue engineering applications.
Poly(lactic acid)-cellulose nanocrystals (PLA/CNC) nanocomposite fibers with 1% weight fraction of nanocrystals were prepared via melt-spinning. In order to improve the compatibility between PLA and the CNC, PLLA chains were grafted onto the CNC surface using a "grafting from" reaction. For comparison, melt-spun PLA fibers and nanocomposites with unmodified CNC were also prepared. The morphology and thermal and mechanical properties of the fibers with different draw ratios were determined. The results of this research show that the surface modification together with drawing resulted in improved fiber properties, which are expected to depend on the alignment of the CNC and PLA molecular chains. The modification is also expected to lead to a flexible interface, which leads to more stretchable fibers. The main conclusion is that PLLA grafting is a very promising approach to improve the dispersion of CNC in PLA, thus creating interfacial adhesion between the phases and making it possible to spin fibers that can be drawn with improved mechanical performance.
New photocatalytic fibers made of sulfonated polyetheretherketone (SPEEK)/polypropylene (PP) are melt compounded and melt spun, first on laboratory scale and then on a semi-industrial scale. Fiber spinnability is optimized and the fibers are characterized using mechanical testing, electron paramagnetic resonance (EPR) spectroscopy, and scanning electron microscopy (SEM). According to the results, the fiber spinnability remains at a good level up to 10 wt % SPEEK concentration. Optimal processing temperature is 200°C due to the thermal degradation at higher temperatures. EPR measurements show good and long-lasting photoactivity after the initial irradiation but also decay in the radical intensity during several irradiation cycles. Mechanical tenacity of the SPEEK/PP 5:95 fiber is approximately 20% lower than for otherwise similar PP fiber. The fiber is a potential alternative to compete against TiO2-based products but more research needs to be done to verify the real-life performance.
The radical-induced cationic frontal photopolymerization (RICFP) of fully biobased epoxy composites is successfully demonstrated. This curing strategy considerably reduces the curing time and improves the efficiency of the composite fabrication. Two different natural fiber fabrics made of cellulose and flax fibers are embedded in two epoxy matrices, one derived from vanillin (diglycidylether of vanillyl alcohol-DGEVA) and the other from petroleum (3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate-CE). After RICFP the composites are characterized by means of dynamic mechanical thermal analysis and tensile tests. The mechanical properties improved with increasing fiber content, confirming a strong adhesion between the matrix and the reinforcing fiber fabrics, which is further evidenced by scanning electron microscopy analyses of the fracture surfaces. Furthermore, these fully bio-based composites possess comparable or even higher mechanical strength compared with the corresponding epoxy composites fabricated with conventional CE resin. A promising facile route to high-performing natural fiber-biobased epoxy resin composites is presented. © 2022 Wiley-VCH GmbH
Fibres are the basic units of textiles and are desirable as scaffold matrix material since they provide a large surface area to volume ratio. Using the textile technology, fibres can also be processed to form a variety of shapes and sizes, thus be used in different biological and medical applications. Poly(lactic acid) is a widely investigated material for use as scaffold matrix material and may be transformed into fibres either by melt spinning or solution spinning [1]. However, its lack of cell recognition signal has limited its use in tissue engineering applications [2]. Hydroxyapatite (HA) particles, which mimics the natural bone mineral has been proven to stimulate and promote cell attachment [3]. From that point of view, the aim of this study was to produce a PLA/HA composite fibres that could be used in a 3D woven scaffold for bone regeneration.
This study presents a method to melt-spun biocompatible composite fibres from poly(lactic acid) (PLA) and nano-sized hydroxyapatite (HAp) particles. Different loading concentrations of HAp particles in the PLA fibres and solid-state draw-ratios (SSDR) were evaluated in order to study their influence on the mechanical, thermal and morphological properties. The results showed that the incorporation of the HAp particles was homogeneously distributed in the PLA fibres towards their surface and that the SSDR played an important role in order to improve the mechanical properties. The melt-spun PLA/HAp composite fibres, produced in this study, had also the potential to be processed into a fibrous scaffold, which was demonstrated by a 3D woven structure.
Biodegradable materials in the form of fibres and yarns have attracted increasing attention due to a large surface area and various geometric possibilities in three-dimensional polymeric scaffolds for tissue engineering applications. In this study, poly(lactic acid) fibres were produced by melt spinning and subsequent solid-state drawing in order to serve as matrix materials for fibre-based scaffold architectures. The processing of both monofilament and multifilament fibres as well as draw ratios and temperatures were investigated to analyze the effect of process variables on the properties. Two different polylactides with different molecular weight were studied and characterized in terms of their tensile and thermal properties and morphology. The relevance of fibre formation, solid-state drawing and drawing temperatures was clearly supported by the results, and it was shown that the physical properties, such as crystallinity, mechanical strength and ductility can be controlled largely by the drawing process. The obtained fibres demonstrated great potential to be further processed into biotextiles (woven, knitted, or nonwoven scaffolds) using the textile technologies.
Composite fibers from poly(lactic acid) (PLA) and hydroxyapatite (HA) particles were prepared using melt spinning. Different loading concentrations of HA particles (i.e., 5, 10, 15, and 20 wt %) in the PLA fibers and solid-state draw ratios (SSDRs) were evaluated in order to investigate their influence on the fibers' morphology and thermal and mechanical properties. A scanning electron microscopy investigation indicated that the HA particles were homogeneously distributed in the PLA fibers. It was also revealed by atomic force microscopy and Fourier transform infrared spectroscopy that HA particles were located on the fiber surface, which is of importance for their intended application in biomedical textiles. Our results also suggest that the mechanical properties were independent of the loading concentration of the HA particles and that the SSDR played an important role in improving the mechanical properties of the composite fibers.
The quality of the initial cell attachment to a biomaterial will influence any further cell function, including spreading, proliferation, differentiation and viability. Cell attachment is influenced by the material's ability to adsorb proteins, which is related to the surface chemistry and topography of the material. In this study, we incorporated hydroxyapatite (HA) particles into a poly(lactic acid) (PLA) composite and evaluated the surface structure and the effects of HA density on the initial cell attachment in vitro of murine calvarial preosteoblasts (MC3T3-EI). Scanning electron microscopy (SEM), atomic force microscopy (AFM) and infrared spectroscopy (FTIR) showed that the HA particles were successfully incorporated into the PLA matrix and located at the surface which is of importance in order to maintain the bioactive effect of the HA particles. SEM and AFM investigation revealed that the HA density (particles/area) as well as surface roughness increased with HA loading concentration (i.e. 5, 10, 15 and 20wt%), which promoted protein adsorption. Furthermore, the presence of HA on the surface enhanced cell spreading, increased the formation of actin stress fibers and significantly improved the expression of vinculin in MC3T3-E1 cells which is a key player in the regulation of cell adhesion. These results suggest the potential utility of PLA/HA composites as biomaterials for use as a bone substitute material and in tissue engineering applications.
Resurser och hållbarhet är nära förknippade. Hållbarhet innebär att hushålla med resurser - materiella, miljömässiga och mänskliga. Och hushållning är per definition kärnan i ekonomi. Man börjar alltmer se framväxten av en hel arsenal av verktyg och förhållnings- och angreppssätt för att bygga hållbarhet. Detta förenas av ett synsätt att det som hitintills setts om avfall och värdelöst, och rent utav besvärligt att ta hand om, nu blir en värdefull resurs. Det glömda och gömda kommer åter. Faktum är att många ord och begrepp kring detta börjar på just åter- eller re- . Internationellt talar man om Redesign, Recycling, Remake, Recycle, Recraft, Reuse, Recreate, Reclaim, Reduce, Repair, Refashion.
Vad är då allt detta? Ja, vill man dra det långt, är det inte mindre än framväxten av ett nyvunnet sätt att tänka, ja av en ny samhällssektor, en bransch och en industri, sammanbundet av filosofin att återanvändningen, spillminskningen, vidarebruket, efterlivet anses som viktiga faktorer för ett miljömedvetet samhälle. Re: blir paraplytermen för detta. I denna antologi av forskare från skilda discipliner vid Högskolan i Borås lyfts ett antal av dessa begrepp inom Re: fram.
In this study bio-nanocomposites were manufactured, using a thermoset resin based on lactic acid and nanoclay (montmorillonite) as a matrix for flax fibers. The obtained composites were characterized by dynamic-mechanical thermal analysis (DMTA) and flexural testing. The aim of this study was to evaluate the mechanical properties of bio-nanocomposites without any surface treatment of the nanoclay and to use the resin/clay blend as a matrix for natural fiber composite. Results showed the nanoclay improved the mechanical properties.
Bio-nanocomposites are a new class of particle-based composites that have attracted much attention due to their environmental and economic advantages these years [1, 2]. In this study a biobased thermoset resin based on lactic acid was used and reinforced with montmorillonite (MMT). This resin consists of star-shaped oligomers of lactic acid, end-capped with methacrylate groups [3]. Thus, the resin can be cross-linked by a free radical polymerization. MMT consists of 1 nm thick aluminosilicate layers. Due to the high surface area, MMT has been evaluated as a reinforcement for several commercial polymers. While most commercial resins are non-polar, MMT is intrinsically polar. Therefore, MMT is usually surface treated in order to make it less polar. However, the resin used in this study is relatively polar and the purpose of this study was to evaluate if untreated MMT could be used to reinforce this resin. The curing was studied with isothermal differential scanning calorimetry (DSC) and the obtained composite were characterized by dynamic-mechanical thermal analysis (DMTA). Also transmission electronic spectroscopy (TEM) was used to characterize the structure. The result showed some improvements in mechanical properties. The DMTA results showed that the storage modulus and also loss modulus of the nanocomposite improved with respect to neat resin. Intercalated structures could be seen from the TEM micrographs.
This investigation deals with the detailed procedure for the extraction of microfibrils from raw bamboo. The microfibrils obtained from raw bamboo were characterized using scanning electron microscope and the average diameter of the fibrils was found to be 10 mu m. These microfibrils were then incorporated into polyhydroxybutyrate (PHB) matrix using conventional plastic processing equipments. The impact strength values of the resulting composites indicate that there is an optimum loading of microfibrils in the PHB matrix, beyond which the effect of fibril loading is not significant.
The article reports the results of studies on the effect of chitosan (0, 5, 10, 20, 30, and 40 wt %) on thermal and mechanical properties of poly(hydroxybutyrate) composites. The addition of chitosan causes an increase in the glass transition temperature (Tg) while a decrease in the enthalpy of fusion (DHfus), crystallization (DHcry) and percentage of crystallinity as determined by differential scanning calorimeter (DSC). The thermogravimetric analysis reveals that high amount of chitosan decreases the thermal stability of the composites. The Young’s modulus of the composite increases and is high for the composite having 40 wt % of chitosan. Increase in the amount of chitosan decreases the elongation at break and impact strength of composites. Finally, the Young’s modulus of the composites has been compared with the theoretical predictions.
The modification of epoxy resin by 3-aminopropyltriethoxysilane (APTES) to improve the tensile properties of warp knitted viscose fabric composites is reported in this study. The study evaluates the efficiency of modification methods adopted to modify the epoxy resin and the influence of the resin modification on various properties of the cured castings. The influence of matrix resin modification on the tensile properties of viscose fabric composite is compared to those prepared from chemically modified fibre. The efficiency of the modification was determined through titration method to determine the epoxide content of epoxy resin, viscosity measurement and FTIR. The effect of APTES modification on various properties of cured castings is studied through differential scanning calorimeter, contact angle measurement and tensile testing. The addition of APTES into the epoxy resin decreased the epoxide content in the resin as evident from the titration method. The tensile strength of cured castings decreased after the resin modification. The tensile strength and elongation at break of the viscose fabric composites prepared from modified resin, increased up to 14 and 41%, respectively. The improved adhesion of APTES-modified epoxy resin to the viscose fibre is confirmed from SEM analysis of tensile fracture surface.
Viscose fabric-reinforced unsaturated polyester composites were successfully prepared through vacuum infusion process. Unidirectional viscose fabric was modified by two different organosilane coupling agents and by acetylation treatment. The main objective was to study the influence of fabric treatment on the mechanical and water absorption properties of the composites. Flexural, tensile and impact properties of composites were studied. The results from mechanical testing of composites pointed out that 3-aminopropyltriethoxy silane treatment increased the flexural and impact strengths of the composites with respect to untreated fabric composite. The impact strength of 3-aminopropyltriethoxy silane-treated fabric composites almost doubled compared to the value of untreated fabric composite. Among all the composites under study, those with fabrics treated by 2 vol% 3-aminopropyltriethoxy silane in ethanol/water (95:5) solution exhibited significant improvement in water uptake resistance. An unsaturated polyester gelcoat and topcoat were applied as the outer surface on the composites with untreated fabric. This was done in order to investigate the visual surface appearance and evaluate the gelcoat and topcoat effect on water absorption after accelerated water immersion test. The regenerated cellulose fibre as reinforcement shows high potential to be used as an alternative for natural bast fibres, especially, when toughness of material matters. Chemical treatment of regenerated cellulose fibres could result in improvement in properties of polymer composites, considering that the appropriate treatment method is selected for the corresponding fibre–matrix system.
Natural fiber composites are known to absorb more water than glass fiber reinforced composites. In this study, hybrid natural fiber composites were prepared by combining different fiber reinforcements, and both the water absorption and the mechanical properties were studied. Compression molding technique was used to manufacture composite laminates from a bio-based resin (acrylated epoxidized soybean oil) and natural fibers: non-woven and woven jute, non-woven regenerated cellulose mat (Lyocell and viscose), and woven glass fiber. The composite laminates were cured at 160–170 C and 40 bar, with a fiber content of 40 wt%. We investigated effect of pretreatment of regenerated cellulose fiber using 4% NaOH solution. The gravimetric water absorption was tested by exposure to water for 10 days. Specimens were cut from composites with laser-cutting technique according to ISO standards, and tested for tensile, flexural, and impact strength. To determine the influence of water absorption on the mechanical properties, specimens were immersed in distilled water for 10 days before testing. As a reference, dry specimens were tested. The results showed that water absorption was reduced by producing hybrid composites with jute fibers, glass fiber, and Lyocell fiber. The tensile, flexural, and impact properties were improved by inclusion of glass fiber and Lyocell in the composite. The tensile and flexural properties of natural fiber reinforced composites were mostly affected by the influence of water, but this was improved considerably by hybridization with glass and Lyocell fibers. The viscoelastic properties of the manufactured composites and hybrid composites were studied using dynamic mechanical thermal analysis.
The effect of surface treatments, silane and alkali, on regenerated cellulose fibers was studied by using the treated fibers as reinforcement in lactic acid thermoset bioresin. The surface treatments were performed to improve the physico–chemical interactions at the fiber–matrix interface. Tensile, flexural and impact tests were used as indicator of the improvement of the interfacial strength. Furthermore, thermal conductivity, viscoelasticity measurements as well as microscopy images were made to characterize the fiber surface treatments and the effect on adhesion to the matrix. The results showed that silane treatment improved the mechanical properties of the composites as the silane molecule acts as link between the cellulose fiber and the resin (the fiber bonds with siloxane bridge while the resin bonds with organofunctional group of the bi-functional silane molecule) which gives molecular continuity in the interphase of the composite. Porosity volume decreased significantly on silane treatment due to improved interface and interlocking between fiber and matrix. Decrease in water absorption and increase in contact angle confirmed the change in the hydrophilicity of the composites. The storage modulus increased when the reinforcements were treated with silane whereas the damping intensity decreased for the same composites indicating a better adhesion between fiber and matrix on silane treatment. Thermogravimetric analysis indicated that the thermal stability of the reinforcement altered after treatments. The resin curing was followed using differential scanning calorimetry and the necessity for post-curing was recommended. Finite element analysis was used to predict the thermal behavior of the composites and a non-destructive resonance analysis was performed to ratify the modulus obtained from tensile testing. The changes were also seen on composites reinforced with alkali treated fiber. Microscopy images confirmed the good adhesion between the silane treated fibers and the resin at the interface.
Natural fiber composites are known to absorb more moisture than glass or carbon fiber reinforced composites. The hybrid natural fiber composites prepared in this study have relatively less moisture absorption than natural fiber composites. The composite laminates were manufactured by compression molding technique. A bio‐based resin known as acrylated epoxidized soybean oil (AESO) was used as a matrix, while jute fiber, regenerated cellulose fiber (Lyocell and viscose) and glass fiber were used as reinforcements. The composite laminates were prepared at temperature between 160‐170°C and pressure of 40 bar with natural fiber reinforcement between 30‐60 wt% of the fiber. Specimens were cut from the laminates with a laser cutting machine according to standard. The effect of pretreatment of natural fiber and regenerated cellulose fiber using 4% NaOH solution was investigated and discussed. The amount of water absorbed by the composites was determined by soaking the specimens in distilled water for 10 days. To see the influence of water absorption on mechanical properties of the composites, specimens were immersed in distilled water for 10 days before testing. Dry specimens were also tested for reference. Charpy Impact testing was performed on the composite laminates in order to calculate the energy absorbed by specimen during fracture. Water absorption behavior of the natural fiber composites was reduced by manufacturing hybrid composites with glass and Lyocell fibers. Tensile, flexural and impact properties of the natural fiber reinforced composites were improved by the inclusion of glass or Lyocell fiber. Tensile and flexural properties of natural fiber reinforced composites were affected largely by the influence of water and it could be improved by hybridization. Viscoelastic properties of the composites and hybrid composites were studied by dynamic mechanical thermal analysis.
Non‐woven Lyocell mats were made from the fibers by carding and needling process at Swerea IVF, Mölndal, Sweden. The carding was done first in order to align the clumps of fibers. And then needle punching was done to obtain compact and entangled fiber mat. The composites were made by compression molding technique at temperature between 160‐170°C and pressure of 40 bar with non‐woven Lyocell, jute and viscose fiber reinforcements. The hybrid bio‐based composites were produced in this study to improve the mechanical properties of the composites. Bio‐based thermoset resin known as acrylated epoxidized soybean oil (AESO) was used as matrix in the composites. Laser cutting technique was adopted to cut specimens from laminates according to standard. The dimensional stability of the composites was determined by soaking the composite specimens in water for 10 days. Tensile and flexural properties of the composites were determined before and after water uptake. Hybridizing the jute fiber with glass and Lyocell fibers reduced the water uptake. Mechanical properties of the non‐woven fiber reinforced composites were studied by tensile, flexural, impact tests. Viscoelastic properties were studied using dynamic mechanical thermal analysis (DMTA). Tensile, flexural and impact properties of natural fiber composites were improved by hybridizing with Lyocell fiber.
Biocomposites were produced from regenerated cellulose fiber reinforcement and soybean based bio-matrix. Mechanical, thermal, viscoelastic and morphological results show the good potential of these composites to be used as structural materials in automotive industries. This article focuses on manufacturing and testing of these composites for engineering materials. Regenerated cellulose fibers such as Lyocell and viscose were reinforced in soybean based thermoset matrix to produce composites by compression molding. Hybrid composites were produced by mixing both these fibers at known ratio and the total fiber content in composite was between 40 and 60 weight %. In general, Lyocell based composites showed better tensile properties than viscose based composites. Composites consisting 60 weight % Lyocell and rest with matrix had tensile strength of 135 MPa and tensile modulus of 17 GPa. These composites also showed good flexural properties; flexural strength of 127 Mpa and flexural modulus of 7 GPa. Dynamic mechanical thermal analysis showed that these composites had good viscoelastic properties. Viscose based composites had better percentage elongation during tensile test. These composites also showed relatively good impact and viscoelastic properties. Scanning electron microscope images showed that the composites had good fiber-matrix adhesion. Several efforts are made to produce sustainable biomaterials to replace synthetic materials due to inherent properties like renewable, biodegradable and low density. Biocomposites play significant role in sustainable materials which has already found applications in automotive and construction industries. Many researchers produced biocomposites from natural fiber and bio-based/synthetic matrix and it had found several applications. There are several disadvantages of using natural fiber in composites; quality variation, place dependent, plant maturity, harvesting method, high water absorption etc. These composites also give odor which has to be avoided in indoor automotive applications. These natural fibers can be replaced with lignocelluloses, agro mass and biomass to develop biocomposites as they are from natural origin. Lyocell and viscose are manmade regenerated cellulose fibers which is from natural origin has excellent properties. These fibers can be used as reinforcements to produce biocomposites which can overcome most of the above listed disadvantages of natural fibers. Many composites were made from natural fiber reinforcement and petroleum based synthetic matrix. Researchers have been finding ways to get matrix out of natural resources like soybean and linseed on chemical modifications. This article is focused on producing and testing sustainable material with regenerated cellulose and soybean based bio-matrix for automotive applications.
Natural fiber composites have got more focus in recent times due to their intrinsic properties such as lightweight, biodegradable, low cost etc. Several researchers have made bio-composites out of many natural fibers such as jute, flax, sisal. These composites have large market in Europe and North America where it is used in automobile and construction industry. A lot of research has been done to improve the properties such as surface modification of fiber, manufacturing hybrid composites. However, the natural fibers are dissimilar and vary largely due to many factors such as variety, harvest, maturity, climate etc. Apart from technical drawbacks, these fibers grow only in certain countries such as India and China. High demand raised the price of these fibers which increases the product price as well. Wood-based fibers such as Lyocell and Viscose was used to make composites in order to make less variation in products, decrease the dependency of natural fibers, promoting locally available fibers and encourage forest products as value-added products. Lyocell and viscose fibers have relatively less variation and high quality. Bio-composites were made by reinforcing wood-based fibers in soybean based thermoset matrix. Hybrid composites were prepared by mixing two different wood-based fibers in known ratio. The fiber content in the composites was between 40 and 60 weight%. Mechanical properties were characterized by tensile, flexural and impact tests. Lyocell and viscose based composites had better mechanical properties than jute fiber composites. Alkali treatment of Lyocell fibers improved the mechanical properties of the composites. The behaviour of wood-based fiber composites were studied under wet environment as well. In wet environment, the mechanical properties of wood-based fiber composites were superior to jute fiber composites. Lyocell based composites had tensile strength of 135 MPa and tensile modulus of 17 GPa. The composites had flexural strength of 127 MPa and flexural modulus of 7 GPa. Better percentage elongation was obtained when viscose fiber was reinforced in matrix. Viscose composites had better impact strength and viscoelastic properties. The change in properties in two different wood-based fibers (Lyocell and viscose) lies in the morphology of the fiber itself. Hybrid composites were produced and the effect of hybridization was clear in most of the cases. The properties were able to be tailored by making hybrid composites, by changing the amount of each fiber in the composites. The results (tensile and flexural) were competitive and fulfil the requirements of these composites to be used in several applications including automotive headliners, car door panel, construction door frame etc. The forest products such as wood fibers could be used in composites to produce environmentally friendly products and promote forest industry. Wood-based fibers such as Lyocell and Viscose was used to make composites in order to make less variation in products, decrease the dependency of natural fibers, promoting locally available fibers and encourage forest products. Bio-composites were made by reinforcing wood-based fibers in soybean based thermoset matrix. Hybrid composites were prepared by mixing two different wood-based fibers in known ratio. Mechanical properties were characterized by tensile, flexural and impact tests. Lyocell and viscose based composites had better mechanical properties than jute fiber composites. Alkali treatment of Lyocell fibers improved the mechanical properties of the composites. The behaviour of wood-based fiber composites were studied under wet environment as well. In wet environment, the mechanical properties of wood-based fiber composites were superior to jute fiber composites. Lyocell based composites had tensile strength of 135 MPa and tensile modulus of 17 GPa. The composites had flexural strength of 127 MPa and flexural modulus of 7 GPa. Viscose composites had better impact strength and viscoelastic properties. The result fulfils the requirements of these composites to be used in several applications including automotive headliners, car door panel etc. The forest products could be used in composites to produce environmentally friendly products and promote forest industry.
Composites were developed by reinforcing available non-woven Lyocell and viscose in acrylated epoxidized soybean oil (AESO). Compression molding was used to make composites with 40–60 wt% fiber content. The fiber content comprises only Lyocell or viscose fiber, or mixture of these fibers in known ratio. Hybrid composites were made by a mixture of both the fibers in known ratio and it affects the properties. The effect of hybridization was evident in most tests which gives us an opportunity to tailor the properties according to requirement. Lyocell fiber reinforced composites with 60 wt% fiber content had a tensile strength and modulus of about 135 MPa and 17 GPa, respectively. Dynamic mechanical analysis showed that the Lyocell fiber reinforced composites had good viscoelastic properties. The viscose fiber reinforced composites had the high percentage elongation and also showed relatively good impact strength and flexural modulus. Good fiber-matrix adhesion reflected in mechanical properties. SEM images were made to see the fiber-matrix compatibility.
Wood pulp based regenerated cellulose fibers like Lyocell and viscose which are from natural origin have high and even quality; used to develop superior composites with good properties. In this project, Lyocell and viscose fibers were reinforced in chemically modified soybean based bio-matrix, acrylated epoxidized soybean oil (AESO) by compression molding technique. The composites are characterized for mechanical performance by tensile, flexural and impact tests, viscoelastic performance by dynamical mechanical thermal analysis (DMTA) and morphological analysis by scanning electron microscopy (SEM). In general, Lyocell composites had better tensile and flexural properties than viscose based composites. The same goes with elastic and viscous response of the composites. Hybrid composites were formed by fiber blending; on addition of Lyocell to viscose based composites improved the properties. The amount of Lyocell and viscose fibers used determined the properties of hybrid composites and the possibility of tailoring properties for specific application was seen. Hybrid composites showed better impact strength. Morphological analysis showed that the viscose composites had small fiber pull out whereas Lyocell composites had few pores. Hybrid composite analysis showed that they had uneven spreading of matrix; delamination occurred on constant heating and cooling. To overcome the above mentioned issue and to reduce the water absorption, surface modification of the fiber was done by alkali treatment and silane treatment. The effect of treatment is done through swelling, water absorption and morphological analysis tests. The properties could be increased on proper modification of the fibers. The results show the good potential of these composites to be used in automotives and construction industries.
Composites were manufactured from regenerated cellulose and biobased matrix by compression molding. The reinforcing materials used were Lyocell and viscose, while the matrix used was chemically modified soybean oil. Hybrid composites were prepared by mixing both the fibers. The total fiber content in the composites was between 40-60 weight %. Lyocell based composites had better tensile properties than viscose based composites; composites consisting 60 weight % Lyocell impregnated with matrix had tensile strength of 135 MPa and tensile modulus of 17 GPa. These composites also showed better flexural properties; flexural strength of 127 MPa and flexural modulus of 7 GPa. Dynamic mechanical thermal analysis results showed that these composites had good viscoelastic properties. Viscose based composites had better percentage elongation; these composites also showed relatively good impact and viscoelastic properties. Hybrid composites showed good mechanical and viscoelastic properties. Scanning electron microscope images showed that the composites had good fiber-matrix adhesion.
Polyester (PET) has wide applications in textile industries as textile fiber and its share continues to grow. Substantial quantities of cotton/polyester blend fabrics are disposed every year due to technical challenges, which pose a big environmental and waste-dumping problem. The aim of this study is to evaluate the potential of discarded cotton/PET fabrics as raw materials for composites. If their inherent reinforcement properties can be used in composites, an ecological footprint issue can be solved. In this study, we investigate three concepts for reuse of cotton/PET fabrics for composites: compression molding above the Tm of PETs, use of a matrix derived from renewable soybean oil, use of thermoplastic copolyester/polyester bi-component fibers as matrix. All three concepts have been explored to make them available for wider applications. The effects of processing parameters such as compression temperature, time and pressure are considered in all three cases. The third concept gives the most appealing properties, which combine good tensile properties with toughness; more than four times better tensile strength than the first concept; and 2.2 times better than the second concept.
Abstract:
Thermoset bioresin was synthesized from lactic acid and glycerol, and the resin was characterized for it to be used in composite applications. On the other hand, regenerated cellulose fibers were surface treated to improve the physico–chemical interactions at the fiber–matrix interface. The effect of surface treatments, silane and alkali, on regenerated cellulose fibers was studied by using the treated fibers as reinforcement in lactic acid thermoset bioresin. Mechanical tests were used as indicator of the improvement of the interfacial strength. Fiber surface treatments and the effect on adhesion to the matrix were characterized using microscopy images and thermal conductivity. Mechanical properties of the composites showed an increase when treated with silane as the bi-functional silane molecule acts as link between the regenerated cellulose fiber and the bioresin.
Porosity volume decreased significantly on silane treatment due to improved interface and interlocking between fiber and matrix. Decrease in water absorption and increase in contact angle confirmed the change in the hydrophilicity of the composites. The storage modulus increased when the reinforcements were treated with silane whereas the damping intensity decreased for the same composites indicating a better adhesion between fiber and matrix on silane treatment. Thermogravimetric analysis indicated that the thermal stability of the reinforcement altered after treatments. The resin curing was followed using differential scanning calorimetry and the necessity for post-curing was recommended. Finite element analysis was used to predict the thermal behavior of the composites and a non-destructive resonance analysis was performed to ratify the modulus obtained from tensile testing. The changes were also seen on composites reinforced with alkali treated fiber. Microscopy images confirmed the good adhesion between the silane treated fibers and the resin at the interface.
Natural fibers today are a popular choice for applications in composite manufacturing. Based on the sustainability benefits, biofibers such as plant fibers are replacing synthetic fibers in composites. These fibers are used to manufacture several biocomposites. The chemical composition and properties of each of the fibers changes, which demands the detailed comparison of these fibers. The reinforcement potential of natural fibers and their properties have been described in numerous papers. Today, high performance biocomposites are produced from several years of research. Plant fibers, particularly bast and leaf, find applications in automotive industries. While most of the other fibers are explored in lab scales they have not yet found large-scale commercial applications. It is necessary to also consider other fibers such as ones made from seed (coir) and animals (chicken feather) as they are secondary or made from waste products. Few plant fibers such as bast fibers are often reviewed briefly but other plant and animal fibers are not discussed in detail. This review paper discusses all the six types of plant fibers such as bast, leaf, seed, straw, grass, and wood, together with animal fibers and regenerated cellulose fibers. Additionally, the review considers developments dealing with natural fibers and their composites. The fiber source, extraction, availability, type, composition, and mechanical properties are discussed. The advantages and disadvantages of using each biofiber are discussed. Three fabric architectures such as nonwoven, woven and knitted have been briefly discussed. Finally, the paper presents the overview of the results from the composites made from each fiber with suitable references for in-depth studies.
Cellulose fibres have significant importance and potential for polymer reinforcement. It is essential to modify the surface of the fibre to obtain good fibre-matrix interface. Surface treatments can increase surface roughness of the fibre, change its chemical composition and introduce new moieties that can effectively interlock with the matrix, resulting in good mechanical properties in the composites. This is mainly due to improved fibre-matrix adhesion. The treatments may also reduce the water absorption rate by converting part of the hydroxyl groups on the fibre surface into other functional groups. Chemical modification of the surface of a regenerated cellulose fibre of the Lyocell type was carried out by alkali and silane treatments, which significantly changed the properties of the Lyocell fibres. Three parameters were considered when the fibre surface treatment was done: concentration (2–15 wt%), temperature (25 and 50 C) and time (30 min–72 h). Fourier transform infrared spectroscopy and Raman spectroscopy were used for chemical analysis and qualitative analysis of the cellulose crystallinity due to the surface treatments; subsequently, mechanical strength of the fibres was tested by tensile testing. Weight loss, moisture regain and swelling measurements were taken before and after treatments, which showed the obvious changes in fibre properties on treatment. Heat capacity of the fibres was measured for untreated and treated fibres, and thermal degradation of fibres was examined to see the stability of fibres at elevated temperatures. Wettability and surface energies were measured using dynamic contact angle method in three wetting mediums. Scanning electron microscopy was used to study the morphological properties of the fibres.
This chapter focuses on physicochemical and mechanical characterization of compositesmade from renewable materials. Most common renewable materials used in composites arenatural fibers and polymers based on starch or vegetable oil. The extent of using renewablematerials in biocomposites has increased during the past decade due to extensive research oncellulosic fibers and biobased polymers. Earlier, the research was focused on using the naturalfibers as reinforcement in crude oil-based polymers such as polypropylene. Later, the emphasisshifted to increase the amount of renewable components in the biocomposites which led tothe introductionof biobased resins in the composites. The properties of some biocompositesare today comparable to the properties for commercially available nonrenewable composites.Several plant biofibers have been used as reinforcement in biobased thermoplastics or thermosetsto manufacture biocomposites. Material characterization is important to understand theperformance of these composites under specific environment. Detailed discussion about themechanical and physicochemical characterization is provided in this chapter. Physicochemicalcharacterization includes chemical composition, density, viscosity, molecular weight, meltingtemperature, crystallinity,morphology, wettability, surface tension, water binding capacity,electricalconductivity, flammability, thermal stability, and swelling. Mechanical characterizationincludes tensile, flexural, impact, compressive, shear, toughness, hardness, brittleness, ductility,creep, fatigue, and dynamic mechanical analysis.
In this study, formaldehyde‐free bioresin adhesives were synthesised from lignin and tannin, which were obtained from softwood bark. The extraction was done via organosolv treatment and hot water extraction, respectively. A non‐volatile, non‐toxic aldehyde, glyoxal, was used as a substitute for formaldehyde in order to modify the chemical structure of both the lignin and tannin. The glyoxal modification reaction was confirmed by ATR–FTIR spectroscopy. Three different resin formulations were prepared using modified lignin along with the modified tannin. The thermal properties of the modified lignin, tannin, and the bioresins were assessed by DSC and TGA. When the bioresins were cured at a high temperature (200 ℃) by compression moulding, they exhibited higher thermal stability as well as an enhanced degree of cross‐linking compared to the low temperature‐cured bioresins. The thermal properties of the resins were strongly affected by the compositions of the resins as well as the curing temperatures.
This work focuses on the development of cross-linked polymer from a highly unsaturated vegetable oil, tung oil (TO) and a bio-based acrylate, furfuryl methacrylate (FMA). The presence of a high degree of unsaturated carbon-carbon bonding in TO makes it a suitable precursor for polymer synthesis. Using this advantage of TO, in this work, we have synthesised a cross-linked polymer from TO and FMA through free radical polymerisation followed by Diels-Alder (DA) reaction. Successful incorporation of both of the raw materials and the two chemical reactions was shown using Fourier-transform infrared (FTIR) and Raman spectroscopy. The development of cross-linked structure was analysed through thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA).
The fabrication of smart biocomposites from sustainable resources that could replace today’s petroleum-derived polymer materials is a growing field of research. Here, we report preparation of novel biocomposites using nanocellulose networks extracted from food residue (onion skin) and a vegetable oil-based bioresin. The resin was synthesized via the Diels-Alder reaction between furfuryl methacrylate and tung oil at various ratios of the components. The onion-skin-extracted cellulose nanofiber and cellulose nanocrystal networks were then impregnated with the resins yielding biocomposites that exhibited improved mechanical strength and higher storage modulus values. The properties of the resins, as well as biocomposites, were affected by the resin compositions. A 190-240-fold increase in mechanical strength was observed in the cellulose nanofiber (CNF) and cellulose nanocrystal (CNC)-reinforced biocomposites with low furfuryl methacrylate content. The biocomposites exhibited interesting shape-memory behavior with 80-96% shape recovery being observed after 7 creep cycles.
New technologies in the automotive industry require lightweight, environment-friendly, and mechanically strong materials. Bast fibers such as kenaf, flax, and hemp reinforced polymers are frequently used composites in semi-structural applications in industry. However, the low mechanical properties of bast fibers limit the applications of these composites in structural applications. The work presented here aims to enhance the mechanical property profile of bast fiber reinforced acrylic-based polyester resin composites by hybridization with basalt fibers. The hybridization was studied in three resin forms, solution, dispersion, and a mixture of solution and dispersion resin forms. The composites were prepared by established processing methods such as carding, resin impregnation, and compression molding. The composites were characterized for their mechanical (tensile, flexural, and Charpy impact strength), thermal, and morphological properties. The mechanical performance of hybrid bast/basalt fiber composites was significantly improved compared to their respective bast fiber composites. For hybrid composites, the specific flexural modulus and strength were on an average about 21 and 19% higher, specific tensile modulus and strength about 31 and 16% higher, respectively, and the specific impact energy was 13% higher than bast fiber reinforced composites. The statistical significance of the results was analyzed using one-way analysis of variance. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
Natural fibers, such as kenaf, hemp, and flax, also known as bast fibers, offer several benefits such as low density, carbon dioxide neutrality, and less dependence on petroleum sources. Their function as reinforcement in polymer composites offers a great potential to replace a segment of the glass fiber-reinforced polymer composites, especially in automotive components. Despite their promising benefits, they cannot meet the structural and durability demands of automobile parts because of their poor mechanical properties compared to glass fibers. The focus of this research work was the improvement of the mechanical property profile of the bast fiber reinforced polypropylene composites by hybridization with natural high-performance basalt fibers and the influence of basalt fibers coating and polymer modification at the mechanical and thermal properties of the composites. The specific tensile strength of the composite with polymer tailored coating was 39% and the flexural strength was 44% higher than the composite with epoxy-based basalt fibers. The mechanical performance was even better when the bast/basalt hybridization was done in maleic anhydride modified polymer. This led to the conclusion that basalt fibers sizing and polymer modification are the deciding factors in defining the optimal mechanical performance of the composites by influencing the fiber-matrix interaction. The composites were analyzed for their mechanical, thermal, and morphological properties. The comparison of bast/basalt hybrid composite with bast/glass fibers hybrid composite showed a 32% higher specific flexural and tensile strength of the basalt hybrid composite, supporting the concept of basalt fibers as a natural alternative of the glass fibers.
With increasing limitation of petrochemical resources, there is a growing demand for the replacement of nonrenewable fiber-reinforced polymer composites by renewable polymer composites. Therefore, the aim of this research work was to improve the mechanical properties of bast (plant) fibers reinforced polymer composites without reducing their renewable material content. To achieve this goal, basalt fibers (natural mineral fibers) were used to partially substitute the amount of bast fibers in the polymer composites. The applied fibers were processed to semi-finished materials by carding and needle punching and processed further by afterwards press-molding. An intense optimization of the carding process led to the production of homogeneous fabrics based on various types of fibers (bast, basalt and PP). The homogeneity of the fabrics was confirmed by scanning electron microscopy (SEM) analysis of the composites. Several composites based on polypropylene and acrylate thermoset resin, reinforced with merely bast fibers, were prepared as reference. In the next steps, the bast fiber content of the reference compositions was partially replaced by basalt fibers. The compression-molded samples were tested for their flexural, tensile, and impact energy properties. The very positive finding was that the addition of basalt fibers not just improved significantly the strength and stiffness of the composites, but simultaneously increased the properties of the composites regarding energy absorption, a key requirement in the automotive industry. The fracture surface analysis confirmed a better fiber matrix adhesion in thermoset composites compared to thermoplastic composites. The tested renewable hybrid polymer composites have great potential to replace nonrenewable fiber-reinforced polymer composites.
Composites with reinforcements based on bast fibers such as flax, hemp and kenaf offer many advantages such as weight reduction, improved specific impact, flexural, acoustic properties, and balanced performance to cost that can be achieved by properly designing the material composition. Their position is well established, especially in the nonstructural automotive applications. However, in structural applications of composites, their mechanical property profile is not comparable to the dominant reinforcements such as glass and carbon fibers. The low mechanical properties of these composites could be improved by hybridization that involves adding high-performance fibers to the bast fiber composites that could improve the low mechanical performance of the bast fiber composites. The review presented in this article provides an overview of the developments in the field of hybrid polymer composites composed of bio-based bast fibers with glass, carbon, and basalt fibers. The focus areas are the composite manufacturing methods, the influence of hybridization on the mechanical properties, and the applications of hybrid composites.
Man-made cellulosic fibres (MMCFs) have attracted widespread interest as the next generation of fibre reinforced composite. However, most studies focused entirely on their performance on single fibre level and little attention has been paid to their behaviour on a larger application scale. In this study, MMCFs were utilized as reinforcement in unidirectionally (UD) manufactured thermoset composites and compared to several commercial UD flax fibre products. Specimens were prepared using a vacuum bag based resin infusion technique and the respective laminates characterized in terms of void fraction and mechanical properties. MMCF laminates had comparable or better mechanical performance when compared to flax fibre laminates. Failure mechanisms of MMCF laminates were noted to differ from those of flax-reinforced laminates. The results demonstrate the potential of MMCFs as a viable alternative to glass fibre for reinforcement on a larger scale of UD laminates. These results were utilized in the Biofore biomaterial demonstration vehicle.