Potential of producing carbon fiber from biorefinery corn stover lignin with high ash content

The possibility of producing carbon fiber from an industrial corn stover lignin was investigated in the present study. As‐received, high‐ash containing lignin was subjected to methanol fractionation, acetylation, and thermal treatment prior to melt spinning and the changes in physiochemical and thermal properties were evaluated. Methanol fractionation removed most of the impurities in the raw lignin and also selectively removed the molecules with high melting points. However, neither methanol fractionation nor thermal treatment rendered melt‐spinnable precursors. The precursors were highly viscous and decomposed easily at low temperatures, attributed to the presence of H, G phenolic units, and abundant hydroxycinnamate groups in herbaceous lignin. A two‐step acetylation of methanol fractionated lignin greatly improved the mobility of lignin, while enhancing the thermal stability of the precursor during melt‐spinning. Fourier Transform Infrared and 2D‐NMR analysis showed that the contents of phenolic and aliphatic hydroxyls, as well as the hydroxycinnamates, decreased in the acetylated precursors. The optimum precursor was a partially acetylated lignin with a glass transition temperature of 85 °C. Upon oxidative stabilization and carbonization, the carbon fibers with an average tensile strength of 454 MPa and modulus of 62 GPa were obtained. The Raman spectroscopy showed the I_D/I_G ratio of the carbon fiber was 2.53. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45736.     

Recent advances in low‐cost carbon fiber manufacture from lignin

The confluence of two US energy policy mandates, the 2012 Corporate Average Fuel Economy Standards and Renewable Fuels Standard #2, provide the opportunity to examine the possibility of high‐value materials from lignin with increased depth. In this case, the desire to provide lighter, low‐cost materials for automobiles to reduce fuel consumption, and to improve the economics of biorefineries for fuel production, have led to an increased interest in low‐cost carbon fiber manufacture from lignin. For this review the authors provide the context of subject matter importance, a cost comparison of potential low‐cost carbon fibers, a brief review of historical work, a review of more recent work, and a limited technical discussion followed by recommendations for future directions. As the available material for review is limited, the author includes many references to publicly available government documents and reviewed proceedings that are generally difficult to locate. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 713‐728, 2013     

Poly(lactic acid)/areca fiber laminate composites processed via film stacking technique

Bio‐based laminate composites, consisting of alternatively stacked poly(lactic acid) (PLA) sheet and randomly oriented areca fiber mat, were processed via film stacking technique (FST). FST was chosen as it is a commercially viable, low energy‐intensive process for fabricating fiber‐reinforced composite, thereby advocating environmental sustainability. Laminate composites exhibited mechanical strength of 6.5 MPa at 16 wt % fiber loading. Crystallinity of as‐received PLA sheets was found to be 26% due to the presence of ～30 wt % inorganic filler, and showed further enhancement to 50% upon the addition of 22 wt % areca fiber. Dynamic mechanical analysis showed higher glass transition temperature (83 °C) for PLA sheets, mainly due to the presence of higher filler content. This work demonstrates the use of bio‐based laminate composite processed at the lowest possible temperatures as viable alternatives to thermoplastic polyolefins in automobiles. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45795.     

Development of lignin carbon fibers: Evaluation of the carbonization process

The use of lignin as a renewable resource for the production of less‐expensive carbon fibers has in recent years attracted great interest. In order to develop the strength properties, the stabilization and carbonization processes have to be optimized. For this reason, the process parameters during carbonization have here been studied on stabilized lignin fibers in the temperature interval from 300 to 1300 °C. The effects of temperature, heating rate, and straining of fibers during carbonization on the strength properties of carbon fibers were investigated. The heating rate, in the range from 1 to 40 °C/min, was shown to have no effect on the property development of the fibers. During carbonization with no load applied to the fibers, a shrinkage of 20% was noted. Counteracting the shrinkage by imposing a load on the fibers during the carbonization resulted in fibers with a greater stiffness. The tensile strength was not, however, affected by this loading. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43965.     

Preparation and evaluation of composite microspheres of polyacrylamide‐grafted polysaccharides

The poor mechanical strength and instability of polysaccharide's gel takes away opportunities for versatile application. The grafting of polyacrylamide (PAM) onto polysaccharide was found to be an efficient tool for transforming its properties and obtaining stable and robust composite microspheres (CMs). In this study, free‐radical polymerization reaction was used for the grafting of PAM onto the polysaccharide backbone, and their hydrogel CMs were obtained through an ionotropic gelation method. Porous and buoyant CMs were obtained through the incorporation of sodium bicarbonate into the reaction mixture. Characterizations were done through Fourier transform infrared spectroscopy, thermal and scanning electron microscopy analysis. The mechanical strength and squeezing capacity were evaluated extensively through a modified syringe method developed in‐house. The squeezing capacity of grafted CMs diminished with the formation of a complex interpenetrating network. The Young's modulus, swelling kinetics, mechanical strength, and squeezing capacity of the grafted microspheres were compared extensively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2912–2922, 2013     

Surface modification of textile material through deposition of regenerated silk fibroin

Regeneration of silk fibroin from calcium chloride/ethanol/water solution is of high interest to shape biomaterial based products for medical and technical application. In this study a continuous process for surface modification of cellulose or polyamide fibers by regenerated fibroin deposits has been investigated. The decomposition of the fibroin‐calcium complex was initiated by addition of K₂CO₃ followed by a methanol rinse. Reactive Blue 19 labeled fibroin was used to monitor the deposition of fibroin on the substrates by colour measurement. The fibroin deposits on the fabric were characterized by microscopy, N‐content, calcium, and protein content. Stiffness and surface resistivity of modified fabrics were determined as representative physical parameters. The reduced mobility of fibers increased fabric stiffness. Surface resistivity of treated samples was reduced by a factor of 10 to 100, which gives an example for the potential of the technique as coating for man‐made fiber textiles. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45098.     

Esterification of Kraft lignin as a method to improve structural and mechanical properties of lignin‐polyethylene blends

Lignin is a promising candidate for blends with thermoplastic polymers. Still, this endeavour is a challenge due to poor compatibility between both components. In this article, the effect of lignin esterification on the improvement of the compatibility between hardwood Kraft lignin and high‐density polyethylene (PE‐HD) is investigated. For this purpose, lignin was esterified with acetic, propionic, and butyric anhydride; its amount in the blends varied from 10 to 40%. Light microscopic images of blends show a reduction in particle size and a more homogeneous distribution with increasing length of the ester carbon chains (C2 to C4). Modification of lignin enhances the moduli and strength characteristics of the blends. Butyrated lignin performs best, as tensile strength of blends can be retained near that of pure PE‐HD with up to 40% lignin content. An additional investigation of unmodified lignin with reduced particle size confirms that modification is the decisive factor to enhance blend properties; a sole reduction of particle size is insufficient. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44582.     

Mechanical and thermal characterization of compression moulded polylactic acid natural fiber composites reinforced with hemp and lyocell fibers

This research evaluates the effects of PLA/PP blend ratio and Lyocell/hemp mixture ratio on the morphology, water absorption, mechanical and thermal properties of PLA‐based composites. The composites were fabricated with 30 mass % hemp using compression moulding. As a reference composites made from PP were also studied. Combining of hemp and Lyocell in PLA composite leads to the reduction of moisture absorption and can improve the impact, tensile, flexural properties when compared with PLA/hemp. Composite based on the PLA/PP blend‐matrix could not improve the tensile and flexural properties compared with PLA/hemp, however; the lighter composite with better impact properties was obtained. The crystallization temperature of the PLA‐PP/hemp increased compared with pure PLA. This result was also confirmed by the SEM micrographs. The moisture absorption of PLA‐PP/hemp was higher than PLA/hemp. Based on theoretical analysis of DMTA data, there was favorable adhesion in all composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40534.     

Characterization of soda hardwood lignin and the formation of lignin fibers by melt spinning

Lignin fibers were developed from a commercial available soda hardwood lignin (SHL) with a melt‐spinning approach. SHL showed spinnability to form the fine fibers when poly(ethylene oxide) was used as a plasticizer with lignin. The thermal properties of lignin provided valuable information to assist the processing steps of the lignin fiber formation. The guaiacyl/syringyl ratio in SHL was determined by ³¹P‐NMR because it had great influence on the thermal mobility of lignin. A suitable temperature profile for the melt spinning was predicted through rheological studies of lignin. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Carbon nanofibers from renewable bioresources (lignin) and a recycled commodity polymer [poly(ethylene terephthalate)]

Utilizing inexpensive biorenewable and waste raw materials for the production of carbon nanofibers can pave the way for lowering their manufacturing cost. In this research, lignin is combined with recycled poly(ethylene terephthalate) (PET) to fabricate precursor fibers via electrospinning. The process is optimized using the Design of Experiments statistical methodology and fibers with minimum average diameter equal to 191 ± 60 nm are prepared. Investigation with Attenuated Total Reflection – Fourier Transform Infrared Spectroscopy reveals the lignin structural changes induced by the solvent (trifluoroacetic acid), which is used for the preparation of homogeneous solutions of lignin and PET in various concentrations, while it gives an indication of the blending of the two electrospun polymers. The good miscibility between lignin and PET is also confirmed with Differential Scanning Calorimetry. The subsequent carbonization of the precursor fibrous mats results in a fibrous carbon structure with average fiber diameters similar to those of the precursor fibers. The successful transformation into carbon nanofibers is affirmed by Energy Dispersive X‐ray Spectroscopy. The Carbon content of these nanofibers amounts to 94.3%. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43936.     

Lignin‐based carbon fibers: Accelerated stabilization of lignin fibers in the presence of hydrogen chloride

Organosolv switchgrass lignin (SGL) and hardwood lignin (HWL) polymers are used as precursors to prepare low cost carbon fibers (CFs). Lignin powder and fiber samples are stabilized and carbonized at different conditions to investigate the effect of HCl on thermal‐oxidative stabilization time, mass yield, fiber diameter, and mechanical properties. The results show that HCl can accelerate stabilization and reduce the stabilization time from many hours to 75 min for the SGL fibers, and to 35 min for the HWL fiber. The rate of rapid stabilization in HCl/air is at least four times faster than conventional stabilization in air. The CFs prepared with two different stabilization methods have almost the same strength and modulus, but higher carbon yield is obtained with the rapid stabilization due to a short time of oxidation. Pores and defects observed on the surface and the cross‐section of the CFs across all stabilization conditions contribute to low fiber strength. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45507.     

Study on the effect of woven sisal fiber mat on mechanical and viscoelastic properties of petroleum based epoxy and bioresin modified toughened epoxy network

Sisal fiber reinforced biocomposites are developed using both unmodified petrol based epoxy and bioresin modified epoxy as base matrix. Two bioresins, epoxidized soybean oil and epoxy methyl soyate (EMS) are used to modify the epoxy matrix for effective toughening and subsequently two layers of sisal fiber mat are incorporated to improve the mechanical and thermomechanical properties. Higher strength and modulus of the EMS modified epoxy composites reveals good interfacial bonding of matrix with the fibers. Fracture toughness parameters K_IC and G_IC are determined and found to be enhanced significantly. Notched impact strength is found to be higher for unmodified epoxy composite, whereas elongation at break is found to be much higher for modified epoxy blend. Dynamic mechanical analysis shows an improvement in the storage modulus for bioresin toughened composites on the account stiffness imparted by fibers. Loss modulus is found to be higher for EMS modified epoxy composite because of strong fiber–matrix interfacial bonding. Loss tangent curves show a strong influence of bioresin on damping behavior of epoxy composite. Strong fiber–matrix interface is found in modified epoxy composite by scanning electron microscopic analysis. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42699.     

Gluten free edible film based on rice flour reinforced by guabiroba (Campomanesia xanthocarpa) pulp

Films based on rice flour were optimized using varying concentrations of guabiroba pulp (0–20%). After production using casting techniques, the films were subsequently characterized and compared to the control film. It was observed that the addition of guabiroba pulp enhanced the mechanical, optical, and water vapor barrier properties of the obtained films. Scanning electron microscopy and Fourier-transform infrared spectroscopy tests indicated a good dispersion and interaction of the guabiroba pulp with the rice flour polymer matrix. Guabiroba pulp can therefore be used as a reinforcing additive in edible food packaging, among other purposes.     

Antimicrobial activity of PLA/PEG nanofibers containing terpinen‐4‐ol against Aggregatibacter actinomycetemcomitans

In this article, nanofibrous mats of poly(lactic acid) (PLA) and poly(ethylene glycol) (PEG) with different PLA/PEG ratios were prepared by solution blow spinning. Terpinen‐4‐ol, a major phytoconstituent from tea tree oil (Melaleuca alternifolia) was added to the fibers and their antimicrobial activity against Aggregatibacter actinomycetemcomitans (ATCC 00078) was tested. Spun mats were characterized by scanning electron microscopy, thermogravimetric analyses, differential scanning calorimetry, Fourier‐transform infrared spectroscopy (FTIR), and cell viability tests by biofilm grown on the surface of inhibitory fibers. Fibers had average diameters dependent on polymer ratio. PEG acted as a plasticizer resulting in a reduction in PLA crystallinity. Addition of PEG lead to a faster drug release. Fibrous mats with terpinen‐4‐ol, whose incorporation was verified by FTIR, showed an effective antimicrobial activity against A. actinomycetemcomitans, similar to those containing 0.12% chlorhexidine gluconate (P < 0.05), used as both the positive control and the dose level recommended for patient treatment. These results confirm the potential of solution blow spun fibrous mats containing terpinen‐4‐ol in the treatment of aggressive periodontitis. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45782.     

Overmolded polylactide/jute-mat eco-composites: A new method to enhance the properties of natural fiber biodegradable composites

Environmentally friendly, biodegradable composites were prepared via overmolding of poly(lactic acid) (PLA) onto PLA/jute-mat, named as “ecosheets,” reinforced continuous fiber composite sheets. Film stacking procedure was used to prepare ecosheets via using a hot-press. The fiber orientation was changed as −45°/+45° and 0°/0°. −45°/+45° orientation exhibited higher properties as compared to 0°/0° for ecosheets; therefore, this construction was used to produce overmolded composites (OMCs). The mechanical tests showed that flexural modulus and strength of OMCs were improved in comparison to neat PLA. The dynamic mechanical analysis exhibited that the thermomechanical resistance of PLA was enhanced for OMCs. Scanning electron microscopy investigation showed that the jute/PLA interphase needs to be improved to further increase the properties. It was concluded that one of the biggest advantages of this novel technique was the increase of mechanical properties of PLA without altering the density. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48692.     

Development and characterization of flax fiber reinforced biocomposite using flaxseed oil‐based bio‐resin

In this study, acrylated epoxidized flaxseed oil (AEFO) resin is synthesized from flaxseed oil, and flax fiber reinforced AEFO biocomposites is produced via a vacuum‐assisted resin transfer molding technique. Different amounts of flax fiber and styrene are added to the resin to improve its mechanical and physical properties. Both flax fiber and styrene improve the mechanical properties of these biocomposites, but the flexural strength decreases with an increase in styrene content. The mass increase during water absorption testing is less than 1.5% (w/w) for all of the AEFO‐based biocomposites. The density of the AEFO resin is 1.166 g/cm³, which increases to 1.191 g/cm³ when reinforced with 10% (w/w) flax fiber. The flax fiber reinforced AEFO‐based biocomposites have a maximum tensile strength of 31.4 ± 1.2 MPa and Young's modulus of 520 ± 31 MPa. These biocomposites also have a maximum flexural strength of 64.5 ± 2.3 MPa and a flexural modulus of 2.98 ± 0.12 GPa. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41807.     

Incorporation of epoxidized soybean oil as co‐matrix in epoxy resin toward developing plastisol/particulate toughened glass fiber composites

Epoxidized soybean oil was incorporated as a co‐matrix into an epoxy resin, and the hybrid resin system was used for preparing glass fiber‐reinforced composites. Effect of addition of poly(vinyl chloride) plastisol and selected particulate fillers (fly ash and wood flour) to epoxy/epoxidized soybean oil matrix on mechanical and water uptake properties of glass fiber‐reinforced composites were studied. Fourier transform infrared spectroscopy was used to reveal the curing state of these composites. It was observed that tensile strengths and moduli decreased with the inclusion of all additives. However, addition of poly(vinyl chloride) plastisol, fly ash, and wood flour particulate fillers showed significant increase in impact strengths compared with neat epoxy composite in a synergistic manner. Water uptake results of the composites were found to be in good agreement with ? OH peak intensities obtained from Fourier transform infrared spectroscopy. Finally, acousto‐ultrasonic nondestructive technique was successfully used to assess damage states and to relate stress wave factors with tensile strength properties of modified epoxy‐based glass fiber composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40586.     

Morphologies of electrospun fibers of lignin in poly(ethylene oxide)/N,N‐dimethylformamide

The effects of polyethylene oxide (PEO) molecular weight (Mv), and volume fraction ( ) on the morphology of electrospun sulfur free softwood lignin nanofibers were investigated. Small amounts of PEO were used during preparations of the solutions to aid the electrospinning process. It was found that tripling the PEO volume fraction resulted in a transition from semi‐dilute un‐entangled to semi‐dilute entangled solutions. Conversely, the solution remained in the semi‐dilute un‐entangled regime as the molecular weight was increased by five times. The effects of molecular weight and volume fraction of PEO both on entanglement density and fiber morphology were unified by scaling PEO viscosities as a function of . We investigated and discussed conditions that would produce smooth fibers and conditions that would produce fibers with beads. In the case of beads‐on‐a‐string formation, bead widths remained constant regardless of the molecular weight and concentration of PEO, but the bead length changed. Additionally, we observed a decrease in the diameter of the fibers and the dimension of beads (length and width of beads) with an increase in the electric field used for electrospinning. The aspect ratio of beads increased with increases to both the electric field and the PEO molecular weight or concentration. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44172.     

Development and characterization of green composites from bio‐based polyethylene and peanut shell

In the present work, different compatibilizers, namely polyethylene‐graft‐maleic anhydride (PE‐g‐MA), polypropylene‐graft‐maleic anhydride (PP‐g‐MA), and polystyrene‐block‐poly(ethylene‐ran‐butylene)‐block‐polystyrene‐graft‐maleic anhydride (SEBS‐g‐MA) were used on green composites derived from biobased polyethylene and peanut shell (PNS) flour to improve particle–polymer interaction. Composites of high‐density polyethylene/peanut shell powder (HDPE/PNS) with 10 wt % PNS flour were compatibilized with 3 wt % of the abovementioned compatibilizers. As per the results, PP‐g‐MA copolymer lead to best optimized properties as evidenced by mechanical characterization. In addition, best particle–matrix interface interactions with PP‐g‐MA were observed by scanning electron microscopy (SEM). Subsequently HDPE/PNS composites with varying PNS flour content in the 5–30 wt % range with PP‐g‐MA compatibilizer were obtained by melt extrusion and compounding followed by injection molding and were characterized by mechanical, thermal, and morphological techniques. The results showed that PNS powder, leads to an increase in mechanical resistant properties (mainly, flexural modulus, and strength) while a decrease in mechanical ductile properties, that is, elongation at break and impact absorbed energy is observed with increasing PNS flour content. Furthermore, PNS flour provides an increase in thermal stability due to the natural antioxidant properties of PNS. In particular, composites containing 30 wt % PNS powder present a flexural strength 24% and a flexural modulus 72% higher than the unfilled polyethylene and the thermo‐oxidative onset degradation temperature is increased from 232 °C up to 254 °C thus indicating a marked thermal stabilization effect. Resultant composites can show a great deal of potential as base materials for wood plastic composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43940.