Electrospinning of ultrafine cellulose fibers and fabrication of poly(butylene succinate) biocomposites reinforced by them

In this study, electrospinning conditions for ultrafine cellulose fibers was systematically studied and poly(butylene succinate) biocomposites reinforced by the ultrafine cellulose fibers (cellulose/PBS biocomposite) were fabricated. The ultrafine cellulose fibers were electrospun from cellulose (DP = 700) solutions in N‐methylmorpholine‐N‐oxide hydrate (85/15 w/w) at 100°C. The optimal electrospinning concentration of the cellulose solutions was determined to be 7 wt % and the average diameter of the resulting cellulose fibers was 560 nm. The cellulose I structure of the native cellulose was converted to the cellulose II structure after electrospinning. The ultrafine cellulose fibers showed a reinforcing effect in the cellulose/PBS biocomposite, suggesting that they have potential applications as reinforcement fibers for biocomposites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Improvement of adhesion between polyethylene and regenerated cellulose fibers by surface fibrillation

Regenerated cellulose fibers spun from straw pulp using the N-methylmorpholine N-oxide (NMMO) process were evaluated as a reinforcement for low-density polyethylene (LDPE). Surface fibrillation was carried out by a mechanical treatment to improve interfacial adhesion. Surface fibrillation resulted in a gradual change in surface topography, as detected by SEM. Long and numerous twisted fibrils were observed on the surface of the treated fibers. The fiber perimeters, determined by the Wilhelmy plate method, increased with an extended degree of fibrillation, while the strength of the fiber was not affected by the surface treatment. Model composites were prepared by embedding untreated and surface-fibrillated single fibers into an LDPE matrix, and the single fiber fragmentation (SEF) test was carried out to determine the critical fiber length. The interfacial shear strength (τ) was then calculated by applying a modified form of the Kelly-Tyson equation. It was found that the interfacial shear strength increased significantly as a result of surface fibrillation. The proposed mechanism for the improvement of interfacial adhesion is a mechanical anchoring between the matrix and the fiber.     

Synthesis and characterization of polypropylene reinforced with cellulose I and II fibers

Recently, cellulose fiber–thermoplastic composites have played an important role in some applications. Plastics reinforced with cellulose and natural fibers have been widely studied. However, composites with regenerated cellulose have rarely been investigated. In this study, the lyocell fiber of Lenzing AG (cellulose II) and its raw material a bleached hardwood pulp (cellulose I) were used as reinforcement materials. The mechanical and thermal properties of polypropylene (PP) reinforced with pulp and lyocell fibers were characterized and compared with regard to the content of the fiber and the addition of maleated polypropylene (MAPP). PPs with cellulose I or II as a reinforcement material had similar mechanical properties. However, when MAPP was used as coupling agent, the mechanical properties of the composites were different. The crystallinity of the composites were determined by differential scanning calorimetry. Cellulose I (pulp) promoted the crystallization of PP, whereas cellulose II did not. MAPP reduced this effect in cellulose I fibers, but it induced crystallization when cellulose II (lyocell) was used as a reinforcement material. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 364–369, 2006     

Characterization and Properties of Treated Oil Palm Empty Fruit Bunch Regenerated Cellulose Biocomposite Films with Butyl Methacrylate Using Ionic Liquid

Regenerated cellulose biocomposite films from oil palm empty fruit bunch and microcrystalline cellulose were prepared using N,N-dimethylacetamide and lithium chloride. The effects of oil palm empty fruit bunch contents and butyl methacrylate on properties of regenerated cellulose biocomposite films were investigated. At 2?wt% of untreated oil palm empty fruit bunch content showed highest crystallinity index, tensile strength, modulus of elasticity, and thermal stability but lower elongation at break than other oil palm empty fruit bunch content. The treated regenerated cellulose biocomposite films with butyl methacrylate showed better tensile strength, modulus of elasticity, thermal stability, and crystallinity index while Fourier transform infrared spectroscopy study showed interaction between cellulose and butyl methacrylate.     

Influence of optimal alkali treated Areca catechu L. peduncle fiber for light weight polymer composites applications

The chemical, physico-mechanical, morphological, and thermal characteristics of alkali treated natural cellulosic sustainable eco-friendly fiber from peduncle of Areca Catechu tree were investigated. Areca Catechu fruit peduncle fiber (ACFPF) treated with 5% (w/v) NaOH solution for 60 min is found as optimally alkali treated ACFPF (OAACFPF) witnessed an increase in cellulose content by 17%. Single fiber tensile test perceived that OAACFPF enhanced tensile strength by 12.9% and x-ray diffraction analysis depicts crystallinity index of OAACFPF improved by 14.2% compared with ACFPF. Also, Fourier transform infrared spectroscopy analysis endorsed partial removal of amorphous contents from fibers due to alkali treatment. In addition, alkali treatment has enhanced thermal stability of OAACFPF from 226°C to 235°C verified through Thermogravimetric analysis. Likewise, Differential scanning calorimetry analysis confirmed improvement in thermal degradation temperature of OAACFPF after alkali treatment. Moreover, the rougher surface of OAACFPF confirmed through scanning electron microscope and atomic force microscopy is due to partial removal of amorphous contents thus ensuing in good interfacial bonding characteristics with the matrix during reinforcement for bio-composite fabrication. The above findings validated OAACFPF as a worthy substitute to harmful synthetic fibers for development of eco-friendly and sustainable bio-composites.     

Engineering Lignocellulose Fibers with Higher Thermal Stability through Natural Fiber Welding

This study reveals how natural fiber welding (NFW) can be used to engineer biopolymer materials with improved thermal stability. First, it is shown how NFW without binders improves lignocellulose yarn thermal stability by ≈17 °C, primarily by condensing microfibril structure. Next, silanized‐cellulose nanofibrils (Si‐CNFs) are developed as NFW binders; this silanization process alters CNF physical and thermal properties. During pyrolysis, Si_x O_y networks form, which delay CNF decomposition (up to 37 °C), slow cellulose mass loss rates (up to 89%), and can enhance char yield more than twofold. When used as NFW binders, Si‐CNFs increase lignocellulose yarn thermal stability (up to 17 °C) proportional to siloxane amount, and can reduce cellulose mass loss rates (≈25% compared to welding without binder). These exciting results highlight the potential of NFW as a green‐engineering process to transform natural fibers into more thermally stable, biocomposite textile yarns.     

Effect of Compound Surface Treatment on the Performance of Poly(butylene succinate)/Chemithermomechanical Pulp Fiber Composites

Chemithermomechanical pulp fiber was pretreated by alkali solution to alter the surface characteristics of fibers. The untreated and treated fibers were used to prepare poly(butylene succinate)/chemithermomechanical pulp fiber composites with or without the incorporation of cellulose fatty acid ester (hydroxyethyl cellulose lauric acid ester). X-ray photoelectron spectrum analysis shows that the O/C ratio on the fiber surface increased after alkali treatment, indicating that part of lignin was removed during alkali treatment process. Scanning electron microcopy images indicate that the fiber surface was changed to rough after alkali treatment. The modification effect of hydroxyethyl cellulose lauric acid ester reflects as the improvement of fiber order in matrix, together with the enhancement of interfacial bonding, whereas, the modification effect of alkali treatment is mainly due to the enhancement of interfacial bonding. The integrated mechanical properties of composite prepared by alkali-treated fibers are superior to those of composite prepared by hydroxyethyl cellulose lauric acid ester-treated fibers. The combination of these two modification methods favors the enhancement of tensile and impact strengths of composite. However, in comparison with the composite prepared only by alkali treatment, the flexural strength and modulus would be despaired in a certain degree. When fibers were alkali treated, the shear viscosity of composite exhibited a larger increase, whereas the shear viscosity of composite prepared fibers with hydroxyethyl cellulose lauric acid ester treatment exhibits a slight decrease.     

Influence of alkali fiber treatment and fiber processing on the mechanical properties of hemp/epoxy composites

Industrial hemp fibers were treated with a 5 wt % NaOH, 2 wt % Na₂SO₃ solution at 120°C for 60 min to remove noncellulosic fiber components. Analysis of fibers by lignin analysis, scanning electron microscopy (SEM), zeta potential, Fourier transform infrared (FTIR) spectroscopy, wide angle X‐ray diffraction (WAXRD) and differential thermal/thermogravimetric analysis (DTA/TGA), supported that alkali treatment had (i) removed lignin, (ii) separated fibers from their fiber bundles, (iii) exposed cellulose hydroxyl groups, (iv) made the fiber surface cleaner, and (v) enhanced thermal stability of the fibers by increasing cellulose crystallinity through better packing of cellulose chains. Untreated and alkali treated short (random and aligned) and long (aligned) hemp fiber/epoxy composites were produced with fiber contents between 40 and 65 wt %. Although alkali treatment generally improved composite strength, better strength at high fiber contents for long fiber composites was achieved with untreated fiber, which appeared to be due to less fiber/fiber contact between alkali treated fibers. Composites with 65 wt % untreated, long aligned fiber were the strongest with a tensile strength (TS) of 165 MPa, Young's modulus (YM) of 17 GPa, flexural strength of 180 MPa, flexural modulus of 9 GPa, impact energy (IE) of 14.5 kJ/m², and fracture toughness (K_Ic) of 5 MPa m^1/2. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Mechanical Properties of Natural Fiber Containing Polymer Composites

We have studied the mechanical properties of ethylene vinyl acetate (EVA) and cellulose acetate (CA) composite containing cellulosic natural fibers (Sterculia villosa) and tried to explain with the help of mixing of fiber in the composite. It is observed that the tensile strength (TS) of EVA composite decreases with the addition of fiber. Whereas in a CA composite, TS increases or reinforcement happens with the fiber content. This anomalous trend could be explained with the adhesion of fiber with the polymer matrix in the composite. The composite shows the same increasing trend for flexural strength (FS) up to a certain composition of fiber. With the further addition of fiber, we have found decreasing FS for the EVA composite, but a gradual increase in the CA composite with the fiber content. It is thought that fiber is well distributed in the CA composite and that the fiber-matrix could bear the load resulting in an increase of FS. This consideration can be well explained from the SEM picture that shows fiber forms a domain in the EVA composite or coagulation of fiber, as a result the FS decrease, but there is no such type of coagulation in the CA composite, resulting in increasing TS and FS with the fiber content. Toughness of the composites are also compared. It is believed that the cellulose-containing EVA and CA composites will be environment-friendly. We also suggest that this composite could be used in a low weight application such as gasket materials, toothbrushes, spoon handles, mirror frames, partition panels, etc.     

Characteristics of banana fibers and banana fiber reinforced phenol formaldehyde composites‐macroscale to nanoscale

Microfibers and nanofibers were prepared from macro banana fibers by a steam explosion process. The fiber surface of chemically modified and unmodified banana fibers was investigated by atomic force microscopy, the studies revealed a reduction in fiber diameter during steam explosion followed by acid treatments. Zeta potential measurements were carried out to measure the acidic property of the fiber surface; the surface acidity was found to be increased from macrofibers to nanofibers. The thermal behavior of macrofibers, microfibers, and nanofibers were compared. Substantial increase in thermal stability was observed from macroscale to nanoscale, which proved the high thermal stability of nanofibers to processing conditions of biocomposite preparation. The composition of the fibers before and after steam explosion and acid hydrolysis were also analyzed using FT‐IR. It was found that the isolation of cellulose nanofibres occurs in the final step of the processing stage. Further macrocomposites, microcomposites, and nanocomposites were prepared and mechanical properties such as tensile, flexural and impact properties were measured and compared. The composites with small amount of nanofibers induces a significant increase in tensile strength (142%), flexural strength (280%), and impact strength (133%) of the phenol formaldehyde (PF) matrix, this increase is due to the interconnected web like structure of the nanofibers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1239‐1246, 2013     

Durability of thermomechanical pulp fiber-cement composites to wet/dry cycling

Previous research efforts on pulp fiber-cement composites have largely concentrated on kraft pulp fiber composites. In this research program, thermomechanical pulp (TMP) fibers were investigated as an economical alternative to kraft pulp fibers as reinforcement in fiber-cement composites. Prior to wet/dry cycling, TMP composites exhibited increased first crack strength, but lower peak strength and lower post-cracking toughness, as compared to unbleached and bleached kraft pulp composites at equivalent fiber volume fractions. It is believed that this behavior can be attributed to the lower tensile strength and shorter fiber length of TMP fibers as compared to kraft fibers. After 25 wet/dry cycles, TMP composites showed losses in first crack (peak) strength and post-cracking toughness. However, TMP composites exhibited a slower progression of degradation during wet/dry cycling than composites containing bleached or unbleached kraft fibers.     

Alkali–methanol–anthraquinone pulping of Miscanthus x giganteus for thermoplastic composite reinforcement

The potential of pulp fiber–reinforced thermoplastics is currently not fully explored in composites. One of the main reasons is that pulp fibers are extracted for the use in papermaking and are thus not optimized for use as reinforcements in thermoplastics. Furthermore, currently used processing methods constitute several severe thermomechanical steps inducing premature degradation of the fibers. A systematic development of these composite materials requires the study of both these aspects. The goal of this work was to optimize fiber extraction against properties relevant to the reinforcement of thermoplastics. To this end, thick‐walled Miscanthus x giganteus pulp fibers were selected. The fibers were pulped by the alkaline–methanol–anthraquinone process. An unreplicated factorial design was applied to determine the effect of key operating variables on fiber thermal stability and mechanical properties. The thermomechanical properties of pulp fibers depend primarily on the morphology and chemical composition of the fiber resource in terms of the respective amounts of lignin, hemicellulose, and cellulose, all strongly influenced by the choice of pulping conditions. Optimal pulping parameters were identified, allowing production of fibers thermally stable up to 255°C with an aspect ratio of 40, a straightness of 95%, and tensile strength as high as 890 MPa. Specific stiffness and strength values with respect to density and material cost of 56 GPa m^?3 $^?1 and 820 MPa m^?3 $^?1 were highly competitive with glass fibers, with corresponding values of 15 GPa m^?3$^?1 and 270–490 MPa m^?3 $^?1, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2132–2143, 2004     

Effects of flocculants and sizing agents on bending strength of fiber cement composites

Wood fiber is used to replace asbestos in the manufacture of fiber cement due to its high availability, low cost and good reinforcement properties. The different chemical composition of the cellulose fibers makes its compatibility with the cement much more complex than that of asbestos fibers. In the Hatschek process a suitable flocculant is needed when using cellulose fibers. The right selection of the flocculant is crucial due to its effect on mineral fines retention, dewatering and formation and, as a consequence, on the overall efficiency of the machine. This paper shows how anionic poly-acryl-amides (A-PAM), the most common flocculants used in Hatschek machines, have a negative effect on the bending strength properties of fiber cement sheets. In order to overcome this problem fiber surface treatment, with sizing agents, is proposed in this paper. Sizing with styrene-acrylate copolymers and alkyl ketene dimer produces an increase in bending strength properties.     

Ionic Liquid Approach Toward Manufacture and Full Recycling of All‐Cellulose Composites

All‐cellulose composites (ACCs) are prepared from high‐strength rayon fibers and cellulose pulp. The procedure comprises the use of a pulp cellulose solution in the ionic liquid (IL) 1‐ethyl‐3‐methyl imidazolium acetate ([EMIM][OAc]) as a precursor for the matrix component. High‐strength rayon fibers/fabrics are embedded in this solution of cellulose in the IL followed by removal of the IL. Different concentrations of cellulose in the IL are investigated and the mechanical properties of the final ACCs are determined via tensile, bending, and impact testing. ACCs prepared in this study show mechanical properties comparable to thermoplastic glass fiber‐reinforced plastics. Apart from being bio‐based, they possess several advantages such as biodegradability and full recyclability. The recycling of ACCs is successfully demonstrated in several cycles by using the recycled cellulose for subsequent matrix preparation.     

Effect of surface treatments of banana fiber on mechanical,thermal, and biodegradability properties of PLA/banana fiber biocomposites

Poly lactic acid (PLA)/Banana fiber (BF) biocomposites were fabricated employing melt blending technique followed by compression molding. BF were surface‐treated by NaOH and various silanes viz. 3‐aminopropyltriethoxysilane (APS) and bis‐(3‐triethoxy silyl propyl) tetrasulfane (Si69) to improve the compatibility of the fibers within the matrix polymer. Mechanical tests revealed an increase of tensile strength to the tune 136% and impact strength to 49% as compared with the untreated biocomposite. Thermal properties of the composites have been evaluated using DSC and TGA. DSC thermograms revealed an increase in the melting transitions thus revealing effective fiber/matrix interface. The thermal stability in the biocomposites also increased in case of banana fiber treated with Si69. Viscoelastic measurements using DMA confirmed an increase of storage modulus and low damping values in the silane treated biocomposites. Biodegradation studies in the biocomposites have been investigated in B. cepacia medium through morphological and weight loss studies. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Biodegradable packaging foams of starch acetate blended with corn stalk fibers

Starch acetate–corn fiber foams were prepared by extrusion. Corn starch was acetylated (DS 2) to introduce thermoplastic properties. Corn stalks were treated with sodium hydroxide to remove the lignin and to obtain purified cellulose fibers. Starch acetate was blended with treated fiber at concentrations of 0, 2, 6, 10, and 14% (w/w) and extruded in a corotating twin‐screw extruder with 12 to 18% w/w ethanol content and 5% talc as a nucleating agent. The samples were extruded at 150°C and selected physical and mechanical properties were evaluated. Micrographic properties were analyzed using scanning electron microscopy to observe the interaction of fiber and starch. Fiber incorporation at the lower concentrations enhanced the physical properties of the foams. Fiber contents greater than 10% decreased expansion and increased density and shear strength. Good compatibility between starch and corn fiber was observed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2627–2633, 2004     

Water sorption properties of regenerated sulfate pulp paper treated with ionic liquid [EMIM]OAc

Abstract

The present study concerns a practical approach to survey water sorption properties of ionic liquid ([EMIM]OAc) treated papers with and without chemical crosslinking. Ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc) can be used to transform sulfate pulp paper to regenerated cellulose film-like material. The fusion process increases both the dry and wet strength of the paper, improves oxygen and grease barrier properties, and increases paper transparency. The transformation is brought about by dissolution of the surfaces of the cellulosic fibers followed by precipitation and fusion of the fiber surfaces. Treatment conditions can be adjusted to produce partial dissolution of the fibers resulting in paper-like materials with improved wet-strength, or to achieve substantial or full dissolution resulting in transparent, regenerated cellulose film-like materials. From the industrial feasibility point of view, understanding the water sorption properties of IL-treated paper and the process parameters to control it are crucial. Results show that the treatment makes the paper more sensitive to both liquid water and water vapor, the magnitude depending on the degree of fiber dissolution and restraint of sheet shrinking during the treatment. Decreased water absorption and improved sheet dimensional stability were achieved by use of chemical crosslinking.     

Effect of Fiber Esterification on Fundamental Properties of Oil Palm Empty Fruit Bunch Fiber/Poly(butylene adipate-co-terephthalate) Biocomposites

A new class of biocomposites based on oil palm empty fruit bunch fiber and poly(butylene adipate-co-terephthalate) (PBAT), which is a biodegradable aliphatic aromatic co-polyester, were prepared using melt blending technique. The composites were prepared at various fiber contents of 10, 20, 30, 40 and 50 wt% and characterized. Chemical treatment of oil palm empty fruit bunch (EFB) fiber was successfully done by grafting succinic anhydride (SAH) onto the EFB fiber surface, and the modified fibers were obtained in two levels of grafting (low and high weight percentage gain, WPG) after 5 and 6 h of grafting. The FTIR characterization showed evidence of successful fiber esterification. The results showed that 40 wt% of fiber loading improved the tensile properties of the biocomposite. The effects of EFB fiber chemical treatments and various organic initiators content on mechanical and thermal properties and water absorption of PBAT/EFB 60/40 wt% biocomposites were also examined. The SAH-g-EFB fiber at low WPG in presence of 1 wt% of dicumyl peroxide (DCP) initiator was found to significantly enhance the tensile and flexural properties as well as water resistance of biocomposite (up to 24%) compared with those of untreated fiber reinforced composites. The thermal behavior of the composites was evaluated from thermogravimetric analysis (TGA)/differential thermogravimetric (DTG) thermograms. It was observed that, the chemical treatment has marginally improved the biocomposites' thermal stability in presence of 1 wt% of dicumyl peroxide at the low WPG level of grafting. The improved fiber-matrix surface enhancement in the chemically treated biocomposite was confirmed by SEM analysis of the tensile fractured specimens.     

The use of Isocyanate as a Bonding Agent to Improve the Mechanical Properties of Polyethylene-Wood Fiber Composites

Abstract

Chemithermomechanical pulp (CTMP) of aspen was used as a filler in high density (HDPE) and linear low density (LLDPE) polyethylenes. To improve the bonding between the fiber and polymer, different chemical treatments of the fiber a) treatment with different isocyanates b) coating with maleic anhydride was carried out. Composites with isocyanate treated wood fibers produced higher tensile strength compared to untreated fiber composites. But when compared to diisocyanate, the polyisocyanate treated fibers produced higher gain in strength. HDPE or LLDPE filled with maleic anhydride coated CTMP aspen fibers showed a slight decrease in strength with the increase in filler concentration. Tensile modulus generally increased with filler loading and was not much affected by fiber treatment.     

Comparison of the structures and properties of Lyocell fibers from high hemicellulose pulp and high α‐cellulose pulp

Lyocell fibers were produced from a cheap pulp with a high hemicellulose content and from a conventional pulp with a high α‐cellulose content. The mechanical properties, supermolecular structure, fibrillation resistance, and dyeing properties as well as the fibril aggregation size of the high hemicellulose Lyocell fiber and high α‐cellulose Lyocell fiber were compared. The results showed that the high hemicellulose spinning solution could be processed at a higher concentration, which improved the mechanical properties and the efficiency of the fiber process. Compared with the high α‐cellulose Lyocell fiber, the high hemicellulose Lyocell fiber had better fibrillation resistance and dyeing properties. Therefore, it is feasible that this cheap pulp with a high hemicellulose content can be used as a raw material for producing Lyocell fibers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008