High Stiffness Cellulose Fibers from Low Molecular Weight Microcrystalline Cellulose Solutions Using DMSO as Co‐Solvent with Ionic Liquid

There is a need to develop high‐performance cellulose fibers as sustainable replacements for glass fibers, and as alternative precursors for carbon filaments. Traditional fiber spinning uses toxic solvents, but in this study, by using dimethyl sulfoxide (DMSO) as a co‐solvent with an ionic liquid, a novel high‐performance fiber with exceptional mechanical properties is produced. This involves a one‐step dissolution, and cost‐effective route to convert high concentrations of low molecular weight microcrystalline cellulose into high stiffness cellulose fibers. As the cellulose concentration increases from 20.8 to 23.6 wt%, strong optically anisotropic patterns appear for cellulose solutions, and the clearing temperature (T _c) increases from ≈100 °C to above 105 °C. Highly aligned, stiff cellulose fibers are dry‐jet wet spun from 20.8 and 23.6 wt% cellulose/1‐ethyl‐3‐methylimidazolium diethyl phosphate/DMSO solutions, with a Young's modulus of up to ≈41 GPa. The significant alignment of cellulose chains along the fiber axis is confirmed by scanning electron microscopy, wide‐angle X‐ray diffraction, and powder X‐ray diffraction. This process presents a new route to convert high concentrations of low molecular weight cellulose into high stiffness fibers, while significantly reducing the processing time and cost.     

Mechanical Performance of Soy‐Hull‐Reinforced Bioplastic Green Composites: A Comparison with Polypropylene Composites

A blend composition of poly(3‐hydroxybutyrate‐co‐valerate) and polylactide is used as a bioplastic matrix and reinforced with soy hull to engineer novel green composites. A comparative study with soy‐hull‐reinforced polypropylene composite system is performed. A compatibilizer is used to engineer the novel class of green composites with a balanced stiffness and toughness performance with the target to substitute PP‐based composites. The flexural and impact strength along with hydrophobicity of compatibilized composites are improved significantly over the noncompatibilized counterpart. The fiber/matrix interaction is investigated by SEM. These green composites have the potential to substitute PP‐based composites in some applications.

     

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.     

Preparation of C/C‐SiC Composites from All‐Cellulose Precursors

All‐cellulose composites (ACCs) are manufactured from high‐performance cellulose fibers and a cellulose‐containing ionic liquid (IL) as matrix‐forming dope via wet‐winding processes, using different concentrations of cellulose in the IL. ACCs are carbonized at 1650 °C and then infiltrated with liquid silicon. Application of a carbonization aid (ammonium dihydrogenphosphate, ADHP) substantially improves the carbon yield after carbonization but also results in the depletion of the mechanical properties of the final carbon/carbon silicon carbide (C/C‐SiC) material. The microstructure of the porous carbon/carbon preforms strongly depends on both the concentration of cellulose in the IL and the concentration of ADHP. A C/C‐SiC composite manufactured from 6 wt% cellulose in the matrix‐forming dope, in the absence of ADHP, has a maximum flexural strength of 60 MPa. New C/C‐SiC composites with different shapes including Z‐profiles and tubes are successfully manufactured from pre‐shaped ACC precursors. These composites keep their shape during carbonization and the final siliconization process step.     

Synthesis and properties of multihydroxy soybean oil from soybean oil and polymeric methylene‐diphenyl‐ 4,4′‐diisocyanate/multihydroxy soybean oil polyurethane adhesive to wood

The reactive multihydroxy soybean oil (MHSBO) was synthesized from epoxidized soybean oil (ESBO). The ESBO was reacted with ethylene glycol to obtain MHSBO having high functionality. This study investigated a feasibility to prepare wood adhesive through the reaction of polymeric methylene‐diphenyl‐4,4′‐diisocyanate (pMDI) with MHSBO. Different polyurethane adhesives were prepared with a variety of equivalent mole ratios (eq. mole ratios) of MHSBO to pMDI. The chemical reactions of adhesives were analyzed using ¹H NMR and Fourier transform infrared (FTIR), and their thermal studies were investigated by DSC and TGA. The MHSBO/pMDI resins (3 : 1 and 2 : 1 eq. mole ratios) showed endothermic peaks, whereas the MHSBO/pMDI resins (1 : 2 and 1 : 3 eq. mole ratios) showed exothermic peaks. The best adhesion strength was found when plywood was bonded with the adhesive of a eq. mole ratio of 2 : 1 (MHSBO : pMDI). These results indicated that the bond strength was not related to the reactivity obtained from the FTIR spectra. But it was explained that the adhesion strength increased as the residual  NCO groups in the adhesive reacted with the hydroxy groups of wood during the manufacturing of plywood. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Biodegradable Green Composites from Distiller's Dried Grains with Solubles (DDGS) and a Polyhydroxy(butyrate‐co‐valerate) (PHBV)‐Based Bioplastic

Biodegradable green composites from distiller's dried grains with solubles (DDGS), a major coproduct of the corn ethanol industry, and a polyhydroxy(butyrate‐co‐valerate) (PHBV)‐based bioplastic were successfully produced. Green surface treatment of DDGS was performed and thermogravimetric analysis showed noticeable improvement in the degradation onset temperature of DDGS from 140 to 235 °C; this was a key point during melt processing of the composite. Utilizing compatibilizer improved the adhesion between DDGS and the matrix, which was observed by scanning electron microscopy. The green composite containing treated and compatibilized DDGS showed an enhanced modulus (by about 28% from 1.77 to 2.26 GPa) and an improved heat deflection temperature (by about 21% from 109 to 132 °C) compared to the polymeric matrix, while having tensile and flexural strengths equal to or greater than the respective properties of the matrix.

     

Microcellular Foamed Wood‐Plastic Composites by Different Processes: a Review

Wood fiber reinforced polymer composites represent a relatively small but rapidly growing material class, extensively applied in interior building applications and in the automotive industry. The polymer‐wood fiber composites utilize fibers as reinforcing filler in the polymer matrix and are known to be advantageous over the neat polymers in terms of the materials cost and mechanical properties such as stiffness and strength. Wood fiber reinforced polymer composites are microcellularly processed to create a new class of materials with unique properties. Most manufacturers are evaluating new alternatives of foamed composites that are lighter and more like wood. Foamed wood composites accept screws and nails like wood, more so than their non‐foamed counterparts. They have other advantages such as better surface definition and sharper contours and corners than non‐foamed profiles, which are created by the internal pressure of foaming. This paper represents a review on microcellular wood fiber reinforced polymer composites obtained by different processes (batch, injection molding, extrusion, and compression molding process) and includes an overview of foaming agents (physical and chemical) and the foaming of wood fiber‐polymer composites (changes in phase morphology, formation of polymer‐gas solution, cell nucleation, and cell growth control).

     

Preparation and characterization of wood‐(nylon 12) composites

The melting temperature of nylon 12 is lower than the degradation temperature of wood, which makes the preparation of wood‐(nylon 12) composites through a regular compounding/compression molding process possible. Results indicated that wood‐(nylon 12) composites had higher modulus of rupture, higher modulus of elasticity, and higher tensile strength than nylon 12, wood‐polypropylene (PP) composites, and wood‐high density polyethylene (HDPE) composites, respectively. Wood‐(nylon 12) composites also had higher thermal stability than wood‐PP composites and wood‐HDPE composites. Acting as a nucleating agent, wood increased the crystallization temperature and the degree of crystallinity of nylon 12 in wood‐(nylon 12) composites. The superior mechanical properties of wood‐(nylon 12) composites were ascribed to the good interfacial adhesion between wood and nylon 12 and the increased transcrystallinity of nylon 12 by wood. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103:270–276, 2007     

Effect of Maleated Compatibilizer on Performance of PLA/Wheat Straw‐Based Green Composites

In this study, the use of PLA‐g‐MA is investigated as a potential method for improving interfacial adhesion between agricultural residues and PLA, with the goal of enhancing mechanical properties. Compatibilization was achieved by using PLA‐g‐MA prepared via reactive extrusion. Green renewable and compatibilized PLA/wheat straw composites were extruded and injection‐molded. Addition of 3 and 5 phr PLA‐g‐MA to the composites resulted in significant improvements in tensile strength (20%) and flexural strength (14%) of the composites, matching that of the neat polymer. The observed improvement in strength was attributed to the good interfacial adhesion between the fiber and matrix.

     

Stimuli‐Responsive Elastic Polyurethane‐Based Superabsorber Nanomat Composites

Photoresponsive superabsorber particles containing a crosslinked hydrophilic core and a hydrophobic azobenzene‐containing shell were used to prepare photoresponsive polymeric nanomats, thus combining photoresponsivity with high porosity, toughness, and hydrophilicity. The properties of the nanomat composites were highly dependent upon the amount of the superabsorber photochromic particles added. Stable, highly elastic composite nanomats with very high loading (up to ≈50 wt.‐%), good water absorption capacity (4 000%) and relatively good tensile strength (3 MPa) were obtained. The photoresponsive behavior of the composites is demonstrated, which leads to relatively fast water desorption.

     

Functionalization and Compatibilization of Poly(ε‐caprolactone) Composites with Cellulose Microfibres: Morphology,Thermal and Mechanical Properties

A comparative study of the preparation and properties of composites of PCL with cellulose microfibres (CFs) containing butanoic‐acid‐modified cellulose (CB) or PCL grafted with maleic anhydride/glycidyl methacrylate as compatibilizers, is reported. The composites are obtained by melt mixing and analyzed using SEM, DSC, TGA, XRD, FT‐IR, NMR and tensile tests. An improved interfacial adhesion is observed in all compatibilized composites, as compared to PCL/CF. The crystallization behavior and crystallinity of PCL is largely affected by CF and CB content. Composites with PCL‐g‐MAGMA display higher values of tensile modulus, tensile strength and elongation at break.

     

Fire retardancy of polypropylene composites reinforced with rice husks: From oxygen index measurements and cone calorimetry to large‐scale single‐burning‐item tests

Rice husks containing 12 wt % inorganic silica were incorporated together with halogen‐free fire retardants in a polypropylene matrix and extruded into facade profiles. An increase in the amount of rice husks resulted in an increase in the oxygen index. The cone calorimetry measurements showed that all of the fire retardants tested significantly reduced the peak heat‐release rate (pHRR) and maximum average rate of heat emission (MARHE) of the formulations and moderately reduced total heat release. The best results in terms of MARHE were achieved for the formulation including 24% melamine‐coated ammonium polyphosphate. pHRR and MARHE were reduced with increasing amount of rice husks. Single‐burning‐item (SBI) tests were performed for the extruded profiles based on rice husks and, for comparison, wood flour. In the best case, a B‐s2, d0 classification was obtained. The results obtained from cone calorimetry and SBI tests were in agreement. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46654.     

Surface treatment of phosphate glass fibers using 2‐hydroxyethyl methacrylate: Fabrication of poly(caprolactone)‐based composites

2‐Hydroxyethyl methacrylate (HEMA) solution (1–10 wt %) was prepared in methanol and phosphate glass fibers were immersed in that solution for 5 min before being cured (irradiation time: 30 min) under UV radiation. Maximum polymer loading (HEMA content) was found for the 5 wt % HEMA solution. Degradation tests of the fibers in aqueous medium at 37°C suggested that the degradation of the HEMA‐treated fibers was lower than that of the untreated fibers. X‐ray photoelectron spectroscopy revealed that HEMA was present on the surface of the fibers. Using 5 wt % HEMA‐treated fibers, poly(caprolactone) matrix unidirectional composites were fabricated by in situ polymerization and compression molding. For in situ polymerization, it was found that 5 wt % HEMA‐treated fiber‐based composites had higher bending strength (13.8% greater) and modulus (14.0% greater) than those of the control composites. For compression molded composites, the bending strength and modulus values for the HEMA‐treated samples were found to be 27.0 and 31.5% higher, respectively, than the control samples. The tensile strength, tensile modulus, and impact strength of the HEMA composites found significant improvement than that of the untreated composites. The composites were investigated by scanning electron microscopy after 6 weeks of degradation in water at 37°C. It was found that HEMA‐treated fibers inside the composite retained much of their original integrity while the control samples degraded significantly. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

From “Strong” to “Much Stronger”: Utilization of Green Tea Extract Dispersant for SWCNT‐Reinforced Polymer Composites

PVA is reinforced with SWCNTs using green tea extract as a dispersant to achieve good dispersion of the SWCNTs in an organic solvent and finally high‐performance composite fibers. A combination of green tea extract/DMSO/SWCNT/PVA is found to disperse larger aggregates of SWCNTs to individual or thin bundles of a few nanotubes. Incorporation of 0.5 wt% SWCNTs into PVA fibers yields a tensile strength of 2.42 GPa, a Young's modulus of 46 GPa, toughness of 105 J · g^?1 at a failure strain of 11%, and a loop strength of 245 MPa, much higher than the values of commercial PVA fibers. The incorporation of highly dispersed SWCNTs suppresses the fibrillation tendency of the PVA fibers. The applied load is effectively transferred from the matrix to the SWCNTs.

     

Biomineralization‐Inspired Green Synthesis of Zinc Phosphate‐Based Nanosheets in Gelatin Hydrogel

Diffusion of inorganic salts in gels is a simple, inexpensive, and versatile technique for the synthesis of inorganic/organic hybrid nanocomposite particles with various morphologies. This paper introduces a novel method for producing zinc phosphate (ZP) nanosheets using single diffusion of zinc ions in gelatin at ambient temperature. FTIR spectra showed the entrapment of gelatin in ZP sheets due to electrostatic interactions between charged groups of gelatin and diffused ions. This study demonstrated that hydrogels can be used for crystallization of ZP. Such a nanocomposite particle may open a new window for producing antimicrobial and materials for use in tissue engineering.     

Ag‐nanocomposite based on carboxymethylcellulose for humidity detection: Green synthesis and sensing performances

A novel highly sensitive Ag‐nanocomposite for humidity detection has been successfully prepared. Initially, cellulose isolated from Tunisian palm date petiole was converted to carboxymethyl cellulose (CMC) as biomatrix under heterogeneous conditions. The synthesized product was thoroughly characterized by means of FT‐IR spectroscopy, viscosity analysis, and high performance size exclusion chromatography multiangle laser light scattering. CMC was used as reducing and stabilizing agent to prepare CMC‐stabilized silver nanoparticles via a rapid green method. The bioreduction of silver ions under different experimental conditions, including Ag⁺ concentration and pH, was investigated. Optimal experimental conditions provided a long‐term stable colloidal suspension and well‐dispersed spherical shape Ag NPs with a size ranging from 13 to 28 nm. Ag‐nanocomposite coated quartz microbalance crystal was used as sensitive layer for humidity detection. A comparative study showed that the immobilized metallic nanostructures greatly reduced changes in visco‐elastic properties, increased surface area as well as surface local charge density of the CMC. Consequently, sensor performances were greatly enhanced: better stability even at higher relative humidity (RH), good reproducibility and linearity (11–98% RH), low hysteresis characteristics, and rapid response and recovery times (14 and 6 s, respectively) were obtained. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43686.     

Synthesis and Characterization of Novel Polyurethane Composites Based on Hybrid Inorganic/Organic Phosphazene‐Containing Microspheres

Novel polyurethane (PU) composites were prepared, based on hybrid inorganic/organic phosphazene‐containing microspheres. The FT‐IR spectra have shown that the microspheres have been linked with PU matrix. The microstructure of the composites is investigated by SEM. In comparison with PU, the glass transition temperatures and thermal stability of the composites are increased. The results from tensile testing of the composites have indicated that tensile strength is improved and elongation at break is almost invariable. The investigation on the surface properties of the composites showed that the water contact angles are obviously increased by adding 2 and 4 wt.‐% microspheres to the matrix.