Nanocomposites of Cellulose Acetate Butyrate Reinforced with Cellulose Nanocrystals

Nanocrystals were prepared by acid hydrolysis of bacterial cellulose microfibrils. These were topochemically trimethylsilylated, in an attempt to reduce their hydrophilicity. Composites were made by dispersing either native or silylated crystals in cellulose acetatebutyrate matrixes and solution casting of the dispersions. Particles were characterized by transmission electron microscopy. The composites were characterized by differential scanning calorimetry and dynamic mechanical analysis. The unmodified cellulose crystals exhibited better reinforcement characteristics than the trimethylsilated crystals.     

Polyhydroxybutyrate-Based Nanocomposites with Cellulose Nanocrystals and Bacterial Cellulose

Polyhydroxybutyrate (PHB) films nanoreinforced with hydrolyzed cellulose nanocrystals (CNC) and bacterial cellulose (BC) were prepared by solvent casting. The influence of different cellulose nanoparticles content (2, 4 and 6 wt% of CNC and 2 wt% of BC) on the PHB properties was studied. CNC nanocomposites presented good dispersion of the nanocrystals, improving transparency, mechanical and barrier properties of the PHB films. On the other hand, reduced thermal stability and mechanical properties were yielded by BC addition due to the intrinsic lower degradation temperature and higher length of the BC nanofibrils compared to CNC. Nanocomposites performance variation is mainly caused by the marked difference in nanoparticles structure. It was demonstrated that PHB–CNC films exhibited higher performance enhancement without detrimental effect of the pristine PHB properties.     

Properties of Regenerated Cellulose Short Fibers/Cellulose Green Composite Films

Green composites of regenerated cellulose short fibers/cellulose were prepared by dissolving cellulose in a green solvent of 7% NaOH/12% Urea aqueous solution that was pre cooled at ?12?°C. The effect of fiber loading on the tensile, optical, thermal degradation and cell viability was studied. The tensile properties of cellulose were improved by the regenerated cellulose fiber reinforcement. The interfacial bonding between the fibers and matrix was assessed using the fractographs and found it to be good.     

Extraction of Cellulose Nanocrystals from Phormium tenax Fibres

Cellulose nanocrystals with an acicular structure ranged from 100 to 200 nm in length and 15 nm in width were extracted from Phormium tenax leaf fibres by acid hydrolysis. A two-step procedure for the extraction of nano-sized cellulose was studied and the obtained nanocrystals were characterized using morphological investigations (optical, scanning electron and atomic force microscopy), as well as physico-chemical characterization by Wide Angle X-ray Scattering, infrared spectroscopy and thermogravimetric analysis. A study of birefringence properties was also performed. The first chemical treatment leads to the production of holocellulose by the gradual removal of lignin, while the subsequent sulphuric acid hydrolysis process allows obtaining cellulose nanocrystals in an aqueous suspension. The results reported support the repeatability and the effectiveness of the procedure performed. Moreover, the high cellulose content of P. tenax fibre and their declining market interest, suggest the interest of this investigation and the possibility to use natural fibres for the production of a reinforcement phase to involve in the nanocomposite approach for industrial applications.     

Valorisation of Vegetal Wastes as a Source of Cellulose and Cellulose Derivatives

Different qualities of CMC were prepared from an agricultural residue (date palm rachis) and a marine waste (Posidonia oceanica). These starting lignocellulosic materials were used as such and after chemical pulping and bleaching. The carboxymethylation reaction was carried out in presence of NaOH (40%) and monochloroacetic acid (ClCH₂COOH, MAC), in n-butanol as the reaction solvent. The substitution degrees (DS) of the obtained CMCs varied from 0.67 to 1.62 and between 0.98 and 1.86, for P. oceanica and date palm rachis, respectively. The CP-MAS ¹³C-NMR spectra of the prepared polyelectrolytes displayed the presence of the main peaks associated with cellulose macromolecules (C1–C6) and that corresponding to carboxyl functions at around 175 ppm. Unfortunately, the peak attributed to methylene groups neighbouring carboxyl moieties are overlapped by C2 and C3, which renders them hardly detectable. Nevertheless, it is worth noting that the CP-MAS ¹³C-NMR spectra revealed the presence of different signals originating from residual impurities (ca. 27 ppm), such as traces of lignin macromolecules (110–150 ppm) and methyl groups attributed to hemicelluloses. Work is in progress to establish a more efficient purification procedure, in order to have more accurate values of DS.     

Biodegradability of PMMA Blends with Some Cellulose Derivatives

High polymer blends of Polymethyl methacrylate (PMMA) with cellulose acetate (CA) and Cellulose acetate phthalate (CAP) of varying blend compositions have been prepared to study their biodegradation behavior and blend miscibility. Films of PMMA–CA, and PMMA–CAP blends have been prepared by solution casting using Acetone and Dimethyl formamide(DMF) as solvents respectively. Biodegradability of these blends has been studied by four different methods namely, soil burial test, enzymatic degradation, and degradation in phosphate buffer and activated sludge degradation followed by water absorption tests to support the degradation studies. Degradation analysis was done by weight loss method. The results of all the tests showed sufficient biodegradability of these blends. Degradability increased with the increase in CA and CAP content in the blend compositions. The miscibility of PMMA–CA and PMMA–CAP blends have been studied by solution viscometric and ultrasonic methods. The results obtained reveal that PMMA forms miscible blends with either CA or CAP in the entire composition range. Miscibility of the blends may be due to the formation of hydrogen bond between the carbonyl group of PMMA and the free hydroxyl group of CA and CAP.     

Lyotropic Liquid Crystal Phases in Cellulose Acetate Phthalate/Hydroxypropyl Cellulose Blends

Cellulose and some of its derivatives form liquid crystalline solutions in a variety of solvents. The present work investigates cellulose acetate phthalate/hydroxypropyl cellulose blends in N,N-dimethylacetamide, in function of concentration and composition, by rheology, considering dynamic viscometry and oscillatory shear tests. The effects of composition, concentration, shear rate, and oscillatory deformation on the rheological functions determines the orientation or mobility of the chain segments in the shear field. Atomic force microscopy and polarized light microscopy studies on corresponding films show that specific interactions, such as the hydrogen bonds between cellulose acetate phthalate and the liquid crystalline component—hydroxypropyl cellulose, stabilizes the morphology, leading to the emergence of different formations typical for lyotropic liquid crystal phases. These studies contribute to a better knowledge of the specific interactions that generate and modify the liquid crystalline properties of cellulose derivatives, required by the applications in electronic domains.     

Biodegradation of Waste Cellulose

Environmental issues such as the depletion of nonrenewable energy resources and pollution are very topical and would need more scientific attention in order to be addressed in a way beneficial to life. The extent of solid waste production is a global concern and development of its bioenergy potential can simultaneously address issues such as pollution control and renewable energy development. Various wastepaper materials, a major component of solid waste, have been treated with cellulase from Trichoderma viride to bioconvert its cellulose component into fermentable sugars that could be utilized as feedstock for bioproduct development. These paper materials exhibited different susceptibilities toward the cellulase and showed different sugarreleasing patterns when increasing amounts of each paper were treated with the enzyme. Bioconversion of paper with different enzyme concentrations and during various time intervals also resulted in nonsimilar sugar-releasing patterns. With all the paper materials, a general decline in efficiency was observed with increasing amounts of sugar produced during the different bioconversion variables investigated.     

Biodegradability of Banana and Plantain Cellulose Microfibrils Films in Anaerobic Conditions

Currently, cellulose microfibrils are being investigated as nanofillers for polymers to increase their biodegradability. However, until now there has been no report on their degradability by microorganisms. In this work the anaerobic degradation of cellulose microfibril films extracted from banana and plantain plant rachis residues has been studied. Samples were exposed to burial tests in nature compost during 14?days. Changes due to the degradation process were investigated by techniques as optical microscopy, tensile tests, viscosity measurements, ATR-FTIR spectroscopy, X-ray diffraction and thermogravimetric analysis. Biodegradability was higher for cellulose microfibril films extracted from banana (BCMF) than plantain films (PCMF). Growth of microorganism colonies on BCMF films and just yellowing on PCMF films was observed by microscopic analysis. New bands characteristic of aldehyde functional groups due to the breaking of ??-(1,4)-glycosidic bonds were observed in infrared spectra. This breakage was also responsible for the fall-down of mechanical properties and polymerization degree. X-ray diffraction and thermogravimetric analysis showed that BCMF films were at the first stage of degradation for the used burial test times because the microorganisms only attacked the amorphous cellulose leading to a slight increase in crystallinity. In the case of PCMF films this variation remained practically invariant.     

All-Cellulose Composite Fibers Obtained by Electrospinning Dispersions of Cellulose Acetate and Cellulose Nanocrystals

All-cellulose composite fibers were produced by electrospinning dispersions containing cellulose acetate (CA) and cellulose nanocrystals (CNCs). Precursor polymer matrices were obtained after dispersion of CA with different degrees of substitution in a binary mixture of organic solvents. The obtained fibers of CA loaded with CNCs had typical widths in the nano- and micro-scale and presented a glass transition temperature of 145?°C. The CA component was converted to cellulose by using alkaline hydrolysis to yield all-cellulose composite fibers that preserved the original morphology of the precursor system. Together with Fourier Transform Infrared Spectroscopy fingerprints the thermal behavior of the all-cellulose composite fibers indicated complete conversion of cellulose acetate to regenerated cellulose. Noticeable changes in the thermal, surface and chemical properties were observed upon deacetylation. Not only the thermal transitions of cellulose acetate disappeared but the initial water contact angle of the web was reduced drastically. Overall, we propose a simple method to produce all-cellulose composite fibers which are expected to display improved thermo-mechanical properties while keeping the unique features of the cellulose polymer.     

Characterization and Properties of Hydrophilic Cellulose Acetate Propionate Derivative

The chemical modification of Acrylamidomethyl Cellulose Acetate Propionate (AMCAP) was carried out by radical addition of acrylic acid. The structural modification was confirmed with the aid of FTIR, MS and NMR techniques. Thermal properties of hydrophilic cellulose derivative (AMCAP–H₂O₂) such as glass transition (T_g 153 °C) and thermal stability (372.7 °C) were determined by DSC and TGA techniques, respectively. These thermal properties confirmed the introduction of carboxylic groups into AMCAP structure, which causes an impact in their properties. The AMCAP–H₂O₂ shows minor contact angle compared to AMCAP, giving a more hydrophilic characteristic, due to acrylic acid addition into the side chains of AMCAP polymer.     

Thermal,Mechanical and Physical Properties of Composite Films Developed from Seaweed Polysaccharides/Cellulose Nanofibers

Journal of Polymers and the Environment - Algae-based materials appear to be promising substitutes for plastics in many applications due to their eco-friendly belongings. However, high solubility,...     

Mechanical Properties of Microcrystalline Cellulose (MCC) Filled Engineering Thermoplastic Composites

In this study, engineering thermoplastic composites were prepared from microcrystalline cellulose (MCC)-filled nylon 6. MCC were added to nylon 6 using melt mixing to produce compounded pellets. The MCC-filled nylon 6 composites with varying concentrations of MCC (from 2.5 to 30 wt%) were prepared by injection molding. The tensile and flexural properties of the nylon 6 composites were increased significantly with the addition of MCC. The maximum strength and modulus of elasticity for the nylon 6 composites were achieved at a MCC weight fraction of 20 %. The Izod impact strength of composites decreased with the incorporation of MCC without any surface treatments and coupling agent. This observation is quite expected for filled polymer systems and has been commonly observed. There was a strong correlation between density and tensile (r = 0.94) and flexural modulus of elasticity (r = 0.9). MCC filled composites manufactured by injection method had highly uniform density distribution through their thickness. The higher mechanical results with lower density demonstrate that MCC can be used as a sufficient reinforcing material for low cost, eco-friendly composites in the automotive industry especially for under-the-hood applications (engine covers, intake manifolds and radiator end tanks) as well as in other applications such as the building and construction industries, packaging, consumer products etc.     

Application of Cellulose Microfibrils in Polymer Nanocomposites

Cellulose microfibrils obtained by the acid hydrolysis of cellulose fibers were added at low concentrations (2–10% w/w) to polymer gels and films as reinforcing agents. Significant changes in mechanical properties, especially maximum load and tensile strength, were obtained for fibrils derived from several cellulosic sources, including cotton, softwood, and bacterial cellulose. For extruded starch plastics, the addition of cotton-derived microfibrils at 10.3% (w/w) concentration increased Young’s modulus by 5-fold relative to a control sample with no cellulose reinforcement. Preliminary data suggests that shear alignment significantly improves tensile strength. Addition of microfibrils does not always change mechanical properties in a predictable direction. Whereas tensile strength and modulus were shown to increase during addition of microfibrils to an extruded starch thermoplastic and a cast latex film, these parameters decreased when microfibrils were added to a starch–pectin blend, implying that complex interactions are involved in the application of these reinforcing agents.     

Poly(lactic acid)/Cellulose Composites Obtained from Modified Cotton Fibers by Successive Acid Hydrolysis

This work is focused on the hydrolysis of cotton fibers from waste textiles to obtain micro and nanofibers to be used as reinforcements in polymer composites. To promote their compatibility with polymeric matrix, hydrolyzed cotton fibers were surface modified with various silane compounds. Thus, these fibers were mixed with commercial poly(lactic acid) (PLA) at 5% w/w loading by melt compounding. Acid treatments caused a decrease of the crystallinity index whereas the thermal stability was significantly improved, especially for cellulose fibers hydrolyzed in two steps. Morphological analysis revealed a reduction of the fibers diameter and a decrease of their length as a consequence of the hydrolysis. NMR analysis confirmed the silanization of the fibers by reaction with the silane agent. Tensile tests revealed that silanization treatments were able to increase the composite Young’s modulus and the stress at break with respect to the neat matrix, indicating that silanization improved the polymer/fiber compatibility interfacial adhesion. The overall results demonstrated that applying suitable surface modification strategies, waste cotton textiles can be effectively recycled as fillers in polymer based composites.     

Hydrophobic and Flame-Retardant Foam Based on Cellulose

Journal of Polymers and the Environment - A study aimed to prepare cellulose-based hydrophobic, lightweight, and flame retardant foam composites. Cellulose was activated by phosphoric acid followed...     

Rheological Studies of Microfibrillar Cellulose Water Dispersions

The rheological behaviour of microfibrillar cellulose (MFC) water dispersions has been investigated. For the first time a detailed study of shear dependent viscosity at low and high shear rate is presented. A peculiar time dependent behaviour measured in the area between 0 and 1000 s⁻¹ was identified. The study shows a hysteresis loop in the shear rate–viscosity relationship at low shear rate. Additional time dependent shear rate measurements were performed, and a hypothesis for a mechanism of interaction and formation of a fibrils network was suggested. Higher temperature caused lower viscosity values, and this difference was increased at higher shear rate values. Oscillatory measurements showed how the closeness of the fibrils helps network creations. Data obtained from high shear measurements showed that 1% MFC water dispersions had a dilatant behaviour at ultra high shear rates with values increasing from 120 to 300 Pa s in the area between 180,000 and 330,000 s⁻¹ .     

Bacterial Cellulose from Simple and Low Cost Production Media by Gluconacetobacter xylinus

Bacterial cellulose pellicles were produced by Gluconacetobacter xylinus using non conventional low-cost carbon sources, such as glycerol remaining from biodiesel production and grape bagasse, a residue of wine production. The carbon sources assayed showed their suitability for microbial cellulose production, with relatively high production values such as 10.0 g/l for the culture medium with glycerol from biodiesel as carbon source and corn steep liquor as nitrogen source; and 8.0 g/l for the culture medium containing grape bagasse and corn steep liquor. Glucose, commercial glycerol and cane molasses were also assayed as carbon sources for comparison. The bacterial celluloses produced were characterized by means of scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and thermogravimetric analysis. Morphological analysis showed that bacterial cellulose microfibrils produced from the non-conventional media used were several micrometers long and had rectangular cross-sections with widths and thicknesses in the range of 35–70 and 13–24 nm, respectively. X-ray patterns showed crystallinity levels in the range of 74–79 % (area method), whereas both X-ray patterns and infrared spectroscopy evidenced the presence of peaks characteristic of Cellulose I polymorph. Besides thermal properties were similar to those found for the pellicle obtained from glucose. The study performed showed the suitability of using wine residues or glycerol remaining from increasing biodiesel production as cheap carbon sources for production of bacterial cellulose microfibrils, with similar characteristics as those obtained by use of more expensive carbon sources such as glucose or commercial glycerol. On the other hand, the low cost nitrogen sources used (corn steep liquor or diammonium phosphate) also contributed to the economy of the bioprocess.     

TEMPO-Mediated Oxidation of Hemp Bast Holocellulose to Prepare Cellulose Nanofibrils Dispersed in Water

Hemp bast holocellulose fiber (Cannabis sativa L. Subsp. Sativa) was oxidized by TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidation at various NaClO addition levels in water at pH 10. When carboxylate contents of the oxidized products were 1.5–1.7 mmol/g, TEMPO-oxidized cellulose nanofibrils almost completely dispersed at the individual nanofibril were obtained by mechanical disintegration of the TEMPO-oxidized hemp bast holocelluloses in water, where the nanofibrillation yields were 98–100 %. The sugar composition analysis revealed that most of hemicelluloses originally present in the hemp bast holocellulose were degraded and removed from the solid oxidized products, providing almost pure TEMPO-oxidized celluloses. X-ray diffraction patterns of all TEMPO-oxidized hemp bast holocelluloses had the same cellulose I crystal structure and similar crystallinity indices and crystal widths, indicating that carboxylate groups formed by the oxidation were selectively present on the crystalline cellulose microfibril surfaces in the holocellulose. However, the weight recovery ratios and viscosity-average degrees of polymerization of the TEMPO-oxidized hemp bast holocelluloses decreased to 69–59 % and 470–380, respectively, when their carboxylate contents increased to 1.5–1.7 mmol/g by the TEMPO-mediated oxidation. Atomic force microscopy height images showed that the nanofibril widths were 2.7–2.9 nm, and the average nanofibril lengths decreased from 590 to 400 nm as the NaClO addition level was increased from 7.5 to 12.5 mmol/g in the TEMPO-mediated oxidation.     

Degradation of Cellulose Acetate-Based Materials: A Review

Cellulose acetate polymer is used to make a variety of consumer products including textiles, plastic films, and cigarette filters. A review of degradation mechanisms, and the possible approaches to diminish the environmental persistence of these materials, will clarify the current and potential degradation rates of these products after disposal. Various studies have been conducted on the biodegradability of cellulose acetate, but no review has been compiled which includes biological, chemical, and photo chemical degradation mechanisms. Cellulose acetate is prepared by acetylating cellulose, the most abundant natural polymer. Cellulose is readily biodegraded by organisms that utilize cellulase enzymes, but due to the additional acetyl groups cellulose acetate requires the presence of esterases for the first step in biodegradation. Once partial deacetylation has been accomplished either by enzymes, or by partial chemical hydrolysis, the polymer’s cellulose backbone is readily biodegraded. Cellulose acetate is photo chemically degraded by UV wavelengths shorter than 280 nm, but has limited photo degradability in sunlight due to the lack of chromophores for absorbing ultraviolet light. Photo degradability can be significantly enhanced by the addition of titanium dioxide, which is used as a whitening agent in many consumer products. Photo degradation with TiO₂ causes surface pitting, thus increasing a material’s surface area which enhances biodegradation. The combination of both photo and biodegradation allows a synergy that enhances the overall degradation rate. The physical design of a consumer product can also facilitate enhanced degradation rate, since rates are highly influenced by the exposure to environmental conditions. The patent literature contains an abundance of ideas for designing consumer products that are less persistent in the outdoors environment, and this review will include insights into enhanced degradability designs.