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The importance of renewable and environmentally friendly wood pulp fibers as an input material for single-use products has grown significantly. However, discarded single-use materials are found in the environment as litter and are sometimes disposed of in wastewater. It is important that these materials are biodegradable and environmentally benign. Wood pulp is mainly comprised of lignocellulosic material, and its composition and structure can vary depending on raw materials and processing, ultimately impacting the biodegradability. In this research, the aquatic biodegradation of five kinds of wood pulp and six different samples of isolated lignocellulosic components (cellulose, hemicellulose, and lignin) have been explored in a consistent detailed manner for the first time, and the effects of chemical composition on the biodegradation discussed. Several lignocellulosic materials were characterized using compositional analysis and were subjected to aquatic biodegradation with bio-solids from a wastewater treatment plant as an inoculum to indicate the potential to biodegrade in the environment. Cellulose and hemicellulose were readily biodegraded over a course of one month. The lignin samples were not biodegradable under these conditions, and the lignin within fibers decreased the biodegradability of the other components of the lignocellulosic fibers. It was also determined that ash and extractives negatively affect the biodegradability. The aerobic aquatic biodegradation results are useful for product designers to select different lignocellulosic materials for applications and for environmental scientists to understand the fate of these fibers in the environment. [ABSTRACT FROM AUTHOR]

In recent years, there have been many advances toward developing sustainable, micro- and nanoscale materials from biobased resources such as lignin aimed at strengthening the bioeconomy. It is critical to study the factors affecting nucleation and growth mechanisms, as well as the stability of lignin micro-and nanoparticles (LPs), to further enhance the development of such materials. However, there remains a gap in the literature examining the many interactions present during and after LP formation. These interactions vary with the chemical composition and molecular weight distribution of different kraft lignin (KL) fractions. To examine the composition of different lignin fractions, KL can be fractionated using water-miscible organic solvents of different polarities such as tetrahydrofuran (THF), acetone, and ethanol. Herein, we show that the micro- and nanoparticles formed from each lignin fraction exhibit significant differences in their size (50–300 nm), particle aggregation and fusion propensity, and spherical morphology in aqueous suspensions. These differences are proposed to be a result of the solvent–lignin–water interactions related to molecular weight and functional groups of the lignin fractions and solvent/water polarity. Another factor affecting the nucleation and growth of LPs is the lignin concentration. The LPs formed at low lignin concentrations exhibit a larger average particle size compared to the LPs formed at higher lignin concentrations due to the aggregation and fusion of the small particles. These results will allow for a stronger foundation in understanding the nucleation and growth of LPs when attempting to develop value-added applications for kraft lignin. [ABSTRACT FROM AUTHOR]

Plasticizers depress the glass transition temperature (Tg) of polymers and produce a flowable material at lower temperatures. The use of plasticizers to depress Tg of lignin is important, since at high processing temperatures lignin crosslinks, making it intractable. The goal of this study was to assess plasticizers and polymer blends for the ability to retard a commercial softwood kraft lignin from crosslinking and also serve as thermal and rheological property modifiers during thermal processing in the attempt to produced moldable and spinnable lignin for lignin and carbon fiber products. The Tg of the lignin and the lignin mixed with various amounts of plasticizers and with different thermo-mechanical mixing were determined using differential scanning calorimetry. The Tg and the change in heat capacity at the glass transition (ΔCp) decreased and increased, respectively, about linearly within this plasticizers range with increased plasticizer weight percentage. Gel permeation chromatography results for extruded lignin as well as extruded lignin-plasticizer blends with glycerol, N-allyurea, citric acid with and without sodium hypophosphite, and oleic acid indicate that the presence of these materials reduced the rate of molecular weight increase at temperatures between 100 and 200 °C. Continuous, homogenous films and fibers could be produced by thermal processing with plasticized lignin samples and plasticized lignin-polymer blends, but not with lignin alone. These fibers could be carbonized, yielding up to about 50% of carbon. The present findings have shown the advantages of plasticizers in thermally processing a commercial softwood kraft lignin. [ABSTRACT FROM AUTHOR]

The extractability of hemicellulose from different lignocellulosics depends on the source of biomass. Differences in hemicellulose extractability are believed to be due to plant-specific hemicellulose arrangement alongside lignin within the cell wall. In this research, six biomasses were used to probe hemicellulose alkaline extractability as a function of the native lignin within the biomasses. Quantitative 2D-HSQC and 13C NMR analysis were performed to determine the S/G (S: syringyl, G: guaiacyl) and lignin-carbohydrate complex (LCC) linkages of milled wood lignin isolated from these biomasses. A strong negative correlation was observed between total lignin content and hemicellulose extractability, demonstrating that a greater presence of lignin in the original material results in lower xylan solubilization. In addition, a correlation between S/G of lignin and xylan dissolution was found within a group of hardwoods and within a group of non-woods. This suggests that monomeric constituency also influences xylan's propensity for dissolution in 10% NaOH. Although there is some uncertainty in the quantification of LCC linkages, both non-woods and hardwoods exhibited negative correlations between alkaline-stable LCC linkages content and xylan extractability. This suggests that alkaline-stable LCC structures are associated with a decrease in the alkaline extractability of hemicellulose. [ABSTRACT FROM AUTHOR]

A process to attach fatty acids to lignin is reported which alters its thermal behavior. By attaching saturated C 18 fatty acids to OH groups, stable lignin stearates (LS) of controllable degrees of substitution (DS) were synthesized. Interesting physical properties were observed, wherein LS was observed to melt and flow at temperatures as low as 50 °C. Melting was possible due to the crystallization of stearate chains when LS was purified by precipitation. A NMR method was established for quantification of the degree of substitution. At very high %DS values (close to 100%), the melting phenomenon was reversible, but at low %DS, melting occurred only during the 1st heating ramp during thermal cycling. The ability of LS to plasticize polystyrene (PS) is reported wherein integral blend films containing up to 25% by weight of LS were formed. The T g of the blended films could be lowered by 22 °C using LS relative to PS. Lignin stearates have the potential to serve as interesting compounds for their ability to plasticize not only PS but other thermoplastic materials as well. [ABSTRACT FROM AUTHOR]

Lignin-based thermoplastic materials have attracted increasing interest as sustainable, cost-effective, and biodegradable alternatives for petroleum-based thermoplastics. As an amorphous thermoplastic material, lignin has a relatively high glass-transition temperature and also undergoes radical-induced self-condensation at high temperatures, which limits its thermal processability. Additionally, lignin-based materials are usually brittle and exhibit poor mechanical properties. To improve the thermoplasticity and mechanical properties of technical lignin, polymers or plasticizers are usually integrated with lignin by blending or chemical modification. This Review attempts to cover the reported approaches towards the development of lignin-based thermoplastic materials on the basis of published information. Approaches reviewed include plasticization, blending with miscible polymers, and chemical modifications by esterification, etherification, polymer grafting, and copolymerization. Those lignin-based thermoplastic materials are expected to show applications as engineering plastics, polymeric foams, thermoplastic elastomers, and carbon-fiber precursors. [ABSTRACT FROM AUTHOR]

Recovered papers are suitable biomass sources for conversion into sugars that can be used in bioethanol production. However, paper materials with a high lignin content have been found to be recalcitrant to enzymatic hydrolysis. To address this issue, several biomass pretreatment methods were employed to evaluate their efficiency on the conversion of newspaper with high lignin content to sugar. Autohydrolysis, a hot water treatment, was identified to adversely affect sugar conversion, presumably as a result of pore collapse under high-temperature pretreatment. Flexo ink, used in newspaper printing, had no effect on the enzymatic hydrolysis, with or without autohydrolysis. The ink was still detachable after autohydrolysis, as measured by hyperwashing. Compared to untreated newspaper, separate treatments of either mechanical refining or a non-ionic surfactant (sorbitan polyoxyethylene monooleate) improved the sugar conversion by 10% at enzyme dosages of 2 and 8 FPU/g substrate. The combination of both refining and surfactant resulted in the highest sugar conversions, i.e., 46.3%, 56.7%, and 64.1% at 2, 4, and 8 FPU/g enzyme dosages, respectively. Oxidative pretreatment (oxygen, 100 °C) marginally increased the sugar conversion, whereas alkaline and green liquor (NaCO3 and Na2S) pretreatments (at 160 °C) had either no effect or decreased the sugar conversion. Based on the results of the pretreatments, higher pretreatment temperatures of newsprint negatively impacted subsequent enzyme hydrolysis. [ABSTRACT FROM AUTHOR]

ABSTRACT Lignin is an abundant, underutilized natural resource that has potential to be used as a biomaterial but is currently hampered in its use by not being uniform in structure and composition and is thermally unstable due to phenolic group. To address these issues and modify its thermal properties, softwood kraft lignin was modified using γ-irradiation at low doses with and without styrene present and characterized. Irradiation of kraft lignin alone with γ-radiation shows an initial decrease in molecular weight due to chain scission up to about 10 kGy followed by an increase in molecular weight due to crosslinking. NMR results indicate a decrease of about 15% in the OH content of the lignin with 30 kGy irradiation. Thermal properties such as Tg, free volume and Δ Cp follow accordingly. Irradiation at very low dosages was determined to facilitate the grafting of styrene monomer to lignin, decreasing the OH content by 23%. This effect increased the hydrophobicity of the material, depressed the value of Tg, increased the Δ Cp, increased the mobility in the liquid state, and made the material more thermally stable relative to the lignin alone, thus improving its processability at high temperatures. Both the irradiation of lignin alone and the grafting of styrene to lignin increased the yield of mass during pyrolysis and the activation energy for mass loss relative to untreated lignin alone. This work has demonstrated that the application of low dosages of γ-irradiation is a promising method to attach functional molecules onto lignin for use in various applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39743. [ABSTRACT FROM AUTHOR]

Abstract: Films of microfibrillated celluloses (MFCs) from pulps of different yields, containing varying amounts of extractives, lignin, and hemicelluloses, were produced by combining refining and high-pressure homogenization techniques. MFC films were produced using a casting-evaporation technique and the physical and mechanical properties (including density, roughness, fold endurance and tensile properties) were determined. Homogenization of bleached and unbleached Kraft pulps gave rise to highly individualized MFCs, but not for thermo-mechanical pulp (TMP). The resulting MFC films had a roughness equivalent to the surface upon which the films were cast. Interestingly, after homogenization, the presence of lignin significantly increased film toughness, tensile index, and elastic modulus. The hornification of fibers through a drying and rewetting cycle prior to refining and homogenization did not produce any significant effect compared to films from never-dried fibers, indicating that MFC films can potentially be made from low-cost recycled cellulosic materials. [Copyright &y& Elsevier]

The interactions with water and the physical properties of microfibrillated celluloses (MFCs) and associated films generated from wood pulps of different yields (containing extractives, lignin, and hemicelluloses) have been investigated. MFCs were produced by combining mechanical refining and a high pressure treatment using a homogenizer. The produced MFCs were characterized by morphology analysis, water retention, hard-to-remove water content, and specific surface area. Regardless of chemical composition, processing to convert macrofibrils to microfibrils resulted in a decrease in water adsorption and water vapor transmission rate, both important properties for food packaging applications. After homogenization, MFCs with high lignin content had a higher water vapor transmission rate, even with a higher initial contact angle, hypothesized to be due to large hydrophobic pores in the film. A small amount of paraffin wax, less than 10%, reduced the WVTR to a similar value as low density polyethylene. Hard-to-remove water content correlated with specific surface area up to approximately 50 m2/g, but not with water retention value. The drying rate of the MFCs increased with the specific surface area. Hornified fibers from recycled paper also have the potential to be used as starting materials for MFC production as the physical and optical properties of the films were similar to the films from virgin fibers. In summary, the utilization of lignin containing MFCs resulted in unique properties and should reduce MFC production costs by reducing wood, chemical, and energy requirements. [ABSTRACT FROM AUTHOR]

Coastal Bermuda grass (CBG) has been shown to have potential as a biomass feedstock for sugar production. In this study, the effectiveness of ozone pretreatment for CBG to improve the sugar recovery via enzyme hydrolysis was investigated. Raw CBG and autohydrolysistreated CBG were pretreated with ozone at ozone consumption of 1.8 to 26.4 % (w/w) at room temperature. Lignin degradation and hemicellulose solubilization increased with increased ozone consumption. At 26.4% ozone consumption by weight on CBG the amount of lignin in the CBG was reduced by 34%. Autohydrolysis of CBG increased the reactivity of cellulose, hemicellulose, and lignin with ozone. The maximum total sugar recovery after enzymatic hydrolysis was 32% for a 14.0% consumption of ozone on raw CBG. For CBG samples pretreated with autohydrolysis followed by a 3.1% ozone consumption pretreatment the maximum total sugar recovery after enzyme hydrolysis was 40.1%. Autohydrolysis pretreatment followed by enzyme hydrolysis yielded a 36.4% sugar recovery, indicating that the application and benefits of ozone after autohydrolysis with the conditions studied herein are marginally better than autohydrolysis alone. [ABSTRACT FROM AUTHOR]

Review: [approaches towards the development and chemical modification; 72 refs. [ABSTRACT FROM AUTHOR]