Effect of Dilute Acid Pretreatment and Lignin Extraction Conditions on Lignin Properties and Suitability as a Phenol Replacement in Phenol-Formaldehyde Wood Adhesives.

Corn stover was subjected to dilute sulfuric acid pretreatment to assess the impact of pretreatment conditions on lignin extractability, properties, and utility as a phenol replacement in wood phenol-formaldehyde (PF) adhesives. It was identified that both formic acid and NaOH could extract and recover 60-70% of the lignin remaining after pretreatment and enzymatic hydrolysis under the mildest pretreatment conditions while simultaneously achieving reasonable enzymatic hydrolysis yields (>60%). The availability of reaction sites for the incorporation of lignins into the PF polymer matrix (i.e., unsubstituted phenolic hydroxyl groups) was shown to be strongly impacted by the pretreatment time and the recovery. Finally, a lignin-based wood adhesive was formulated by replacing 100% of the phenol with formic-acid-extracted lignin, which exhibited a dry shear strength exceeding a conventional PF adhesive. These findings suggest that both pretreatment and lignin extraction conditions can be tailored to yield lignins with properties targeted for this co-product application.

Kraft Lignin with Improved Homogeneity Recovered Directly from Black Liquor and Its Application in Flexible Polyurethane Foams.

An effective method that can produce a large amount of Kraft lignin with improved homogeneity is strongly desired for Kraft lignin's high-value applications and scientific advancements. Herein, a one-pot acid-catalyzed liquefaction method was developed to recover Kraft lignin directly from black liquor. The recovery rate and properties of the recovered lignin were affected by the reaction time, reaction temperature, moisture content (MC), pH, and acid categories. The highest lignin recovery rate of 75% was achieved when the concentrated black liquor (MC = 25%) reacted with methanol at pH = 7 and 160 °C for 10 min using acetic acid as the catalyst. Most of the recovered lignin from this method showed an average molecular weight (Mw) value less than 2000 Da and a polydispersity (PDI) value less than 2.0. Such a PDI value was lower than that of current acid precipitated lignin (around 2.2-5.4). The recovered lignin was directly used to replace 20% of the petroleum-based polyol in the formula of a flexible polyurethane (PU) foam, and it was found that the molecular weight characteristics of the lignin affected the physical and mechanical properties of the flexible PU foams. The recovered lignin with the Mw value of 1600 Da and the PDI value of 1.8 was able to maintain the major physical and mechanical properties of the flexible PU foams. This study provided a promising way to recover lignin with improved homogeneity from black liquor with the potential to customize lignin properties to meet the requirements of downstream processes.

Studying the Suitability of Nineteen Lignins as Partial Polyol Replacement in Rigid Polyurethane/Polyisocyanurate Foam.

In this study, nineteen unmodified lignins from various sources (hardwood, softwood, wheat straw, and corn stover) and isolation processes (kraft, soda, organosolv, sulfite, and enzymatic hydrolysis) were used to replace 30 wt.% of petroleum-based polyol in rigid polyurethane/polyisocyanurate (PUR/PIR) foam formulations. Lignin samples were characterized by measuring their ash content, hydroxyl content (Phosphorus Nuclear Magnetic Resonance Spectroscopy), impurities (Inductively Coupled Plasma), and pH. After foam formulation, properties of lignin-based foams were evaluated and compared with a control foam (with no lignin) via cell morphology, closed-cell content, compression strength, apparent density, thermal conductivity, and color analysis. Lignin-based foams passed all measured standard specifications required by ASTM International C1029-15 for type 1 rigid insulation foams, except for three foams. These three foams had poor compressive strengths, significantly larger cell sizes, darker color, lower closed-cell contents, and slower foaming times. The foam made with corn stover enzymatic hydrolysis lignin showed no significant difference from the control foam in terms of compressive strength and outperformed all other lignin-based foams due to its higher aliphatic and p-hydroxyphenyl hydroxyl contents. Lignin-based foams that passed all required performance testing were made with lignins having higher pH, potassium, sodium, calcium, magnesium, and aliphatic/p-hydroxyphenyl hydroxyl group contents than those that failed.

Enzymatic synthesis of kraft lignin-acrylate copolymers using an alkaline tolerant laccase.

Softwood kraft lignin is a major bioresource relevant to the production of sustainable bio-based products. Continued challenges to lignin valorization, however, include poor solubility in organic solvents and in aqueous solutions at neutral pH. Herein, an alkaline tolerant laccase was used to graft acrylate functionalities onto softwood kraft lignin, which is expected to enhance the reactivity of lignin with isocyanate when producing bio-based polyurethanes. Proton nuclear magnetic resonance, Fourier-transform infrared spectroscopy, and high-performance liquid chromatography were used to confirm successful grafting of the acrylate monomer onto lignin and verify the importance of including tert-butyl hydroperoxide as an initiator in the grafting reaction. Laccase-mediated grafting of softwood kraft lignin under alkaline conditions produced lignin products with approximately 30% higher hydroxyl value and higher reactivity toward isocyanate. The reported enzymatic and aqueous process presents an opportunity for the sustainable valorization of softwood kraft lignin. KEY POINTS: • Softwood kraft lignin displayed high phenolic hydroxyl content, polydispersity index and average molecular weight • Grafting hydroxyethyl acrylate (HEA) monomer onto kraft lignin by laccase was successful at 60 °C and alkaline conditions • Lignin-HEA grafted copolymer showed an increase in total OH value and an increase in average molecular weight.

Lignin as a Partial Polyol Replacement in Polyurethane Flexible Foam.

This study was focused on evaluating the suitability of a wide range of lignins, a natural polymer isolated from different plant sources and chemical extractions, in replacing 20 wt.% of petroleum-based polyol in the formulation of PU flexible foams. The main goal was to investigate the effect of unmodified lignin incorporation on the foam's structural, mechanical, and thermal properties. The hydroxyl contents of the commercial lignins were measured using phosphorus nuclear magnetic resonance (31P NMR) spectroscopy, molar mass distributions with gel permeation chromatography (GPC), and thermal properties with differential scanning calorimetry (DSC) techniques. The results showed that incorporating 20 wt.% lignin increased tensile, compression, tear propagation strengths, thermal stability, and the support factor of the developed PU flexible foams. Additionally, statistical analysis of the results showed that foam properties such as density and compression force deflection were positively correlated with lignin's total hydroxyl content. Studying correlations between lignin properties and the performance of the developed lignin-based PU foams showed that lignins with low hydroxyl content, high flexibility (low Tg), and high solubility in the co-polyol are better candidates for partially substituting petroleum-based polyols in the formulation of flexible PU foams intended for the automotive applications.

Choosing the Right Lignin to Fully Replace Bisphenol A in Epoxy Resin Formulation.

Thirteen unmodified lignin samples from different biomass sources and isolation processes were characterized and used to entirely replace bisphenol A (BPA) in the formulation of solubilized epoxy resins using a developed novel method. The objective was to measure the reactivity of different lignins toward bio-based epichlorohydrin (ECH). The epoxy contents of various bio-based epoxidized lignins were measured by titration and 1 H NMR spectroscopy methods. A partial least square regression (PLS-R) model with 92 % fitting accuracy and 90 % prediction ability was developed to find correlations between lignin properties and their epoxy contents. The results showed that lignins with higher phenolic hydroxy content and lower molecular weights were more suitable for replacing 100 % of toxic BPA in the formulation of epoxy resins. Additionally, two epoxidized lignin samples (highest epoxy contents) cured by using a bio-based hardener (Cardolite GX-3090) were found to show comparable thermomechanical performances and thermal stabilities to a petroleum-based (DGEBA) epoxy system.

Lignin-Based Polyurethanes: Opportunities for Bio-Based Foams, Elastomers, Coatings and Adhesives.

Polyurethane chemistry can yield diverse sets of polymeric materials exhibiting a wide range of properties for various applications and market segments. Utilizing lignin as a polyol presents an opportunity to incorporate a currently underutilized renewable aromatic polymer into these products. In this work, we will review the current state of technology for utilizing lignin as a polyol replacement in different polyurethane products. This will include a discussion of lignin structure, diversity, and modification during chemical pulping and cellulosic biofuels processes, approaches for lignin extraction, recovery, fractionation, and modification/functionalization. We will discuss the potential of incorporation of lignins into polyurethane products that include rigid and flexible foams, adhesives, coatings, and elastomers. Finally, we will discuss challenges in incorporating lignin in polyurethane formulations, potential solutions and approaches that have been taken to resolve those issues.

A survey of ophthalmologists and gynecologists regarding termination of pregnancy and choice of delivery mode in the presence of eye diseases.

PURPOSE: To evaluate and compare the attitudes of ophthalmologists and gynecologists in suggesting appropriate approach to pregnancy in different ocular conditions. METHODS: Specialty-specific questionnaires on delivery mode and abortion indications for ophthalmic patients (refractive, vascular, oncologic, retinal, glaucoma, postoperation, posttrauma, and infectious) were designed and distributed among physician staff of Farabi Eye Hospital and Yas Women Hospital in Tehran. Attitudes and preferences of the ophthalmologists and gynecologists were quantified and compared. RESULTS: Participants were 29 ophthalmologists and 19 gynecologists. Their mean age was 49.73 ± 7.57 and 46.79 ± 1.36 years, respectively. More than 50-70% ophthalmologists were in favor of normal vaginal delivery (NVD) in all ocular diseases. All gynecologists (100%) expressed their need for an ophthalmologist's opinion for decision-making. Ophthalmologists' top choices for conditions potentially requiring a caesarean section were corneal transplants (34.5%), high myopia (23%), retinal detachment (29%), and orbital tumors (34.5%), while two gynecologists recommended abortion in the presence of intraocular and orbital tumors and retinal detachment. In the case of a history of refractive surgery, orbital tumor and intraocular tumor, ophthalmologists recommend NVD over caesarean section twice as much as their gynecologist peers. For history of retinal detachment, glaucoma, retinal vascular accident and intraocular hemorrhage, no single gynecologist recommend NVD. The corresponding figure for ophthalmologist-recommended NVD were 67, 84, 72, and 81%. CONCLUSIONS: There is extreme inconsistency among ophthalmologists and gynecologists in managing ophthalmic-obstetric scenarios, especially for caesarean section indications. Clinical guideline development and consultation for decision-making in challenging cases are recommended.

Coatings to reduce wood preservative leaching.

The efficiency of semitransparent penetrating stains to reduce leaching of wood preservative components was evaluated. Five commercial wood deck finishes were applied to untreated and chromated copper arsenate (CCA), alkaline copper quat (ACQ), and copper azole (CA) treated wood, and leachates were collected and analyzed during 3 years of natural weathering exposure in Toronto, Canada. All stains evaluated effectively reduced the cumulative leaching of all inorganic preservative components by about 60% on average. Although most coatings showed significant film degradation starting around 12 months, the reduced leaching persisted even after 3 years. This suggests that temporary protection of wood with a coating during the early stages of use resulted in long-term reduction in preservative leaching potential. A two-week screening leaching test was able to predict the long-term leaching performance of different coatings reasonably well. Cured coating glass transition temperature (Tg) and liquid coating viscosity were the most important variables affecting a leaching prediction model. To effectively reduce leaching of preservative components from treated wood, coatings should have Tg low enough to withstand stresses caused by freezing in winter and have adequate viscosity to form a barrier film layer on the wood surface.

Sticker reminders improve thromboprophylaxis appropriateness in hospitalized patients.

BACKGROUND: Venous thromboembolism (VTE) is a major health problem. Even though effective thromboprophylaxis measures exist to prevent VTE, close adherence to guidelines is missing. We assessed the effects of pasting VTE prophylaxis sticker reminders, on the appropriateness of thromboprophylaxis and prophylaxis underutilization. METHODS: Thromboprophylaxis reception was sought prospectively in two time points before and two time points after pasting sticker reminders in hospitalized patients of Masih Daneshvari Medical Center, Tehran, Iran. Thromboprophylaxis reception appropriateness was evaluated by the eighth American College of Chest Physicians (ACCP) guidelines on antithrombotic and thrombolytic therapy. Co-morbidities and conditions considered to affect the risk of venous thromboembolism were also recorded. RESULTS: Prophylaxis reception and appropriateness were studied in 298 patients before and 306 patients after the intervention. Based on the ACCP guidelines, overall thromboprophylaxis appropriateness was improved after the intervention (70.4% before, and 78.1% after the intervention, P=0.03). Prophylaxis underutilization, and prophylaxis initiation delay in those who needed thromboprophylaxis, were also reduced (P=0.03, and P=0.011 respectively). The intervention did not result in an increased rate of overprophylaxis (P=0.45). CONCLUSION: Sticker reminders could be safely and effectively incorporated into strategies to improve VTE prophylaxis and prophylaxis appropriateness, particularly in healthcare settings where electronic alert systems are not available.