@article{ye_li_lu_zhang_rojas_2016, title={Antioxidant and Thermal Stabilization of Polypropylene by Addition of Butylated Lignin at Low Loadings}, volume={4}, ISSN={["2168-0485"]}, DOI={10.1021/acssuschemeng.6b01241}, abstractNote={The effect of phenolic hydroxyl group content and molecular mass of a technical lignin on the thermo-oxidation resistance and compatibility with polypropylene (PP) was studied by a combination of approaches, including 31P NMR, gel permeation chromatography (GPC), thermogravimetry (TG), dynamic scanning calorimetry (DSC), accelerated aging tests, scanning electron microscopy (SEM), and dynamic mechanical analysis (DMA). The compatibility of lignin with PP upon melt compounding in a screw system was improved after modification of lignin with n-butyric anhydride. The thermal oxidation stability of films of PP blends, as measured in an oxygen atmosphere, was increased by low addition levels of the butylated lignins while maintaining, and in some cases improving, their thermo-mechanical performance. Notably, the oxidation induction time (OIT) and induction aging time of PP blended with butylated lignins (<5% loadings) reached maximum values of 16 min and 576 h, respectively, indicating an effect equivalent to ...}, number={10}, journal={ACS SUSTAINABLE CHEMISTRY & ENGINEERING}, author={Ye, Dezhan and Li, Shuai and Lu, Xiaomin and Zhang, Xi and Rojas, Orlando J.}, year={2016}, month={Oct}, pages={5248–5257} }
 @article{li_ogunkoya_fang_willoughby_rojas_2016, title={Carboxymethylated lignins with low surface tension toward low viscosity and highly stable emulsions of crude bitumen and refined oils}, volume={482}, ISSN={["1095-7103"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84979781362&partnerID=MN8TOARS}, DOI={10.1016/j.jcis.2016.07.063}, abstractNote={Kraft and organosolv lignins were subjected to carboxymethylation to produce fractions that were soluble in water, displayed a minimum surface tension as low as 34mN/m (25°C) and a critical aggregation concentration of ∼1.5wt%. The carboxymethylated lignins (CML), which were characterized in terms of their degree of substitution ((31)P NMR), elemental composition, and molecular weight (GPC), were found suitable in the formulation of emulsions with bitumens of ultra-high viscosity, such as those from the Canadian oil sands. Remarkably, the interfacial features of the CML enabled fuel emulsions that were synthesized in a very broad range of internal phase content (30-70%). Cryo-replica transmission electron microscopy, which was used here the first time to assess the morphology of the lignin-based emulsions, revealed the droplets of the emulsion stabilized with the modified lignin. The observed drop size (diameters<2μm) was confirmed by light scattering, which revealed a normal size distribution. Such characteristics led to stable emulsified systems that are amenable for a wide range of applications. Emulsification with CML afforded bitumen emulsions with very high colloidal stability (no change was noted for over one month) and with a strong shear thinning behavior. Both features indicate excellent prospects for storage, transport and spraying, which are relevant in operations for power generation, which also take advantage of the high heating value of the emulsion components. The ability of CML to stabilize emulsions and to contribute in their combustion was tested with light fuels (kerosene, diesel, and jet fuel) after formulation of high internal phase systems (70% oil) that enabled operation of a fuel engine. A significant finding is that under certain conditions and compared to the respective pure fuel, combustion of the O/W emulsions stabilized by CML presented lower NOx and CO emissions and maintained a relatively high combustion efficiency. The results highlight the possibilities in high volume application for lignin biomacromolecules.}, journal={JOURNAL OF COLLOID AND INTERFACE SCIENCE}, author={Li, Shuai and Ogunkoya, Dolanimi and Fang, Tiegang and Willoughby, Julie and Rojas, Orlando J.}, year={2016}, month={Nov}, pages={27–38} }
 @article{li_xiang_jarvinen_lappalainen_salminen_rojas_2016, title={Interfacial Stabilization of Fiber-Laden Foams with Carboxymethylated Lignin toward Strong Nonwoven Networks}, volume={8}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.6b06418}, abstractNote={Wet foams were produced via agitation and compressed air bubbling of aqueous solutions of carboxymethylated lignin (CML). Bubble size and distribution were assessed in situ via optical microscopy. Foamability, bubble collapse rate, and foam stability (half-life time) were analyzed as a function of CML concentration, temperature, pH, and air content. Dynamic changes of the CML liquid foam were monitored by light transmission and backscattering. Cellulosic fibers of different aspect ratios (long pine fibers and short birch fibers) were suspended under agitation by the liquid foams (0.6% CML in the aqueous phase) with an air (bubble) content as high as 75% in volume. Remarkably, the half-life time of fiber-laden CML foams was 10-fold higher than that of the corresponding fiber-free liquid foam. Such lignin-based foams were demonstrated, after dewatering, as a precursor for the synthesis of nonwoven, layered structures. The resulting fiber networks (paper), obtained here for the first time with lignin-based foams, were characterized for pore size distribution, lignin retention, morphology, and physical-mechanical properties (network formation quality, density, air permeability, surface roughness, and tensile and internal bond strengths). The results were compared against structures obtained from foams stabilized with an anionic surfactant (SDS) as well as those from foam-free, water-based web-laying. Remarkably, compared to SDS, the foam-formed materials produced with CML displayed better bonding and tensile strengths. Overall, CML-based foams were found to be suitable carriers of cellulosic fibers and have opened the possibility for integrating fully biobased systems in foam-forming. This is an emerging option to increase the effective solids content in the system without compromising the quality of formed nonwoven materials while achieving reductions in water and energy consumption.}, number={30}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Li, Shuai and Xiang, Wenchao and Jarvinen, Marjo and Lappalainen, Timo and Salminen, Kristian and Rojas, Orlando J.}, year={2016}, month={Aug}, pages={19827–19835} }
 @article{li_willoughby_rojas_2016, title={Oil-in-Water Emulsions Stabilized by Carboxymethylated Lignins: Properties and Energy Prospects}, volume={9}, ISSN={["1864-564X"]}, DOI={10.1002/cssc.201600704}, abstractNote={AbstractWe take advantage of the amphiphilic properties of technical lignin macromolecules and their inherent high calorific values to formulate oil‐in‐water (O/W) fuel emulsions with high internal‐phase ratios. For the oil phase, we used a combustible hydrocarbon (kerosene) with a measured equivalent alkane carbon number of 12. To adjust the balance of affinity with the oil and water phases and their surface activity, pine kraft lignins were carboxymethylated to different degrees, as quantified by 13C NMR spectroscopy, potentiometric titrations, and zeta potential measurements. Carboxymethylated lignins (CMLs) with a degree of substitution of 30 % displayed a critical aggregation concentration of 3 %. The salinity and pH of the aqueous phase were chosen as formulation variables and adjusted within the Winsor framework. The O/W emulsions were produced by following standard protocols. The drop‐size distributions of emulsions with varying pH, degree of substitution, and composition (water‐to‐oil ratio, WOR) were determined, and the long‐term stabilities and rheological behavior of these emulsions were analyzed. Most of the obtained O/W fuel emulsions showed shear‐thinning behavior with a drop size of approximately 2.5 μm and were stable for over 30 days. The combustion of the lignins and their respective emulsions was performed, and their higher heating values (HHVs) were quantified. The HHVs of CML and a high‐internal‐phase (WOR=30:70) O/W emulsion were 20 and 30 MJ kg−1, respectively. Overall, we propose the stabilization of O/W fuel emulsions by lignin as an important avenue in the utilization of this abundant biomacromolecule.}, number={17}, journal={CHEMSUSCHEM}, author={Li, Shuai and Willoughby, Julie A. and Rojas, Orlando J.}, year={2016}, month={Sep}, pages={2460–2469} }
 @article{ogunkoya_li_rojas_fang_2015, title={Performance, combustion, and emissions in a diesel engine operated with fuel-in-water emulsions based on lignin}, volume={154}, ISSN={["1872-9118"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84930675094&partnerID=MN8TOARS}, DOI={10.1016/j.apenergy.2015.05.036}, abstractNote={We report for the first time on the use of water-continuous emulsions stabilized by a bio-based macromolecule in a compression-ignition diesel engine and compare their performance, combustion and emissions against the base fuels (diesel, biodiesel, and jet fuel). For this purpose, high internal phase ratio emulsions (70:30 fuel-to-water) were produced by mechanical emulsification using carboxymethylated wood lignin as stabilizer. Combusting experiments were performed with the engine operating at 2000 rpm under three loads (0, 1.26 and 3.26 bar brake mean effective pressure, BMEP). Engine performance, in-cylinder combustion, and exhaust emissions were monitored and compared for the fuels tested. At no load condition and when compared to the respective base (single phase) fuels, an increase in the indicated work was observed for diesel and biodiesel emulsions. Compared to the base fuels, the emulsions resulted in higher engine mechanical efficiency at 1.26 and 3.26 bar BMEP except for jet fuel emulsion at 1.26 bar. Additionally, they displayed a lower brake specific fuel consumption (BSFC), if calculated on the basis of effective fuel content discounting emulsion water, and higher brake thermal efficiency. Compared to the base fuel, the respective emulsions generally presented lower peak in-cylinder pressure, lower heat release rates, and longer ignition delays at 1.26 bar and 3.26 bar BMEP; the opposite effect was observed at no-load conditions. Remarkably, a large reduction of nitrogen oxides (NOx) emissions was noted in the combustion of the fuel emulsions, which was accompanied with a relatively higher carbon monoxide (CO) release at 1.26 and 3.26 bar (at 0 bar BMEP, the emulsions produced less CO emissions). The effect of emulsions on hydrocarbon emissions and smoke opacity depended on the fuel type and the engine load. Overall, it is concluded that while reports on fuel emulsions involve oil-continuous systems, the proposed water-continuous alternative represents an opportunity for diesel engines, whereby the fuel is dispersed as micrometric droplets for improved combustion and reduced emissions. At the same time, the fuel emulsion formulation takes advantage of the surface activity and high calorific value of widely available, inexpensive lignin stabilizers, making the proposed system a viable option towards cleaner or fully bio-based fuels.}, journal={APPLIED ENERGY}, author={Ogunkoya, Dolanimi and Li, Shuai and Rojas, Orlando J. and Fang, Tiegang}, year={2015}, month={Sep}, pages={851–861} }