Lignin characterization by acetylation procedures

The amount of the total hydroxyl content of lignin is of great importance in the formulation of a lignin based polyurethane system since it allows the quantity of the polyisocyanate counterpart within the right stoichiometry. In this work, the reliability of an acetylation procedure, regarding the determination of total hydroxyl content of a commercial kraft lignin, was studied. Lignin was acetylated using acetic anhydride reagent in solution in pyridine and the recovered acetylated samples were analysed by FTIR using KBr pellets. The experimental variables investigated were: reaction time, reaction temperature, composition of the acetylation reagent, presence of a catalyst and drying process of the acetylated samples. Within this work, the obtained results indicate that acetylation was incomplete for all the studied conditions, resulting in an unreliable total hydroxyl determination and shows the limitation of this technique. This observation is in accordance with recent published works (see, for example, Gosselink et al., 2004) and could justify the lack of agreement among some published experimental results concerning interlaboratory analysis

Monitoring of lignin-based polyurethane synthesis by FTIR-ATR

FTIR-ATR (Fourier Transform Infrared Spectroscopy working in the mode of Attenuated Total Reflectance) was applied to study the formation of lignin-based polyurethanes. Although some studies related to the use of lignin in polyurethane synthesis, are available in literature, still persist a gap for a systematic study of this kind of systems, involving the measurement of kinetic data, modelling and optimization of the polymerization process. The present methodology allows the test of different formulations at a scale of 3–5 g, considering several process variables: temperature, NCO/OH ratio, type and average molecular weight of the polyol, type of isocyanate, type and weight content of lignin. This work aims to describe the methodology used to perform the FTIR experiments by presenting a case study. The polyurethane samples have been prepared starting with 4,4′-methylene-diphenylene isocyanate (MDI), policaprolactonediol (PCL) of three different average molecular weights (1000, 750 and 400) and a commercial lignin (Indulin AT from Meadwestvaco) at different weight contents (10, 15, 20 and 25%). The results obtained in this work point out for the validation of the proposed experimental technique and confirm that lignin was incorporated in the final three-component polyurethane sample by chemical reaction with isocyanates, i.e., formation of urethane linkages

Monitoring of lignin-based polyurethane synthesis by FTIR-ATR

FTIR (Fourier Transform Infrared Spectroscopy), working in ATR (Attenuated Total Reflectance) mode was applied to study the formation of lignin-based polyurethanes. Although some studies related to the use of lignins in polyurethane synthesis, are available in literature, still persist a gap for a systematic study of this kind of systems involving the measurement of kinetic data, optimization and modelling of the process. This methodology allows the test of different formulations at a scale of 3-5 grams, considering several process variables: temperature, NCO/OH ratio, type and MW of the polyol, type of isocyanate, type and weight content of lignin. This work aims to describe the methodology used to perform the FTIR experiments by presenting a case study

Rigid polyurethane foams from lignin based polyols

Rigid polyurethane (RPU) foams were synthesized using lignin-based polyols obtained by an oxypropylation process. Alcell, Indulin AT, Curan 27-11P and Sarkanda lignins have been oxypropylated using formulations deduced from an optimization study with Alcell. L/PO/C (ratio between lignin, PO and catalyst content) of 30/70/2 and 20/80/5 were used to obtain the desired polyols. The resulting RPU foams were characterized in terms of density, mechanical properties, conductivity and morphology. All Sarkanda lignin based polyols and the 30/70/2 Curan 27-11P polyol were found inadequate for RPU formulations. Alcell and Indulin AT based polyols and the 20/80/5 Curan 27-11P polyol resulted in RPU foams with properties very similar to those obtained from conventional commercial polyols. RPU foams produced with the 30/70/2 Alcell and the 30/70/2 Indulin AT polyols exhibited improved properties compared with those from 20/80/5 based formulations.Foundation for Science and Technology (grant SFRH/BD/18415/2004) and the French-Portuguese Scientific Cooperation Programme (action F-32/08

Lignin-based polyurethane materials

Four technical lignins (Alcell, Indulin AT, Sarkanda and Curan 27-11P) were used as macromonomers in the synthesis of polyurethane materials following two global approaches. In the first one Alcell and Indulin AT lignins were used directly as co-monomers in combination with a linear polycaprolactone (PCL) in order to produce polyurethane elastomers where lignin content varied between 10 and 25% (w/w) with respect to polyol mixture (PCL+lignin). The thermomechanical properties of the resulting materials were determined by dynamical mechanical analysis (DMA), differential scanning calorimetry (DSC) and swelling tests. In lignin-based elastomers Indulin AT showed to be more efficiently incorporated in the polyurethane network compared with Alcell lignin. Elastomers prepared with Indulin AT lignin exhibited a cross-linking density and storage modulus (rubbery plateau) higher than those of Alcell lignin-based counterpart and a lower soluble fraction. For both Alcell and Indulin AT based elastomers the glass transition temperature increased and extended over a wide temperature range with the increase of lignin content. The second approach consisted of producing rigid polyurethane foams (RPU) using ligninbased polyols obtained after chemical modification by an oxypropylation procedure. Two polyol formulations (20/80 and 30/70, in what concerns the weight ratios between lignin and propylene oxide, PO), were used in RPU formulations and their content varied from 0 to 100% (w/w with respect to a commercial polyol, used as a reference). The resulting RPU foams were characterized in terms of density, mechanical properties, conductivity and morphology. The prepared RPU foams with lignin-based polyols presented properties, very similar to those obtained from conventional commercial polyols. RPU foams prepared with 30/70 polyols exhibited improved properties comparatively to those arising from 20/80 formulations. Exceptions were however detected in RPU foams prepared with all Sarkanda lignin based polyols and Curan 27-11P 30/70 formulation, which were found to be inadequate for RPU formulation.Foundation for Science and Technology (grant SFRH/BD/18415/2004) and French-Portuguese Scientific Cooperation Programme (action F- 32/08)

Rigid composite materials from olive brush seed and unsaturated polyester resin

A composite material using unsaturated commercial polyester resin (UPE) and olive brush seed (OBS) was prepared. OBS was treated with sodium hydroxide and maleic anhydride (MAN) and subsequently utilized in a proportion of 35 wt.% to prepare a composite material. These materials were evaluated in terms of moisture absorption, surface density, and mechanical properties such as flexure and tensile tests

Valorisation of kraft lignin by using vanillin and lignin-based polyurethanes: Use of the biorefinery concept

In kraft pulp mills, the capacity of the recovery boiler is very often a limiting factor to the increase of the pulp production. Until several decades ago, an upgrade to boiler system for dealing with higher quantities of black liquor was the only alternative. The possibility of lignin extraction from black liquor seems to be much more attractive, either for energy production or combustion elsewhere, or to serve as feedstock for chemicals production. Since the beginning of the 90’s, associate Laboratory LSRE/LCM has been focused on overcoming expansion limitations in pulp industries and, in this work, we show an alternative to this industry segment for the utilization of lignin and producing high added value chemicals from renewable biomass materials. Based on the biorefinery concepts, an integrated process for producing vanillin from kraft lignin oxidation has been proposed and each of the needed unit operations has been investigated to provide a deeper scientific understanding on this subject.FCT - projects POCTI/EQU/33198/99, POCI/EQU/61738/2004 and Grant SFRH/BD/18415/2004. CYTED IV.17/2002-2006. Luso-French actions F13/06 and F32/08

Biodegradation study of I lignin-based rigid polyrethane foams

Polyurethanes are considered as one of the most versatile polymeric materials offering a wide range of products with applications in diverse sectors. Rigid polyurethane (RPU) foams belong to this class of products and represent a commercially important class of expanded materials. In the present work RPU foams have been prepared from lignin-based polyols (LP) obtained by oxypropylation of two technical lignins (Alcell and Indulin AT) and biodegradability evaluated using respirometry tests in liquid and solid media. A RPU foam produced from a commercial polyether polyol (CP) based on sorbitol (Lupranol® 3323) was used as reference. Lignin biodegradation by P. chrysogenum, T. harzianum, T. reesei, T. versicolor and P. chrysosporium fungi was tested. Respirometry tests (in liquid and solid media) were performed and foam’s biodegradation evaluated based on the produced CO2.FCT (grant SFRH/BD/18415/2004) and the French-Portuguese Scientific Cooperation (actions F-13/06 and F-32/08)

Study on the (bio)degradation process of bioplastic materials under industrial composting conditions

The objective of this study was to determine the biodegradability of bioplastic materials-sponge cloths-available on the European market. They are labeled as 100 % biodegradable but not certified as compostable. The test was carried out in real composting environment. The project duration was 12 weeks. The emphasis was put on discovering whether the sponge cloths are biodegradable or not. Based on the results, it can be concluded that sponge cloths have decomposed completely (sample C and sample D). Samples A have decomposed but exhibited slower degradation rate. Samples B exhibited the higher degradation rate. The main conclusion from this study is that biodegradation of bioplastics materials strongly depends on both, the environment where they are placed and the chemical nature of the material.O