POLIURETANOS DERIVADOS DA LENHINA: FORMAÇÃO, CARACTERIZAÇÃO E APLICAÇÕES

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Lignin characterization by acetylation procedures

Publication . Cateto, Carolina; Rodrigues, Alírio; Barreiro, M.F.

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.

2005Conference object

Restricted access

Bioactivity evaluation of four technical lignins: Alcell, Indulin-AT, Sarkanda and Curan 27-11P

Publication . Marques, A.; Cateto, Carolina; Calhelha, Ricardo C.; Barros, Lillian; Queiroz, Maria João R.P.; Belgacem, Mohamed Naceur; Rodrigues, Alírio; Ferreira, Isabel C.F.R.; Barreiro, M.F.

In what concerns bioactive properties, and due to its phenolic character, lignin is mostly studied for their antioxidant activity. In this work four technical lignins (Alcell, Indulin-AT, Sarkanda and Curan 27-11P) have been evaluated for their antioxidant activity (DPPH radical scavenging activity, reducing power and inhibition of β-carotene bleaching) and antitumor potential against MCF-7, NCI-H460, HCT-15, HeLa and HepG2 cell lines. Additionally, the toxicity for non-tumour cells (PLP2) was also evaluated. The obtained results were correlated with the chemical and structural features of the studied lignins. Based on the achieved results, lignins of GS type, i.e. lignins rich in syringyl phenol units and poor in p-hydroxyphenyl ones result in better antitumor potential.

2014Conference object

Open access

Kinetic study of the formation of lignin-based polyurethanes in bulk

Publication . Cateto, Carolina; Barreiro, M.F.; Rodrigues, Alírio; Belgacem, Mohamed Naceur

The formation of lignin-based polyurethanes was monitored by Fourier transform infrared spectroscopy working in attenuated total reflectance mode (FTIR-ATR) and kinetics was analyzed according to a global second order model. The used chemical system consisted of 4,40-methylene-diphenylene diisocyanate (MDI), polycaprolactone (PCL) of three different average-molecular weights (400, 750 and 1000) and two lignin (L) samples (Alcell (A) and Indulin AT (IAT)), incorporated at different weight contents (10%, 15%, 20% and 25%) in the polyol mixture. The polymerization reaction was carried in bulk and without the presence of any catalyst. Results showed that isocyanate conversion decreases with the increase of both lignin content and PCL molecular weight. Moreover, the Indulin AT series leaded to lower isocyanate conversions compared to Alcell counterparts. The global second order treatment showed to be dependent of lignin type and content as well as PCL molecular weight. In fact, for the studied system this model was found to be more adequate for low lignin contents. After the region of linearity, a negative deviation was always observed and found to be more pronounced with increasing the lignin content.

2011Journal article

Restricted access