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- Polyurethane foams from liquefied orange peel wastesPublication . Domingos, Idalina; Ferreira, José; Cruz-Lopes, Luísa; Esteves, BrunoWaste conversion into value added materials is a growing subject due to environmental concerns. In the production of orange juice high amounts of orange peel waste are generated and although they are used for the extraction of some extractable compounds a new waste is generated not much different from before. The aim of this work was to determine the possibility of efficiently converting orange peel waste into a liquefied material for the production of more environmentally benign polyurethane foams and test the influence of the proportion of isocyanate, catalyst, surfactant and blowing agent in physical and mechanical properties of the foams. Dry orange peel was liquefied using a mixture of ethyleneglycol and glycerol (1:1) as solvents, catalysed by sulphuric acid at 180 °C for 60 min. A ratio of 9:1 solvent/lignocellulosic material was used and 3% of sulphuric acid was added based on the solvent mass. Density, compressive stress at 10% and young modulus were determined for each foam. The results show that a good liquefaction yield can be achieved by polyalcohol liquefaction of orange peel waste and that this material can successfully be converted into a polyurethane foam with satisfying properties. Moreover the results showed that the physical and mechanical properties of the foam could be tailored by a careful choice of the additives used in foam formation
- Optimizing Douglas-fir bark liquefaction in mixtures of glycerol and polyethylene glycol and KOHPublication . Esteves, Bruno; Cruz-Lopes, Luísa; Ferreira, José; Domingos, Idalina; Nunes, Lina; Pereira, HelenaThe outer bark of Douglas-fir (Pseudotsuga menziesii) has a significant amount of cork tissue that may be an important source of chemicals derived from its natural polymers, suberin, cellulose, hemicelluloses and lignin. The present work focuses on the polyalcohol liquefaction of Douglas-fir bark with glycerol and polyethylene glycol (PEG) in order to obtain a liquid that can be further processed to other chemicals and products. The results show that Pseudotsuga bark can be liquefied in a significant percentage in presence of alkali. The best liquefaction yield was obtained with 6% KOH as agents. Although the use of a cosolvent is favorable, good liquefaction yields can also be obtained by glycerol alone. Lower temperatures are favorable as they lead to acceptable liquefaction yields. FTIR-ATR studies showed that all the structural compounds of the bark were attacked and depolymerized. The process tested has a high potential for generation of value-added products from liquefied Douglas-fir bark.
- Polyurethane foams from liquefied orange peel wastesPublication . Domingos, Idalina; Ferreira, José; Cruz-Lopes, Luísa; Esteves, BrunoWaste conversion into value added materials is a growing subject due to environmental concerns. In the production of orange juice high amounts of orange peel waste are generated and although they are used for the extraction of some extractable compounds a new waste is generated not much different from before. The aim of this work was to determine the possibility of efficiently converting orange peel waste into a liquefied material for the production of more environmentally benign polyurethane foams and test the influence of the proportion of isocyanate, catalyst, surfactant and blowing agent in physical and mechanical properties of the foams. Dry orange peel was liquefied using a mixture of ethyleneglycol and glycerol (1:1) as solvents, catalysed by sulphuric acid at 180ºC for 60 min. A ratio of 9:1 solvent/lignocellulosic material was used and 3% of sulphuric acid was added based on the solvent mass. Density, compressive stress at 10% and young modulus were determined for each foam. The results show that a good liquefaction yield can be achieved by polyalcohol liquefaction of orange peel waste and that this material can successfully be converted into a polyurethane foam with satisfying properties. Moreover the results showed that the physical and mechanical properties of the foam could be tailored by a careful choice of the additives used in foam formation.
- FTIR Monitoring of Polyurethane Foams Derived from Acid-Liquefied and Base-Liquefied PolyolsPublication . Dulyanska, Yuliya; Cruz-Lopes, Luísa; Esteves, Bruno; Guiné, Raquel; Domingos, IdalinaPolyalcohol liquefaction can be performed by acid or base catalysis, producing polyols with different properties. This study compared the mechanical properties of foams produced using polyols from liquefied Cytisus scoparius obtained by acid and base catalysis and using two different foam catalysts. The differences were monitored using FTIR analysis. Acid-catalyzed liquefaction yielded 95.1%, with the resultant polyol having an OH index of 1081 mg KOH/g, while base catalysis yielded 82.5%, with a similar OH index of 1070 mg KOH/g. Generally, compressive strength with dibutyltin dilaurate (DBTDL) ranged from 16 to 31 kPa (acid-liquefied polyol) and 12 to 21 kPa (base-liquefied polyol), while with stannous octoate (TIN), it ranged from 17 to 42 kPa (acid) and 29 to 68 kPa (base). Increasing water content generally decreased the compressive modulus and strength of the foams. Higher water content led to a higher absorption at 1670 cm−1 in the FTIR spectrum due to the formation of urea. Higher isocyanate indices generally improved compressive strength, but high amounts led to unreacted isocyanate that could be seen by a higher absorption at 2265 cm−1 and 3290 cm−1. DBTL was shown to be the best foam catalyst due to higher trimer conversion seen in the spectra by a higher absorption at 1410 cm−1. Acid- and base-derived polyols lead to different polyurethane foams with different FTIR spectra, particularly with a higher absorption at 1670 cm−1 for foams from acid-derived liquefaction.