Ioan Bicu

Cellulose extraction from orange peel using sulfite digestion reagents

Orange peel (OP) was used as raw material for cellulose extraction. Two different pulping reagents were used, sodium sulfite and sodium metabisulfite. The effect of the main process parameters, sulfite agent dosage and reaction duration, on cellulose yield was investigated. A central composite rotatable design involving two variables at five levels and response surface methodology were used for the optimization of cellulose recovery. Other two invariable parameters were reaction temperature and hydromodulus. The optimum yields, referred to the weight of double extracted OP, were 40.4% and 45.2% for sodium sulfite and sodium metabisulfite digestions, respectively. The crude celluloses were bleached with hypochlorite and oxygen. The physicochemical characterization data of these cellulose materials indicate good levels of purity, low crystallinities, good whitenesses, good water retention and moderate molecular weights. According to these specific properties the recovered celluloses could be used as fillers, water absorbents, or as raw materials for cellulose derivatives.

Diels-Alder polymerization of some derivatives of abietic acid

The Diels-Alder polymerization reaction between a bisdiene derived from abietic acid and 4,4′-diphenylmethanedimaleimide (bismaleimide) was studied. The bisdiene was the dehydrodecarboxylation product of abietic acid, denoted here as diabietyl ketone. An insoluble and infusible polymer with high molecular weight was obtained. It is a poly(ketoimide) with hydrophenanthrene moieties in the backbone. The analyses showed that the chemical structure of the polymer was different from that expected. The polymer structural unit was found to contain bismaleimide and diabietyl ketone units not in a molar ratio of 1 : 1, as expected, but in a ratio of 5–6 : 1. The phenomenon was ascribed to the difference between the rates of the two concomitant reactions in the synthesis; the homopolymerization of bismaleimide and the proper Diels-Alder polymerization. The polymer having in structure the monomer units in 1 : 1 ratio was, however, obtained by both the dehydrodecarboxylation of the diacid resulted from the Diels-Alder reaction between abietic acid and 4,4′-diphenylmethanedimaleimide and the polycondensation of the ketone of maleated abietic acid with 4,4′-diaminodiphenylmethane. The monomers and the polymers were investigated by usual physical and chemical methods. The thermal stability of polymers was evaluated by TGA. The synthesized polymers were identical heat-resistant as the crosslinked polymer obtained from 4,4′-diphenylmethanedimaleimide. They were stable in air up to 360°C. Die Diels-Alder-Polymerisation von einem aus Abietinsaure hergestellten Bisdien und 4,4′-Diphenylmethandimaleimid wurde untersucht. Das Bisdien war das Produkt der Dehydrodecarboxylierung von Abietinsaure, hier mit Diabietylketon bezeichnet. Daraus resultierte ein hochmolekulares, unlosliches und nicht schmelzbares Polymeres. Das Polymere ist ein Poly(ketoimid) mit Hydrophenanthren-Einheiten in der Hauptkette. Die Analysen zeigten, das die Struktur des Polymeren anders ist als vorausgesagt. Das Verhaltnis von Bismaleinimid zu Bisdien im Polymeren betragt nicht 1 : 1, sondern liegt zwischen 5 : 1 und 6 : 1. Dieser Befund wurde mit der Differenz der Reaktionsgeschwindigkeiten der beiden konkurrierenden Reaktionen in der Synthese erklart, der Homopolymerisation des Bismaleinimids und der eigentlichen Diels-Alder-Polymerisation. Das Polymere mit einem Monomerverhaltnis von 1 : 1 wurde auf zwei Wegen erhalten: Zum einen durch Dehydrodecarboxilierung der Disaure aus der Diels-Alder-Reaktion von Abietinsaure und 4,4′-Diphenylmethandimaleimid, zum anderen durch Polykondensation des Ketons von maleinierter Abietinsaure mit 4,4′-Diaminodiphenylmethan. Die Monomeren und Polymeren wurden mit den gangigen physikalischen und chemischen Methoden untersucht. Die thermische Stabilitat der Polymeren wurde mit der TGA bestimmt. Die synthetisierten Polymeren sind genauso hitzebestandig wie das vernetzte Polymere aus 4,4′-Diphenylmethandimaleimid. Sie sind in Luft bis 360°C stabil.

Optimization of isolation of cellulose from orange peel using sodium hydroxide and chelating agents.

Response surface methodology was used to optimize cellulose recovery from orange peel using sodium hydroxide (NaOH) as isolation reagent, and to minimize its ash content using ethylenediaminetetraacetic acid (EDTA) as chelating agent. The independent variables were NaOH charge, EDTA charge and cooking time. Other two constant parameters were cooking temperature (98 °C) and liquid-to-solid ratio (7.5). The dependent variables were cellulose yield and ash content. A second-order polynomial model was used for plotting response surfaces and for determining optimum cooking conditions. The analysis of coefficient values for independent variables in the regression equation showed that NaOH and EDTA charges were major factors influencing the cellulose yield and ash content, respectively. Optimum conditions were defined by: NaOH charge 38.2%, EDTA charge 9.56%, and cooking time 317 min. The predicted cellulose yield was 24.06% and ash content 0.69%. A good agreement between the experimental values and the predicted was observed.

Rheological and thermal behaviour of DGEBA/EA and DGEHQ/EA epoxy systems crosslinked with TETA

Abstract Isothermal variation of the viscosity has been investigated in the temperature range 20–60°C for diglycidyl ether of bisphenol A/epoxy aniline/triethylenetetramine (DGEBA/EA/TETA) and diglycidyl ether of hydroquinone/epoxy aniline triethylenetetramine (DGEHQ/EA/TETA) systems. The variation of the viscosity versus time and temperature has been determined using a ‘Rheotest 2.1’ viscometer equipped with cone and plate geometry (36 mm diameter and 0.3° angle) at a shear rate of 1 s−1. The cure kinetics were studied using the DSC technique. The thermal behaviour of cured products was investigated by thermogravimetric analysis using a MOM Budapest derivatograph. The activation energies for the curing reaction calculated from the gel time have values between 18.78 kJ mol−1 for the DGEBA/EA/TETA and 60.93 kJ mol−1 for the DGEHQ/EA/TETA system. The cured products present good thermal stability, the activation energies of decomposition have values of 96.46 kJ mol−1 for the DGEBA/EA/TETA and 93.70 kJ mol−1 for the DGEHQ/EA/TETA system.

Allylic polymers from resin acids. Monomer synthesis at high temperature

New chemical compounds, i. e. ketones of the abietic acid-diallyl maleate Diels-Alder adduct, have been synthesized when the reaction of abietic acid and diallyl maleate was carried out at high temperatures (up to 250°C). Having unsaturated groups in their structure, they are polymerizable substances. The monomers and the polymers have been investigated by commonly used chemical and physical methods. The polymers are soluble in polar organic solvents only at low molecular weights. The behavior of these compounds as crosslinking monomers in copolymer systems has been examined.

Pressure sensitive adhesives modified with resinic acids

Pressure sensitive adhesives containing resinic acid derivatives in their structure were synthesized. The insertion of resinic acid derivatives as pendant group was carried out to improve the cohesive strength of acrylic polymers. IR, 1 H-NMR spectroscopy and other methods were used to characterize the monomers and polymers. The inherent viscosity of the polymers was found to be in the range 0.16-0.81 dL/g and the energy of thermal decomposition in the range 42-156 kJ/mol.

Formaldehyde resins from p-nonylphenol and resin acids

p-Nonylphenol, resin acids, and paraformaldehyde, in varying molar rations, were condensed under acid catalysis (hydrochloric acid). The resins thus obtained were characterized by spectroscopic methods and used as a starting material in pressure-sensitive formulae. The presence of these resins confers high adhesiveness and acceptable cohesive strength.