M.A. Pèlach

Effect of the combination of biobeating and NFC on the physico-mechanical properties of paper

The combined effect of enzymatic treatment (biobeating) and NFC addition on the mechanical and physical properties of a papermaking pulp suspension was investigated. The influence of pH, consistency of pulp and reaction time of the enzyme on the pulp strength was evaluated by measuring the breaking length of paper sheets made thereof. The results showed that the enzymatic treatment improved mechanical properties of fibres without modifying drainability. After biobeating, NFC was added to the enzyme-treated pulps. Mechanical properties were enhanced, obtaining length at break values similar to those observed in commercial printing/writing paper. Opacity remained constant, whereas porosity was gradually reduced as more amount of NFC was added. The presence of NFC also reduced drainability, although it remained at suitable levels for the papermaking industry. The results suggest that the combination of biobeating and NFC addition can be considered as an alternative to mechanical beating.

Evaluation of the influence of the addition of biodegradable polymer matrices in the formulation of self-curing polymer systems for biomedical purposes.

The solid phase of self-curing formulations of poly(methyl methacrylate) was modified by different biodegradable polymer matrices, such as poly(l-lactic acid), poly(beta-hydroxybutyrate) and thermoplastic starches (TPSs). The aim of this modification was the acquisition of a short- to medium-term drug delivery system to release bisphosphonates for hard tissue treatment. Different physico-chemical characterization techniques were used in order to determine the influence of these matrices and their mechanical capacity, in vitro behaviour, curing parameters, residual monomer content and surface topography for the preparation of the self-curing formulations. The incorporation of the polyesters did not induce an increase in water uptake capacity of the system due to their apolar aliphatic character. On the other hand, TPSs exhibited values of water absorption up to 15.3%, related with their hydrophilic chemical structure, dependent on the commercial formulation and the particle size distribution of the powder. The modifications of the solid phase led in all cases to a decrease in the mechanical behaviour of the material, although the formulations modified with TPS were in the range of accepted values according to standard specifications. The immersion of TPS formulations in a simulated physiological environment (phosphate buffer solution, pH 7.4, 37 degrees C) conducted to a surface porosity related with release of plasticizers of the domains of the biodegradable component of the formulation. Finally drug release capacity was studied by loading the material with Ibandronate, observing high dependence with the kind of TPS added, as well as its particle size.

Low environmental impact bleaching sequences for attaining high brightness level with eucalyptus SPP pulp

The alternatives used for minimizing the usage of chlorine dioxide in bleaching sequences included a hot acid hydrolysis (Ahot) stage, the use of hot chlorine dioxide (Dhot) and ozone stages at medium consistency and high consistency (Zmc and Zhc), in addition to stages with atmospheric hydrogen peroxide (P) and pressurized hydrogen peroxide (PO). The results were interpreted based on the cost of the chemical products, bleaching process yields and on minimizing the environmental impact of the bleaching process. In spite of some process restrictions, high ISO brightness levels were kept around 90 % brightness. Additionally, the inclusion of stages like acid hydrolysis, pressurized peroxide and ozone in the bleaching sequences provided an increase in operating flexibility, aimed at reducing environmental impact (ECF Light). The Dhot(EOP)D(PO) sequence presented lower operating cost for ISO brightness above 92 %. However, this kind of sequence was not allowed for closing the wastewater circuit, even partially. For ISO brightness level around 91%, the AhotZhcDP sequence presented a lower operating cost than the others.