Fabiola Vilaseca

Biocomposites from abaca strands and polypropylene. Part I: Evaluation of the tensile properties

In this paper, abaca strands were used as reinforcement of polypropylene matrix and their tensile mechanical properties were studied. It was found relevant increments on the tensile properties of the abaca strand-PP composites despite the lack of good adhesion at fiber-matrix interface. Afterwards, it was stated the influence of using maleated polypropylene (MAPP) as compatibilizer to promote the interaction between abaca strands and polypropylene. The intrinsic mechanical properties of the reinforcement were evaluated and used for modeling both the tensile strength and elastic modulus of the composites. For these cases, the compatibility factor for the ultimate tensile strength was deduced from the modified rule of mixtures. Additionally, the experimental fiber orientation coefficient was measured, allowing determining the interfacial shear strengths of the composites and the critical fiber length of the abaca strand reinforcement. The mechanical improvement was compared to that obtained for fiberglass-reinforced PP composites and evaluated under an economical and technical point of view.

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.

Enzymic deinking of old newspapers with cellulase

Abstract Paper recycling industries are oriented towards re-use and sustainability. These effects are combined in different ways to achieve the requirements on printing and writing papers. Biodeinking is an alternative analysed in this study. Cellulase uses improve ink detachment from old newspapers giving similar or better results when cellulase is used in place of classical chemicals. Cellulase needs an optimal contact time with the pulp suspension. Ink detachment can also be optimised by means of defibering efficiency and specific energy consumption. Increasing the consistency and decreasing the repulping time enhance savings and therefore sustainability. These two parameters are analysed in terms of shear factor λ .

Strong and electrically conductive nanopaper from cellulose nanofibers and polypyrrole

In this work, we prepare cellulose nanopapers of high mechanical performance and with the electrical conductivity of a semiconductor. Cellulose nanofibers (CNF) from bleached softwood pulp were coated with polypyrrole (PPy) via in situ chemical polymerization, in presence of iron chloride (III) as oxidant agent. The structure and morphology of nanopapers were studied, as well as their thermal, mechanical and conductive properties. Nanopaper from pure CNF exhibited a very high tensile response (224MPa tensile strength and 14.5GPa elastic modulus). The addition of up to maximum 20% of polypyrrole gave CNF/PPy nanopapers of high flexibility and still good mechanical properties (94MPa strength and 8.8GPa modulus). The electrical conductivity of the resulting CNF/PPy nanopaper was of 5.2 10(-2)Scm(-1), with a specific capacitance of 7.4Fg(-1). The final materials are strong and conductive nanopapers that can find application as biodegradable flexible thin-film transistor (TFT) or as flexible biosensor.

Chemical treatment for improving wettability of biofibres into thermoplastic matrices

The use of biofibres as reinforcing agents for composite materials is one of the most promising areas of composite development, but the handicap of their hydrophilic nature has to be resolved to ensure stable composites. This article concerns the effectiveness of chemical modification using fatty acid derivates followed by graft copolymerisation with vinyl monomers to confer hydrophobicity and resistance to enzymatic degradation to biofibres. Oleoyl chloride was used as a fatty acid derivative to modify jute fibres leaving one double bond available for further co-polymerisation with styrene. The chemical modification was applied in swelling and non-swelling solvents and different extents of modification were obtained. The reaction was monitored by FTIR spectroscopy and the extent of modification was calculated from elemental analysis. The copolymerisation reaction was carried out from 2–3 molar% modified jute fibres resulting in highly hydrophobic jute fibres with large resistance to microorganisms. The copolymerisation reaction was also followed by FTIR spectroscopy and covering styrene ratios were deduced from elemental analysis. Additional investigations such as SEM, optical microscopy, enzymatic degradation and floatation techniques were used to support the efficacy of the proposed method.

Smart nanopaper based on cellulose nanofibers with hybrid PEDOT:PSS/polypyrrole for energy storage devices

In the current work, flexible, lightweight, and strong conductive nanopapers based on cellulose nanofibers (CNFs) with poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and/or polypyrrole (PPy) were prepared by following a mixing and in situ chemical polymerization method. A successful homogeneous coating of PEDOT:PSS on cellulose nanofibers occurred by means hydrogen-bonding interactions between the hydroxyl functionalized CNF and the electronically charged PEDOT:PSS, as shown by FTIR spectra. The electrical conductivity and the specific capacitance of CNF-PEDOT:PSS nanopapers were 2.58Scm-1 and 6.21Fg-1, respectively. Further coating of PPy produced a substantial improvement on the electrical conductivity (10.55Scm-1) and the specific capacitance (315.5Fg-1) of the resulting CNF-PEDOT:PSS-PPy nanopaper. A synergistic phenomenon between both conductive polymers supported the high electrical conductivity and specific capacitance of the ternary formulation. Moreover, CNF-PEDOT:PSS-PPy nanopaper showed higher mechanical properties and it was more flexible than the nanopaper containing only polypyrrole conducting polymer (CNF-PPy). It is concluded that the good mechanical, electrical and electrochemical properties of the ternary formulation can apply for smart nanopaper in flexible electronics and energy storage devices.

Cellulose polymer composites (WPC)

Abstract Cellulose polymer composites have been studied with great results in enhancing mechanical properties compared to matrices. The following chapter gives a global vision of all the components involved in wood plastic composite formulation: the polymer matrix, natural fibres and additives. It makes a special remark to the interface wood–polymer behaviour and how it influences the desired mechanical properties through modelling using a well-known rule of mixtures (RoM) and the Kelly Tyson model. It also explains the main manufacturing process for wood plastic composites, which can be found in the market, and their basic process parameters. Finally, some remarks of future trends are exposed.

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.