Andreas Kandelbauer

LACCASE CATALYZED COVALENT COUPLING OF FLUOROPHENOLS INCREASES LIGNOCELLULOSE SURFACE HYDROPHOBICITY

This work presents for the first time the mechanistic evidence of a laccase-catalyzed method of covalently grafting hydrophobicity enhancing fluorophenols onto Fagus sylvatica veneers. Coupling of fluorophenols onto complex lignin model compounds guaiacylglycerol beta-guaiacyl ether and syringylglycerol beta-guaiacyl ether was demonstrated by LC-MS and NMR. Laccase-mediated coupling increased binding of 4-[4-(trifluoromethyl)phenoxy]phenol (4,4-F3MPP) and 4-(trifluoromethoxy)phenol (4-F3MP) to veneers by 77.1% and 39.2%, respectively. XPS studies showed that laccase-catalyzed grafting of fluorophenols resulted in a fluorine content of 6.39% for 4,4-F3MPP, 3.01% for 4-F3MP and 0.26% for 4-fluoro-2-methylphenol (4,2-FMP). Grafting of the fluorophenols 4,2-FMP, 4-F3MP and 4,4-F3MPP led to a 9.6%, 28.6% and 65.5% increase in hydrophobicity, respectively, when compared to treatments with the respective fluorophenols in the absence of laccase, in good agreement with XPS data.

Analysis of myeloperoxidase activity in wound fluids as a marker of infection

Background Neutrophilic polymorphonuclear leukocytes play a crucial role in the host defence against bacterial and fungal infections. They participate in the inflammatory response through the liberation of peptides and enzymes like myeloperoxidase (MPO). Therefore, MPO has a potential as a marker enzyme for the diagnosis of wound infection. Methods Substrate specificities and reaction pathways of MPO were investigated for new MPO substrates: crystal violet, leuco crystal violet, fast blue RR (4-benzoylamino-2,5-dimethoxybenzenediazonium chloride hemi(zinc chloride) salt) and various systematically substituted model substrates based on 2,7-dihydroxy-1-(4-hydroxyphenylazo)naphtalene-3,6-disulphonic acid. In addition, fast blue RR was covalently bound to siloxanes allowing immobilization of the substrate, while cellobiosedehydrogenase was integrated for generation of hydrogen peroxide required by MPO. Results Elevated concentrations of MPO were found in infected wounds compared with non-infected wounds (92.2 ± 45.0 versus 1.9 ± 1.8 U/mL). Various soluble and immobilized substrates were oxidized by MPO in wound samples and the influence of substrate structure and reaction pathways were elucidated for selected compounds. Conclusions Incubation of different MPO substrates with infected wound fluid samples resulted in a clear colour change in the case of elevated MPO concentrations, thus allowing early diagnosis of wound infection.

Thermal cure kinetics of epoxidized linseed oil with anhydride hardener

The thermal cure kinetics of an epoxidized linseed oil with methyl nadic anhydride as curing agent and 1-methyl imidazole as catalyst was studied by differential scanning calorimetry (DSC). The curing process was evaluated by non-isothermal DSC measurements; three iso-conversional methods for kinetic analysis of the original thermo-chemical data were applied to calculate the changes in apparent activation energy in dependence of conversion during the cross-linking reaction. All three iso-conversional methods provided consistent activation energy versus time profiles for the complex curing process. The accuracy and predictive power of the kinetic methods were evaluated by isothermal DSC measurements performed at temperatures above the glass transition temperature of the completely cured mixture (Tg∞). It was found that the predictions obtained from the iso-conversional method by Vyazovkin yielded the best agreement with the experimental values. The corresponding activation energy (Ea) regime showed an increase in Ea at the beginning of the curing which was followed by a continuous decrease as the cross-linking proceeded. This decrease in Ea is explained by a diffusion controlled reaction kinetics which is caused by two phenomena, gelation and vitrification. Gelation during curing of the epoxidized linseed/methyl nadic anhydride system was characterized by rheological measurements using a plate/plate rheometer and vitrification of the system was confirmed experimentally by detecting a significant decrease in complex heat capacity using alternating differential scanning calorimetry (ADSC) measurements.

Thermal Characterization of Kraft Lignin Phenol-Formaldehyde Resin for Paper Impregnation

Both kraft lignin phenol-formaldehyde (KLPF) and phenol-formaldehyde (PF) resins were synthesized and the curing kinetics of the resins was determined using thermal analysis data. The kinetic parameters were predicted using two popular model-free kinetic (MFK) methods: the advanced form of the Vyazovkin method and the Kissinger–Akahira–Sunose method. From the experimental and predicted values, the rate of kraft lignin phenol-formaldehyde curing was less compared to the phenol-formaldehyde resin. To increase the cure rate different cure additives were tried. Among these, only potassium carbonate (KC) showed a positive effect: An increase in additive concentration to 4% reduced the curing time to almost 50% as compared to pure KLPF resin at 160°C. Comparison of the predicted values from MFK calculations with isothermal experimental data showed that both MFK approaches were suitable to predict the curing characteristics.

On the warping behaviour of particleboards coated with melamine formaldehyde resin impregnated papers

AbstractImpregnated papers are widely used as decorative, protective and balance sheets in decorative laminates for the furniture, flooring and building industries. One important property of such composites is their warping behaviour. Especially for laminate flooring, warping of the lamellae is undesirable. In the present study the influence of important process parameters in the manufacturing of impregnated papers is quantitatively analyzed based on an industrial experiment carried out at an Austrian impregnation plant. Catalyst concentration, moisture content, resin loading and base paper supplier were varied according to an experimental design. The thermal properties of the impregnated papers and the warping behaviour of the corresponding boards were evaluated using response surface methodology. The resulting models allowed quantifying the relative importance of single factors on composite warp and defining the useful working range. Determination of the thermal properties of impregnated papers using DSC and TMA was not sufficient to predict laminate warp. ZusammenfassungImprägnierte Papiere werden in dekorativen Schichtstoffen in großen Mengen als Dekoroberflächen, Schutzfilme und Gegenzugpapiere in der Möbel-, Fußboden- und Bauindustrie eingesetzt. Das Verbiegungsverhalten derartiger Schichtstoffe spielt dabei eine wichtige Rolle. Insbesondere bei der Anwendung in Laminatfußböden ist eine zu starke Verbiegung der Lamellen unerwünscht. In der vorliegenden Studie wird anhand eines industriellen Versuchs an einer österreichischen Papierbeschichtungsanlage der Einfluss zentraler Prozessparameter der Papierimprägnierung auf die Verbiegung quantitativ analysiert. Die Faktoren Härterkonzentration, Feuchte, Harzbeladung und Rohpapierlieferant wurden nach einem statistischen Versuchsplan variiert. Die thermischen Eigenschaften der imprägnierten Papiere und das Biegeverhalten der beschichteten Platten wurden mittels Response Surface Analyse untersucht. Damit war es möglich, die relative Bedeutung der einzelnen Prozessfaktoren auf die Biegung des Verbunds zu quantifizieren und ein Prozessfenster zu definieren. Die Bestimmung der thermischen Eigenschaften von imprägnierten Papieren mittels DSC und TMA war nicht ausreichend um das Biegeverhalten vorherzusagen.

Adhesion Improvement of Powder Coating on Medium Density Fibreboard (MDF) by Thermal Pre-treatment

In the powder coating of non-conventional substrates such as engineered wood, natural fibre composites or synthetic polymers, several technological problems must be resolved which result from the substantial differences between such coating substrates and metallic ones. Unlike metals, non-conventional carrier materials show low temperature stability, much rougher and more irregular surface texture, large dependence of their dimensional stability on the moisture content of the surrounding environment and significantly less electrical conductivity. Hence, when powder technology is transferred from coating metals to coating fiberboards, for example, the surfaces of the boards need to be engineered in order to provide ideal adhesion for the coating layer. One major problem is the lack of electrical conductivity. Since the powder coatings are preferably applied using electrostatic spraying equipment, sufficient electrical conductivity of the surface is a major requirement and the correct moisture content plays an important role as well. In the present study, a pre-heating process was used to improve the powder application during powder coating of medium density fibreboards (MDFs). Electrical resistance, treatment temperature and moisture content were systematically studied to better understand the complex physical mechanisms leading to an improvement in powder application by such a pre-heating process. To this end, a new sophisticated procedure was developed to measure the electrical resistance (surface and core resistance) during pre-heating. The results show, that the electrical resistance of MDF is influenced by board temperature and moisture content. Moreover, it is confirmed that pre-heating proves to be an efficient method to improve the powder application onto non-conventional substrates.

Production of Cellulase-Free Polygalacturonase Preparation by Sclerotium rolfsii for Bioscouring of Cotton

SUMMARY Cultivation media for the production of both a cellulase containing and a cellulase-free polygalacturonase (PG) preparation by a highly productive strain of Sclerotium rolfsii (CBS 350.80) were developed. These enzyme preparations both contained a PG activity higher than 500 IUmL−1 and were applied in a bioscouring sequence of knitted cotton at various activity levels. The progress of bioscouring was evaluated by weight loss, water absorption time and determination of residual pectin. Released sugars have been determined and compared to bioscouring effects. No significant differences among the tested preparations were obtained for water absorption and pectin removal. However, considerably higher weight losses were observed for the preparations containing cellulase. A minimal enzyme dosage of 100 IUg−1 cotton was necessary to achieve suitable scouring results under the applied conditions.

Factors influencing the processing and technological properties of laminates based on phenolic resin impregnated papers

High quality decorative laminate panels typically consist of two major types of components: the surface layers comprising décor and overlay papers that are impregnated with melamine-based resins, and the core which is made of stacks of kraft papers impregnated with phenolic (PF) resin. The PF-impregnated layers impart superior hydrolytic stability, mechanical strength and fire-resistance to the composite. The manufacturing involves the complex interplay between resin, paper and impregnation/drying processes. Changes in the input variables cause significant alterations in the process characteristics and adaptations of the used materials and specific process conditions may, in turn, be required. This review summarizes the main variables influencing both processability and technological properties of phenolic resin impregnated papers and laminates produced therefrom. It is aimed at presenting the main influences from the involved components (resin and paper), how these may be controlled during the respective process steps (resin preparation and paper production), how they influence the impregnation and lamination conditions, how they affect specific aspects of paper and laminate performance, and how they interact with each other (synergies).

Unsaturated polyesters and vinyl esters

Unsaturated polyester resins (UPR) and vinyl ester resins (VER) are among the most commercially important thermosetting matrix materials for composites. Although comparatively low cost, their technological performance is suitable for a wide range of applications, such as fiber-reinforced plastics, artificial marble or onyx, polymer concrete, or gel coats. The main areas of UPR consumption include the wind energy, marine, pipe and tank, transportation, and construction industries. This chapter discusses basic UPR and VER chemistry and technology of manufacturing, and consequent applications. Some important properties and performance characteristics are discussed, such as shrinkage behavior, flame retardance, and property modification by nanoparticles. Also briefly introduced and described are the practical aspects of UPR and VER processing, with special emphasis on the most widely used technological approaches, such as hand and spray layup, resin infusion, resin transfer molding, sheet and bulk molding, pultrusion, winding, and centrifugal casting.

Processing and Characterization of Natural Fibre Reinforced Composites Using Lignin Phenolic Binder

Natural fibre-reinforced composites were prepared using a lignin-phenolic resol binder, in which 30 wt.-% of the phenol was substituted by a modified lignosulfonate from renewable resources. The reinforcement of the lignin phenolic binder matrix was accomplished by different natural fibres. The non-woven flax, flax/wood and flax/kenaf fibre mats were impregnated with the lignin-phenolic binder and they were compression-moulded at elevated temperature. The curing condensations of the synthesized lignin phenolic resins were characterized by differential scanning calorimetry. Water absorption, thickness swelling and flexural strengths of the natural fibre-reinforced composites were determined, as well as their thermal stability using thermogravimetric analysis. The flexural strengths of the flax/wood and flax/kenaf composites were higher than those of the flax reinforced composite. Morphological analysis using scanning electron microscopy showed an enhancement in fibre/matrix interaction for the flax/wood and flax/kenaf fibre mixtures.