Risto Kuisma

Wetting and wicking of fibre plant straw fractions

Abstract Bast fibre plants are attracting increasing attention in Europe, and the plant straw fractions have already been used as a raw material in many new applications. This study focuses on characterising the liquid–fibre interactions of frost-retted and unretted bast fibre plant ( Linum usitatissimum L. and Cannabis sativa L.) straw fractions. A novel approach was used in order to overcome the problems introduced by the surface heterogeneity in contact angle measurements. First, the wicking rates of water, oil and ethanol in plant straw fractions were measured with a capillary rise method. The results were compared with the results calculated from the Lucas–Washburn equation. Second, the wetting properties of a compressed sample were studied by measuring the contact angle of a liquid. Third, the absorption time of a liquid droplet on a compressed sample was measured. Fibre hemp absorbed water better than flax/linseed. After 100 s the difference was about one order of magnitude. For oil the differences were marginal. Wicking and wetting turned out to be very rapid even when the measured (static) contact angle was almost 90°. Big variations in dynamic contact angle calculated from wicking measurements were observed. The wicking rates and droplet absorption times give suitable information when selecting fibre plant straw fractions as raw materials for new industrial products. On the contrary, a droplet based contact angle measurement does not give useful information of dynamic wetting behaviour.

Capillarity of flax/linseed (Linum usitatissimum L.) and fibre hemp (Cannabis sativa L.) straw fractions

Abstract In a study of the wetting properties of the fractions of unretted and frost-retted fibre straws a method to separate fibre, fine shive, and coarse shive from fibre plants is introduced and tested on bast fibre plants ( Linum usitatissimum L. and Cannabis sativa L.) The method consists of optional drying of stalks, cutting of straws, milling the straws with a hammer mill, separating fibres from shives with a drum separator, separating coarse shives from fine shives with a screen and a stream of air and finally cleaning of the fine shive with sieve vibrator. The described method works best for frost-retted plants and for unretted, green flax. The capillarity properties of these fractions were studied by measuring the amount of absorbed water as a function of time. The required time for the best-absorbing fibres of unretted and frost-retted hemp and unretted flax to absorb their own masses of water is less than 10 min compared with 2 h for the poorest-absorbing frost-retted flax. Overretting by frost retting seems to have an opposite effect on flax/linseed and hemp fibre capillarity. Both unretted and frost-retted coarse shive fractions behave quite similarly. If good absorption is needed, (over)retted hemp fibre should be used. If poor fibre absorption is desirable, (over)retted flax/linseed seems to have this feature.

Soiling Tendency of Worn, Plastic Flooring Materials Related to their Surface Topography

Abstract The soiling and cleanability of eleven worn commercial plastic floor coverings were examined. The new and worn floor coverings appeared very similar in both visual and stereo microscopic inspection. However, wear had caused changes to both topography and cleanability parameters. Profilometer measurements provided information on the topography of new and worn floor coverings. According to the results new surfaces did not always clean better or become soiled more easily than worn coverings. Therefore, we cannot derive a general rule of relationship between wear, soiling and cleanability. The general premise that a rough surface will yield poor cleanability was not confirmed here for all materials.

Cleanability of Plastic Flooring Materials Related to their Surface Properties

Abstract The purpose of this study was to test the feasibility of contact angle measurement in evaluating soilability and cleanability of 11 different surfaces of flooring materials. The surface properties were examined using an expanding contact angle technique and the cleanability was evaluated colorimetrically. The values of advancing contact angles θA were related to the soil residues on particle-soiled surfaces and oil-soiled surfaces. The results indicate the potential of contact angle measurements to evaluate cleanability of flooring materials.

Microbiological Quality of Fresh-Cut Carrots and Process Waters

Fresh vegetables may be contaminated by pathogens in different ways after harvest. Pathogenic microorganisms associated with fresh vegetables can cause severe outbreaks of foodborne disease. We discuss here the results of microbiological analysis of carrot samples, as well as of washing, processing, and wastewater samples. Washed, unpeeled carrots generally contained the highest aerobic plate counts (mean, 5.5 log CFU/g). Escherichia coli was not detected in any carrot or water sample examined. The amounts of coliform bacteria and enterobacteria were higher in carrot samples taken from the first steps in the processing line than in samples taken in later phases of the process. Yersinia pseudotuberculosis was not detected in any of the samples by the cultivation method; however, nonpathogenic Yersinia enterocolitica was detected from most carrot samples and almost all washing water and wastewater samples but only from 2 of 10 process water samples. Using a more-sensitive real-time PCR method, pathogenic Y. enterocolitica was found from several carrot samples, and when these positive samples were cultivated, no pathogenic Y. enterocolitica strains were detected.

Evaluation of different floor materials in cattle barns.

Floor surfaces in livestock barns are of special interest, since they should withstand strong mechanical and chemical stress and they should also be as comfortable as possible to stand and lie on. Furthermore, the floors should be easy to clean. The aim of this project was to develop well-functioning floor surface materials for use in animal houses. Both laboratory and field tests were performed. Changes in repellence and surface properties, cleanability, colour and gloss of materials were measured. Materials for the field test were chosen according to the results of laboratory studies with the exception of silane-impregnated concrete. The other materials selected were epoxy-, polyurethane- and acrylic coatings for floorings and feeding tables, and polyester coating for feeding tables. Two materials not tested in the laboratory were also included in the field tests. Traditional concrete was used as reference. The surface materials had more effect on changes in cleanability and repellence of tested materials than the chemical stresses introduced. SEM pictures showed that during wear the surfaces became rougher or scratches appeared on them. According to profilometer measurements no significant differences between the changes in the surface roughness of test materials were observed. The results of colour and gloss measurements varied considerably, but in general, coating decreased the changes of colour and gloss of the surface materials. The field study provides practical information about the behaviour of the surface materials examined.