Results of tensile tests on “wet” and “dry” flax yarn are presented and these show the large effect that moisture content (MC) has on flax fiber modulus of elasticity (MOE). These results are ...compared to others from tensile tests on flax fiber reinforced epoxy unidirectional composites (FFREUC) made from “wet” and “dry” fiber. The homogenized fiber MOEs have been estimated for the composites using the inverse rule of mixture. Fiber MOE appears better for dry fiber (by around 20%) for both the yarn and composite. It is proposed that this difference is the result of changes to the quality of adhesion between matrix and fiber. Adhesion would appear to be better for wet fibers.
This study investigates the effects of fiber dimensions on hardboard properties. Fiber size is determined by the amount of energy applied during refining, and fiber size affects board properties; ...that is, production cost and board performance are closely related. Therefore, in the present paper, the effects of fiber dimensions on hardboard performance have been investigated. To optimize the hardboard process, fiber size was varied via screening, and the screen fractions were further classified using a Bauer-McNett apparatus. Hardboards were produced with mixtures of classified fibers. Bending strength, internal bond, and thickness swelling of the final boards were evaluated according to EN 310, EN 319, and EN 317, respectively. The effects of fiber size on the investigated properties were analyzed by means of multivariate linear regression. Generally, a higher proportion of small fibers appears to improve board performance presumably due to the higher specific surface area of fibers, which facilitate interfiber bonding.
The weathering of wood through abiotic factors has been extensively studied. Much less research has been conducted on the influence of biotic factors on wood in exterior use that is not in ground ...contact, i.e. use class 3. There is especially a lack of research concerning the influence of the presence of bacterial and fungal communities on the weathering process of wood. The project aim is to identify any synergistic effects between biotic factors such as bacteria (Actinomycetes and Eubacteria) and fungi (Basidiomycota and Ascomycota) and abiotic factors such as light, temperature and moisture on the weathering of wood surfaces in use class 3. This paper presents results such as the amount of colony forming units (CFU), environmental scanning electron microscope analysis, colour changes and moisture content (MC) from preliminary experiments where wood surfaces were either naturally or artificially weathered. In order to study the interactions of fungi and bacteria on wood during the weathering process, the presence of microorganisms on natural weathered oak and Douglas fir surfaces had to be validated first. With the help of a surface contact test, microorganisms on the wood surfaces were transferred to agar plates and consequently incubated so that they could grow in appropriate conditions. Once the microbiological colonies had developed sufficiently, they were separated by selecting sections from the colonies and replated on fresh agar. A microcosm scale experiment, meaning the transfer of one specific bacteria and one fungi together in one petri dish, was carried out. This trial revealed that certain bacteria have an influence on the growth rate of certain fungi. In addition, an artificial weathering test was carried out in a QUV, which allows the degradation of samples using specific and known abiotic degrading parameters. The observation of the artificial weathered wood samples revealed that microorganisms are most definitely present in the QUV test apparatus and may influence the test results.
The Lifespans of Products Made with MDF Irie, M.; Lebreton, F.; Kutter, M.
Bulletin of the Transilvania University of Brașov. Series II, Forestry, wood industry, agricultural food engineering,
2023, Letnik:
16
Journal Article
Odprti dostop
The Horizon Europe funded EcoReFibre project (www.ecorefibre.eu) is concerned with recycling fibreboards and, in particular, Medium Density Fibreboard. This paper covers our research on determining ...the typical lifespans of products containing fibreboard. Knowing the lifespan of a product is important as it is the main determining factor that influences the age when it becomes waste. This paper proposes that the average age at which a product containing MDF becomes waste is between 10.7 and 12.1 years.
The quality of a sanded wood surface is represented by its roughness, which can be separated from the originally measured data by a procedure of filtering. Past experience has shown that the robust ...Gaussian regression filter (RGRF) is suitable for wood surfaces because it does not introduce distortions into the roughness profiles. The filter works iteratively until a user-defined convergence condition is met. The iterations stop when the difference between two consecutive profile median values becomes smaller than a given tolerance. This paper examines the convergence of RGRF when applied to wood surfaces sanded with various grit sizes in order to establish the tolerance value, which leads to convergence with the minimum number of iterations. This study was based on monitoring the variation of roughness parameters with the number of iterations for a range of tolerance values. A tolerance of 0.01 μm was found acceptable for filtering sanded wood surfaces.
A study of cracks in dry cereal products Bailhache, Chloé; Pontoire, Bruno; Ribourg, Lucie ...
Food hydrocolloids,
September 2019, 2019-09-00, 2019-09, Letnik:
94
Journal Article
Recenzirano
Odprti dostop
This paper is a study of checking and breakage of dry cereal products like crackers. The products studied were produced on an industrial line; almost no cracks were observed for Plain crackers (PCs), ...whereas 100% of the crackers with topping (CTs) exhibited cracks. Environmental SEM images suggested that miniature cracks initiated around the piercing holes of the crackers and then extended during storage.
A study of the impact of each ingredient and of their interaction on the degree of starch gelatinization was carried out using a simplified model system (wheat flour, water and gradual enrichment until a model cracker dough was obtained). The addition of salt or sugar to flour at 40% water content shifted the starch gelatinization temperature slightly higher in comparison to a control mixture (only flour and 40% water content). A comparison of the residual gelatinization enthalpy between the PCs and the CTs made during storage (up to 3 weeks) showed that the degree of gelatinization of the CTs was more significant than the PCs (especially in the center) because of the presence of water in the topping in the center of the cracker. X-ray diffraction confirmed that the center of the CTs was indeed very different from the PCs.
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•Checking and breakage of cracker with and without topping has been investigated.•The strong heterogeneity of water distribution contributes to a higher checking risk.•Checking starts from the piercing done in the crackers as observed by SEM.•Crackers with topping have a higher amount of gelatinized starch under the topping.•A higher amount of amylose lipid complex was present in crackers with topping.
The present research investigates the antifungal efficiency of clove (Eugenia caryophyllata) essential oil (C-EO) combined with linseed oil (LO) at different concentrations (1%, 5%, 10%) using two ...types of mycological tests: a qualitative screening test by agar diffusion method and a quantitative mini-block test on treated beech (Fagus sylvatica) wood.The agar diffusion test indicated improved protection of wood should be possible with a mixture of C-EO and LO from a concentration of 5%. In contrast, the mini-block test indicated that wood is partially protect by LO alone and that adding increasing quantities of C-EO gradually reduces this protection.One possible explanation of this unexpected result could be the antioxidant effect of C-EO which could negatively interfere in the oxidative curing process of LO. ESEM investigation revealed the penetration of LO and C-EO/LO mixtures into the wood structure and non-uniform fungal colonization of all the samples exposed to Postia placenta, as well as some characteristic features of consequent wood structure degradation, which was found more advanced for the untreated beech wood samples.
Three-layer polymeric diphenyl-methane-diisocyanate (pMDI)-bonded particleboards (PBs) were produced with different proportions of simulated recovered wood (rW) in the core layers (cLs) to assess the ...effect of rW on the formaldehyde (FA) release of PB. A pre-test was conducted on furniture and particle mixtures of rW to determine the range of expectable FA emission of rW. The FA content of the raw particle mixtures could be predicted from the contents of the individual raw material and did not change compared to the PB. FA content correlated strongly with PB-FA emission. It was possible to predict the maximum PB-FA contents, which should not be exceeded according to F*** and CARB 2 by linear regression models. At moderate and high total FA emission levels, the FA emission of the particle mixtures was approximately 60% higher than the emission of PB blocks. At low total FA level, the flask method and the gas analysis method exhibited different results with regard to the emissions from particles and their respective PBs.
The present investigation aimed to utilize a direct wood disc diffusion method to study the influence of plane of cutting, cutting method, sterilization method, and origin of tree on the ...antimicrobial activity of wood material. Six oak wood trees (Quercus petraea) were collected from 3 different locations in France. They were cut into 4 mm thick slices with either transverse (RT), tangential (LT) or radial (LR) faces. Round discs (diameter 9.95 + or - 0.1 mm) were cut from the slices via a laser machine or a manual punch machine, and were sterilized with gamma irradiation (25 kGy) or autoclaving (121 degreesC). The antimicrobial activity of wood was tested using a direct diffusion method against Staphylococcus aureus and Acinetobacter baumannii isolates. The zone of inhibition around the wooden disc was recorded following the recommendations used for antibiotics tests. The results showed that S. aureus was more susceptible than A. baumannii, to the chemicals that diffused from the wood. The transverse face discs exhibited higher antimicrobial activity. Samples that had been sterilized by autoclaving showed significantly (p < 0.05) lower antimicrobial activity, whereas the cutting method and origin of tree did not influence the antimicrobial activity of wood material. Therefore, the choice of sterilization method and cutting planes must be taken into account while studying and interpreting the antibacterial properties of wood material.
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