Thermal modification of wood changes its mechanical properties, generally reducing its strength, such that it is more easily chipped during processing than untreated hardwood. This study presents ...specific parameters used in the determination of mass concentration of thermally modified (TM) hardwood by gravimetric and photometric methods. An optical device, the Split 2, was used in the active mode, of which the holder of the inhalable dust IOM (Institute of Occupational Medicine) filter was the input part. Side-by-side determination of the respirable and inhalable mass concentration was made using the Higgins-Dewell respirable dust cyclone and an inhalable dust IOM sampler. Side-by-side determination of inhalable and total dust mass concentration was made using an IOM and open-faced (OF) filter holder to establish an IOM / OF sampling ratio. A correction factor of 1.16 was calculated for applying the photometric method as the ratio of mass concentration determined by gravimetric and photometric methods. Minimal concentrations of respirable and inhalable wood dust (geometric mean: cr = 0.058 mg/m3; cinh = 0.882 mg/m3) and a 12.76% share of respirable dust in the inhalable concentration cr / cinh, had a significant influence on the efficiency of the photometric method. The mass concentration obtained by IOM and OF samplers did not significantly differ (p = 0.36).
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Bending of solid wood from European oak is one of the most demanding technological processes due to its specific structural and physical properties and variability. We investigated the influence of ...wood moisture content (MC) and stiffness, determined by NDT, as well as previous drying methods on the bending ability of the wood. The best quality was obtained with bending specimens bent at a moisture content of at least 16% and quarter- or semi-quartersawn. The number of rejected specimens increased slightly when HF bending was used. Single-stage predrying of oak to a final MC of 8% resulted in a high rejection rate (>70%) regardless of drying technique. The acceptance rate was higher for less stiff specimens where the ratio of ultrasonic velocity in the straight (vS) and bent region (vB) was less than 0.5 (vB/vS).
Given the well-known carcinogenicity of hardwood dust, occupational exposure to oak wood dust has been determined in a furniture factory on different wood processing machines during sanding, planing, ...and milling. Determination of the mass concentrations of respirable and inhalable oak wood dust from ambient air was performed using personal sampling pumps and two types of filter holders: the Higgins-Dewell respirable dust cyclone, manufactured by Casella (Bedford, UK), and the inhalable dust IOM sampler manufactured by SKC (Dorset, UK). Out of a total of 30 values of inhalable mass concentration, 7 (23%) exceeded the occupational exposure level (OEL). The highest exposure levels for inhalable and respirable wood dust from the belt sander were 1.569 to 3.710 mg/m3 and 0.243 to 1.342 mg/m3, respectively. Worker exposure may be below the level of increased risk of 2 mg/m3 if a machine such as a planer or router is connected to a suction system. The share of respirable particles in the inhalable fraction ranged between 12% and 31%, and for samples with an inhalable mass concentration exceeding 2 mg/m3, the share was lower than 16%, with a slightly decreasing tendency. Thus, the risk of lower respiratory tract diseases increases with higher exposure to inhalable particles, and the OEL is an indirect measure of protection against exposure to respirable particles.
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The effect of temperature and moisture on the behaviour of solid wood is a well-known fact that directly affects wood creep as well. Wood creep includes three types of behaviour, such as viscoelastic ...creep, mechano-sorptive creep, and pseudo-creep and recovery. All these types can occur simultaneously, and it is sometimes complicated for researchers to isolate or distinct one from another. This paper presents a review of literature on wood rheology and creep properties, as well as factors that influence them, mainly time, temperature, and moisture content. The study of the viscoelasticity and wood creep is very important for gaining knowledge to be applied in solid wood bending.
Utjecaj temperature i vlage na ponašanje drva dobro je poznata činjenica koja ima izravan utjecaj i na puzanje drva. Puzanje drva obuhvaća tri tipa ponašanja: viskoelastično puzanje, mehaničko puzanje uzrokovano sorpcijom vode te prividno puzanje i oporavak. Svi ti tipovi ponašanja drva mogu se pojaviti istodobno, a istraživačima je katkad komplicirano izolirati ili razlikovati jedan tip od drugoga. Ovim je radom prikazan pregled literature vezane za reologiju i svojstva puzanja drva, kao i čimbenika koji na njih utječu, a uglavnom su to vrijeme, temperatura i sadržaj vode u drvu. Proučavanje viskoelastičnosti i puzanja drva iznimno je važno radi stjecanja specifičnih znanja potrebnih za istraživanja i razvoj tehnološkog procesa savijanja cjelovitog drva.
Specific Heat Capacity of Wood Radmanović, Kristijan; Đukić, Igor; Pervan, Stjepan
Drvna industrija,
01/2014, Volume:
65, Issue:
2
Journal Article
Peer reviewed
Open access
Specifi c heat capacity is defi ned as the amount of heat that a kilogram of a given substance is required to absorb in order to increase its temperature by one degree. The temperature of a given ...substance can change either at constant pressure or at constant volume, so we differentiate between specifi c heat capacity at constant pressure (cp) and specifi c heat capacity at constant volume (cv). When doing research into the heat propertiesof wood, the quantity that most frequently remains constant is pressure, thus restricting our study on specifi c heat capacity to cp. This paper provides an overview of the research that has so far been carried out into the specifi c heat capacity of wood depending on the temperature and moisture content. An analytical and graphical comparison has been performed of the results published in the Wood Industry Manual (1967) (DIP), Wood Handbook (1999) (WH) and work published by Deliiski (2012) (DEL).
This paper deals with an overview of additive manufacturing and its segment - 3D printing, which is today rapidly and widely used (Agashe et al., 2020) for personal and high-capacity production. The ...paper discusses the possible positive factors such as small and personalized production series, cheaper design and production process, complex geometry, bionic structures (whose surfaces are complicated to make, and are copy of biological organisms) and negative factors such as lack of educated specialists and trainings. Those facts are affecting the implementation of these technologies in different segments of the design, product development and furniture production. The impacts of new technologies on the design and production of rapid prototypes and finished products in furniture industry are analyzed. The positive results of using additive manufacturing indicate that, in spite of minor obstacles and problems with connecting different production processes, additive production will have a significant place in the future of furniture design and production. The most important advantages of 3D printing is fast prototyping, one piece production, free form designing and the use of bio-based materials and their possibility of recycling.
U radu se opisuje aditivna tehnologija 3D printanja koja se danas ubrzano i široko primjenjuje (Agashe et al., 2020.) u maloj i industrijskoj proizvodnji. U radu se opisuju mogući pozitivni čimbenici kao što su male i personalizirane proizvodne serije, jeftiniji dizajn i proizvodni proces, složena geometrija, bioničke strukture (površine složene za izradu, a kopije su bioloških organizama), ali i negativni čimbenici poput nedostatka obuke i educiranih stručnjaka. Navedeni čimbenici utječu na implementaciju tih tehnologija u različitim segmentima dizajna, razvoja proizvoda i proizvodnje namještaja. Analizirani su utjecaji novih tehnologija na dizajn i proizvodnju brzih prototipova i gotovih proizvoda u industriji namještaja. Pozitivni rezultati primjene aditivne tehnologije pokazuju da će ona, usprkos manjim preprekama i problemima povezivanja različitih proizvodnih procesa, imati važno mjesto u budućnosti dizajniranja i proizvodnje namještaja. Najvažnije prednosti 3D printanja jesu brza izrada prototipova, proizvodnja u jednom komadu, dizajn slobodnih formi i upotreba proizvodnih materijala te mogućnost njihova recikliranja.
The paper gives an overview of chemical changes during heat treatment of wood and their influence on environment. Wood is one of the most used building materials because of its physical and ...technological properties. Various procedures improve its properties, and due to its environmental acceptability, heat treatment of wood is one of the most commonly used. Heat treatment causes changes in the cell walls and degradation of the main components of the wood structure (cellulose, hemicelluloses, lignin) and extractives. Hemicelluloses, as the most unstable components, are broken down first, followed by cellulose and finally lignin. Degradation results in a change in chemical composition and chemical reactions of colour change causing a technological problem because wood processing tends to make the colour as uniform as possible. The uniformity of colour and the desired colour tone are obtained by the process of steaming and thermal modification. The processing temperature is the most important factor that causes all the changes. Due to its wide use, need has arisen to investigate the ecological consequences of such a heat treatment process, as well as the impact of harmful substances and types of compounds released during the process and their toxicity.
U radu je naveden pregled kemijskih promjena tijekom procesa toplinske obrade drva te njihova utjecaja na okoliš. Zbog svojih fizikalnih i tehnoloških svojstava drvo je jedan od najčešće upotrebljavanih građevnih materijala. Njegova se svojstva poboljšavaju raznovrsnim postupcima, a toplinska je obrada drva zbog njezine ekološke prihvatljivosti jedna od najzastupljenijih metoda obrade. Pri toplinskoj obradi drva dolazi do promjena u staničnim stijenkama drva i do razgradnje njegovih glavnih gradivnih komponenata (celuloza, hemiceluloze i lignin) i ekstraktivnih tvari. Hemiceluloze se kao najnestabilnije komponenete razgrađuju prve, zatim slijedi razgradnja celuloze te, na kraju, lignina. Razgradnja rezultira promjenom kemijskog sastava drva i kemijskim reakcijama promjene boje, što je tehnološki problem jer se pri preradi drva teži tome da boja bude što ujednačenija. Stoga se ujednačavanje boje i željeni ton nastoje postići procesom parenja i pregrijavanja drva. Najvažniji činitelj koji uzrokuje sve promjene jest temperatura obrade drva. Zbog vrlo česte primjene toplinske obrade drva nametnula se potreba za istraživanjem ekoloških posljedica tog postupka, pri čemu se istražuje i utjecaj nusprodukata i vrsta spojeva koji se oslobađaju za vrijeme tog procesa, kao i toksičnost oslobođenih spojeva.
Wood extractives, especially polyphenols, have great influence on the xylem colour of many wood species, which affects the success of hydrothermal wood processing, such as wood drying. One such wood ...species is European black alder (Alnus glutinosa (L.) Gaertn.), which is prone to forming intense and uneven reddish-orange or reddish-brown discolourations immediately upon harvesting and processing. However, there is lack of published scientific data on the wood and bark extractives of black alder, as well as the most suitable solvents to extract them. In this work, total soluble extractives, phenols, and flavonoids have been quantified in the wood and bark of black alder. Furthermore, the influence of four different polar organic solvents and deionized water on extractives removal yields has been measured. It was found that the bark has much higher levels of extractives as compared to the wood. Furthermore, it has been found that the highest extractive yields were obtained by using methanol as the extraction solvent for all observed compound group classifications.
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During wood drying, the formation of limescale deposits on conventional drying kiln components frequently causes difficulties, especially on nozzles for dispersion of water mist, as a result of the ...use of “hard water” and technologically unprepared water. Frequently inadequate cleaners for the removal of limescale are used, which have harmful effects on the equipment and people. In order to reduce costs incurred due to the use of inadequate cleaners for the removal of limescale and to eliminate potentially harmful effects on the health of employees, the use of citric acid has been researched in procedures of removal of limescale from the moisturizer nozzles of the conventional drying kilns. Used and unused metal moisturizer nozzles of the conventional drying kilns have been treated with different concentrations of water solution of citric acid at ambient temperature and in boiled state for 5 and 10 minutes. It has been determined that the water solution of citric acid at ambient temperature does not give positive results, while the treatment of nozzles in the boiled water solution of citric acid gives very good results already at minimum concentration of citric acid, both for the cleaning of limescale and for the cleaning of corrosion, resulting in fully renewed functionality of nozzles. No adverse effects of citric acid on the body of metal nozzles have been recorded.
It is of great importance for wood industrial production processes to provide the correct way of determining and estimating the moisture content of wood, in order to dry wood adequately without the ...occurrence of drying defects and achieve the desired final moisture content, to increase the quality of the drying process and final product quality. Therefore, this paper gives a detailed review of all applicable harmonized standards in the Republic of Croatia related to the procedures for determining and estimating wood moisture content. It outlines the correct procedures and recommendations for the proper implementation of wood moisture content measuring, and presents the comparison between different methods. Suggestions are also given as to practical application of specific methods.
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