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.
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.
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.
Croatian State Forest Enterprise covers more than seventy five percent of forest area in the Republic of Croatia and it is the biggest supplier of Croatian wood industry companies. From the year of ...national forests FSC certifi cation (2002) onwards, the number of issued FSC CoC certifi cates has exceeded two hundred. The increase of issued FSC certifi cates confirms that CoC certification has become a very important segment of the Croatian wood industry. In this research, the survey among Croatian FSC CoC certifi cate holders has been conducted. The aim of the research was to determine the reasons of implementing FSC CoC certifi cation, benefits of certification and problems arising out of implementation. The research has shown that the respondents were forced to implement FSC CoC by the request from their customers. Furthermore, respondents stated that the most important benefit from FSC CoC implementation was to keep the existing customers and for the largest part of respondents the main problem in FSC CoC implementation was related to high certification costs. Regarding the financial benefits of FSC CoC certification for respondents, the results showed small, but signifi cant positive correlation between certification duration and efficiency of total equity, as well as between certifi cation duration and return on assets.
Infrared and hot air drying characteristics of thin ash (Fraxinus excelsior L.) and oak (Quercus robur L.) wood lamellas were experimentally determined using an infrared and hot air laboratory ...device. Drying curves of 2 mm thick lamellas were established in the temperature range between 60 °C and 90 °C, and fitted by Fick’s diffusion model. Drying efficiency, drying rate and effective diffusivity have been estimated and compared between the used drying techniques. Moisture ratio exponentially decayed with duration of the process at all used temperatures. Effective diffusivity was greater in ash than oak wood, and it was not significantly influenced by the drying technique. The increased bound water diffusivity with increased drying temperature that caused shortening of the drying process was confirmed in both wood species. Similar activation energy was determined with both wood species, lower when the IR drying technique was used.
Obilježja infracrvenog sušenja i sušenja vrućim zrakom tankih lamela drva jasena (Fraxinus excelsior L.) i drva hrasta (Quercus robur L.) utvrđene su eksperimentalno uz pomoć laboratorijskih uređaja za infracrveno sušenje i sušenje vrućim zrakom. Krivulje sušenja lamela debljine 2 mm utvrđene su u rasponu temperatura između 60 i 90 °C te su prilagođene Fickovu difuzijskome modelu. Učinkovitost i brzina sušenja te efektivna difuznost procijenjene su i uspoređene unutar primijenjenih tehnika sušenja. Omjer sadržaja vode eksponencijalno se smanjuje s trajanjem procesa pri svim temperaturama primijenjenima u eksperimentu. Efektivna je difuznost drva jasena bila veća nego drva hrasta, a tehnike sušenja nisu znatnije utjecale na nju. Za obje vrste drva potvrđena je veća difuznost vezane vode s povećanjem temperature sušenja, što je uzrokovalo skraćenje procesa sušenja. Slična je energija aktivacije utvrđena za obje vrste drva, a niža je zabilježena pri IC tehnikama sušenja.
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.
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.
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.
PDF