Učinak upotrebe urea-formaldehida modificiranog ekstraktima na emisiju formaldehida furnirske ploče

Formaldehyde-based adhesives are used in the forestry industry. This is because formaldehyde is inexpensive, easy to use and resistant to moisture; it also has particular mechanical effects. Formaldehyde has both advantages and disadvantages. It is known that various diseases such as lung cancer occur in humans as a result of the release of formaldehyde into the air during and after board production. In this study, a urea formaldehyde glue mixture was prepared by using four different fillers (extract of maritime pine (Pinus pinaster) and elm (Ulmus glabra) bark, extract of hazelnut (Corylus avellana) husk and acorn tannins) at two different ratios. The bonding shear strength of pine (Pinus sylvestris) and spruce (Picea orientalis) plywood produced with urea formaldehyde adhesive was tested according to EN 314-1 standard. All plywood, except the plywood with acorn tannin, met the requirements of the standard. A formaldehyde emission test of the plywood was carried out in accordance with EN 713-3 standard. With this approach, it is possible to quickly determine formaldehyde emissions. Experimental results were obtained for subsequent measurements, including chamber tests. It was observed that the elm bark extract reduced the formaldehyde emission of pine plywood by 40 %, while other fillers reduced it by 3-37 %.U drvoprerađivačkoj industriji upotrebljavaju se ljepila na bazi formaldehida zato što je taj aldehid jeftin, jednostavan za uporabu, otporan na vlagu i ima posebne mehaničke učinke. Formaldehid ima određenih prednosti i nedostataka. Poznato je da se u ljudi koji rade u drvoprerađivačkoj industriji pojavljuju različite bolesti poput raka pluća, što može biti posljedica ispuštanja formaldehida u zrak tijekom i nakon proizvodnje ploča. Za ovo je istraživanje pripremljena smjesa urea-formaldehidnog ljepila dodavanjem četiriju različitih punila: ekstrakta kore primorskog bora (Pinus pinaster) i brijesta (Ulmus glabra), ekstrakta ljuske lješnjaka (Corylus avellana) i tanina žira u dva različita omjera. Posmična čvrstoća furnirske ploče od borovine (Pinus sylvestris) i smrekovine (Picea orientalis), proizvedene uporabom urea-formaldehidnog ljepila, ispitana je prema normi EN 314-1. Sve furnirske ploče, osim onih s taninom iz žira, zadovoljile su zahtjeve norme. Ispitivanje emisije formaldehida iz furnirskih ploča provedeno je prema normi EN 713-3. Tim je pristupom moguće brzo odrediti emisije formaldehida. Dobiveni su eksperimentalni rezultati za naknadna mjerenja, uključujući ispitivanje u komori. Primijećeno je da je ekstrakt kore brijesta smanjio emisiju formaldehida furnirske ploče od borovine za 40 %, dok su ostala punila smanjila tu emisiju za 3 – 37 %

The effect of grain direction on lateral nail strength and thermal conductivity of structural plywood panels

The aim of study was to determine the effects of grain direction on the lateral nail strength and thermal conductivity of structural plywood panels. Experiment were made with plywood manufactured from Scots pine, maritime pine and black pine. A rotary peeler with a maximum horizontal holding capacity of 80 cm was used for veneer manufacturing. The highest values of max load (2,17 kN), stiffness (2,52 kN/ mm) and displacement at ultimate load (36,8 mm) were obtained from C1PR group panels manufactured from black pine. Also, it was determined the mechanical properties in perpendicular to grain were higher than those in parallel to grain. The black pine panels gave highest average thermal conductivity value (0,168 W/mK), while that of Scots pine was lowest (0,145 W/mK). Thermal conductivity of panels in perpendicular to the grain of main axis of plywood was always found to be higher than the values obtained from measurements parallel to the grain

Utjecaj procesa sušenja furnira na tehnološka svojstva kompozitnih uslojenih drvnih ploča vezanih polistirenom

The aim of study was to determine the effect of veneer drying process on some technological properties of polystyrene composite plywood panels. For this reason, 2 mm-thick rotary cut veneers were obtained from beech (Fagus orientalis, Lipsky), Alder (Alnus glutinosa subsp. Barbata) and Scots pine (Pinus sylvestris L.) logs. The veneers obtained from three different wood species were divided into two groups to produce polystyrene composite plywood (PCP) and traditional plywood. While PCP was produced both air dried (at 20 °C) and oven dried (at 110 °C), the veneer sheets for production of traditional plywood were dried at 110 °C until reaching 7 % equilibrium moisture content. Two different types of polystyrene with high density (30 kg/m3) and low density (16 kg/m3) were used as bonding material for PCP panel production. The urea-formaldehyde adhesive was used as a bonding material for traditional plywood panels. Bonding shear strength, bending strength, modulus of elasticity and density of plywood and polystyrene composite plywood panels were investigated. It was found that the technological properties observed in the study of composite plywood panels manufactured with natural dried veneers gave similar results compared to those of composites produced with technical dried veneers.Cilj ovog istraživanja bio je utvrditi utjecaj procesa sušenja furnira na tehnološka svojstva kompozitnih uslojenih drvnih ploča vezanih polistirenom. Ljušteni furniri debljine 2 mm pripremljeni su od trupaca drva bukve (Fagus orientalis, Lipsky), drva johe (Alnus glutinosa subsp. Barbata) i drva običnog bora (Pinus sylvestris L.). Furniri od tri različite vrste drva podijeljeni su u dvije skupine kako bi se proizvela kompozitna uslojena ploča vezana polistirenom (PCP) i tradicionalna uslojena ploča. Za proizvodnju PCP ploča rabljeni su furniri sušeni na zraku (na 20 °C) i u sušioniku (na 110 °C), a za proizvodnju tradicionalne uslojene ploče upotrijebljeni su furniri sušeni pri 110 °C sve do postizanja ravnotežnog sadržaja vode od 7 %. Kao vezivo za PCP ploče uporabljene su dvije vrste polistirena – polistiren velike gustoće (30 kg/m3) i polistiren male gustoće (16 kg/m3). Za proizvodnju tradicionalne uslojene ploče kao vezivo je služilo urea-formaldehidno ljepilo. Istraživani su smična čvrstoća lijepljenog spoja, čvrstoća na savijanje, modul elastičnosti te gustoća uslojene i kompozitne uslojene ploče vezane polistirenom. Utvrđeno je da kompozitne uslojene drvne ploče proizvedene od prirodno sušenih furnira imaju slična promatrana tehnološka svojstva kao i kompoziti proizvedeni od tehnički sušenih furnira

Effect of Using Urea Formaldehyde Modified with Extracts in Plywood on Formaldehyde Emission

Formaldehyde-based adhesives are used in the forestry industry. This is because formaldehyde is inexpensive, easy to use and resistant to moisture; it also has particular mechanical effects. Formaldehyde has both advantages and disadvantages. It is known that various diseases such as lung cancer occur in humans as a result of the release of formaldehyde into the air during and after board production. In this study, a urea formaldehyde glue mixture was prepared by using four different fillers (extract of maritime pine (Pinus pinaster) and elm (Ulmus glabra) bark, extract of hazelnut (Corylus avellana) husk and acorn tannins) at two different ratios. The bonding shear strength of pine (Pinus sylvestris) and spruce (Picea orientalis) plywood produced with urea formaldehyde adhesive was tested according to EN 314-1 standard. All plywood, except the plywood with acorn tannin, met the requirements of the standard. A formaldehyde emission test of the plywood was carried out in accordance with EN 713-3 standard. With this approach, it is possible to quickly determine formaldehyde emissions. Experimental results were obtained for subsequent measurements, including chamber tests. It was observed that the elm bark extract reduced the formaldehyde emission of pine plywood by 40 %, while other fillers reduced it by 3-37 %.</jats:p

Surface characteristics of spruce veneers and shear strength of plywood as a function of log temperature in peeling process

AbstractThe objective of this study was to determine the effect of temperature of spruce (Picea orientalis L.) logs during peeling process on surface roughness, adhesive wettability, colour variation of veneer, and shear strength of plywood made from these veneer sheets. Veneer samples were manufactured from the logs after they were kept for 3h and 24h to reach to average temperatures of 52°C and 32°C, respectively. A fine stylus method was used for surface roughness evaluation of the veneer produced from two types of the logs and it was found that the samples peeled from the logs with a temperature of 52°C had significantly better roughness values than those of manufactured from the logs with 32°C at a 95% confidence level. Wettability of veneer samples was determined with contact angle measurements according to the sessile drop method. Urea formaldehyde (UF) and phenol formaldehyde (PF) resin drops were used in contact angle measurements. Contact angles of PF resin drops on veneers were similar for each peeling temperature while the contact angles of UF glue resin on veneers produced from the logs with 32°C were lower than those of produced from the logs with 52°C. Small colour difference was measured (indicated by a low ΔE value) on veneer samples depending on the log temperature. The highest shear strength value was determined for the plywood manufactured from veneers obtained from the logs with 52°C by using UF glue

Effect of veneer drying process on some technological properties of polystyrene composite plywood panels

The aim of study was to determine the effect of veneer drying process on some technological properties of polystyrene composite plywood panels. For this reason, 2 mm-thick rotary cut veneers were obtained from beech (Fagus orientalis, Lipsky), Alder (Alnus glutinosa subsp. Barbata) and Scots pine (Pinus sylvestris L.) logs. The veneers obtained from three different wood species were divided into two groups to produce polystyrene composite plywood (PCP) and traditional plywood. While PCP was produced both air dried (at 20 °C) and oven dried (at 110 °C), the veneer sheets for production of traditional plywood were dried at 110 °C until reaching 7 % equilibrium moisture content. Two different types of polystyrene with high density (30 kg/m3) and low density (16 kg/m3) were used as bonding material for PCP panel production. The urea-formaldehyde adhesive was used as a bonding material for traditional plywood panels. Bonding shear strength, bending strength, modulus of elasticity and density of plywood and polystyrene composite plywood panels were investigated. It was found that the technological properties observed in the study of composite plywood panels manufactured with natural dried veneers gave similar results compared to those of composites produced with technical dried veneers.</jats:p