Hibridno ljepilo UF-pMDI za vodootporne ploče iverice proizvedene uz skraćeno vrijeme prešanja

The aim of the study was to determine properties and potential shortening of pressing time of particleboards resinated with urea-formaldehyde (UF) resin thanks to its modification with pMDI (polymeric 4,4’ - methylene diphenyl isocyanate), introduced to the resin at 2.5 – 10 %. Tests showed that strength properties and water resistance of manufactured boards were improved with the increase of the pMDI amount introduced to UF resin. Furthermore, particleboards manufactured at a shortened pressing time were characterized by better mechanical and physical properties than those of reference boards manufactured under identical conditions, resinated with pure UF resin. It should be emphasized that boards, manufactured with a 10 % share of pMDI in the glue mixture, irrespective of their pressing time, were characterized by water resistance measured by the V100 test at the level required by the standard for exterior boards not bearing loads (type P3).Cilj provedene studije bio je odrediti svojstva i mogućnosti skraćenja vremena prešanja ploča iverica lijepljenih urea-formaldehidnim (UF) ljepilom modificiranim pMDI-jem (polimerni 4,4’ – metilen difenil izocijanat) u količini 2,5 do 10 %. Testiranje je pokazalo da se s povećanjem količine pMDI-ja u UF ljepilu poboljšava čvrstoća i vodootpornost ploča. Nadalje, ploče iverice proizvedene uz kraće vrijeme prešanja imale su bolja mehanička i fizikalna svojstva od referentnih ploča proizvedenih uz jednake uvjete i lijepljene čistim UF ljepilom. Treba naglasiti da su ploče proizvedene s ljepilom koje ima udjel pMDI-ja 10 %, neovisno o vremenu prešanja, imale vodootpornost mjerenu testom V100 na razini koju zahtijeva norma za ploče u vanjskoj uporabi bez opterećenja (tip P3)

Svojstva tekuće i polikondenzirane UF smole modificirane s pMDI

The aim of this study was to determine the properties of liquid and cured UF (urea-formaldehyde) resin modified with pMDI (polymeric 4, 4′-methylenediphenyl isocyanate). Analyses showed that when introduced to liquid UF resin already at 10 %, its reactivity increases, which is reflected in a shortening of gel time and reduction of activation energy of the polycondensation process. In turn, analyses performed on polycondensed resin showed that, thanks to modification with pMDI, its hydrophobicity is considerably improved, as manifested in a reduction of absorbability and swelling in thickness of cured resin.Cilj istraživanja bio je utvrditi svojstva tekuće i otvrdnute UF smole (urea-formaldehida) modificirane s pMDI-jem (polimernim 4, 4′-metilendifenil izocijanatom). Analiza je pokazala da dodavanjem pMDI-ja tekućoj UF smoli već u 10 %-tnoj količini rezultira povećanjem reaktivnosti, izraženoj skraćivanjem vremena želiranja i smanjenjem energije aktiviranja procesa polikondenzacije. Osim toga, analiza svojstava polikondenzirane smole pokazala je da je, zahvaljujući modifikaciji s pMDI-jem, znatno poboljšana hidrofobnost, što se očituje smanjenjem apsorpcije i bubrenja otvrdnute smole u debljinu

Hibridno ljepilo UF-pMDI za vodootporne ploče iverice proizvedene uz skraćeno vrijeme prešanja

The aim of the study was to determine properties and potential shortening of pressing time of particleboards resinated with urea-formaldehyde (UF) resin thanks to its modification with pMDI (polymeric 4,4’ - methylene diphenyl isocyanate), introduced to the resin at 2.5 – 10 %. Tests showed that strength properties and water resistance of manufactured boards were improved with the increase of the pMDI amount introduced to UF resin. Furthermore, particleboards manufactured at a shortened pressing time were characterized by better mechanical and physical properties than those of reference boards manufactured under identical conditions, resinated with pure UF resin. It should be emphasized that boards, manufactured with a 10 % share of pMDI in the glue mixture, irrespective of their pressing time, were characterized by water resistance measured by the V100 test at the level required by the standard for exterior boards not bearing loads (type P3).Cilj provedene studije bio je odrediti svojstva i mogućnosti skraćenja vremena prešanja ploča iverica lijepljenih urea-formaldehidnim (UF) ljepilom modificiranim pMDI-jem (polimerni 4,4’ – metilen difenil izocijanat) u količini 2,5 do 10 %. Testiranje je pokazalo da se s povećanjem količine pMDI-ja u UF ljepilu poboljšava čvrstoća i vodootpornost ploča. Nadalje, ploče iverice proizvedene uz kraće vrijeme prešanja imale su bolja mehanička i fizikalna svojstva od referentnih ploča proizvedenih uz jednake uvjete i lijepljene čistim UF ljepilom. Treba naglasiti da su ploče proizvedene s ljepilom koje ima udjel pMDI-ja 10 %, neovisno o vremenu prešanja, imale vodootpornost mjerenu testom V100 na razini koju zahtijeva norma za ploče u vanjskoj uporabi bez opterećenja (tip P3)

Svojstva furnirskih ploča proizvedenih s ureaformaldehidnim adhezivom modificiranim nanocelulozom i mikrocelulozom

Urea-formaldehyde adhesives are widely used in the wood-based materials industry. The study investigates the possibility of using cellulosic particles as a filler that modifies the properties of the resin and consequently improves the properties of plywood. Moreover, the study also examines the differences between microcellulose and nanocellulose used as a filler for UF adhesive. Based on the investigations, it was found that the addition of MFC and NCC significantly affected the curing process and rheological behaviour of adhesive mixtures. Modification led to increase of viscosity and extension of a gel time caused by lowering solid content of the resin. The experimental and reference plywood were tested in terms of bonding quality and mechanical properties such as modulus of elasticity and modulus of rigidity in accordance with applicable standards. The results of the tests confirmed that both the amount and the type of modifier added to the resin had a significant effect on the properties of plywood. The bonding quality and the above mentioned mechanical properties improved in all variants of modification; however the most effective was the addition of NCC in the amount of 10 %/100 g of solid resin. The slight decrease of formaldehyde emission was only observed for 5 % cellulosic particles added to 100 g of solid UF.Urea-formaldehidni (UF) adhezivi imaju široku primjenu u industriji materijala na bazi drva. U radu je opisano istraživanje mogućnosti upotrebe celuloznih čestica kao punila koje mijenja svojstva smole i posljedično poboljšava svojstva furnirske ploče. Nadalje, u istraživanju su ispitane razlike između mikroceluloze (MFC) i nanoceluloze (NCC) koje su upotrijebljene kao punilo za adheziv na bazi UF adheziva. Na temelju ispitivanja utvrđeno je da MFC i NCC dodatci znatno utječu na postupak stvrdnjavanja i reološko ponašanje adhezivnih smjesa. Modifikacija je rezultirala povećanjem viskoznosti i produljenjem vremena geliranja uzrokovanoga smanjenjem sadržaja čvrste smole. Ispitani su kvaliteta vezanja i mehanička svojstva eksperimentalne i referentne furnirske ploče poput modula elastičnosti i modula krutosti, sukladno odgovarajućim normama. Rezultati ispitivanja potvrdili su da i količina i vrsta modifikatora dodanoga u smolu imaju znatan utjecaj na svojstva furnirske ploče. Kvaliteta vezanja i spomenuta mehanička svojstva poboljšana su pri svim varijantama modifikacija, no najučinkovitije je bilo dodavanje NCC-a u količini od 10 % na 100 g čvrste smole. Blago smanjenje emisije formaldehida uočeno je samo za 5 % celuloznih čestica dodanih u 100 g čvrstog UF adheziva

Mogućnost uporabe melamin-ureaformaldehidnog ljepila ojačanog nanocelulozom u proizvodnji furnirskih ploča

The possibility of using nanocellulose (NCC) as a filling substance for melamine-urea-formaldehyde (MUF) adhesive was investigated for the process of manufacturing plywood. The adhesive mixtures were prepared with various nanocellulose concentrations. The amount of introduced filler had a significant effect on both resin and plywood characteristics. Fourier transform infrared spectroscopy (FTIR) did not show any major changes between experimental and reference variants. The viscosity of resin increased after the introduction of nanocellulose. The addition of NCC in the amount of 5 g and 10 g per 100 g of solid resin led to an improvement in bonding quality, modulus of elasticity and bending strength. Further increase of NCC concentration caused a deterioration of manufactured plywood properties. In summary, the addition of proper amount of nanocellulose resulted in manufacturing plywood with improved properties.U radu je prikazano istraživanje mogućnosti uporabe nanoceluloze (NCC) kao punila za melaminurea-formaldehidno ljepilo (MUF) koje se upotrebljava u proizvodnji furnirskih ploča. Smjese ljepila pripremljene su dodavanjem različitih koncentracija nanoceluloze. Količina dodanog punila znatno je utjecala na svojstva smole i furnirske ploče. Furierovom infracrvenom spektroskopijom (FTIR) nisu utvrđene veće promjene između eksperimentalnih i referentnih varijanti. Viskoznost smole povećala se nakon dodatka nanoceluloze. Dodatak 5 i 10 g nanoceluloze na 100 g otvrdnute smole rezultirao je poboljšanjem kvalitete vezanja, modula elastičnosti i čvrstoće na savijanje. Daljnje povećanje koncentracije nanoceluloze uzrokovalo je pogoršanje svojstava proizvedenih furnirskih ploča. Ukratko, dodatak odgovarajuće količine nanoceluloze rezultirao je furnirskom pločom poboljšanih svojstava

Odabrana kemijska i fizička svojstva drvne sječke od borovine inokulirane plijesnima Aspergillus i Penicillium

Mold fungi representing genera of Penicillium and Aspergillus commonly develop on the surface of freshly harvested wood chips during storage. As a result, they are often considered as low-quality material and intended for incineration. Thus, the aim of the present study was to investigate the effect of wood chips infestation with mold fungi representing genera of Aspergillus and Penicillium on their basic chemical and physical properties, such as: chemical structure (evaluated with FTIR spectroscopy), mass loss and hygroscopicity, after an incubation of 3, 6 and 9 weeks. Based on the visual assessment and ergosterol content analysis, it was found that inoculation of wood chips with molds led to the intense fungal development on their surface. However, as observed in FTIR spectra, the presence of molds caused no changes in wood chemical structure. Furthermore, no mass loss and no significant increase in the hygroscopicity of wood were observed. Therefore, pine wood chips overgrown by studied genera of fungi seem to be a valuable material for various applications.Plijesni rodova Aspergillus i Penicillium najčešće se razvijaju na površini svježe pripremljene drvne sječke tijekom skladištenja, zbog čega se takva sječka često smatra nekvalitetnim materijalom i spaljuje se. Stoga je cilj ovoga istraživanja bio istražiti utjecaj zaraženosti drvne sječke plijesnima rodova Aspergillus i Penicillium na njezina osnovna kemijska i fizička svojstva kao što su kemijska struktura (ispitano FTIR spektroskopijom), gubitak mase i higroskopnost nakon ikubacije od tri, šest i devet tjedana. Na temelju vizualne procjene i analize sadržaja ergosterola, utvrđeno je ddrvne sječke. Međutim, na FTIR spektrima je uočeno da plijesni nisu uzrokovale promjene u kemijskoj strukturi drva. Nadalje, nije uočen gubitak mase niti znatno povećanje higroskopnosti drva. Stoga se može zaključiti da je drvna sječka od borovine zaražena promatranim rodovima plijesni upotrebljiv materijal za različite primjenea je inokulacija drvne sječke plijesnima prouzročila intenzivan razvoj plijesni na površin

The Effect of Periodic Loading of Glued Laminated Beams on Their Static Bending Strength

Engineered wood products (EWP) such as glulam beams are gaining more and more popularity due to several advantages resulting from the wood itself, as well as the constant search for structural materials of natural origin. However, building materials face some requirements regarding their strength. Thus, the study aimed to assess the static bending strength of structural beams produced with the use of pine wood, after the periodic loading of approximately 80 kN for a year. The manufactured beams differed in the type of facing layers, i.e., pine timber with a high modulus of elasticity and plywood. The produced beams, regardless of their structure, are characterized by a similar static bending strength. Moreover, it has been shown that the loading of beams in the range of about 45% of their immediate capacity does not significantly affect their static bending strength and linear modulus of elasticity

Low-Density Oriented Strand Boards

This study evaluated the possibility of producing low-density oriented strand boards (OSB) from industrial chips of Pinus sylvestris L. Statistical analysis was used to determine the lowest possible density of resulting OSBs meeting the requirements of EN standard 300 for type 3 boards. The analysis revealed that this type of board could be obtained with a density as low as 425 kg/m3, corresponding to a compression ratio of about 0.85 for pine wood. An important parameter was the quality of the pine chips, the dimensions of which should be as close as possible to the dimensions of standard wood strands

Properties of Oriented Strand Boards with External Layers made of Non-Strand Chips

This study evaluated the possibility of producing oriented strand boards (OSB) from non-strand chips. Properties of the produced boards were compared with commercially available OSB/3. Research has shown that replacing the strand chips of external layers with smaller chips allowed for the manufacturing of OSB/3 using chips up to four times shorter than standard strand chips. Oriented strand board manufacturers should consider preparing a new standard and introducing the market to a new type of OSB with very good mechanical properties and made of selected strand chips comprising one of the fractions obtained during screening

Possibility of using the expanded polystyrene and rape straw to the manufacture of lightweight particleboards

The study investigated the possibility of using rape straw and expanded polystyrene for the production of low density particleboards. Particleboards with the core layer made of wood chips or rape straw, partly substituted with polystyrene (7%), were manufactured within the density range of 500 – 650 kg/ m3, and resinated with MUF resin. Our study confirmed that wood chip-expanded polystyrene (WP) and wood chip-rape straw-expanded polystyrene boards (WRP), of density reduced to 600 kg/m3, metthe mechanical requirements of the subject standard for boards intended for interior design (including furniture) and used in dry conditions. However, further density reduction required an increased resinationof the core layer