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

Development of Harvesting Machines for Willow Small-Sizes Plantations in East-Central Europe

The production of plant biomass in small farms within the Central and Eastern European countries requires the application of agricultural machines adjusted to the scale of production. In the article, new machines for small-sized plantations of energy crops have been presented. Furthermore, the results of strength analysis of three-point linkage mower frame are presented by finite element method. The advantage of the proposed solutions is their simple construction, which is connected with low production cost and simple machine operation. The energy-crop harvesting machines are especially intended for small biomass producers in East-Central Europe, and the purchase of professional machines is financially inaccessible. The proposed machines are mounted in front or at the back of a typical farm tractor and the chipping units are power-take-off driven. The numerical simulation was carried out using finite element method to study the structural strength of a mower frame. All machine designs proposed by the Rzeszow University of Technology are legally protected by patents and utility models. The presented agricultural solutions have been worked out by authors and a part of them is still being developed in cooperation with biomass producers

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

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

Ozone fumigation increases the abundance of nutrients in Brassica vegetables : broccoli (Brassica oleracea var. italica) and Chinese cabbage (Brassica pekinensis)

Brassicaceae vegetables, among them broccoli and Chinese cabbage, are well recognized due to the nutritional properties. Four-week-old Chinese cabbage and broccoli seedlings were fumigated with O3 for 3 days before being transplanted into the field. The effect of O3 treatment was determined after reaching marketable quality (ca. 10 weeks). The inflorescences of O3-treated broccoli were enriched in vitamin E (α-tocopherol and γ-tocopherol), whereas Chinese cabbage heads had an increased content of anthocyanins and β-carotene. Ozone treatment did not significantly affect the productivity of both examined vegetables