Fizička i mehanička svojstva termoplastičnih kompozita punjenih drvnim brašnom rijetko upotrebljavane konopljike

The potential use of a lignocellulosic filler, Vitex agnus-castus plant (Chaste tree), which is a deciduous invasive shrub, in thermoplastic composites was investigated. The stems of chaste trees with a diameter of 5-10 cm from Mugla city, Western Turkey, were used for the study. The different amounts (0 to 50 wt%, by 10 % increments) of the wood flour passing through the screen openings of 0.237 mm were added to the polypropylene matrix. Premixed raw materials were put into the volumetric feeder of the twin-screw extruder. The extruder barrel temperature was gradually increased from 170 °C (feeding zone) to the die zone (190 °C) at a constant screw speed (40 rpm). Then, the dried granules were hot-pressed into the 4 mm thick WPC panels at 2 MPa and 190 °C for 5 min. 3 wt% of maleic anhydride grafted polypropylene (MAPP) was added as compatibilizer into the formulation. The WPCs showed an increase in the thickness swelling (0.58 to 5.68 %) as the amount of the filler increased from 10 to 50 wt% in the polypropylene. The bending strength of the polypropylene composites increased from 33.9 to 44.8 MPa as the amount of the chaste wood flour was increased to 30 wt%, but further increase caused the decrease in the tensile strength (25.7 MPa). As for the bending modulus, it increased from 815 to 3250 MPa when the wood content reached 50 wt%. The tensile modulus increased from 1690 to 2253 MPa when the wood content arised from 10 to 50 wt%. The tensile strength, tensile modulus, flexural strength and flexural modulus of the unfilled polypropylene were found to be 19.6 MPa, 1505 MPa, 30.2 MPa and 664 MPa, respectively. According to the test results, it was concluded that the 30-40 wt% of Vitex agnus-castus wood could be efficiently used in the polypropylene composites for the semi-building applications such as decking or siding. The evaluation of underused invasive chaste wood in the production of tWPC production may result in an effective way to utilize this resource.U radu je istražena potencijalna primjena lignoceluloznog punila u termoplastičnim kompozitima od biljke Vitex agnus-castus (konopljike), koja je listopadni invazivni grm. Stabljike konopljike promjera 5 – 10 cm nabavljene su iz grada Mugla, iz zapadne Turske. U polipropilensku matricu dodane su različite količine drvnog brašna (0 – 50 wt. %, uz povećanje od 10 %) koje je prolazilo kroz sito otvora 0,237 mm. Prethodno pomiješane sirovine stavljene su u lijevak dvovijčanog ekstrudera. Temperatura spremnika ekstrudera postupno je povećavana od 170 °C (zona uvlačenja) do 190 °C (zona istiskivanja), uz konstantnu brzinu vijka (40 okr./min). Zatim su osušene pelete 5 min vruće prešane pri 2 MPa i 190 °C u oblik WPC ploče debljine 4 mm. Kao kompatibilizator formulaciji je dodan MAPP (3 wt. %). Kako se količina punila u polipropilenu povećavala s 10 na 50 wt. %, kompoziti su pokazivali povećanje debljinskog bubrenja (od 0,58 do 5,68 %). S povećanjem količine čistoga drvnog brašna na 30 wt. %, čvrstoća na savijanje polipropilenskih kompozita povećala se s 33,9 na 44,8 MPa, ali daljnje je povećanje dovelo do smanjenja vlačne čvrstoće (25,7 MPa). Kada je udio drva dosegnuo 50 wt. %, modul savijanja povećao se s 815 na 3250 MPa. Pri povećanju udjela drva s 10 na 50 wt%, modul elastičnosti pri vlačnom se naprezanju povećao s 1690 na 2253 MPa. Utvrđeno je da su vlačna čvrstoća, modul elastičnosti pri vlačnom naprezanju, čvrstoća na savijanje i modul na savijanje polipropilena bez punila redom 19,6 MPa, 1505 MPa, 30,2 MPa i 664 MPa. Prema rezultatima ispitivanja, zaključeno je da se 30 – 40 wt. % drva konopljike može učinkovito iskoristiti u polipropilenskim kompozitima za primjenu u graditeljstvu kao što su podne ili zidne obloge. Istraživanje slabo iskorištene konopljike u proizvodnji WPC-a može rezultirati učinkovitim načinom upotrebe te sirovine

EFFECT OF FIRE RETARDANTS ON SURFACE ROUGHNESS AND WETTABILITY OF WOOD PLASTIC COMPOSITE PANELS

Surface roughness and wettability of flat-pressed wood plastic composites (WPCs) incorporated with various fire retardants (FRs) (5, 10, or 15% by weight (wt)) at 50 wt-% content of the wood flour (WF) were investigated. The most common FRs, zinc borate (ZB), magnesium hydroxide (MH), and ammonium polyphosphate (APP), were used in the experiments. The WPC panels were made from dry-blended wood flour (WF), fire retardant (FR) powder, and polypropylene (PP) powder with maleic anhydride-grafted PP (2 wt-%) formulations using a conventional flat-pressing process under laboratory conditions. The contact angle measurements were obtained by using a goniometer connected with a digital camera and computer system. Three roughness measurements, average roughness (Ra), mean peak-to-valley height (Rz), and maximum roughness (Ry), were taken from the WPC panel surface using a fine stylus tracing technique. It was found that the surface smoothness of the WPC panels decreased with increasing content of the FR powder while the wettability increased. The control WPC panel without the FR had the smoothest surface, followed by the WPC panels containing the MH, ZB, and APP, respectively

Effect of resination technique on mechanical properties of medium density fiberboard

Effects of different resination techniques relative to the mechanical properties of commercially produced thick medium density fiberboard (MDF) were investigated. The amount of urea-formaldehyde resin (11 wt%) applied to the wood fibers was gradually decreased in the blowline (11, 10.5, 10, and 9.5 wt%), while it was gradually increased in the short-retention blender (0, 0.5, 1, and 1.5. wt%). The internal bond strength of the MDF boards considerably improved as the amount of the resin applied to the fibers in the short-retention blender was increased to 1.5 wt%. In particular, the increase in the IB strength was most pronounced as the resin content increased from 1 to 1.5%. The edge and face screw withdrawal resistances increased by 7.7 and 7.9% as the amount of the resin applied to the fibers in the blender was increased. Similar values were also observed for the flexural properties. Overall, the total resin content in the production of thick MDF can be decreased as blender resination, a means of post-dryer resin addition, is incorporated into the blowline resination technique

Otpornost prema izvlačenju vijaka i međuslojna čvrstoća troslojne ploče vlaknatice s grubim vlaknima u središnjem sloju

Screw withdrawal resistance (SWR) and surface soundness of three-layer MDF were investigated and the results were compared to the single-layer MDF. For this aim, effects of various formulation variables such as coarse fiber length (24.4 to 4.3 mm), resin content (10.5 to 6.5 wt%) in the core layer, average panel density (730 to 650 kg/m3), and surface/core layer ratio (70/30 to 30/70) were determined. The face and edge SWR and surface soundness of three-layer MDF panels were determined according to EN 320 and EN 311 standards, respectively. The results showed that the face SWR and edge SWR of MDF panels improved as the fi ber length increased from 4.3 to 11.5 mm in the core layer. Similar results were determined for the surface soundness. The surface soundness of MDF panels improved with increasing fiber length in the core layer up to 17.8 mm. SWR and surface soundness improved with increasing resin content in the core layer, shelling ratio, and panel density.U radu je prikazano istraživanje otpornosti prema izvlačenju vijaka i međuslojne čvrstoće troslojne MDF ploče, a rezultati su uspoređeni sa svojstvima jednoslojne MDF ploče. Za tu su svrhu istraživani učinci različitih parametara na pripremu ploče, primjerice duljina grubih vlakana (24,4 – 4,3 mm) i sadržaj smole (6,5 –10,5 %) u središnjem sloju, prosječna gustoća ploče (650 to 730 kg/m3) i omjer površinskoga i središnjeg sloja (70/30 – 30/70). Otpornost prema izvlačenju vijaka na licu i rubu ploče te međuslojna čvrstoća ispitivane su prema normama EN 320 i EN 311. Rezultati su pokazali da se otpornost prema izvlačenju vijaka na licu i rubu ploče povećala s povećanjem duljine vlakana u središnjem sloju s 4,3 na 11,5 mm. Slični su rezultati utvrđeni i za međuslojnu čvrstoću. Naime, međuslojna se čvrstoća MDF ploča također povećala s povećanjem duljine vlakana u središnjem sloju sve do 17,8 mm. Otpornost prema izvlačenju vijaka i međuslojna čvrstoća ploča povećale su se i s povećanjem udjela smole u središnjem sloju, omjera površinskoga i središnjeg sloja te gustoće ploče

Utjecaj predimpregnacije anhidridom octene kiseline i vremena zagrijavanja na mehanička i fizička svojstva drvno-plastičnih kompozita

This research aimed to assess the influence of different pre-impregnation times (PITs) (60, 180, and 300 min), heating or reaction times (H/RTs) (60, 90, and 120 min), and chemical modification of wood flour (WF) on the mechanical and physical properties of wood-plastic composites (WPCs). The study employed acetylated beech (Fagus orientalis L.) flour as the filler and polypropylene (PP) as the matrix phase producing of WPC samples through melt compounding and injection molding. The resulting composites underwent testing for their physical and mechanical properties. The findings revealed that WPCs derived from acetylated wood with PITs of 60 min and H/RTs of 60 min exhibited the highest mechanical properties, except for the bending modulus. Moreover, the lowest water absorption (WA) was observed in the PITs-H/RTs combination of 60-120 min, while the lowest thickness swelling (TS) occurred in the PITs-H/RTs combination of 300-60 min. The simultaneous utilization of pre-impregnation and reaction times demonstrated a synergistic effect on the physical and mechanical properties. Consequently, the chemical modification of wood flour and the application of suitable reaction times improved the interfacial adhesion, thereby enhancing the overall performance of the WPCs.Cilj ovog istraživanja bio je procijeniti utjecaj različitih vremena predimpregnacije (PIT) (60, 180 i 300 min), vremena zagrijavanja (H/RT) (60, 90 i 120 min) i kemijske modifikacije drvnog brašna (WF) na mehanička i fizička svojstva drvno-plastičnih kompozita (WPC). U istraživanju je za proizvodnju uzoraka WPC-a taljenjem i injekcijskim prešanjem upotrijebljeno drvno brašno acetilirane bukovine (Fagus orientalis L.) kao punilo i polipropilen (PP) kao matrica. Zatim su ispitana fizička i mehanička svojstva dobivenih kompozita. Rezultati su pokazali da drvno-plastični kompoziti dobiveni od acetiliranog drva s vremenom predimpregnacije i zagrijavanja od 60 min imaju najbolja mehanička svojstva, osim modula na savijanje. Nadalje, najmanje upijanje vode (WA) zabilježeno je za kombinaciju PIT-H/RT 60-120 min, dok je najmanje debljinsko bubrenje (TS) izmjereno za kombinaciju PIT-H/RT 300-60 min. Istodobno je primjena predimpregnacije i zagrijavanja pokazala sinergijski utjecaj na fizička i mehanička svojstva. Posljedično su kemijska modifikacija drvnog brašna i odabir odgovarajućih vremena zagrijavanja poboljšali adheziju između faza, a time i svojstva drvno-plastičnih kompozita

Brzina dugotrajnoga higroskopskog debljinskog bubrenja kompozita od polipropilena i hidrotermički tretirane bukovine

Long-term hygroscopic thickness swelling rate of polypropylene (PP) composites filled with thermally treated wood flour was investigated. The beech wood chips were heat treated at 120 °C, 150 °C or 180 °C for 30 or 120 min using saturated steam in a digester. The composites based on PP, beech wood flour (BF), and coupling agents (PP-g-MA) were made by melt compounding and injection molding. The weight ratio of BF to PP was controlled at 50/47 for all blends. The amount of coupling agent was fixed at 3 wt.% for all formulations. Further study was conducted to model thickness swelling of the composites, a swelling rate parameter (KSR). The thickness swelling of thermally-treated samples at 120 ºC for 30 min and at 150 ºC for 30 min were lower than that of control samples, followed by thermally-treated samples at 180 ºC for 120 min, at 180 ºC for 30 min, at 120 ºC for 120 min, and at 150 ºC for 120 min, respectively. Furthermore, the thickness swelling of the BF/PP composites decreased with increasing time and temperature of the thermal-treatment. In addition, at 120 ºC for 30 min, the composites showed a lower swelling rate than control samples. The KSR of the composites was influenced both by the time and temperature of thermal treatment.U radu je istražen dugotrajni stupanj higroskopskoga debljinskog bubrenja polipropilenskih (PP) kompozita punjenih toplinski obrađenim drvnim brašnom. Iverje od bukovine bilo je toplinski tretirano na 120, 150 ili 180 °C tijekom 30 ili 120 minuta uz pomoć zasićene pare u digestoru. Kompoziti na bazi PP-a, brašna od bukovine (BF)-a i veziva (PP-g-MA) izrađeni su taljenjem i injekcijskim prešanjem. Maseni je omjer BF/PP za sve smjese bio 50/47. Količina veziva za sve formulacije bila je na 3 wt.%. Nadalje, provedeno je modeliranje debljinskog bubrenja kompozita i parametra brzine bubrenja (KSR). Debljinsko bubrenje uzoraka toplinski tretiranih 30 min na 120 ºC i 30 min na 150 ºC bilo je niže nego na kontrolnim uzorcima, zatim slijede uzorci toplinski tretirani 120 min na 180 ºC, 30 min na 180 ºC, 120 min na 120 ºC, odnosno 120 min na 150 ºC. Nadalje, debljinsko bubrenje BF/PP kompozita smanjivalo se s povećanjem vremena i temperature toplinskog postupka. Osim toga, kompoziti su pri 30 min na 120 ºC pokazali niži parametar brzine bubrenja od kontrolnih uzoraka. Na parametar brzine bubrenja kompozita utjecali su vrijeme toplinskog tretmana i temperatura

Utjecaj brušenja na svojstva površine MDF ploče

The objective of this research was to investigate the effects of sanding on the surface properties of the medium density fiberboard (MDF) panels made from Rhododendron ponticum L. wood. The MDF panels were sanded with different sizes of the sand paper grit: 60-, 60+80- or 60+80+120-grit. Surface absorption and surface roughness of the MDF panels were determined based on EN 382-1 standard and ISO 4287 by using a fi ne stylus profi lometer, respectively. Sessile water drop technique was used to determine contact angle values of the panel surface. The results indicated that sanding process improved the surface smoothness of the panels. However, the wettability and surface absorption of the panels were negatively affected by increasing grit size. The MDF surface sanded with 60-grit size had a lower contact angle, more wettable surface, compared to those that were sanded with 60+80+120-grit size. For example, the average contact angle value of the panels sanded with 60-grit sandpaper was 43.3° as compared to the panels sanded with 60+80+120-grit sand paper which was 76.1°. The rougher surface was more wettable and absorbent compared to smoother surface. Based on the fi ndings obtained from the present study, sanding has a signifi cant effect on the wettability, surface roughness, and surface absorption of the MDF panels, which could provide useful information on the bonding and finishing of the MDF panels.Cilj je istraživanja bio ispitati utjecaj brušenja na svojstva površine srednje gustih ploča vlaknatica (MDF ploča) proizvedenih od drva rododendrona (Rhododendron ponticum L.) MDF ploče brušene su brusnim papirima različitih granulacija: 60, 60+80 ili 60+80+120. Određena su apsorptivna svojstva prema normi EN 382-1 i hrapavost površine MDF ploča prema normi ISO 4287 uz pomoć finog profilometra. Za određivanje kontaktnog kuta površine ploča primijenjena je metoda ispitivanja s kapljicom vode. Rezultati istraživanja pokazuju da brušenje pozitivno utječe na glatkoću površine ploča. Međutim, povećanje granulacije brusnog papira negativno utječe na kvašenje i apsorpciju površine ploča. Površina MDF ploča brušenih brusnim papirom granulacije 60 imala je manji kontaktni kut i bolje kvašenje u usporedbi s površinom koja je brušena brusnim papirima granulacije 60+80+120. Na primjer, srednja vrijednost kontaktnog kuta ploča brušenih brusnim papirom granulacije 60 bila je 43,3°, a ploča brušenih papirom granulacija 60+80+120 bila je 76,1°. Hrapavija površina imala je bolje kvašenje i apsorpciju nego glatkije površine. Na temelju rezultata dobivenih istraživanjem može se zaključiti da proces brušenja ima znatan utjecaj na kvašenje i hrapavost te na apsorptivna svojstva površine MDF ploča, što je osobito važno za proces lijepljenja i površinske obrade brušenih površina

Improving dimensional stability of injection molded wood plastic composites using cold and hot water extraction methods

Dimensional stability of wood plastic composites (WPCs) made from polypropylene and pine wood flour with and without coupling agent was investigated. The pine wood flour was prepared from wood chips which had been immersed, respectively, in boiling water for 1 h, 3 h, and 5 h or in distilled water for 1 day, 3 days, and 5 days at room temperature. It was found that thickness swelling (TS) and water absorption (WA) of the WPCs made using extracted wood were lower than those of WPCs produced with unextracted wood. The TS and WA values of WPCs decreased with extraction duration both for cold and hot water extraction. The effect of hot water extraction on the TS and WA properties of the WPCs was more pronounced than cold water extraction

Physical, mechanical and thermal properties of wood/zeolite/plastic hybrid composites

Effect of zeolite content on the physical, mechanical and thermal properties of wood plastic composites was investigated in this study. To meet this objective, pine wood flour (0, 10, 20, 30, 40, 50 wt%) with compatibilizing agent, zeolite (0, 10, 20, 30, 40, 50 wt%), and polypropylene were compounded in a twin screw co-rotating extruder. The mass ratio of the wood flour to polypropylene was 50/50 (w/w) in all compounds. Test specimens were produced using injection molding machine from the pellets. Physical and mechanical, and thermal (Thermogravimetry Analysis/Differential Scanning Calorimetry) properties of the wood plastic composites were determined. The water absorption and thickness swelling properties of wood plastic composites improved with increasing zeolite content. The flexural and tensile properties of the wood plastic composites decreased with increasing zeolite content. All the wood plastic composites provided the values of flexural strength (58,4-72,9 MPa) and flexural modulus (2718-5024 MPa) that were well over the requirement by the standard specified in ASTM D 6662. The mass loss rates values of wood plastic composites increased with increasing zeolite contents. The Differential Scanning Calorimetry analysis showed that the melt crystallization enthalpies and degree of crystallization of wood plastic composites decreased with increasing zeolite content. The decrease in the Tc and Xc indicated that zeolite was the poor nucleating agent for the wood plastic composites

Hrapavost i stupanj kvašenja ugušćene površine pregrijane smrekovine (Picea abies L. Karst.)

Surface roughness and wettability of the heat-treated and then surface densified spruce (Picea abies L. Karst.) wood were measured to determine the effect of densification and heat-treatment on wood surface properties. The process of heat-treatment with an initial vacuum was performed in a vacuum chamber on oven dried lamellas with dimensions of 630 mm (longitudinal direction) x 45 mm (tangential direction) x 25 mm (radial direction). The lamellas were heat-treated at four different temperatures which were 170 °C, 190 °C, 210 °C and 230 °C. Control specimens were not exposed to heat-treatment. The lamellas were first heated to 100 °C, the creation of a vacuum taking 30 min at this temperature, and then heated to the desired temperature, and treated at this constant temperature for 3 h. The lamellas were then cooled down by using coils with cold water inside the chamber. Surface densification of lamellas with compression from 22 mm to 15 mm thickness was made by press platens heated at 150 °C and held in that position for 60 s. After the 1 min, the heated platen was cooled to 90 °C, whilst the specimen remained under compression to minimize immediate spring back. The total time of compression was 2 min (30 s closing, 60 s pressing and approx. 30 s cooling). In the treatment groups, the optimum treatment temperature on the one-side densified wood specimens was found to be 170 °C based on the surface roughness and wettability values. Surface densification significantly decreased the surface roughness of the wood specimens. The surface quality of wood can be improved when the wood is exposed to the heat-treatment and then surface densification.Cilj istraživanja bio je izmjeriti hrapavost i stupanj kvašenja površine pregrijane i površinski ugušćene smrekovine (Picea abies L. Karst.) kako bi se utvrdio utjecaj ugušćivanja i pregrijavanja na svojstva površine drva. Proces pregrijavanja s početnim vakuumom proveden je u vakuumskoj komori na apsolutno suhim lamelama dimenzija 630 mm (uzdužni smjer) × 45 mm (tangentni smjer) × 25 mm (radijalni smjer). Lamele su pregrijane na četiri različite temperature: 170 °C, 190 °C, 210 °C i 230 °C. Kontrolni uzorci nisu bili pregrijani. Lamele su najprije zagrijane na 100 °C i pri toj je temperaturi za postizanje vakuuma bilo potrebno 30 min. Uzorci su nakon toga zagrijani na željenu temperaturu koja je konstantno održavana tri sata. Potom su lamele ohlađene uz pomoć hladne vode koja se nalazila u spiralnim cijevima unutar komore. Ugušćivanje površine lamela s 22 mm na 15 mm debljine provedeno je prešanjem zagrijanim pločama na temperaturi 150 °C u trajanju 60 s. Nakon jedne minute zagrijana je ploča ohlađena na 90 °C, dok je uzorak ostao pod pritiskom kako bi se umanjio trenutačni povrat. Ukupno vrijeme prešanja iznosilo je 2 min (30 s zatvaranje, 60 s prešanje i oko 30 s hlađenje). Na temelju vrijednosti hrapavosti i stupnja kvašenja utvrđeno je da je optimalna temperatura za jednostrano ugušćivanje ploče 170 °C. Ugušćivanjem površine znatno se smanjila hrapavost površine uzoraka drva. Zaključeno je da se kvaliteta površine drva može poboljšati pregrijavanjem i ugušćivanjem površine