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Strength properties of slash pine wood and castor oil polyurethane medium density fiberboard (MDF)

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  • Save International Journal of Composite M aterials 2013, 3(1): 7-14 DOI: 10.5923/j.cmaterials.20130301.02 Strength Properties of Medium Density Fiberboards (MDF) Manufactured with Pinus Elliottii Wood and Polyurethane Resin Derived from Castor Oil Sé rgio Augusto Me llo Da Silva1, André Luis Christoforo2,*, Raque l Gonçalves3, Francisco Antonio Rocco Lahr4 1Department of Civil Engineering, State University “Júlio M esquita Filho” (UNESP), Ilha Solteira, 15.385-000, Brazil 2Department of M echanical Engineering, Federal University of São João del Rei (UFSJ), São João del-Rei, 36.307-352, Brazil 3Department of Rural Buildings, A gricultural Engineering College, State University of Campinas (UNICAMP), 13083-875, Brazil 4Department of Structural Engineering, University of São Paulo (EESC/U SP), São Carlos, 13.566-590, Brazil Abstract The Ob jective of this work was to evaluate the mechanical properties: modulus of rupture (MOR), tensile strength in perpendicular direction (TP) and tensile strength in surface direction (TS) of Mediu m Density Fiberboards (MDF) manufactured with polyurethane resin prepared with castor oil (PU Castor Oil) and fibers of Pinus elliottii wood. To the essay characterizat ion was used the European Standard EM B/IS-2:1995, and was prepared fiberboards with 500×500 mm and two thickness (8mm and 15 mm), one proportion of resin (6%), hot pressing (50 bar and 160°C), no mina l density of 0,75 g/cm3 and fiber with 12% of mo isture content. The results of the mechanical properties obtained shows that the Medium Density Fiberboards can be manufactured with 6% of the PU Castor Oil. Keywords Med iu m Density Fiberboard, Mechanical Properties, Polyurethane Resin Derived Fro m Castor Oil 1. Introduction According to the Brazilian Association of Wood Industry of Panels – ABIPA[1], Brazil is one of the most advanced countries in the wo rld in the production of part icleboard (PB) and Medium Density Fiberboard (M DF), having industrial factories with the latest generation with annual production estimated at 1.8 million cubic meters. In the literature on production of wood panels there are several studies to improve the quality of these products with respect to moisture resistance, mechanical strength, dimensional stability and fitting and fixing, ease of mach ining to produce art ifacts turned and details below and embossed, surface fin ishes with paint, varnish and lacquer. An important aspect to be considered is the need for the identification and characterizat ion of novel binders (resins, adhesives), which provide best quality to the products and to minimize problems caused by the emission of to xic gases fro m the use of phenolic resins. Ro zman et al.[2] evaluated the use ofmelamine-anhydrid e- mo d if ied (P P); p o l i met i len o fen i l (PM P PI C ) an d 3-t rimetho xysily l-po ly methacry late (TPM) co mb ined with * Corresponding author: (André Luis Christoforo) Published online at Copyright © 2013 Scientific & Academic Publishing. All Rights Reserved EFB type of vegetable fibers and glass fibers. The tests performed showed the best results of static bending strength in specimens with PP and TPM. Gouveia et al.[3] evaluated the density, bending strength, the internal adhesion and pullout strength of screws of OSB produced with fibers of Pinus and Eucalyptus wood and three levels of phenol-formaldehyde resin (4, 6 and 8%). The assays were performed according to ASTM D 1037-91 and the best results were obtained with 6 and 8% resin in panels with 50% of fibers of each species. Co mparative analyses conducted by Maciel et al.[4] between agglomerated particleboards of Pinus wood with 25 and 50% polystyrene (PS) and polyethylene terephthalate (PET) and commercial panels with phenolic resins and urea resins, it was observed that the panels with PS and PET had higher values for modulus of elasticity, bending strength, perpendicular strength and pullout strength of screws. Panels with Urea resins without toluene were those with the smallest screw pullout strength, and panels with phenolic resin not observed any increase in strength. It is noteworthy that the values of PS and PET were all above the minimu m required by ANSI/A 208.1-1993. O'Donel et al.[5] studied the influence of vacuum permeate and the infusion of epo xy resins based acrylic soybean oil (A ESO) in flax fibers, cellu lose pulp to recycled paper and fiberglass in the manufacture of panels. In the panels with flax fiber and moisture content ranging between 8 Sérgio Augusto M ello da Silva et al.: Strength Properties of M edium Density Fiberboards (MDF) M anufactured with Pinus Elliottii Wood and Polyurethane Resin Derived from Castor Oil 10 and 50% was observed an increase in the bending strength fro m 1.5 to 6 GPa and 17 GPa to the panels with fiberglass; panels with cellu losic pulp fibers was five t imes higher than the values of panels with conventional resins. Rozman et al.[6] evaluated the use of vegetable oil in EFB matrix-type polyurethane (PU) with isocyanates (MDI, HMDI, TDI and PEG) in the manufacture o f panels with vegetable fibers of fruit stalk (EFB). A mong the isocyanates the best results were obtained with HMDI. Campos and Lahr[7] studied the strength properties of MDF panels with Pinus and Eucalyptus fibers with 8, 10 and 12% urea fo rmaldehyde, polyurethane bi-component derived fro m castor oil and inorganic resin, found that the best internal adhesion (0.91 and 0.89 MPa) and bending strength (29.4 MPa and 28) were obtained in the panels made with Pinus and Eucalyptus fibers with 12% polyurethane ad h es iv e. Brady et al.[8] studied the influence of a mixture of vegetable oil (EFB), matrix polyurethane (PU) in proportions (by weight) of 25:75, 30:70 and 35:65 to verify the mechanical strength of wood fiber panels. The 35:65 ratio gave the best values of bending strength, and also observed that this ratio provided better coating the fibers and consequently greater compliance. Silva[9] studied the characterizat ion of the composite fiber long and short sisal and coconut with PU resin de rived fro m castor oil, found in general that the tensile, bending strength, impact, fracture toughness and water absorption were lower in co mposites made fro m coconut fibers. The best results were obtained for composites with long fibers of sisal in tensile strength and fracture toughness. The composites made with short fibers coconut exhibited a percentage of water absorption equal to 17%. Silva and Lahr[10] evaluated the production of particleboard with homogeneous particles of wood fro m the Amazon (Erisma uncinatum, Nectranda lanceolata, Erisma sp). The boards were made with nominal thickness of 10 mm, nominal density of 0.75 g/cm3, using 10% bico mponent polyurethane resin derived fro m castor oil and particles having lengths of fro m 0.02 mm to 6 mm, under conditions of hot pressing at a temperature of 90oC, 40 MPa and a time of 10 min. In the assessments performed according to ABNT NBR14810 standard, panels of wood particles Nectranda lanceolata showed higher strength values, which are above the limit set by the normative standard. Dias et al.[11] evaluated the mechanical properties of plywood panels made of polyurethane resin-based on castor oil. The results obtained for the bending modulus of elasticity not reached the min imu m value of 18 MPa, is substantiated by the poor distribution of adhesive during the panel forming process. Fiorelli et al.[12] developed particle boards bonded with bagasse and polyurethane resin derived fro m castor oil investigating the response variables: density, swelling, absorption and bending modulus and bending strength. The results indicated the material as being manufactured fro m high density, suitable for industrial use, demonstrating the efficiency of the polyurethane resin-based adhesive such as castor oil. Paes et al.[13] evaluated the effect of the combination of pressure (2.0, 3.0, 3.5 M Pa) and temperature (50, 60, 90oC) in panels of wood waste particles with Pinus elliottii and polyurethane resin derived fro m castor oil in response variables: density, swelling and water absorption (0-2h, 2-24h; 0-24h) and bending strength, screw pullout and internal adhesion, concluding that co mbinations: 3.0 M Pa and 90°C and 3.5 MPa and 60°C showed the best results, proving to be the pressing temperature as the most significant variab le quality (finish) in the prepared panels. Sartori et a l.[14] eva luated the mechanical performance of wood panels and reforestation particles boards made with sugar cane bagasse and bicomponent polyurethane resin derived fro m castor oil as an alternative to the system of lateral closing of the trunk co llect ive management center for beef cattle. The physical and mechanica l properties obtained have proved the efficiency of the structural model proposed for use in management center. Considering the positive aspects of the current production of particle boards in Brazil and the need for studies that enable the use of new adhesives, this study aims to evaluate, with the support of the European normative standard EM B/IS-2[15], the mechanical propert ies: modulus of rupture (MOR), tensile strength in perpendicular direction (TP) and tensile strength in surface directions (TS) in the panels made fro m fibers of Pinus elliottii wood and monocomponent polyurethane resin derived fro m castor oil (PU -Castor). 2. Materials and Methods The studies for preparation and evaluation of MDF panels were performed at the Laboratory of Quality Control and Product Develop ment of DURATEX Industry according to the experimental procedures proposed by EM B/IS-2[15] standard and according to the expe rimental design shown in Table 1. Table 1. Experimental design PU (%) Thicknes s (mm) Temp erat u re (oC) Pressure (bar) Mo ist ure (%) Density (g/cm3) 6 15 160 50 12 0,75 6 8 160 The panels were prepared with fibers of Pinus elliottii wood, obtained by thermo-mechanical shredding, according to the following steps: First step: Setting the fiber mass, of nominal density and addition of 12% water (dry weight basis) using hand sprayer. The addition of water was performed using a balance with infrared heating system for controlling the moisture content of the fibers. Second step: Addition of PU-adhesive Castor to the fibers (6% dry weight basis) and fiber mat formation. International Journal of Composite M aterials 2013, 3(1): 7-14 9 The addition and mixing of adhesive fibers were made using a mix fiber and resin (Figure 1), equipped with a central axis in the longitudinal direction with mixing b lades in the radia l direction and pneumatic guns for distribution of adhesive to the fibers. Then the fibers were deposited with adhesive forming the mattress to define the volume of fibers (Figure 2). Figure 4. Machine to press the board with control of pressure and t emp erat ure Figure 1. Cylinder to mix fiber and resin Fourth Step: Manufacture of the specimens. Were made three panels with dimensions 500× 500× 8mm and three other with dimensions of 500×500×15mm, resulting in 6 panels. These panels remained for approximately 72 hours to achieve therma l equilibriu m. Were obtained six specimens of dimensions 500×50×(8 and 15) mm of each panel produced to determine the modulus of rupture (M OR). To determine the perpendicular tensile strength (TP) and surface tensile strength (TS), were prepared specimens with dimensions of 50×50×(8 and 15) mm, twelve specimens of each panel to TP and five specimens for TS. Fifth Step: Essays on characterization of the panels. The results (Table 2) of the strength tests were compared with the min imu m values of the properties proposed by EM B/IS-2[15] standard. Figure 2. Pattern to board formation Third Step: Pre-cold pressing of the mattress and pressing fibers with controlled temperature and pressure for the production of MDF panels. The mattress of fibers prepared above was subjected to cold pressing to the equipment of Figure 3, in order to adapt its dimensions to press with pressure and temperature control working (Figure 4). Th is has the press panels (upper and lower instead of inferred) provided with resistances which are heated and transfers instead of transfers heat to the mat of fibers. The heat reacts with the PU-Castor resin providing immed iate cure. Table 2. P ropert ies of the MDF, St andards, minimum values proposed by EuroMDFBoard/1995 and average values obt ained from test s Standards and prope rties according to EMB/IS-2: 1995 Minimum values de pending on the thickness according to EMB/IS-2: 1995 standard EN310[16] MOR 23 MPa 20 MPa EN319[17] TP 0,55 MPa 0,55 MPa EN311[18] EN318[19] - TS Density Thickness 1,20 MPa 0,5 a 0,8 g/cm3 > 6 a 9 mm 1,20 MPa 0,5 a 0,8 g/cm3 > 12 a 19 mm The equipment tests to characterize the MDF are illustrated in Figures 5, 6 and 7. Fi gure 3. Machine for pre-press the board Figure 5. Static bending test 10 Sérgio Augusto M ello da Silva et al.: Strength Properties of M edium Density Fiberboards (MDF) M anufactured with Pinus Elliottii Wood and Polyurethane Resin Derived from Castor Oil 2,0 TP (MPa) 1,5 1,4 Figure 6. Perpendicular tensile test TS (MPa) 1,0 0,8 0,55 0,5 TP8mm TP15mm EMB6a19mm Fi gure 9. Average values of TP 2,0 1,62 1,5 1,5 1,2 1,0 0,5 TS8mm TS15mm EMB6a19mm Figure 10. Average values of T S Table 3. Average propert ies of st rengt h and st iffnes Properties TK (mm) Mean SD CV Figure 7. Superficialtensile test Sixth Step: To prove the significance of the test results, statistical analysis were performed with the " General Linear Model" proposed by Tukey, using the software Minitab ® 13. The analysis allowed the generation of g raphs in which it is possible to evaluate if the test results satisfy the experimental model, namely if there random distribution of variance and normality of the data. MOR 34,93 2,29 6,57 8 36,66 4,86 13,25 37,41 3,39 9,05 32,25 3,25 12,71 15 37,40 4,75 8,35 33,59 2,80 8,35 1,32 0,10 7,63 3. Results and Discussions Table 3 shows the mean of the MOR, TP and TS and their respective standard deviations (SD) and coefficients of variation (CV) as a function of the thickness (TK) of the p an els . 50 8 1,50 0,10 6,55 1,38 0,12 8,91 TP 0,79 0,60 7,52 15 0,90 0,60 6,29 0,72 0,60 8,70 1,55 0,10 6,43 8 1,60 0,22 13,56 MOR (MPa) 40 36,33 35,2 30 23 20 20 10 1,70 0,15 8,85 TS 1,43 0,04 2,90 15 1,65 0,21 12,72 1,30 0,08 5,94 0 MOR8mm MOR15mm EMB6a9mm EMB12a19mm Fi gure 8. Average values of MOR Figures 8, 9 and 10 illustrate graphs of the strength properties obtained with the characterizat ion tests of MDF panels with 8 and 15 mm thickness, compared with the minimu m strength value proposed by EM B/IS-2[15] International Journal of Composite M aterials 2013, 3(1): 7-14 11 s tan d ard . As shown in Figures 8, 9 and 10, in all cases, considering the two thicknesses measured values obtained with the assays for the characterization of M DF were higher than the minimu m values proposed by EMB/ IS-2[15] standard. Regarding the density, average values were determined equal to 0.75 and 0.80 g/cm3 respectively, within the range recommended by EMB/IS-2[15] standard, as presented previously in Table 2. To verify the efficiency of the manufacture process and the homogeneity of the panels, statistical analyses were performed in the values of the MOR, TP and TS. The verification of the significance of these values was performed considering the simu ltaneous analysis of two thicknesses, 8 and 15 mm. Then relat ions were established between residues with calcu lated values and the scores of norma l strength values determined for the MOR, TP and TS. Figure 11 shows the verificat ion of the random distribution of variance values of M OR, which shows the relation of the residual with the estimated values, it is possible to verify that there was random distribution of variance with two events highlighted, showing high values of residues. These events correspond to specimens with 8 and 15mm of thic kness obtained by the edge regions of MDF, which showed MOR with values equal to 29.89 MPa and 28.14 M Pa, above the min imal values (23 and 20 MPa) proposed by EMB/IS-2: 1995 standard. Figure 12 shows the verification of the hypothesis of normality between the values of MOR, that although the events highlighted with high amounts of residual, it is observed that the events are linearly distributed with a determination coefficient (R2) equal to 0.9286. In checking the homogeneity of the MDF by co mparing the MOR, Table 4 shows the mu ltiple analysis of variance which evaluated the averages of these values between the MDF with same thickness (TK), ie, 8 mm (1 and 2); (1 and 3); (2 and 3) and with 15 mm (4 and 5); (4 and 6), (5 and6), which verifies that the confidence intervals (CI) were determined with opposite signs values (- and +). These results, as the analysis model proposed indicate that panels are similar (equivalent) and are characterized by being identical repetitions. Figure 11. Residual distribution – MOR Figure 12. Residual Plot – MOR Figure 13 shows the random d istribution of variance values of TP, revealing that there were no events with high values of residual and are presented randomly. Figure 14 presents the hypothesis of normality between the values of TP, revealing that the events are distributed linearly, with determination coefficient equals to 0.9847. Figure 13. Residual distribution – TP Figure 14. Residual Plot – TP The verificat ion of consistency between the MDF fro m the comparison of the values of TP can be observed in mu ltip le analyses of variance shown in Table 5, where there is a comparison between MDF (1 and 3), (4 and 5) and (4 and 6) showed that ranges of values with different signs (+ and -), indicating that these panels are similar and allowing inferring that the process of manufacture of these panels was similar, however the MDF (1 and 2), (2 and 3) and (5 and 6) showed ranges of values with equal signs (+ and +) and (- e -), indicating that these panels are different, possibly due to process manual d istribution of the fibers. However, it is noteworthy that there was no reduction in the average value of TP, which were h igher than the minimu m value (0.55 M Pa) proposed by EMB/IS-2[15] standard. 12 Sérgio Augusto M ello da Silva et al.: Strength Properties of M edium Density Fiberboards (MDF) M anufactured with Pinus Elliottii Wood and Polyurethane Resin Derived from Castor Oil TK 8 mm 15 mm Table 4. Comparison of MOR average values using multiple variance analysis P an els Mean P an els Mean DMA DMS CI RM 1 34,9 2 36,7 1,73 -6,46 -8,190 4,737 0,95 1 34,9 3 37,4 2,49 -6,46 -8,949 3,979 0,93 2 36,7 3 37,4 0,76 -6,46 -7,222 5,705 0,98 4 32,2 5 37,4 5,16 -6,46 -11,620 1,310 0,86 4 32,2 6 33,6 1,35 -6,46 -7,810 5,110 0,96 5 37,4 6 33,6 3,81 1,15 -2,660 10,27 1,11 TK 8 mm 15 mm Table 5. Comparison of average TP values using Multiple Variance analysis P an els 1 1 2 4 4 5 Mean 1,3 1,3 1,5 0,8 0,8 0,9 P an els 2 3 3 5 6 6 Mean 1,5 1,4 1,4 0,9 0,7 0,7 DMA 0,20 0,10 0,10 0,11 0,07 0,20 DMS -0,08 -0,07 0,11 -0,10 0,04 0,28 CI RM -0,280 -0,10 0,87 -0,170 0,04 0,93 0,008 0,21 1,07 -0,210 0,00 0,88 -0,030 0,20 1,10 0,080 0,30 1,29 In Figure 15 there is a rando m d istribution of variance values of TS performed by using the relationship between residual and estimated values. In the graph are identified two events with high values of residues that correspond to the MDF with 8 and 15mm o f thickness obtained in the reg ion of the edges of the panels, with TS equal to 1.60 MPa and 1.43 MPa, which although having high residues are superior to minimu m values (1.2 MPa) proposed by EMB/IS-2[15]. straight events distributed with determination coefficient R2 = 0.9067. This graph also observe the events that showed high levels of residual. Figure 16. Residual Plot – T S Figure 15. Residual distribution – T S Figure 16 shows the hypothesis of normality values of TS by means of the rat io between residual and normal scores. This relationship determines a region on the graph with a The verification of consistency between MDF fro m the values of TS can be seen in Tab le 6 (mult iple ANOVA), where there is only a co mparison between the MDF 5 and 6 presented value range with equal signs (+ and +), considering that the values of TS are determined above the minimu m required value (1.2 M Pa) by EMB/IS-2[15]. It is emphasized that the problems in the process of making the MDF did not influence the final TS. International Journal of Composite M aterials 2013, 3(1): 7-14 13 TK 8mm 15mm Table 6. Comparison of average of T Svalues using multiple variance analysis P an els 1 1 Mean 1,55 1,55 P an els 2 3 Mean 1,59 1,70 DMA 0,04 0,15 DMS -0,29 -0,28 CI RM -0,33 0,24 0,97 -0,43 0,14 0,91 2 1,59 3 1,70 0,11 -0,28 -0,39 0,18 0,94 4 1,43 5 1,64 0,21 -0,29 -0,50 0,05 0,87 4 1,43 6 1,29 0,14 -0,01 -0,15 0,42 1,11 5 1,64 6 1,29 0,35 0,41 0,06 0,63 1,27 4. Conclusions 559 - 565. Publisher: Elsevier Science LTD, The Boulevard, Langford Lane, Kidlington, O xford OX5 1GB, England. Aug., According to the test results it can be concluded that the 2004. adhesive PU-Castor Oil in the rat io of 6% gave the MDF [7] Campos, C. I.; Lahr, F. A. R. “Propriedades físico-mecânicas made with fiber o f Pinus elliottii wood present mechanical de MDF a partir de fibras de madeira de reflorestamento e properties compatible with the requirements of the standard adesivos alternativos”. Tese de doutorado apresentada no EM B/IS-2: 1995 for both thicknesses. Statistical analy zes showed that the homogeneity problems arising fro m the procedures of making the MDF in the curso de pós-graduação Ciência e Engenharia de M ateriais, Programa Interunidades, EESC/IFSC/IQSC - U SP; p. 113; São Carlos – SP, 2005. laboratory were not significant. [8] Bradi, K. H.; Amim, K.A.M .; Othman, Z.; M anaf, H.A.; Khalid, N. K. “Effect of filler-to-matrix blending ratio on the mechanical strength of palm-based”. Source: Polymer International 55 (2): p. 190 - 195. Publisher: John Wiley & REFERENCES Sons LDT, The Atrium, Southern Gate, Chichester PO19 8SQ, 2006. [1] Associação Brasileira das Indústrias de Painéis de M adeira (ABIPA) - Produtos e Tecnologias. “Sobre consumo mundial de aglomerado em 2004/2005”,, São Paulo (SP). 2006. [9] Silva, R. V. Da; Spinelli, D. “Compósito de resina poliuretano derivada de óleo de mamona e fibras vegetais”. 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E. “Avaliação de três tipos de estruturas de colchão e três níveis de resina fenólica na produção de chapa de partícula orientada - OSB”. mamona na fabricação de painéis de madeira aglomerada”. Capítulo de Livro: LAHR, F. A. R. Produtos derivados da madeira. São Carlos: EESC/USP, p. 37-160, 2008. Revista Árvore, v. 27, n. 3, p. 365 - 370. Viçosa - M G, 2003. [12] Fiorelli, J.; Rocco Lahr, F. A.; Nascimento, M F.; Savastano [4] M aciel, A.S.; Vital, B.R.; Lucia, R.M .D.; Pimenta, A. S. “Painéis de partículas aglomeradas de madeira de Pinus elliiottii Engelm Poliestireno (PS) e Polietileno tereftalato (PET)”. Revista Árvore, v.28, n.2,p. 257 - 266. Viçosa - MG, Jr., H.; Rossignolo, J. A. “Painéis de partículas à base de bagaço de cana e resina de mamona – produção e propriedades”. Acta Scientiarum Technology, M aringá, v. 33, n. 4, p. 401-406, 2011. 2004. [13] Paes, J. B.; Nunes, S. T; Rocco Lahr, F. A.; Nascimento, M . [5] O’donnell, A.; Dweib, M .A.; Woll, R. 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M DF - M edium density fiberboard 14 Sérgio Augusto M ello da Silva et al.: Strength Properties of M edium Density Fiberboards (MDF) M anufactured with Pinus Elliottii Wood and Polyurethane Resin Derived from Castor Oil definition. Test M ethods and Requirements. “Industry Standard. Part I: Generalities and Part II: Requirements for General Purpose Boards”, EM B/IS – 1:1995. [16] European Committee for Standardization. European Standard EN 319 – Particleboard and Fiberboards – “Determination of modulus of elasticity in bending and of bending strength.” Bruxelas, 1993. [17] European Committee for Standardization. European Standard EN 319 – Particleboard and Fiberboard – “Determination of tensile strength perpendicular to the plane of the board”. Bruxelas, 1993. [18] European Committee for Standardization. European Standard EN 319 – Particleboard and Fiberboard – “Determination of swelling in thickness after immersion in water”. Bruxelas, 1993. [19] European Committee for Standardization. European Standard EN 319 – Particleboard and Fiberboard – “Determination of density”. Bruxelas, 1993.

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