HAL Id: hal-01612472
https://hal.archives-ouvertes.fr/hal-01612472
Submitted on 6 Oct 2017
HAL
is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from
L’archive ouverte pluridisciplinaire
HAL, estdestinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de
Impact of Hot Pressing Pressure on Medium Density Fiberboard (MDF) Performance
Waheed Gul, A Khan, A Shakoor
To cite this version:
Waheed Gul, A Khan, A Shakoor. Impact of Hot Pressing Pressure on Medium Density Fiberboard
(MDF) Performance. AAPPS Bulletin, Association of Asia Pacific Physical Societies, In press. �hal-
01612472�
Impact of Hot Pressing Pressure on Medium Density Fiberboard (MDF) Performance
W. Gul
1*, A. Khan
2, and A.Shakoor
21*
Department of Mechanical Technology, University of Technology,Nowshera,Pakistan
2
Department of Mechanical Engineering,
University of Engineering and Technology, Peshawar, Pakistan
*Corresponding Author: waheed@uotnowshera.edu.pk
Abstract— This paper investigates the impact of hot pressing pressure onto the MDF Physical and Mechanical properties. It has been observed that Physical and Mechanical properties of the products are improved but not too much when the maximum pressure rises from 3.5 MPa to 5.5 MPa. It is indicated from the result that when the pressure is added after the hot pressing, it overcomes the rebound force and the hot press plate contacts the thickness gauge, only the gauge is subjected to force and the raw board is not affected too much. Therefore, under the aforementioned test conditions, a maximum pressure of 3.5 MPa can meet the requirement.
Keywords— Hot press Pressure, I.B, MDF, MOE, MOR, Water absorption rate,Thickness expansion rate
I. INTRODUCTION
Medium density fiberboard (MDF) is a type of wood sheet formed under optimum Pressure and temperature by using wood fiber or other plant fiber as a raw material with the help of urea formaldehyde resin. The density of MDF in production is generally controlled between 690 – 750 Kg/M3. The raw materials used for MDF are Firewood from nearby plantations and forest, Mango, Ghaz wood (Tamarix aphylla), Poplar wood (Populus caspica), eucalypt, Wheat straws, Rice husk, Cotton stalks, Sesbania and Sugarcane bagasse etc.
The performance index of MDF is divided into three categories, i.e. Physical performance, Mechanical performance and Biological performance. The Physical performance mainly includes Density, Moisture content, thickness swelling etc. The Mechanical performance mainly includes internal bonding, Modulus of Elasticity (MOE), Modulus of rupture (MOR), screw holding force (face and side). The Biological performance mainly includes the release of formaldehyde. [1].
Figure.1 shows the whole manufacturing process associated with different work stations, i.e. Material Preparation, fiber formation, fiber treatment, mat forming and hot pressing, board treatment and ware house. In material preparation section, the wood is converted into chips through chipper machine. [7]. The chips are then screened to separate the required size. The confirmed chips are then transported to chips washer through a belt conveyor with iron remover installed over it. These chips are then washed to improve its quality. They are then transfer to fiber separation section. In fiber Separation Section, the chips are cooked at a temperature (160 – 180 ºC) @ (6-8 bar) pressure for about 3-5 min to make it softer. About 1-2 (wt %) of paraffin wax is added to the softened chips to make its swelling resistant. The softened chips are then delivered to grinding chamber.
Where, the materials are mechanically decomposed with the function of water and heat. Pulps are formed and passed in blow line where urea formaldehyde resin is added into pulp. After this process, the pulp in the form of fiber enters into the dryer. [8]. In Fiber treatment section, the moisture is vaporized in fiber and controlled it within the required range. The final moisture content
in the fiber is controlled within 8 – 13 (wt %). In mat forming Section, the fiber is spread evenly into the matting conveyor belt.
Under the function of air blow, the mat of specified thickness is formed. The pre-press dispel the air out of mat and gives strength to the mat.
Figure 1: MDF Manufacturing Process [wood Force plant]
In Board Trimming Section, the board is cooled and conveying to the longitudinal and transversal saw for cutting. The dust is removed from sides of board. In Sanding Section, the board is polished to the required size by removing the extra surface. The board is then inspected and transferred to ware house.
II. METHODOLOGY
Hot pressing is an important process to manufacture the MDF and plays a decisive role on the product quality and productivity.
Hot pressing refers to a process that the raw board under the combined function of temperature and pressure, is subjected to moisture evaporation, increase of density, glue solidification and water proof agent redistribution. The compositions in the raw materials are subjected to a series of physical and chemical change to form bonding force between the fibers and form the products confirming to quality requirements. Plant fiber material is a micro-molecular organic substance complicated in chemical compositions. Hot pressing process involves the change in geometric shape, chemical change and physical change. There are some factors which affect this method,i.e. temperature of the process, type of raw materials, separation mass of fiber, moisture content, resin type and performance, hot pressing method, and the temperature, pressure and time of hot pressing. A multi opening Hot press is shown in figure 2. The number of hot platens depend upon the production capacity of the plant.
Figure 2: Multi opening Hot Press
The press cycle and parameters are shown in the following table 1and figure 3. In table 1, for 16mm board thickness the whole press cycle time is 280 sec plus position time, i.e. (s1 + 30).
Table 1: Hot Press Parameters for different thickness of board
S1 is the press closing time normally 10 second. So the total cycle of the hot press for 16mm is calculates as 320 second. The adjustment is based on the gel time of Urea formaldehyde (UF) resin. Similarly, for different thickness and curing of resin, different parameters are adjusted. The main function of the pressure during hot pressing is to encounter the rebound force of the raw fiberboard, further discharges the air out of the raw board, enhances the contact and weaving between fibers and meet the requirements for thickness and density. The Pressure of the hot press during various stages of board varies from P1 to P7. At P7, the pressure value in the press cycle becomes constant till the pressure reached to P9.
Th(mm) P1 P2 P3 P4 P5 P6 P7 P8 P9 t0 t1 t2 t3 t4 t5 t6 S2 T(˚c)
8 170 30 40 90 80 20 12 11 10 55 35 15 15 10 15 S1+25 170
11 170 35 45 90 80 19 12 11 10 80 50 15 15 12 15 S1+30 170
16 190 30 40 160 140 19 12 11 10 100 100 15 20 20 20 S1+30 190
18 190 35 45 170 150 16 12 11 10 120 100 15 20 20 25 S1+30 190
Figure 3: Hot press cycle Graph
The graph shown in figure 3 is formed from the hot press parameters mentioned in table 1.
The main experiment was carried out on 16mm board. Four samples of 16mm MDF were manufactured with initial parameters as shown in table 2.
Table 2. Initial fixed process parameters for hot pressing
S. No Parameters Value
1 Moisture in fiber
11 %
2 UF resin 10 %
3 Hot press plates temperature 190 ⁰ C 4 Thickness of board to be produces 16 mm 5 Press closing time 40 sec 6 Total press cycle time 320 sec
III. RESULTS AND DISCUSSION
Final manufactured MDF properties are concisely summarized in Table 3. The comparative analysis of the well-defined MDF properties, such as Water Absorption rate (Wt), Thickness Expansion rate (Ts), Modulus of Rupture (MOR) and Internal Bond (I.B) and density can be accomplished on the basis of Pressure variation under fixed process conditions. Wt ,Ts and density are physical properties of MDF while MOR and I.B are Mechanical properties of the formed MDF.
Table 3. The final MDF properties at various pressures
P (MPa) I.B (MPa) Wt (%) Density (gm/cm³) MOR (MPa) Ts (%)
3.5 0.67 21.4 0.74 28.7 8.6
4.5 0.7 20.1 0.73 29.4 8.2
5.5 0.74 19.2 0.74 31.3 8.5
Three samples of MDF are produced at Pressure 3.5 MPa, 4.5 MPa, and 5.5 MPa. While during manufacturing the initial parameters, i.e. preheating time, UF resin, Wax, Press timing and board size were kept constant.
The physical property, Thickness Expansion rate (Ts) of MDF is consummate with Pressure variation ranging from 3.5 MPa – 5.5 MPa. At Pressure 3.5 MPa, 4.5 MPa, and 5.5 MPa, the Ts values were recorded as 8.6 %, 8.2 % and 8.2 % and 8.5 % respectively as shown in figure 4.
Figure 4: Relationship between Hot Press Pressure and Thickness Expansion rate
As the Pressure increases from 3.5 MPa to 4.5 MPa, the value of Ts decreases from 8.6 % to 8.2 %, but when we increase the Pressure from 4.5 MPa to5.5 MPa, the Ts value is slightly increases from 8.2 % to 8.5 %. It means that if we further increase the Pressure, the Ts value will move in ascending order and the strength of MDF will be reduced. Calculated Ts values also depend upon the nature of curing of resin used as binder and hot press time and temperature. High Pressure is strictly prohibited for MDF in normal case of resin curing. While the Ts value according to standard (EN-317) is <12 %.
In record of the manufactured MDF samples, the experimental values of Mechanical adhesive property i.e. Internal Bond (I.B) is ranging from 0.67 Mpa to 0.74 Mpa for a Pressure range from 3.5 MPa to 5.5 MPa as shown in figure 5.
Figure 5: Relationship between Hot Press Pressure and Internal Bond (I.B)
The I.B value at low Pressure (3.5 MPa) is 0.0.67 Mpa, while for a 16mm MDF the I.B value is standardize (EN-319) as 0.6 Mpa. Hence at 3.5 MPa, the MDF will have a very good strength. But when the Pressure exceeding from 3.5 MPa to 4.5 MPa, the I.B value is reached to 0.70 Mpa. So at 4.5 MPa, the MDF exceeding from the standard value and strength. If we further increase the Pressure from 4.5 MPa to 5.5 MPa, a direct relation is setup between Pressure and I.B and the I.B value is continuously increases.
The samples of MDF are also tested for a very important Mechanical property, i.e. Modulus of Rupture (MOR). The experimental values of MOR are calculated as 28.7 Mpa, 29.4 Mpa and 31.3Mpa for a pressure range from 3.5 MPa to 5.5 MPa as shown in figure 6.
Figure 6: Relationship between Hot Press Pressure and Modulus of Rupture (MOR)
At low Pressure (3.5 MPa), the MOR value is 28.7 MPa which is below the standard (EN-310) value (≥ 30 MPa). At 4.5 MPa, the MOR value is close to the standard value, i.e 29.4 MPa. However, at 5.5 MPa, the MOR value is at its peak (31.3 Mpa).
Figure 7 demonstrates the effect of Pressure over the density.
Figure 7: Relationship between Hot Press Pressure and density of MDF
The physical property, density of MDF is consummate with Pressure variation ranging from 3.5 MPA – 5.5 MPa. At 3.5 MPa, 4.5 MPa and 5.5 MPa, The values of density were recorded as 0.74 g/cm3 ,0.73 g/cm3 and 0.74 g/cm3 .At low Pressure, the density value is maximum,i.e. (0.74 g/cm3 ). If we increase the Pressure from 3.5 MPa to 4.5 MPa, the density value dropped from 0.74 g/cm3 to 0.73 g/cm3. If we further increase the temperature from 4.5 MPa to 5.5 MPa, the value of density increases from 0.73 gm/cm3 to 0.74 g/cm3.
For systematic judgment of the MDF property, the hot press Pressure values are drawn against Water absorption rate. The water absorption rate at Pressure 3.5 MPa is 21.4 % as shown in figure 8.
Figure 8: Relationship between Hot Press Pressure and Water Absorption rate of MDF
However when the Pressure increases from 3.5 MPa to 4.5 MPa, the water absorption rate value decreases from 21.4 % to 20.1 %.
At 5.5 MPa, the water absorption rate value is ideal, i.e 19.2 % among all the three values and the strength of MDF is at its peak.
IV. CONCLUSIONS
In this research, the impact of high pressure onto board property under fixed process conditions was described. It was observed that that Physical and Mechanical properties of the products are improved but not too much when the maximum pressure rises from 3.5 MPa to 5.5 MPa. It is indicated from the result that when the pressure is added after the hot pressing, it overcomes the rebound force and the hot press plate contacts the thickness gauge, only the gauge is subjected to force and the raw board is not affected too much. Therefore, the pressure shall be such as the hot press plate is in contact with the thickness gauge, otherwise too high pressure will cause the damage to Hot Press plate, deformed the thickness gauge or even affect the thickness and density of the products. It may also increase the design tonnage and price of the press. Therefore, under the aforementioned test conditions, a maximum pressure of 3.5 MPa can meet the requirement. In addition, too high pressure in hot pressing process may also affect the distribution of the board sectional density. Generally, the surface density is high and the density of the core is low, forming a
density gradient. The main reason causing density gradient is the surface of raw board is in direct contact with the hot press plate, so that it will be quickly heated, the moisture will be quickly dried, the glue will be solidifies in advance and loses elasticity for shrinkage. However the core layer of raw board remains its elasticity for insufficient heating and continuous to generate compression resistance, resulting in reduced compression and decrease density. The layers with different distance to the center differ in heating, which causes the density gradient. The higher the pressure, the faster the compression and the more obvious the density difference between each layer. Therefore, to reduce the uniformity of the board density, it is better not to use too high pressure during hot pressing process. Also too high pressure may cause the steam difficult to vaporize and thus the hot pressing cycle shall be extended.
V. REFRENCES
1. Ashori, Alireza, Amir Nourbakhsh, and Abolfazl Karegarfard. "Properties of Medium Density Fiberboard Based on Bagasse Fibers." Journal of composite materials 43, no. 18 (2009): 1927-34.
2. Ayrilmis, N, SONGKLOD Jarusombuti, Vallayuth Fueangvivat, and Piyawade Bauchongkol. "Effects of Thermal Treatment of Rubberwood Fibres on Physical and Mechanical Properties of Medium Density Fibreboard." Journal of Tropical Forest Science (2011): 10-16.
3. Balatinecz, John J, and David E Kretschmann. "Properties and Utilization of Poplar Wood." Poplar Culture in North America, no. Part A (2001): 277-91.
4. Büyüksarı, Ümit, Salim Hiziroglu, Hüseyin Akkılıç, and Nadir Ayrılmış. "Mechanical and Physical Properties of Medium Density Fiberboard Panels Laminated with Thermally Compressed Veneer." Composites Part B: Engineering 43, no. 2 (2012): 110-14.
5. Carvalho, LMH, MRN Costa, and CAV Costa. "A Global Model for the Hot-Pressing of Mdf." Wood science and technology 37, no. 3-4 (2003): 241-58.
6. Halvarsson, Sören Bernhard, Håkan Edlund, and Magnus Norgren. "Wheat Straw as Raw Material for Manufacture of Straw Mdf." BioResources 5, no. 2 (2010): 1215-31.
7. Ibrahim, Z, A Abdul Aziz, R Ramli, WH WanHassan, and NH Zainal. "Optimum Parameters for the Production of Mdf Using 100% Oil Palm Trunks." MPOB Information Series 566 (2006).
8. Kargarfard, A, A Nourbakhsh, and H Hosseinkhani. "Investigation on Medium Density Fiberboard (Mdf) Properties Produced from Horn Beam Wood." Pajouhesh and Sazandegi (2007).
9. Kargarfard, Abolfazl, and Ahmad Jahan Latibari. "The Performance of Corn and Cotton Stalks for Medium Density Fiberboard Production." BioResources 6, no. 2 (2011): 1147-57.
10. Lee, S, TF Shupe, and CY Hse. "Mechanical and Physical Properties of Agro-Based Fiberboard." Holz als Roh-und Werkstoff 64, no. 1 (2006): 74-79.
11. Li, Kaiyuan. "On Determining Density and Specific Heat of New Zealand Medium Density Fibreboard." Procedia Engineering 62 (2013): 769-77.
12. Li, Xiaobo. "Physical, Chemical, and Mechanical Properties of Bamboo and Its Utilization Potential for Fiberboard Manufacturing." Beijing Forestry University, 2004.
13. Mantanis, George, and Jochem Berns. "Strawboards Bonded with Urea Formaldehyde Resins." Paper presented at the 35th International Particleboard/Composite Materials Symposium Proceedings, 2001.
14. Mohebby, Behbood, Firooz Ilbeighi, and Saeid Kazemi-Najafi. "Influence of Hydrothermal Modification of Fibers on Some Physical and Mechanical Properties of Medium Density Fiberboard (Mdf)." Holz als Roh-und Werkstoff 66, no. 3 (2008): 213-18.
15. Nazerian, Morteza, Amin Dalirzadeh, and Saeid Reza Farrokhpayam. "Use of Almond Shell Powder in Modification of the Physical and Mechanical Properties of Medium Density Fiberboard." BioResources 10, no. 1 (2014): 169-81.
16. Ramli, Ridzuan, Stephen Shaler, and Mohd Ariff Jamaludin. "Properties of Medium Density Fibreboard from Oil Palm Empty Fruit Bunch Fibre." Journal of Oil Palm Research 14, no. 2 (2002): 34-40.
17. Rashid, Md Mamunur, Atanu Kumar Das, Md Iftekhar Shams, and Subir Kumar Biswas. "Physical and Mechanical Properties of Medium Density Fiber Board (Mdf) Fabricated from Banana Plant (Musa Sapientum) Stem and Midrib."
Journal of the Indian Academy of Wood Science 11, no. 1 (2014): 1-4.
18. Rials, Timothy G, Stephen S Kelley, and Chi-Leung So. "Use of Advanced Spectroscopic Techniques for Predicting the Mechanical Properties of Wood Composites." (2002).
19. Sundin, Mats. "Design of Blowline Resin Injector for Mdf Production." Master’s Thesis, Lulea University of Technology, Lulea, Sweden, 2007.
20. Valenzuela, J, E Von Leyser, A Pizzi, C Westermeyer, and B Gorrini. "Industrial Production of Pine Tannin-Bonded Particleboard and Mdf." European Journal of Wood and Wood Products 70, no. 5 (2012): 735-40.
21. Winandy, Jerrold E, and Andrzej M Krzysik. "Thermal Degradation of Wood Fibers During Hot-Pressing of Mdf Composites: Part I. Relative Effects and Benefits of Thermal Exposure." Wood and Fiber Science 39, no. 3 (2007): 450- 61.
22. Xu, Wei. "Influence of Vertical Density Distribution on Bending Modulus of Elasticity of Wood Composite Panels: A Theoretical Consideration." Wood and fiber science 31, no. 3 (2007): 277-82.
23. Yang, Han-Seung, Hyun-Joong Kim, Hee-Jun Park, Bum-Jae Lee, and Taek-Sung Hwang. "Water Absorption Behavior and Mechanical Properties of Lignocellulosic Filler–Polyolefin Bio-Composites." Composite Structures 72, no. 4 (2006):
429-37.
24. W.Gul,A.Khan and A.Shakoor."Improving Physical and Mechanical Properties of Medium Density Fiberboard." in proceedings of the 4th International Conference on Aerospace Science and Engineering (ICASE '15),pp. 57-62, ,Islamabad,Pakistan,September,2015.
25. W.Gul,A.Khan and A. Shakoor." Investigation and Analysis of Tamarix aphylla (Ghaz wood) and Populus caspica (poplar wood) used as Raw Materials for Manufacturing of Medium Density Fiberboard (MDF)."Journal of Advanced Materials Science." (2016).
26. Impact of Hot Pressing Temperature on the Medium Density Fiberboard Performance (MDF)," Article in Advances in Materials Science and Engineering 2017(1):1-6 · January 2017 ,DOI: 10.1155/2017/4056360 · License: CC BY 4.0.
