Step-closing pressing of medium density fiberboard; Part 1. Influences on the vertical density profile

2001 ◽  
Vol 59 (1-2) ◽  
pp. 19-26 ◽  
Author(s):  
Siqun Wang ◽  
Paul M. Winistorfer ◽  
Timothy M. Young ◽  
Chris Helton
Keyword(s):  
Density Profile ◽  
Medium Density Fiberboard ◽  
Medium Density ◽  
Vertical Density Profile ◽  
Vertical Density

scholarly journals Experimental Investigation of Vertical Density Profile of Medium Density Fiberboard in Hot Press

2021 ◽  
Vol 11 (22) ◽  
pp. 10769
Author(s):  
Asfar Hameed Minhas ◽  
Naveed Ullah ◽  
Asim Ahmad Riaz ◽  
Muftooh Ur Rehman Siddiqi ◽  
Khamael M. Abualnaja ◽  
...  
Keyword(s):  
Moisture Content ◽  
Density Profile ◽  
Cycle Time ◽  
Medium Density Fiberboard ◽  
Medium Density ◽  
Internal Bonding ◽  
Hot Press ◽  
Vertical Density Profile ◽  
Pressure Cycle ◽  
Vertical Density

This research investigates the performance of medium density fiberboard (MDF) with respect to hot press parameters. The performance of the board, type of glue, and production efficiency determine the optimum temperature and pressure for hot pressing. The actual temperature of the hot press inside the MDF board determines the properties of the final product. Hence, the optimal hot press parameters for the desired product are experimentally obtained. Moreover, MDF is experimentally investigated in terms of its vertical density profile, bending, and internal bonding under the various input parameters of temperature, pressure, cycle time, and moisture content during the manufacturing process. The experimental study is carried out by varying the temperature, pressure, cycle time, and moisture content in the ranges of 200–220 °C, 145–155 bar, 260–275 s, and 8–10%, respectively. Consequently, the optimum input parameters of a hot-pressing temperature of 220 °C, pressure of 155 bar, cycle time of 256 s, and moisture content of 8% are identified for the required internal bonding (0.64 N/mm2), bending (32 N/mm2), and increase in both the core and peak density of the vertical density profile as per the ASTM standard.

Modelling of the Development of the Vertical Density Profile of MDF during Hot Pressing

2007 ◽  
Vol 2 (2) ◽  
Author(s):  
Arun Gupta ◽  
Patrick Jordan ◽  
Shusheng Pang
Keyword(s):  
Moisture Content ◽  
Density Profile ◽  
Hot Pressing ◽  
Major Influence ◽  
Transfer Model ◽  
Uniform Density ◽  
Moisture Movement ◽  
Vertical Density Profile ◽  
Vertical Density ◽  
Pressing Operation

The hot pressing operation is one of the most important operations in medium density fibreboard (MDF) manufacture. Complicated dynamic interactions occur during pressing, including heat transfer, moisture movement, development of gas pressure, internal stress development and relaxation, wood consolidation, resin curing, bonding between particles and eventual development of a non-uniform density distribution through the panel thickness. Consequently the mat experiences continuously changing internal conditions (temperature and moisture content) as the pressing operation proceeds. The vertical density profile (VDP) has a major influence on the MDF strength and physical properties. This influence of the VDP on the board properties is generally recognised, but the formation of the density profile and their specific effects on the board performance have proved difficult to quantify. A mathematical model based on theoretical analysis and experimental information is being developed. In the model, the mat is divided into a number of thin parallel layers. The deformation of each layer is a function of stress, temperature and moisture content of the layer. The model incorporates the variation of the mat mechanical and rheological properties with moisture content and temperature. The changes in temperature and moisture content are provided by a separate heat and mass transfer model. The present model can predict stress, strain, layer deformation and density across the thickness during pressing. The performance of the model was validated by experiments conducted in a pilot-scale press. Twelve MDF boards were made with different pressing parameters, and the VDP were measured and compared with the simulation results from the model. The model could predict the density profile with an acceptable accuracy for the main variables that control the manufacturing of MDF boards.

Poisson’s ratio of the MDF in respect to vertical density profile

2014 ◽  
Vol 72 (3) ◽  
pp. 407-410 ◽  
Author(s):  
Václav Sebera ◽  
Jan Tippner ◽  
Milan Šimek ◽  
Jan Šrajer ◽  
David Děcký ◽  
...  
Keyword(s):  
Density Profile ◽  
Poisson’S Ratio ◽  
Poisson's Ratio ◽  
Vertical Density Profile ◽  
Vertical Density

scholarly journals PAG Concentration Dependence of the Vertical Density Profile in Photoresist

2010 ◽  
Vol 23 (5) ◽  
pp. 709-713 ◽  
Author(s):  
Jae Hyun Kim ◽  
Sung II Ahn ◽  
Yong-ho Kim ◽  
Jin Goo Yoon ◽  
Wang-Cheol Zin ◽  
...  
Keyword(s):  
Concentration Dependence ◽  
Density Profile ◽  
Vertical Density Profile ◽  
Vertical Density

Predicted Model of Section Stress Distribution and Bending Strength of Fiberboard Based on Vertical Density Profile

2011 ◽  
Vol 704-705 ◽  
pp. 424-433
Author(s):  
Yang Zhang ◽  
Zhi Ming Yu
Keyword(s):  
Stress Distribution ◽  
Density Profile ◽  
Bending Strength ◽  
Theory Of Elasticity ◽  
Average Density ◽  
Predicting Model ◽  
Vertical Density Profile ◽  
Bending Process ◽  
Vertical Density ◽  
The Impact

To study the impact of VDP on the bending process of fiberboard, this paper deeply researched into the dynamic changes of section stress distribution of fiberboard during the process of loading and bending and built a static bending strength predicting model, which is based on the piecewise function by simulating fiberboard VDP, theory of elasticity and plasticity, lamella inter-bedded theory and VDP model. The results show: The bending process of fiberboard can be divided into two stages which are elasticity period and elasticity-plasticity period. The latter includes both elasticity region and plasticity region, and compression region comes to elasticity bending before pulling region. The curve of bending section stress distribution is nonlinear and affected by loads and VDP. Critical section stress distribution of bending breakage and breakage load can be predicted by VDP with other condition unchanged. The value of static bending strength predicted by model is basically consistent with testing data. And the static bending strength is closely related to qualification factors of VDP. Fiberboard with high average density doesn’t always contain high static bending strength. VDP is a significant physical parameter which has impact on the bending process and performance of fiberboard, so it must be optimized and controlled in production according to for specific purpose. Key words: fiberboard, vertical density profile, section stress distribution, bending strength, predicting model

High-Pressure Treatment Effects on Density Profile, Surface Roughness, Hardness, and Abrasion Resistance of Paulownia Wood Boards

2018 ◽  
Vol 61 (3) ◽  
pp. 1181-1188 ◽  
Author(s):  
Huanhuan Li ◽  
Xiuping Jiang ◽  
Hosahalli S. Ramaswamy ◽  
Songming Zhu ◽  
Yong Yu
Keyword(s):  
Surface Roughness ◽  
High Pressure ◽  
Density Profile ◽  
Abrasion Resistance ◽  
Mechanical Performance ◽  
Treated Wood ◽  
Performance Properties ◽  
Vertical Density Profile ◽  
Vertical Density ◽  
Paulownia Wood

Abstract. The goal of this study was to investigate the effects of high-pressure (HP) treatment on the mechanical performance properties of Paulownia ( spp.) wood boards. The boards were HP treated at selected pressures (20, 40, 60, 80, and 100 MPa) for 30 s. A special vacuum-packing technique that sandwiched the test boards between two steel plates was used for the HP treatment to prevent board distortion. Thickness, density, vertical density profile (VDP), cell wall percentage (VC), porosity percentage (VH), surface roughness, hardness, and abrasion resistance were evaluated to assess the performance properties of the treated and untreated boards. HP treatment resulted in 45.7% to 60.0% reduction in thickness of the boards, while it increased the density by 88% to 170%. The VDP of densified boards was distributed uniformly, and core densities were only slightly higher than surface densities. HP treatment made the Paulownia board surfaces much smoother, and three roughness parameters were reduced with increasing treatment pressure level. Hardness values of the boards were improved by 84% to 173%. The mass loss values of HP treated wood samples in abrasion tests were significantly reduced by 40.7% to 75.0%. The results of this study demonstrate that HP treatment is a useful method to improve the end-use properties of low-density wood like Paulownia. Keywords: Abrasion resistance, Hardness, High-pressure densification, Paulownia wood boards, Vertical density profile, Surface roughness.

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