Modeling rheology in the hot-pressing of MDF: Comparison of mechanical models

• Type: Article in International Scientific Journal
• Date: 2001

Authors

costa, cav (Author) FEUP; costa, mrn (Author) FEUP; Luísa Carvalho (Author) FEUP

Journal

Title: Wood and Fiber Science

Vol. 33 No. 3

Pages: 395-411

ISSN: 0735-6161

Publisher: Society of Wood Science and Technology

Indexing

ISI Web of Knowledge - 17 Citations

Scopus - 17 Citations

Scientific classification

FOS: Agrarian Sciences > Agriculture, Forestry, and Fisheries

Other information

Authenticus ID: P-000-V5H

Abstract (EN): The hot-pressing operation is the final stage in the MDF manufacture where the mattress of fibers is compressed and heated to promote the cure of the resin. The press cycle has a major effect on the balance of properties of the resulting panel, so rigorous control of all processing variables is necessary to improve product quality and to reduce pressing time. The rheological behavior of the mattress during pressing involves complex phenomena that are dependent on temperature, moisture content, gas pressure, and density distributions. Following a three-dimensional model of heat and mass transfer already built, mechanical models were developed to describe the viscoelastic behavior of the material. The elastic and viscous properties for the wood-resin composite were estimated based upon several kinds of "rules of mixtures," taking into account the relationship with the simulations already undertaken for temperature, moisture content, and gas pressure profiles, as well as the adhesive polymerization. These dynamic models were used to predict the evolution of compression stress, strain, modulus of elasticity, and density with time at a given position in the mattress, as well as the density profiles. The models were compared in relation to the influential factors affecting the composite compressibility. The simulation results are useful to identify the controlling factors of a hot-pressing operation and to understand better the complex mechanisms involved in panel formation.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 17