eprintid: 296
rev_number: 9
eprint_status: archive
userid: 7
dir: disk0/00/00/02/96
datestamp: 2010-05-12 18:00:24
lastmod: 2015-05-29 19:55:07
status_changed: 2010-05-12 18:00:23
type: report
metadata_visibility: show
item_issues_count: 0
creators_name: =, =
title: Thermally Pressing Corner Profiles
ispublished: pub
subjects: materials
studygroups: esgi33
companyname: Trespa International B.V
full_text_status: public
abstract: The process of pressing a corner profile is less stable than the regular flat panel process. Density variations and surface blisters have been observed that are supposedly due to captured air and water. The question is to explain or clarify, by suitable mathematical modelling, the physical processes leading to this adverse behaviour, and to suggest (ways to obtain) more favourable mould shapes.
problem_statement: Trespa International B.V. (Weert, The Netherlands) is a manufacturer of high quality panel material for exterior and interior uses, made of polymerized resin, reinforced with wood fibres or sulphate paper. Typical applications are office
desk tops and facade cladding.

The production process starts with impregnating large sheets of paper with resin. Then a pile of sheets of 8-13mm is pressed together under high pressure (90 bar) in a mould until all of the air is squeezed out. In simplistic terms, the pressing of a plate occurs in two distinct stages; compression followed by heating. 

During the first stage of the process, which last approximately two minutes, the components are compressed to within 10% of the final thickness. During this stage very little heat has reached the components. During the second stage the temperature reaches a critical value and the resin starts to polymerize, eventually resulting in the solidification of the melt. During polymerization water is formed, which is partly dissolved in the polymer and fibers, partly squeezed out sideways, and partly evaporated through the upper and lower surfaces.

The majority of the production involves the manufacture of large rectangular flat plates. Here, the process is well controlled, with little failure losses. A minority of the production consists of, so-called, corner profiles, where a two-dimensional corner (legs of 30 cm, a lateral extension of 4 m) is made by heat-pressing a pile of sheets, folded into a corner shaped mould. The upper and lower surfaces of the legs are not exactly parallel. The angle between the legs of the inner mould is 90 degrees, and of the outer mould 91.5 degrees, which is a small but critical amount more. In this way the mould slightly diverges, such that it closes first in the corner, while the contact area between the sheets moves from the corner into the legs. The legs are connected by circular arcs
of 10 mm (inner) and 20 mm (outer) radius. This shape may be modified if necessary.

The process of pressing a corner profile is less stable than the regular flat panel process. Density variations and surface blisters have been observed that are supposedly due to captured air and water. The question is to explain or clarify, by suitable mathematical modelling, the physical processes leading to this adverse behaviour, and to suggest (ways to obtain) more favourable mould shapes.
date: 1998
citation:   =, =  (1998) Thermally Pressing Corner Profiles.  [Study Group Report]     
document_url: http://miis.maths.ox.ac.uk/miis/296/1/trespav.ps