Page 76 - Between light and shade

between light and shade, TRANSPARENCy and reflection

strength (and/or thickness) varies as desired over
their surface (for example, in perforated metal
sheets) or, for textiles, whose strength/stiffness
is differentiated in the warp and weft, or even
for sewn nets made from para-aramid or HPPE
rope 81. These surfaces also have the virtue of not
needing to be pre-stressed in order to acquire
and maintain their shape.

Consequently, in 1987, for the vast atrium of
the extension of the Solvay Research Centre in
Neder-over-Heembeek [01/190, Fig. 73], I desi-
gned a membrane of this kind, ultra light, in
transparent ETFE film 82 on a para-aramid net.

I then had to wait until 2008 and the compe-
tition, which we won, for the “East Vesuvio”

81 The para-aramid in question here (PPD-I) was discovered
in 1965 by Stéphanie Kwolet and Hubert Blades at Dupont.
It was launched in 1971 under the brand name Kevlar. This
was followed in 1978 by Twaron from Akzo (now produced by
Teijin). It has a breaking strength of 3000 MPa (greater than
the best steels but, with a density of 1.45, it is 5.5 times lighter)
and a modulus of elasticity of 100 GPa.
It has now been surpassed by “ultra high molecular weight
polyethylene” (HMPE or HPPE) whose fibre was invented by
Albert Pennings in 1963 and marketed from 1990 onwards by
DSM in the Netherlands under the brand name Dyneema.
Its fibre is lighter, with a density of 0.97, a yield strength σ of
between 1400 and 3000 MPa and E = 100 GPa. Finally, carbon
fibre ropes are starting to make an appearance, while awaiting
carbon nanotubes with a breaking stress of 50 GPa and 6 times
lighter than steel!
82 Ethylene tetrafluoroethylene, produced by Solvay, among

others. I developed this membrane with PTL (Plastiques and
Textilles Lyonnais), it has light transmission of more than 90%.

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