Page 53 - Glass-Technology International no. 3-2019

Gianfranco Rivaroli

glass sizes have now been
approved by RINA – a body THE EVOLUTION
that controls the standards
for glass used in nautical OF TEMPERED GLASS
applications – is an impor-
tant step forward. Chemical tempering is moving forward, gaining more and more
Roberta Cometti This means that we are appreciation and demand, thus extending its application to several
continuing to propose our industries: aeronautic, aerospace, naval, military, automotive, electronic,
plants in diverse sectors optical and in all those projects demanding special curves and reduced
and companies – from im- glass thicknesses.
portant global groups to Chemical tempering, especially important for the curved glass, is the par
excellence and definitive answer to the compromise between thicknesses
small companies, because and shapes, achieving perfect flatness, mainly for glass thicknesses lower
our plants can temper both than 2mm., allowing chemical tempered glass to be perfectly coupled
small sizes and large glass and laminated accordingly.
Alessandro Rivaroli sheets.
The process
Roberta Cometti, RCN: Let’s Chemically tempered glass is a glass which has been strengthened by an
only for special glass types say that we are working on ion exchange process, occurring at a temperature of about 450°C.
or standard sizes, but now creating and increasing the After pre-heating, the glass is immersed in a fused potassium salt bath
also customized. ‘idea’ of chemical temper- thus starting the chemical process. During this time, the glass is exposed to
ing in sectors in which up an ion exchange between sodium (Na+), contained into the molecular
Gianfranco Rivaroli, RIVA: to now it has not been tak- structure of the glass, and potassium (K+), the chemical element the salt
Thanks to the collabora- en into consideration for is made of.
This process takes place thanks to the difference of the electro-chemical
tion between RCN and diverse reasons. potentials of the ions themselves.
RIVA, we are moving for- As we all know, chemi-
ward in the development cal tempering is not a new How does it work?
of chemical tempering, to process, but its use has The process provokes a space reduction between the glass particles that
have furnaces of ‘impor- never been, until now, so are compressed by the bigger size of the potassium ions. It results in a
tant’ sizes, used for archi- widespread. This was due complex system of stress and tension on the glass surface, increasing the
tectural, automotive and to the fact that the bene- mechanical stress resistance three times more than thermally tempered
naval glass – so large glass fits of chemical tempering glass, thus granting an excellent quality standard.
sizes. And the fact that were not so well-known
chemically tempered large compared to thermal tem- What are the advantages?
Chemically tempered glass has no visual surface imperfections in
comparison to thermally tempered glass. Thus, curved glass can also be
chemically tempered.
Thin glass can be tempered without the risk of breakage or distortion.
In addition, the results of chemical tempering create perfect coupling
in the case of later lamination with EVA or PVB, with results free from
visual defects, with a great difference from the most recurrent defects of
thermal tempering.

Scope
• Tempering of glass thickness lower than 2.5mm;
• Complex glass curves and big sizes that cannot be thermally tempered;
• For all applications demanding resistance to high stress and impact
(boats; aeronautic, military, aerospace industry, etc.)
• In all applications where, in addition to the mechanical properties of
the process, high quality glass is also required: transparency and flat
surface (no distortion caused by the contact of the glass with the rolls).

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