Chemistry Reference
In-Depth Information
poisonous phosgene and large amounts of sodium chloride as byproduct. The
second method avoids phosgene when diphenylcarbonate is produced from CO or
CO
2
, but disadvantageous are a high risk of discoloration and branching. The third
method is particularly suitable for reaction-injection molding, but it is expensive.
A less expensive variant avoiding isolation of individual macrocycles has recently
been developed by researchers of General Electric [
89
].
According to information disclosed by researchers of Bayer AG to the author
more than 300 bisphenols were transformed into polycarbonates, but none of these
polymers showed a better balance of low costs and useful properties than the
polycarbonate of bisphenol-A. Several modifications of PAC were commercial-
ized. Incorporation of bulkier bisphenols, such as 3,3
0
5,5
0
-tetramethyl bisphenol-A
or 1,1-bis(4-hydroxyphenyl)cyclohexane raises the Tg above 150 C and reduces
the sensitivity to hydrolysis, it also reduces the unusually high impact strength of
the parent homopolymer. In corporation of 3,3
0
5,5
0
-tetrabromobisphenol-A lowers
the
flammability
and
modification
of
end
groups
influences
the
rheological
properties.
Characteristic for PAC is a high impact strength, which results from group
motions which occur even below 0 C and transform the impact energy into heat.
A consequence of this useful property is applications, such as safety glasses,
protective helmets, and unbreakable lenses. Yet, for applications as lenses or
visors PAC needs to be coated to reduce its sensitivity to scratches and organic
solvents. Numerous physical properties and applications are compiled in Refs. [
84
,
85
,
90
,
91
].
Finally, it should be mentioned that even before H. Schnell was elected to the
plastic Hall of Fame, a former coworker, Dieter Freitag had received this Honor.
D. Freitag invented a polycarbonate suited for rapid injection moulding, and on the
basis of this invention billions of compact discs were produced worldwide.
Another achievement was the development of aromatic poly(ester carbonate)s,
APECs. D. Freitag was born in Offenbach (Germany) were he grew up. He studied
chemistry in Freiburg i.Br. and Frankfurt a. M., where he received the doctor's
degree in 1967. Immediately afterwards he started his career at Bayer AG, where
he spent over 30 years. His career proceeded from the role of Group Leader to the
Director of Research and development of the Plastic Business and ultimately to the
Head of Bayers material Research Department. After his retirement in 2001, he
joined the Triton Systems (USA) as Chief Technical Officer and developed with
his new team the technical production of Polyphosphonates, an extremely flame
retardant class of engineering plastics and additives which is now produced in
more than six countries. He received numerous honors and awards, for instance,
the Otto Bayer Medal and the Herrmann Mark Medal [
92
,
93
].
