Underground Construction - March 2022 - 34
LIGHT CURE CIPP
By NASSCO Pipe Rehab Committee Chair Bill Moore, AOC
The Cured-In-Place Pipe (CIPP) process
has a track record of more than 50 years. It
has a demonstrated success record for the
trenchless rehabilitation of underground linear
infrastructure. As the name implies, the process
involves inserting a flexible liner into the pipe to
be rehabilitated, and then curing the liner inside
the pipe, resulting in a new pipe.
Most CIPP uses polyester or vinyl ester
thermosetting resins. These resins are cured by
a process known as free radical polymerization.
During this polymerization process, the
polymer is cross-linked with a reactive diluent
or monomer. This free radical polymerization
requires an initiator to start the reaction. Heat
cured systems use organic peroxides to initiate
the reaction. When heat is applied, the organic
peroxide breaks down to form free radicals
which attack the double bonds in the polymer
chains and reactive diluent, starting the reaction
process. The reactive diluent, or monomer,
creates cross links between the polymer
chains during the curing process, eventually
forming the composite matrix. For light cure
applications, the reaction is similar, but light
curing initiators are used. These initiators form
free radicals when exposed to a particular
wavelength of light.
Light curing has found an increasing presence
in the CIPP industry, and actually has a larger
market share than heat curing in Europe. Most
light cure systems use metal halide bulbs.
These bulbs supply light over a wide range of
the light spectrum with the largest amount of
energy focused in the UVA (320 to 400 nm) and
UVB (280 to 320 nm) spectrums. Different light
cure initiators react more efficiently to particular
wavelengths of light. The UV initiator package
used in the resin can therefore be optimized
to match a particular light curing system. Over
the last decade or two, a number of light cure
systems using LED lights have been introduced
to the industry. Unlike the metal halide systems,
LED lights are generally focused at a particular
wavelength on the light spectrum. The most
common systems are concentrated around
410 nm or 450 nm, which actually falls in the
blue light spectrum. Because the LED systems
only produce light at a particular wavelength,
it is even more important to have the light
Light curing has found an increasing
presence in the CIPP industry, and
actually has a larger market share than
heat curing in Europe.
34 MARCH 2022 | UCONonline.com
Underground Construction - March 2022
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Contents
Underground Construction - March 2022 - Cover1
Underground Construction - March 2022 - Cover2
Underground Construction - March 2022 - Contents
Underground Construction - March 2022 - 4
Underground Construction - March 2022 - 5
Underground Construction - March 2022 - 6
Underground Construction - March 2022 - 7
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Underground Construction - March 2022 - 9
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Underground Construction - March 2022 - Cover3
Underground Construction - March 2022 - Cover4
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