User Guide

Plumbing Design Assistance Manual l Chapter 1 – Uponor PEX properties l 1
Chapter 1:
Uponor PEX properties
Uponor PEX properties
PEX is an acronym for
crosslinked polyethylene.
The “PE” refers to the raw
material used to make
polyethylene; the “X” refers
to the crosslinking of the
polyethylene across its
molecular chains.
The molecular chains are
linked into a three-dimensional
network that makes PEX
remarkably durable within a
wide range of temperatures
and pressures.
Currently, three methods exist
for producing PEX.
• Engel or peroxide method
(PEX-a)
• Silane method (PEX-b)
• Electron beam (e-beam) or
radiation method (PEX-c)
All three processes generate
pipe that is crosslinked to
various degrees according
to ASTM F876 and F877
standards.
Uponor manufactures Engel-
method PEX-a pipe. The
PEX industry considers this
pipe superior because the
crosslinking is done during
the manufacturing process
when the polyethylene is in
its amorphic state (above
the crystalline melting point).
Accordingly, the degree of
crosslinking reaches more
than 80%, resulting in a more
uniform product with no weak
links in the molecular chain.
PEX-a distinctions
The properties of PEX-a pipe
make it the most exible PEX
on the market. This exibility
allows the tightest bend
radius available — six times
the outside diameter of the
pipe. Its exibility also greatly
reduces instances of kinked
pipe. And in the rare instance
of a kink, the thermal memory
of PEX-a allows kink repair
with a simple shot of heat from
a heat gun.
The pipe’s shape memory
also offers the unique
opportunity for ProPEX
®
tting
connections. Shape memory
allows PEX-a to expand and
then shrink back to normal
size — creating strong,
durable and reliable tting
connections.
Finally, PEX-a pipe offers
more resistance to crack
propagation (how a crack
grows) than PEX-b or PEX-c
pipe. A crack that occurs in
PEX-a pipe is the least likely
to grow over time and cause
leaks or damage.
Stress resistance
Pipe installed in commercial
applications must be capable
of withstanding the stresses
that result from installation
within commercial buildings.
Typical stresses include:
• Expansion and contraction
that result from repeated
heating and subsequent
cooling of the heat-transfer
uid
• Mechanical abrasion,
shearing and stretching
that occurs as a result of
installation, normal structural
movement and heating
and cooling from seasonal
weather changes
Uponor PEX provides the
durability and reliability that is
needed for these applications
and currently holds the
unofcial world record for
long-term testing at elevated
temperature and pressure.
From 1973 to 2009, the pipe
was subjected to ongoing
testing at 203°F (95°C) at 175
psi by Studvik in Sweden and
BASF in Germany.
Cleanliness of
Uponor PEX
The quality materials and
exacting process used
in manufacturing Uponor
AquaPEX
®
yield remarkably
clean water-distribution piping.
Uponor PEX piping is made by
crosslinking high-density, high-
molecular weight, 100% virgin
polyethylene ake. It is subject
to the highest testing, codes,
listings and standards.
In addition to testing
and certication at NSF
International, Canadian
Standards Association (CSA)
and Underwriters Laboratories
(UL), Uponor PEX piping has
been tested and approved for
potable-water applications by
the most demanding agencies
in the world, including
DVWG-Germany, KIWA-
Netherlands, CTSB-France
and BSI-Great Britain.
Toxicity extraction testing
performed in accordance
with ANSI/NSF 61 Drinking
Water System Components —
Health Effects veries Uponor
PEX piping does not leach
potentially harmful substances
into the drinking water.
Figure 1-1: PEX-a (Engel)
80%+ crosslinked
Figure 1-2: PEX-b (Silane)
65-70% crosslinked
Figure 1-3: PEX-c (Radiation)
70-75% crosslinked