DUPONT™ ELVALOY® KEE POLYMER OVERVIEW
Better PVC roofing membranes
begin at the molecular level
DuPont™ Elvaloy® ketone ethylene ester (KEE) roofing resins lock in membrane flexibility
Premium-performance commercial roofing made with DuPont’s endurance-proven solids-phase
flexibilizer delivers the ease and reliability of heat-welded seams, along with long-lasting toughness,
weatherability and resistance to chemical attack.
DUPONT™ ELVALOY® KEE RESINS
Improved roofing membrane performance begins at the
molecular level
When PVC roofing membranes were first developed, they
were made flexible by adding oils or liquid plasticizers to the
PVC compound. The problem with this approach was that hot
weather caused the plasticizers to migrate to the membrane
surface where they were permanently lost. With each such
heating cycle, the membrane would become more brittle,
eventially causing it to crack (typically in winter), as it expanded
and contracted with the temperature cycling.
Solid, high-molecular-weight DuPont™ Elvaloy® KEE
resins help manufacturers create roofing membranes
that stay supple with age, because there are no liquid
plasticizers to migrate out..
The proof is in the roof
• Easy heat-welded seams deliver the added
weather protection of a monolithic rooftop
membrane
• Decades-long flexibility, for easy future tie-ins
and repairs
• Proven, reliable compounding with PVC and
performance-enhancing additives
• White or light colors reflect light and reduce
heat buildup, helping cut energy consumption
To address the problem, DuPont scientists developed a process
that eliminated the need for liquid plasticizers. They found
that PVC membrane flexibility and impact resistance could
be “locked in” by changing to a solid, flexible high-molecular
weight interpolymer during membrane manufacturing. Today,
the roofing industry knows this material as DuPont™ Elvaloy®
KEE. It’s a unique ethylene terpolymer tailored to specific
performance needs during polymerization. The resin grades
most often used in roofing membranes are profiled in Table
1. As the data indicate, these are soft, flexible polymers with
elastomer-like properties and convenient melting points for
thermoplastic processing.
Suppleness and strength to extend membrane life
When extruded or calendered into a sheet, a compound with
DuPont™ Elvaloy® KEE is both flexible and exceptionally tough.
(The terpolymer manufacturing technology is closely related to
that used by DuPont to make Surlyn®, the tough cover material
found on many of the world’s finest golf balls). Elvaloy® KEE
is also highly resistant to chemicals, which can be important
for roofing exposed to vent exhausts, air pollutants or acid rain.
This inherent toughness, chemical resistance and flexibility
combine to help roofing membranes last longer.
• Roofing resists chemical attack
• A premium performer when roofing or reroofing
Because Elvaloy® KEE is both solid and flexible, there are no
liquid plasticizers to migrate out during hot weather, so the
membrane retains its flexibility even in the hottest regions,
where roofing membranes are put to the test. And since the
flexibility is permanent, membranes based on Elvaloy® KEE
offer the advantage of easy workability in cold temperatures,
an important consideration for many contractors. Elvaloy® KEE
has been so effective in roofing applications, that engineers
have developed and recognize an ASTM test standard (D-6754)
to assure membranes contain KEE … a standard that literally
redefines expectations for roofing membrane performance.
PROVEN PERFORMANCE IN SINGLE-PLY ROOFING MEMBRANES
Easier installations, seaming and repairs
Inseparable membrane components
Elvaloy® KEE alone will melt at 140°F (60°C), a temperature
too low for most stand-alone plastics applications. However,
this characteristic offers an advantage when Elvaloy® KEE is
combined with another plastic such as PVC: it facilitates the
thermoplastic welding process. When a membrane based on
Elvaloy® KEE is welded, the seam becomes a monolithic layer
that is absolutely weather-tight. The material fuses to itself in a
totally integrated bond that won’t come apart.
Elvaloy® KEE has a natural ability to melt and bind with many
different polymers and secondary materials. This is important
to roofing membrane manufacturers as they consider how
all ingredients in the compound will interact, whether a UV
stabilizer, whitening agent, or biocide. With Elvaloy® KEE as
the “flexibilizer” and binding agent, the manufacturer is better
assured that all the ingredients will work in harmony, without
separation or breakdown. The roofing membrane’s long-term
performance is “locked in.”
Experienced contractors recognize the importance of skilled
crews, efficient installations and reliable product performance
to keep profitability high. Installing membranes based on
Elvaloy® KEE goes faster due to the easier seaming, and there
are fewer costly site revisits needed to correct problems.
Single ply membranes based on Elvaloy® KEE are also thin and
lightweight, yet with all the durability manufacturers require for
commercial performance. Inherently high in viscosity, the solid
flexibilizer gives more melt strength to the extruded compound
making it easier to calender and reinforce. Membranes based
on Elvaloy® KEE have greater strength per unit of thickness,
too, eliminating the need for thick, multi-ply construction.
Lighter weight also means easier installations with less lifting
effort, and less installed weight on the rooftop.
Energy-efficient white roofing
Energy issues are growing in importance in the selection of
all building materials, and roofing is no exception. Factoring in
overall energy performance as part of system’s life-cycle cost,
many customers and contractors are insisting on “white” as
the color of choice in roofing.
The exceptional light and heat reflective properties of a white
membrane can reduce a building’s internal cooling costs
dramatically. In urban areas, white roofing can also help
mitigate the “heat island” effect, helping reduce outdoor
ambient temperatures. Urban heat islands are often 6 to 8
degrees hotter than nearby rural areas due to the concentration
of black rooftops, paved surfaces and dark masonry surfaces.
Light-reflective roofing based on Elvaloy® KEE can be part of a
community’s effort to reduce ambient heat buildup.
Table 1. Typical physical properties
for roofing grades of DuPont™ Elvaloy® KEE
PROPERTY
TEST METHOD
TYPICAL REPORTED VALUE (a)
ELVALOY® 741
ELVALOY® 742
ELVALOY® HP661
>300,000
>250,000
>300,000
Molecular weight
See note (b)
Density(g/cm3)
ASTM D792
1.00
1.02
0.96
Tensile strength, MPa (psi)
ASTM D1708
6.60 (957)
4.14 (600)
4.44 (644)
415
466
342
(rate 20 in./min.)
Elongation at break, %
ASTM D1708
(rate 20 in./min.)
Hardness, Shore A
ASTM D2240
70
55
69
Glass transition temp., °C (°F)
ASTM D3418
-32 (-25)
-32 (-25)
-54 (-65)
Crystalline melting temp., °C (°F)
ASTM D3418
63 (145)
56 (133)
63 (145)
Notes: (a) Data are typical and not intended as specifications; (b) Average molecular weight determined by gel permeation chromatography, source: E106239-09
DUPONT™ ELVALOY® KEE ROOFING RESINS
Contributes to low-smoke safety engineering
With today’s tougher fire codes, flame and smoke resistance
must be considered in the selection of all building materials.
In commercial buildings, some of the most restrictive fire
codes have been targeted at the plenum area, that air space
immediately above ceilings where computer cabling and
other device wiring is routed between connection points. To
meet today’s rigorous plenum area fire codes, a number of
cable manufacturers have turned to Elvaloy® KEE as the PVC
flexibilizer of choice to reduce smoke potential while keeping
the cable insulation flexible.
As architects and engineers consider further ways to reduce
flame and smoke risk, all building materials are coming under
review. Roofing and other waterproofing membranes based on
Elvaloy® KEE offer a distinct advantage because they reduce
the use of easily ignited liquid plasticizers which produce black,
oily smoke.
White, energy-efficient roofing membranes made with
DuPont™ Elvaloy® KEE offer long service, easy installation
and upkeep, and low lifetime ownership costs.
Available from leading membrane manufacturers
PVC roofing membranes based on Elvaloy® KEE bring together
attributes desired by quality-oriented contractors and building
owners: toughness and flexibility in a thin profile; easy
installation and repair; reduced smoke hazard; long-lasting
resistance to pollutants, aging and brittleness; and the potential
energy-savings of cool white roofing. Factor these benefits
into your next roofing decision. Ask your contractor or system
supplier to give you a choice based on DuPont™ Elvaloy®
KEE, available from leading roofing system manufacturers
worldwide.
The data listed here fall within the normal range of properties, but they should not be used
to establish specification limits nor used alone as the basis of design. The DuPont Company
assumes no obligations or liability for any advice furnished or for any results obtained with
respect to this information. All such advice is given and accepted at the buyer’s risk. The
disclosure of information herein is not a licence to operate under, or a recommendation to
infringe, any patent of DuPont or others. Since DuPont cannot anticipate all variations in actual
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Copyright © 2010 E.I. du Pont de Nemours and Company. All rights reserved.
K-23607_1 (2010/08)