Technical Data Sheet
RHOPLEX™ EC-1791
100% Acrylic Latex Polymer
Introduction
RHOPLEX™ EC-1791 is an all-acrylic latex polymer developed specifically to help improve
wet and dry adhesion to spray polyurethane foam (SPF) and other substrates for protective elastomeric
roof coatings. RHOPLEX™ EC-1791 provides excellent durability and dirt pickup resistance, helping
to reduce the darkening of light-colored roof coatings over time for long-term energy efficiency.
Advantages
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Excellent exterior durability
UV light resistance
Low-temperature flexibility down to -15°F
Dirt pickup resistance
Excellent adhesion to SPF and many other construction substrates
High solar reflectivity, which reduces roof surface temperatures, helping prolong roof life and
reduce energy costs
Tensile strength and elongation
Easy application by spray, brush or roller, resulting in low installation costs
Low toxicity and odor
Simple cleanup with water
Typical Physical Properties
These properties are typical but should not be considered specifications.
Solids content, %
54.5-55.5
pH
9.0-9.6
Brookfield viscosity, cPs, max.
140
Density, wet, lbs/gal
8.7
Glass transition temperature -40.0
(Tg), onset, °C
Minimum film formation temperature 0.0 (MFFT), °C
Storage stability
Protect from freezing
Performance
Properties
RHOPLEX™ EC-1791 latex was developed in 1979 specifically for exceptional wet and dry adhesion to low- and high-density polyurethane foam. Coatings based on RHOPLEX™ EC-1791 also
exhibit excellent adhesion to a variety of other construction and roofing substrates.
Durability
Since the advent of Plexiglas acrylic plastic sheet (trademark of Arkema, Inc.) during World War II,
acrylics have been known for their exceptional durability, offering unequaled resistance to degradation by sunlight and moisture. It was the UV resistance of acrylic polymer – the lack of which is the
major cause of failure in conventional roofing systems – that first led manufacturers to consider
acrylic polymers for elastomeric roof coatings. RHOPLEX™ EC-1791 technology is one example
of acrylic polymers having been tailored specifically for elastomeric roof applications.
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®™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow
RHOPLEX™ EC-1791 / Dow Construction Chemicals
July 2010
Low-temperature Flexibility
Coatings for dimensionally unstable roofing substrates must have long-term, low-temperature
flexibility. This is necessary to accommodate thermal expansion and contraction of the substrate,
so that coatings will not fail over an extended period of time or with extreme weather conditions.
It should be remembered that the effects of extreme weather conditions are not restricted to cold
climates. Water contact after a sudden thunderstorm on a hot day in any geographic location can
rapidly drop the roof temperature as much as 100°F, causing severe thermal stress to the roof
surface.
Formulations based on RHOPLEX™ EC-1791 technology can withstand a 180° flexibility bend at
-15°F without cracking. Since there is no plasticizer to migrate from the system, good flexibility is
retained over time. Long-term resistance to cracking can extend the life of the roof.
It is important to note that elastomeric roof coatings should exhibit good mechanical properties at
room and low temperatures before and after exterior exposure.
Tensile Strength and Elongation
Thermal movement of a roof requires high tensile strength and elongation. The tolerance for movement of these coatings is essential due to the dynamic nature of roofing substrates that expand
and contract due to climatic and weather conditions, and the shifting and settling of the foundation.
These properties also give properly formulated elastomeric roof coatings the needed flexibility and
elasticity to withstand impact from foot traffic and other abuse without rupturing.
Dirt Pickup Resistance
Polymers designed for elastomeric roof coatings combine the inherent flexibility of pliable, low
Tg polymers with long-term resistance to dirt pickup. Without dirt pickup resistance, roof coatings would quickly darken with age. Because dark materials tend to absorb heat, dirt pickup can
significantly increase roof surface temperatures, which in turn increases interior temperatures and
energy costs. RHOPLEX™ EC-1791 based coatings, however, resist dirt pickup and retain their
white, reflective appearance.
Test roofs have shown that after 5 years of exposure, the surface temperature of the RHOPLEX™
EC-1791 based acrylic coating was 35°F cooler than that of a conventional caulk polymer coating
and 85°F cooler than a black uncoated roof.
Substrate Adhesion
Although designed specifically for superior wet and dry adhesion to high- and low-density polyurethane foam, elastomeric roof coatings properly formulated with RHOPLEX™ EC-1791 latex
polymer exhibit excellent adhesion to other typical roofing substrates. It should be noted, however,
that significant departure from recommended formulations, especially use of other wetting agents
or water-sensitive components, may adversely affect the wet adhesion.
Pigments and Extenders
RHOPLEX™ EC-1791 emulsions offer wide formulation latitude in the selection of pigments
and extenders.
Please review the suggested starting point formulations for RHOPLEX™ EC-1791, published
separately.
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®™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow
RHOPLEX™ EC-1791 / Dow Construction Chemicals
July 2010
Dirt Pickup Resistance and Low-temperature Flexibility
The combination of dirt pickup resistance and low-temperature flexibility is a distinct characteristic of
formulations based on RHOPLEX™ EC acrylic polymers. Surfaces coated with these formulations
retain their initial white, reflective color, thereby decreasing the exterior surface temperature of
the roof and further reducing interior building temperatures. This could mean a savings in
air conditioning costs.
Low-temperature flexibility is necessary for roof coatings because they must accommodate the
thermal expansion and contraction of the roofing substrate. In addition, they must resist the impact
of hailstones prevalent in most climates. Standard formulations based on RHOPLEX™
EC-1791 can be bent 180° over a 1/8" mandrel at -15°F without breaking or cracking.
Product Specifications
Appearance
Solids content, %
pH Brookfield viscosity at 25°C, mPa•s
LV #2 spindle, 60 rpm
Gel particle on 150 micron, ppm
Gel particle on 45 micron, ppm
Specification date: October 4, 2006
Milky white fluid, free of coagulated gum and visible impurity
54.5-55.5
9.0-9.6
25-200 CPO
Formulation
Guidelines
Contact your local Dow representative for suggested starting point formulations and related information.
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®™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow
RHOPLEX™ EC-1791 / Dow Construction Chemicals
July 2010
Product
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environment in which we live. This concern is the basis for our product stewardship philosophy
by which we assess the safety, health and environmental information on our products and
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success of our product stewardship program rests with each and every individual involved with
Dow products – from the initial concept and research to manufacture, use, sale, disposal and
recycle of each product.
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their applications of Dow products from the standpoint of human health and environmental
quality to ensure that Dow products are not used in ways for which they are not intended or
tested. Dow personnel are available to answer your questions and to provide reasonable
technical support. Dow product literature, including safety data sheets, should be consulted
prior to use of Dow products. Current safety data sheets are available from Dow.
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NOTICE: No freedom from infringement of any patent owned by Dow or others is to be
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and may change with time, the Customer is responsible for determining whether products and
the information in this document are appropriate for the Customer’s use and for ensuring that
the Customer’s workplace and disposal practices are in compliance with applicable laws and
other governmental enactments. The product shown in this literature may not be available for
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have been approved for use in all countries. Dow assumes no obligation or liability for the
information in this document. References to “Dow” or the “Company” mean the Dow legal
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The Dow Chemical Company
www.dowconstructionchemicals.com
215-592-3000
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®™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow
RHOPLEX™ EC-1791 / Dow Construction Chemicals
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July 2010