Elastomeric Roof Coatings
Performance Comparison of Rinseable Primer RP-1 and RP-2
While Rinseable Primer RP-1 has been successfully used for many years as a pretreatment for black EPDM roofing prior to the
application of an elastomeric roof coating, Dow Construction Chemicals has also designed Rinseable Primer RP-2 as a solution
with lower pH levels. This document provides an overview of Rinseable Primer RP-2 and compares performance of the two
products, especially regarding adhesion.
Adhesion Performance
Rinseable Primer RP-2 is the second generation product in our Rinseable Primer line. This product was originally developed to
offer the performance of Rinseable Primer RP-1, but without the high pH. As you can see in the table below, Rinseable Primer
RP-2 offers a similar enhancement to the EPDM adhesion of certain Rhoplex™ EC acrylic-based coatings.
Environmental Health and Safety Information
Rinseable Primer RP-2 provides similar adhesion performance to RP-1. In addition, Rinseable Primer RP-2 is not classified as
corrosive according to the U.S. Department of Transportation (DOT) regulations. This means that no special DOT corrosive
markings are needed on the finished product. Rinseable Primer RP-2 is APEO-free and is supplied at a neutral pH, making it easier
for roofing contractors to handle and to comply with upcoming international regulations.
New EPDM
Aged EPDM
Water
RP-1
RP-2
Water
RP-1
RP-2
Dry Adhesion
0.6 A
0.9 A
0.9 A
Dry Adhesion
1.4 A
2.7 F
2.9 F
Wet Adhesion
0.8 A
1.5 F/A
1.7 F/A
Wet Adhesion
0.8 A
1.4 F
1.5 F/A
A=Adhesive failure; F=Fabric delamination
These results were taken from a sales service project that involved Rinseable Primer RP-1 and RP-2.
The aged EPDM used in this study was exposed for a minimum of 1 year prior to testing.
Look and Feel
End users may notice minimal qualitative differences between Rinseable Primer RP-1 and RP-2. Two differences often mentioned
are a color difference between the two products and a slight difference in the look of the treated EPDM. Rinseable Primer RP-2
is typically a light purple color, whereas RP-1 has historically been pale pink. Also, the treated EPDM may have a slight gray
appearance when treated with RP-2 compared to jet black when treated with RP-1. Neither of these qualitative differences will
impact performance.
TECHNICAL BULLETIN
TECHNICAL PAPER: CASE STUDY I 1
may look slightly greyer when treated with the RP-2 compared to a more jet black when treated
with RP-1. Neither of these qualitative difference will have an impact on performance.
Performance Consistent with RP-1
Besides the qualitative issues mentioned above, RP-2 delivers the same consistent
Performance
Consistent
with
performance that contractors
have
comeRP-1
to expect from the Rinseable Primer line. Both RP-1
Besides
the
qualitative
issues
mentioned
previously,
Rinseable
Primer
RP-2with
delivers
the success.
same consistent
performance
and RP-2 have been used for several years over
black
EPDM
great
As with
RP-1,
that contractors have come to expect from the Rinseable Primer line. Both RP-1 and RP-2 have been used for several
RP-2 should only be used with coatings based on Rhoplex EC-1791 and formulated in a high
years over black EPDM with great success. As with RP-1, RP-2 should only be used with coatings based on Rhoplex™
quality formulation. The proprietary technology used in Rinseable Primer RP-2 acts in a “lock
EC-1791, RHOPLEX EC-3000 or RHOPLEX EC-3100 acrylic polymers and formulated in a high quality formulation. The
and key” technology
fashion with
toPrimer
provide
adhesion
on black
proprietary
usedEC-1791
in Rinseable
RP-2dramatically
acts in a “lock increased
and key” fashion
with these
acrylicEPDM
polymers to
roofing.
provide dramatically increased adhesion on black EPDM roofing.
with RP-1
AdhesionAdhesion
with RP-1
Adhesion with RP-2
Adhesion
with RP-2
Photos taken from an exposure series on Building 48 at Spring House Technical Center (Spring House, PA.)
*Photos taken from an exposure series on building 48 at Spring House Technical Center.
Basic Technical Details
Basic
Technical
Details
•
Designed
to increase
the adhesion of Rhoplex™ EC acrylic-based coatings to black EPDM roofing systems
•
Designed
to
increase
the adhesion
EC-1791
coatings to black
• Used as a wash primer that is applied,
allowedof
to Rhoplex
set for 15 minutes,
andbased
then power-washed
off EPDM
roofing
systems
the roof prior to coating application
• Application
ratesquare
is 500
square
feet per gallon
• Application
rate is 500
feet
per gallon
• Density
is 8.46
pounds
per gallon
• Density
is between
8.3 and
8.6 lb/gal
•
pH
is
typically
between
6 and 7
• pH is between 6 and 6.8
• Used
as a wash
primer
which is applied, allowed to set for 15 minutes, and then
• Typically
supplied
in 55 gallon
drums
powerwashed
off
the
roof
the application of the coating.
• No additional formulation necessary prior
(ready to
to use)
•
Typically supplied in 55 gallon drums
Finding Out More
If you are interested in a sample of Rinseable Primer RP-2 or have pricing and supply
questions, please contact your local account manger.
Want to Learn More? Start Here.
DowConstructionChemicals.com
RHOPLEX is a registered trademarks of the Rohm and Haas Company or of its subsidiaries or affiliates and are intended to designate goods
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The information contained herein is offered in good faith, but without guarantee or warranty, as analytical conditions and methods of use of the
materials described herein may vary. The data and assessments contained herein are based on information we believe to be reliable and accurate,
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