History of EPDM (Ethylene-Propylene-Diene-Monomer)
There are very many different types of EPDM roofing materials in the market today. Some of the most common materials include; shingles, metal decking, single ply systems, built-up systems, double and single component liquid coatings. Each roofing materials have its own performance function and cost that makes it unique. Some materials are sophisticated and high-tech and expensive while others are less sophisticated and low-tech thus and obviously more affordable i.e. asphalt shingles. Expensive high tech and sophisticated roofing materials require skill to install. They also last longer than low tech roofing materials.
Regardless of the roofing materials you choose to install, there is still a probability that some failures will occur resulting in leaks. These failures are usually caused by factors such as material failure, improper installation, roof penetrations that aren't adequately sealed and so on. Some thermoplastics and single ply roofing membranes i.e. Hypalon and SHEET EPDM rubber were believed to offer permanent solutions to leaking roofs however this hasn't been the case over the past few decades. These membrane systems haven't performed as expected as most of them last depending on the quality of their seam seals which are bonded using adhesives or heat when using thermoplastics.
Both seam seal methods demand clean contact surfaces and matching dimensions to avoid wrinkles. Some roofs for example sloped roofs can last with imperfect seam seals however flat roofs which develop ponding water can't handle imperfect seam seals. Other common factors that contribute to roofs developing leaks include; number of joints and number of seams.
Liquid Elastomeric Coatings and EPDM Rubber Coatings exist to repair leaks thus extending the life of roofs. These products are among the 4 generic types of coatings for ambient cure:
Single Ply Membranes
Hypalon synthetic rubbers and EPDM were first introduced into the United States between 1955 and 1965. Hypalon has a polymer polyethylene backbone which is inert and converted to a semi-crystalline or an amorphous polymer with elastomeric characteristics through chlorosulfonation and chlorination.
EPDM and EPDM Rubbers are made of copolymers and ethylene propylene which are all polymers. These polymers undergo compounding with fillers, plasticizers and catalysts to form sheets which are vulcanized afterwards to produce cured elastomeric membranes.
How Liquid EPDM Rubber Differs from Vulcanized EPDM
Liquid Rubber is composed of an ethylene terpolymer and propylene (a dicyclopentadiene pendant group).The backbone of Ethylene-Propylene is saturated and cross linking happens through the DCPD group. The low molecular polymer is dissolved in a solvent and then compounded with curatives and pigments which enable curing at appropriate temperature.
Liquid Rubber Cure Mechanism
Cross linking happens at ambient temperatures. The free radicals formed during peroxide decomposition are responsible for causing cross linking at DCPD sites. The rate of peroxide decomposition therefore determines the rate of curing of the system. This rate is in turn determined by the availability of oxygen and temperature. Oxygen is important for activating a catalyst responsible for promoting peroxide decomposition at low temperatures.
EPDM Liquid Rubber cure mechanism varies i.e. active to inactive. This variation is determined by temperature. Slow and faster cures over extended time periods cause identical physical properties. It is important to note that broad day and night temperature swings that are experienced during spring and fall don't compromise/affect the final EPDM Liquid Rubber membrane physical properties.
It is also important to note that there is enough substantial performance data about EPDM and EPDM rubbers accumulated over the last three decades. The polymers have proven themselves in automotive, roofing and industrial applications.
EPDM Curing Systems
The industry has for a long time been trying to come up with a cure mechanism for cross linking EPDM polymers. In 1990, one such polymer was developed and later made available commercially. This has resulted in the development and worldwide sales of Liquid rubber ( Liquid EPDM). The chemistry used in developing the liquid version is similar to the chemistry used to develop a single EPDM rubber ply sheet. The major advantages and differences are in the cure mechanism and a pendant group which is grafted on the polymer chain.
The EPDM Liquid Rubber cure mechanism is known as initiated free radical polymerization. The catalyst for this mechanism is an organic peroxide because it produces the most appropriate cured properties resulting in a longer pot life.
EPDM Liquid Rubber cured films have excellent weather ability. Also, they aren't thermoplastic which means they can be able to withstand high temperatures of up to 300° F and still remain flexible at temperatures as low as -62° F. Cured films are also resistance to polar solvents, acids and alkalis. They can also cope with total water immersion for an indefinite time period.