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34 JULY 2016 COATINGSPROMAG.COM Science Behind It Dex-O-Tex Vapor Control Primer 200 By John A. Nutt, Eastern Technical Director for Dex-O-Tex Division of Crossfield Products Corp. C oating the new foor at Nut Up Industries' state- of-the-art facility meant working with a smart coating system that would help with moisture mitigation. Because the project was on new concrete, the Concrete by Hallack coating crew started the system with a vapor-controlled primer from Dex-O-Tex. Tis product was designed to bond to the concrete substrate and avoid delamination. Addressing the Issues Vapor Control Primer 200 is a two-part epoxy consisting of a bisphenol A epoxy resin and a polyamide curing agent. Bisphenol A epoxy is the most widely used resin in the foor- ing industry. In fact, most epoxy materials available in big box stores (Home Depot, Lowes, etc.) consist of bisphenol A resin. Te other side — the polyamide curing agents — are also widely used and are known for their superior bond strength and toughness. Epoxies are often used for industrial foors, mainly because of the ability to create decorative looks not known with cement-based products; however, manufacturers and installers are aware of a delamination issue due to moisture vapor transmission (MV T). For the coating system to be successful, it needed to be developed specifcally to mitigate those issues; the two main functions required for success were deeper penetration into the concrete substrate and a more tenacious bond to that substrate. Physical Properties Vapor Control Pr imer 200 was developed to have a higher than nor ma l compressive streng th, toughness, and per me - abi lit y to achieve a tenacious bond w ith the concrete. T he compressive streng th of the pr imer was deter mined by per for ming A STM D695 Standard Test Method for Compressive Proper ties of R ig id Plastics. T he bond streng th was deter mined per A STM D4541 Standard Test Method for Pu l l- Of f Streng th of Coatings Using Por table Ad hesion Testers. Ty pica l ly, pr imers do not require high compressive streng th; however, because the goa l of a tenacious bond was a pr ior it y, the goa l for this pr imer dur ing its develop - ment was in the 10,000 pounds (4,535.9 kg ) per 1 square inch (0.0006 m²) range. For bond streng th, instead of the average 100 percent concrete fai lure at 400 psi (2,757.9 kPa), Dex- O -Tex looked instead at the depth of the concrete fai lure. After months of testing and evaluation, the result, Vapor Control Primer 200, has a compressive strength of 12,000 psi (82.7 MPa) and adhesion testing showing double the normal concrete residue at failure. Tis means that the 100 percent solids primer penetrates deep into the concrete's voids, fastening onto the material and increasing the strength of the concrete. Additionally, by creating a film over the still-curing concrete, any coatings applied on top of the vapor barrier (in this case, the Quick Glaze) are protected from possible water evaporating from the concrete. Vapor Control Primer 200 was developed to w ithstand moisture vapor emission rates (MVER) of 10 pounds (4.5 kg ) per 1,000 square feet (92.9 m²) per 24 hours. T hat was determined using perme- ability testing as outlined under ASTM E96 Standard Test Methods for Water Vapor Transmission of Materials. T hat testing showed a perm rating of 0.158, which gave a product that Dex- O -Tex felt comfortable w ith. System Backed Based on g reater compressive, bond streng th, and per me - abi lit y rating , Dex- O -Tex ( by Crossf ield Products Cor p.) was conf ident in of fer ing a war rantee that not only covered our mater ia ls, but a l l mater ia ls applied over our system. CP