1 Aging and Hail Research of PVC Membranes Frank J. Foley, Jim ...
1 Aging and Hail Research of PVC Membranes Frank J. Foley, Jim ...
1 Aging and Hail Research of PVC Membranes Frank J. Foley, Jim ...
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A complete absence <strong>of</strong> answers to questions from many membrane suppliers promptedthis study in the spring <strong>of</strong> 2000. Manufacturers were asked to supply empirical dataavailable regarding the aging <strong>of</strong> ro<strong>of</strong> membrane products <strong>and</strong> the product's hailvulnerability. In other words, should an owner in a hail-prone location plan for a ro<strong>of</strong>replacement at a certain age, or at a certain measure <strong>of</strong> membrane degradation, eventhough the ro<strong>of</strong> system it is still performing?This research focuses on the hail performance <strong>of</strong> only one <strong>of</strong> these classes <strong>of</strong> ro<strong>of</strong>ingsystems -- reinforced, monomeric-plasticized, <strong>PVC</strong> membranes. In the mid to late1980s, the reputation <strong>and</strong> use <strong>of</strong> <strong>PVC</strong> ro<strong>of</strong> systems were negatively impacted byfrequent reports <strong>of</strong> membranes shattering across the United States. Those shatteringswere caused by the impact <strong>of</strong> cold weather contraction on aged <strong>and</strong> embrittled <strong>PVC</strong>membranes. The membranes <strong>of</strong> those reports were non-reinforced <strong>and</strong> <strong>of</strong>ten thinmembranes. Design improvements have been made to <strong>PVC</strong> membranes such as theroutine use <strong>of</strong> fabric reinforcements <strong>and</strong> increased thicknesses. These designimprovements largely restored the reputation <strong>and</strong> acceptance <strong>of</strong> conventional <strong>PVC</strong>membranes. However, the agent <strong>of</strong> destruction in those shatters remains intact -membrane embrittlement caused by plasticizer migration as a result <strong>of</strong> weathering.<strong>Hail</strong>stone impact causes most catastrophic damage to embrittled, current design <strong>PVC</strong>membranes. Owners <strong>and</strong> specifiers <strong>of</strong> <strong>PVC</strong> membranes, appreciating the benefits <strong>of</strong>this class <strong>of</strong> ro<strong>of</strong>s, need to manage against this event.Features <strong>of</strong> <strong>PVC</strong> Ro<strong>of</strong>ing <strong>Membranes</strong><strong>PVC</strong> (polyvinyl chloride) is a ubiquitous polymer. Web sites <strong>of</strong> plastic trade institutesindicate that annual North American dem<strong>and</strong> for <strong>PVC</strong> resin is 14 billion pounds (threebillion kilograms). A large percentage <strong>of</strong> this polymer is used in the constructionindustry as rigid piping, cable sheathing, cabinetry, wall covering, flooring <strong>and</strong> to a smallextent, flat ro<strong>of</strong>ing. <strong>PVC</strong> ro<strong>of</strong> membranes were introduced from Europe to the NorthAmerican low-slope ro<strong>of</strong>ing market in the 1970s. There are many successful <strong>PVC</strong>ro<strong>of</strong>ing applications in service today that are older than 15 years, a common single plywarranty period in the U.S. market.Building owners <strong>and</strong> specifiers <strong>of</strong> exposed <strong>PVC</strong> ro<strong>of</strong> systems <strong>of</strong>ten focus on thefollowing distinct benefits <strong>of</strong> <strong>PVC</strong> ro<strong>of</strong> installations:. competitive installation cost. verification <strong>of</strong> details <strong>and</strong> workmanship ease. installation may occur during very cold <strong>and</strong>/or damp conditions that would impairor prevent installations <strong>of</strong> other ro<strong>of</strong> systems. provision <strong>of</strong> inherent flame-resistant chemistry <strong>of</strong> the base polymer to the ro<strong>of</strong> <strong>of</strong>commercial buildings. across the entire ro<strong>of</strong>, if properly installed is a consistent, predictable fusion <strong>of</strong>membrane panels into a single, flexible waterpro<strong>of</strong>ing skin. ease <strong>of</strong> leak detection, ease <strong>of</strong> repair <strong>and</strong> long-term integrity <strong>of</strong> “the patch”4
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