1 Aging and Hail Research of PVC Membranes Frank J. Foley, Jim ...

new sample. Another example is found in Sample 1 on Table 12. The significant levelof plasticizer loss for this sample (19.24 %) was not characteristic for this group. Thisdata point is also the lone, high data point on Graph 2.For these reasons, the authors consider hail simulation result to be indicative ratherthan definitive of a relationship between plasticizer loss and impact damage. Theseanomalies may be the result of excess “play” in one or more variables such as tensionor formula dispersion.6.0 CONCLUSIONS1. The older a PVC membrane, the more vulnerable the membrane to impactdamage. While this is true of all roof membranes eroding or becoming morerigid, with exposed PVC membranes, this vulnerability is a particular concern.2. Not all PVC membranes are of the same quality. The data on plasticizer lossand impact resistance demonstrates one of the four manufacturers provides asuperior product to the U.S. low-slope roofing market.3. The data suggests an initial higher content of plasticizer provides a better startingpoint than a lower level. What content of monomeric plasticizer is appropriate fora PVC membrane to be sold in hail states? The data suggests less than 32%would be reason for concern depending upon the quality, type, and stability of theplasticizing agent(s). More significantly, the data suggests beginning a servicelife below 32% plasticizer content with instable plasticizers invites impactvulnerability. The data also suggests that plasticizer levels below 28% innominal 50 mil (1.2 mm) membrane would be a concern in hail-prone locations ofthe central United States.7.0 RECOMMENDATIONS1. On behalf of building owners in the central United States, the roofing industryneeds focused research into hail protection of all classes of roofing systemsachieving the level of expertise and consensus now taken for granted for windengineering.2. Building owners in hail-prone states should demand suppliers, regardless ofclass of roof system, provide warranty coverage against small hail, 1-1/2-inch (38mm) or less. Conventional PVC roofs in hail-prone locations must be monitoredfor degradation. This monitoring should be a timely measurement of reducedthickness, increased durometer hardness, rising specific gravity and/or plasticizerextraction analysis. Samples and lot numbers of new membranes should be filedin contract documents, providing a “benchmark” for degradation measurement.3. PVC membrane manufacturers have a market opportunity in definingspecifications and warranties reflecting hail engineering. Thicker membranes, 60mils (1.5 mm) and greater, may provide increased impact resistance. It stands to24