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ASTM D4434 Standard for
Poly (Vinyl Chloride) Sheet Roofing
The American Society for Testing and Materials (ASTM) D4434 Standard, originally published in 1985, was the result of a due process procedure that produced a consensus among roofing industry professionals. The development of the document came at a time when PVC membranes as roof coverings were just beginning to recover from early failures in the 1960's.
Even though PVC Roofing Membranes were successfully re-introduced to the market in the late 1970's, uncertainty with regard to their "in-place" performance prompted the following note, or more appropriately "warning" in the 1981 edition of the NRCA Roofing & Waterproofing Manual.
Note: The roof membrane systems described in this section of the manual are relatively new in the United States marketplace and, as a group, have not undergone rigorous field performance tests over a period of time as have more "conventional" roof membrane systems. Most of these systems are undergoing some developmental changes. They are included in this manual FOR INFORMATION PURPOSES ONLY. Prior to installing these systems, users are urged to become fully knowledgeable of and carefully follow manufacturer's current specifications.
The adoption of the D4434 Standard provided the industry with a set of "values to ensure minimum quality" as they would relate to the characterization of a good PVC roofing membrane. On the other hand, the current version of the standard states that "In-place roof system design criteria such as fire resistance, material compatibility, wind uplift resistance, in-situ shrinkage, among others, are factors which must be considered but are beyond the scope of this material specification."
The D4434 slowly became the "Standard" by which all thermoplastic membranes would be characterized. However, Seaman Corporation has always taken exception to the standard as it relates to FiberTite® Roofing Systems. In fact, in-place roof system design criteria combined with an acute understanding of the factors that lead to the early failures of PVC roofing membranes directed Seaman Corporation's approach to the development of FiberTite Roofing Systems.
Section 4.1 of ASTM D4434-96 defines the applicable material as follows: The sheet shall consist of poly (vinyl chloride) resin in amounts greater than 50% of the total polymer content suitably compounded with plasticizers, stabilizers, fillers, pigments, and other ingredients to satisfy the physical property requirements and accelerated durability tests.
Seaman Corporation's FiberTite Membrane(s) are formulated in a manner contrary to the D4434 definition. In fact, FiberTite, which has a polymer structure based upon DuPont's Elvaloy Ketone Ethylene Ester (KEE) polymer, differs significantly in formulation from membranes based upon PVC.
FiberTite's Ethylene Inter-Polymer (EIP) coating begins with Elvaloy KEE, a solid, high molecular weight, flexible, thermoplastic polymer. PVC is added to impart certain properties beneficial in single-ply roofing like additional strength and flame retardancy. Elvaloy and PVC are completely miscible and become a single phase polymer when mixed. Both polymers are high in molecular weight and cannot migrate away from each other after being alloyed together.
PVC membranes characterized by the D4434 Standard begin with a high molecular weight PVC resin, but they are made flexible with low molecular weight liquid plasticizers. Therefore, PVC roofing membranes are significantly different from FiberTite in that PVC is the only high molecular weight polymer in the system. Since flexibility is created by adding a low molecular weight liquid plasticizer, the low molecular weight plasticizer can migrate out of the PVC membrane promoting in-situ shrinkage and an embrittled membrane.
To further differentiate between typical liquid plasticized PVC roofing membranes and those based upon KEE, Seaman Corporation has been at the forefront of an effort to develop an ASTM Standard for KEE based Single-Ply Roofing Membranes. The standard should receive consensus among the ASTM D08 Subcommittee Members this summer. The following are a couple notable excerpts from the most recent draft of the proposed KEE Standard.
3.3 Polymer Content: In this specification, polymer content shall be defined as polymeric materials which are in the solid state at room temperature, and are high (greater than 50,000) in molecular weight. Other ingredients, known to the art of polymer compounding, such as certain waxes, stabilizers, and other additives, while polymeric in nature are not considered to be part of the base polymer system.
4.1 The sheet shall be formulated from the appropriate polymers and other compounding ingredients. The KEE polymer shall be a minimum of 50% by weight of the polymer content of the sheet.
Apart from the significant difference in polymer structure, FiberTite meets or exceeds 75% of the physical property requirements characterizing Type III PVC membranes. The properties that FiberTite comes in conflict with are more of a reflection of the polymer difference than any physical shortfall. The most significant conflict is the minimum thickness requirements for PVC membranes. Thickness can be relevant in the characterization of "liquid plasticized" PVC membranes but only if it provides an appreciable advantage.
The D4434 Standard specifies a minimum thickness of 0.045 inches but many manufacturers have gone way beyond the minimum and are aggressively promoting 0.050, 0.060 and 0.080 inch thick membranes. Nevertheless, the 10%, 25% or 30% increase in thickness over the standard's minimum values rarely contribute to a proportional increase in the overall physical properties of the sheets. Depending upon the internal reinforcements, the only real contribution provided by increased thickness is puncture resistance, but puncture is rarely a major factor in the premature failures typically associated with PVC membranes. Loss of membrane flexibility due to plasticizer loss has been and will continue to be the principle factor affecting in-situ performance of PVC roofing systems.
The tenure and liabilities associated with commercial roofing warranties have increased over the past ten years. Is it just a coincidence that PVC membranes have also been increasing in thickness during this time period? The ASTM D4434 actually provides the answer when it defines the design service life of the membrane sheets.
"Design service life is defined as the designated time period of intended system performance."
By increasing the mass or thickness of liquid plasticized PVC membranes, in-situ performance is extended because it's going to take longer for the environmental elements to extract the mechanism that gives the products their flexibility.
There are a few additional tests and property limits proposed for the KEE Standard that not only characterize minimum values for KEE Membranes but should be considered essential to the overall performance of roofing membranes. Adhesion of the coating to the reinforcement, hydrostatic resistance, fungus resistance and abrasion all contribute to the "design service life" of single-ply roofing systems but are conspicuously absent in the D4434 Standard Specification for Poly (Vinyl Chloride) Sheet Roofing.
The permanence of the polymer structure within the FiberTite EIP coating, the inability to separate the coating from the base fabric, superior resistance to chemical and micro-biological attack are all factors that contributed to FiberTite's in-situ performance over the last eighteen years. Today, FiberTite is manufactured to a nominal 0.036 inch thickness and in 1981 it was also manufactured to a nominal 0.036 inch thickness. This isn't a coincidence; Seaman Corporation began with the end in mind. Therefore, FiberTite was designed to be the most balanced single-ply membrane available and provide real customer value through extended service life.
It's ironic that Seaman Corporation has FiberTite Roofing Systems in-place, doing what they were designed to do, that are older than the ASTM D4434 Standard. However, the D4434 continues to carry more weight by proxy toward the characterization of a good single-ply membrane than the historical record.
The attached tables will assist in evaluating the tests and property limits for the ASTM D4434 Standard, the proposed KEE Standard and FiberTite's relative characteristics. However, if you want to see the proof and develop a real empirical knowledge for single-ply performance, please contact your local FiberTite Representative.
| Property | D 4434 Spec. |
KEE Spec. | FiberTite Spec. |
| Thickness, min, in. / D 751 | 0.045 | 0.031 | 0.031 |
| Thickness over Fiber, min, in. ASTM ANNEX / Optical Method |
na | 0.006 | 0.01 |
| Breaking Strength, min, lbf / D 751 Grab | 200 | 400 | 400 |
| Elongation at break, min, % / D 751 | 15 / 15 | 15 / 15 | 15 / 15 |
| Seam Strength, min, % of breaking strength / D 751 | 75 | 80 | 100 |
| Tearing Strength, min, lbf / D 751 Tongue Tear | 45 | 75 | 75 |
| Heat Aging | |||
| D 3045 176°F for 56 days | X | na | na |
| or 185°F for 28 days | X | na | na |
| or 158°F for 28 days | na | X | X |
| Retention of properties after heat aging: | |||
| Breaking strength, min % original | 90 | 90 | 90 |
| Elongation, min % of original | 90 | 80 | 90 |
| Low temperature bend / D 2136 | |||
| at -40°F | pass | na | na |
| at -30°F | na | pass | pass |
| Change in weight after exposure in water, max % / D 471 one side exposure |
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| 158°F for 166 h. | na | +/-5 | +/-5 |
| Change in weight after immersion | |||
| in water, max % / D 570 except -158°F for 168 h. | +/-3 | na | na |
| Accelerated weathering test: (5,000 h.) | |||
| G 26 Xenon Arc Cracking or crazing (7x magnification) |
none | none | none |
| G 53 Fluorescent UVA Cracking or crazing (7x magnification) |
none | none | none |
| Linear dimensional change, max % | |||
| D 1204 176°F for 6 h. | 0.5 | na | na |
| 212°F for 1 h. | na | 1.0 | 0.5 |
| Static puncture resistance | |||
| D 5602 33 lbf | pass | pass | pass |
| Dynamic puncture resistance | |||
| D 5635 20 J | pass | na | na |
| 10 J | pass | pass | pass |
| Fabric Adhesion, min, lbf / D 751 12in./min jaw speed | na | 15 | cannot peel |
| Fungi resistance G 21, 28 days | |||
| Sustained growth | na | no growth | no growth |
| Discoloration | na | no growth | no growth |
| Abrasion test, min cycles | na | 1500 | 1500 |
| Hydrostatic resistance, min psi | |||
| D 751 Method A | na | 500 | 500 |
