SpecTopics: PVC Type III and Type IV ASTM D4434 Standards
- Type I is no longer used, and no manufacturer currently produces a Type I membrane product.
- Type II usually includes fiberglass reinforcement; however, that reinforcement is not used for improving its performance in elongation or tensile strength, it is used for dimensional stability of the membrane. Membrane minimum thickness is 45 mils.
- Type III products are internally reinforced and may include a fabric backing. Membrane minimum thickness is 45 mils.
- Type IV products are internally reinforced and may include a fabric backing. Membrane minimum thickness is 36 mils.
Minimum Membrane Properties | Type III | Type IV | % Increase |
Breaking Strength (lbf/in) | 200 | 275 | 38% |
Elongation (min %) | 15 | 25 | 66% |
Tensile Strength (lbf) | 45 | 90 | 100% |
Even though the minimum membrane thickness of the Type IV category is only 36 mils, its performance requirements are higher than those of Type III membranes, which are 4 mils thicker. Choosing a Type IV membrane means superior PVC membrane performance. As the thickness of the membrane increases, the qualities of breaking and tearing strength similarly rise, resulting in a product with enhanced performance.
For further information on PVC and KEE HP membranes, consult the Carlisle SynTec website.
For more information on Type III versus Type IV, consult the Sure-Flex PVC Type III vs. Type IV Sell Sheet.
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