Polymeric membranes roofing

Fleece-Back Sheet. A fleece-back sheet is a nonreinforced polymeric membrane that has had a nonwoven mat made of polyester, weighing 101.7—203.4 g/m, laminated to the back of the sheet. The prime use of the fleece-back sheet is in the fully adhered roofing systems. The fleece provides the chemical separator, which eliminates the need for an adhesive that is compatible with the specific membrane or a compatible substrate. 

Data for thermal movement of various bitumens and felts and for composite membranes have been given (1). These describe the development of a thermal shock factor based on strength factors and the linear thermal expansion coefficient. Tensile and flexural fatigue tests on roofing membranes were taken at 21 and 18°C, and performance criteria were recommended. A study of four types of fluid-appHed roofing membranes under cycHc conditions showed that they could not withstand movements of <1.0 mm over joiats. The limitations of present test methods for new roofing materials, such as prefabricated polymeric and elastomeric sheets and Hquid-appHed membranes, have also been described (1). For evaluation, both laboratory and field work are needed. 

ASTM D5019, Standard Specification for Reinforced Non-Vulcanized Polymeric Sheet Used in Roofing Membrane, ASTM, Philadelphia, Pa. 

PVC. Poly(vinyl chloride) (PVC), a very versatile polymer, is manufactured by the polymerization of vinyl chloride monomer, a gaseous substance obtained from the reaction of ethylene with oxygen and hydrochloric acid. In its most basic form, the resin is a relatively hard material that requires the addition of other compounds, commonly plasticizers and stabilizers as well as certain other ingredients, to produce the desired physical properties for roofing use. The membranes come in both reinforced and nonreinforced constructions, but since the 1980s the direction has been toward offering only reinforced membranes. The membrane thickness typically runs from 0.8—1.5 mm and widths typically in the range of 1.5—4.6 m. 

Polymeric materials -for dialysis membranes [DIALYSIS] (Vol 8) -from hydrocarbons [HYDROCARBONS - SURVEY] (Vol 13) -as roofing material [ROOFING MATERIALS] (Vol 21) -stabilization of [ANTIOXIDANTS] (Vol 3)... 

Although the material most used for single-ply membranes is EPDM, in competition with it are several other materials— Du Pont s Hypalon (a chlorosulfonated polyethylene), its Neoprene products, and modified PVC. It is believed that future growth in the roofing market will depend on products, such as Hypalon, that are easy to handle and have good ozone resistance, and on PVCs modified with polymeric plasticizers. 

Another group of polymeric plasticizer is the ethylene-vinyl acetate-carbon monoxide products sold by Dupont, as Elvaloy 741 and 742. These nonmigrating plasticizers are very useful in highly demanding products such as PVC roofing membranes and PVC geomembranes. They are also effective in reducing the r of the product. 

Dutt, O., Paroli, R. M., Mailvaganam, N. P., and Turenne, R. G., Glass T ransition in Polymeric Roofing Membranes— Determination by Dynamic Mechanical Analysis, Proc. 1991 Int. Symp. on Roofing Technol., pp. 495-501(1991)... 

Polymeric Sheets. Single-ply pol5mier roofing membranes have been available in North America since the 1950s. Many new products were introduced to the market such as polychloroprene (CR), chlorosulfonated polyethylene (CSPE), EPDM, and PVC. Unfortunately, since these products were different from the traditional asphalt, new installation techniques... 

Most types of roofing materials are bituminous and synthetic (polymeric) roofing membranes. The most commonly used roofing and waterproofing membrane is made by combining asphalt or coal tar pitch (bitumen) with felts or mats, or fabrics of organic or inorganic fibers. 

Polymer-modified bituminous membranes were developed in Europe in the mid- 1960s and have been in use in North America since 1975. The polymeric systems have varied from natural rubber to more complex synthetic systems sueh as block copolymers and polymer blends. Most common polymers used as modifiers are polyisobutylenes, polybutadienes, polyisopienes, styrene-butiene-monomer, styrene-butadiene-rubber, butyl rubber, ethylene-vinylaeetate (EVA), atactic polypropylene (APP) as well as natural rubber. Polymers, such as atactic polypropylene or styrene-butadiene-styiene (SBS), impart flexibility and elasticity, improve cohesive strength, resist flow at high temperatures, and toughness.1 1 They are the most widely used modifiers of bitumen-based roofing materials. 

Polymeric roofing membranes are evaluated using various test methods developed for assessment of durability. Mechanical properties of polymeric materials have two facets one is related to the macroscopic behavior and the other to the molecular behavior. PI Engineers are concerned only with the description of the mechanical behavior (physical properties) under the design conditions. Evaluation of the mechanical properties of roofing membranes (tensile properties at different temperatures, load at break, elongation at break, and energy to break) provides information about the material structural failures and how it can be improved, but does not offer an explanation. If the failure is related to molecular activity, additional information is necessary to comprehend the problem fully. 

Paroli, R. M., and Dutt, 0., Dynamic Mechanical Analysis Studies of Reinforced Polyvinyl Chloride (PVC) Roofing Membranes, Polymeric Mater. Sci. Eng., 65 362-363 (1991)... 

Alloys of PVC prepared with high-molecular-weight ethylene-carbon monoxide (CO)-ester terpolymers are finding increasing use in PVC roofing membranes. To help offset some of the formulation costs, lower-cost branched phthalates such as DIDP or DPHP are being used as partial replacement of the linear phthalates and the ethylene-CO-ester-type polymeric plasticizers. 

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