Flexible PVC Modification

DuPont™ Elvaloy® solid-phase (polymeric) plasticizer adds permanent flexibility, enabling the development of higher-value products for flexible PVC

- January 01, 2016 -

For flexible PVC, Dow™ Elvaloy® solid-phase (polymeric) plasticizer adds permanent flexibility, enabling the development of higher-value products such as single-ply roofing, environmental liners, \"no-dig\" water and sewer pipe repair liners, coated fabrics, footwear, and wire and cable jacketing.

Many flexible PVC products such as these are built for long service life, requiring decades of flexibility and retained thermoplastic properties. There are polymeric plasticizers on the market which have low migration characteristics. However, Elvaloy® goes far beyond these in molecular weight (see table).

 Monomeric  Up to 500
 Polymeric  1,000 to 5,000
 DuPont™ Elvaloy®  250,000 to 400,000

The high molecular weight Elvaloy® (or permanent flexibilizer) won’t migrate to the surface of the flexible PVC and be lost to the environment. By “locking in” flexibility, it helps prevent brittle failure of the flexible PVC sheet or component. As shown in Graph 1, using Elvaloy® HP661 PVC modifier instead of another common plasticizer results in flexibility at much lower temperatures, with properties retained after extraction testing. 

Increasing Flexible PVC Service Life

Dow™ Elvaloy® is a pliable polymer that’s highly miscible with PVC. This makes it possible to incorporate into a superior compound for flexible PVC. It can be especially useful in applications calling for long service life in climate or environmental exposures that might extract liquid plasticizers. Elvaloy® can’t migrate out of the system; its unique chemistry forms an alloy with PVC, locking in flexibility at the molecular level, rather than just mixing in like other plasticizers.

Product Selection for Flexible PVC

Popular DuPont resins used to flexibilize (plasticize) polyvinyl chloride (PVC) compounds include the following, arranged by melt index:

 Elvaloy® HP 441  8
 Elvaloy® HP 661  12
 Elvaloy® HP 662  25
 Elvaloy® 741  35
 Elvaloy® 742  35
 Elvaloy® HP 771  100

Elvaloy® PVC Plasticizer Resin Imparts Longer-Lasting Flexibility

DuPont™ Elvaloy® is a flexible polymer that is highly miscible with PVC during the PVC compounding stage. This makes it a useful PVC plasticizer.

Because it is a high-molecular-weight, solids-phase (non-liquid) PVC plasticizer, Elvaloy® resin adds permanent flexibility to the PVC compound, enabling higher-value use in more demanding applications such as weather-exposed roofing and environmental protection membranes.

PVC plasticizer extraction issues, from PVC weathering or exposure to chemicals, can be reduced by using a polymer such as Elvaloy® that locks itself into the flexibilized compound. Elvaloy® performance helps increase the compound’s acceptance of other performance additives such as flame retardants, fillers and stabilizers.

Elvaloy® flexible PVC plasticizer applications include single-ply roofing, geo-membranes, cable jacketing compounds, and “no-dig” fold-and-form pipe liners.

Application Examples

One of the leading applications for flexible PVC made with Elvaloy® is single-ply roofing, where membranes modified with Elvaloy® KEE face sun, hail, dropped tools, spilled or airborne oils and chemicals, and increasing foot traffic lately from “green roof” gardeners and white “cool roof” cleaners.

In flexible PVC fold-and-form pipe liners, durable wire and cable jacketing, pond liners, geomembranes and inflatable boats, building flexibility that lasts begins by choosing Elvaloy® plasticizer.

Shape-Changing PVC Pipe Liner Unfolds a \"No-Dig\" Answer to Underground Repairs

Aging underground conduits ... especially old sewer pipelines and storm drains ... can lead to higher public utility costs from uncorrected leaks and inflows. Often, the most cost-effective way to repair the pipes is to line them with a snug plastic sleeve.

Called \"trenchless\" or \"no-dig\" repair, the sealing of leaks in underground pipes without digging up streets and landscapes means huge construction savings for the utility, and a lot less disturbance in the local neighborhood.

Available no-dig technologies include \"fold-and-form\" pipe liners made with specially compounded PVC that can be extruded into pre-folded shapes ... such as \"C\" or \"U\" or \"H\" shape (shown above). The folded liner is delivered to a project site on a large spool. Repair crews then unwind the folded PVC liner from the spool and pull it through the pipe. Special equipment is used to seal both ends, and then apply heat and pressure to \"inflate\" the plastic. The liner is inflated until it meets with and conforms to the inner wall of the old pipe.

Compounding the PVC with Elvaloy® adds fold-and-form flexibility during pipe liner manufacture, plus in situ installer efficiency through precisely controlled viscoeastic and thermal processing properties of the PVC used for the liner.

Several leading underground pipe repair companies use PVC modified with Elvaloy® to assure successful handling in this application.

Dig for more information: Learn more about successful compounding of fold-and-form PVC-based pipe liners made with Elvaloy®. Read \"Analysis of Thermoplastics Used in Fold-and-Form Pipe Liners\" by E. R. Griffin, Dow Sr. Technical Specialist.