Polymeric Thermoplastic Geomembranes

This article on thermoplastic polymeric geomembranes is intended to familiarize readers with these relatively new materials. Geomembranes are flexible, waterproof materials used in civil engineering structures, such as :

• tanks ;

• DAMS;

• canals ;

• waste storage facilities ;

• tailings storage and many other types of structures.

Thermoplastic geomembranes are the most widely used geomembranes in France and worldwide. The special feature of thermoplastic geomembranes is that they soften under the effect of heat. They melt at temperatures of between 100 and 200°C. They can therefore be thermally welded.

There is a wide variety of geomembranes available today. It is therefore important to introduce the reader to the most widely used geomembranes. One of the aims of this article is to enable the reader to interact with geomembrane suppliers, testing laboratories and experts.

Each geomembrane is described in terms of its composition, production and assembly methods, followed by information on its main properties, durability and use. This information is presented simply, so that the reader can benefit from it without requiring advanced knowledge of material behavior. There is intentional repetition between texts relating to different geomembranes, to enable the reader to read only the section relating to the geomembrane of interest. The organization of the text, identical for each type of geomembrane, facilitates comparisons between different geomembranes.

The properties of geomembranes are generally presented in qualitative terms. This enables the reader to better understand the behavior of geomembranes than by consulting endless tables of numerical values, which are only useful when it comes to dimensioning structures.

The geomembranes described in this article are PVC, polyethylene (high and low density) and polypropylene. The names of these geomembranes are sometimes misleading. For example, the polyethylene in HDPE geomembranes (i.e. high-density polyethylene) is medium-density, not high-density; and PP geomembranes contain relatively little polypropylene. As the base polymer is never alone, but is combined with additives, we say, for example, "PVC geomembrane" and not "PVC geomembrane".

The mass of information presented in this article is such that errors and omissions are inevitable. Corrections and additions submitted to the author will be used in future updates.

At the end of the article, readers will find a list of technical terms encountered here, both...