How to choose and produce a performing dimple membrane with a recycled HDPE granule

The function of textured ashlar Dimple membranes in recycled HDPE in the field of building waterproofing has been known for many years, although probably not everyone knows about the many opportunities for using this useful separator-protector-waterproofing element.

The partition of membranes depends on:

● Geometric conformation of the dimples

● High of dimples in relation to the lower surface

● Thickness of the lower surface

● Weight per square meter

● Mechanic resistance to compression and traction

● Eventual sandwiches which can be installed during the production:

○ Fabrics not fabrics in polyester

○ Fabrics not fabrics in polypropylene

○ Fabrics not fabrics in grid polyethylene

○ Plaster-saver nets

○ Smooth sliding sheets in PE

● Utilization in building

We will not dwell here on the various uses to which the membrane lends itself to technically improve the work but on aspects related to the raw materials that are used for the production of the product and the quality of the same producing the product with extrusion machines per head flat.

In the past, standard dimple membranes were produced using virgin HDPE resin which gave technical constant supplies and excellent physical qualities.

They were 600 grams per square meter. From the end of 90’s to 2000’s the high augmentation of product request has brought to the offer increase on market and to a consequent pressure on prices.

It took producers to use the majority of the time regenerated HDPE granules for the production.

Meanwhile new membranes have come to the market: they are 500/450 and 400 grams per square meter. The reduction of the weight and the use of regenerated granules could mean a mechanical performance under the expectations.

In relation to first materials involved in the production, we have to keep attention on some basic questions:

● The normal input used is composed by HDPE bottles and vials. It’s taken from the separate collection in which there are PP stoppers. PP has a pejorative behavior considering the membrane’s quality. An high percentage of PP takes to the fragility of the material, especially during the resistance to anchorage and the re-interred of the foundation plan. The reduction of PP percentage is solved using separating machine-readable machineries.

● The flakes’ cleaning phase from HDPE vial is important because little rigid residues in it can not be stopped completely by the filters during extrusion phase and so they can be incorporated into granules. This could be cause the formation of holes on the product’s surface and a consequent loss of impermeability and traction resistance. Therefore a good cleaning, choice of filters and periodic change-filters can help us to have a cleaner granule.

● The utilization of mineral fillers to increase dimple’s mechanical resistance can be useful until the limit over which the product’s fragility and vitreousness begin to reduce the mechanical caracteristiques requested. Mineral fillers can change the resistance by reducing the employment of the HDPE polymer for a lower price of first materials.

In relation to membrane’s use in building, we can list some fundamental factors:

– For the vertical laying, such as in the waterproof cladding’s protection and for the vertical drainage’s function, it’s requested traction resistance instead of compression resistance

– For the horizontal laying, such as in separator layers in floors, it’s more frequent the vertical mechanical resistance

– For membrane laying with plaster-saver net for the walls’ dehumidification, it’s preeminent the quality of traction resistance of the membrane in relation to nails.

– For drenant and separator layers in tunnels, it’s necessary both a good mechanical resistance and a traction one

– For soundproofing membrane’s layer, the mechanical solicitation in civil building is reduced.

With this list we don’t want to run out of both employments, which are innumerable, and productive aspect. With this last aspect we have also to consider the impact of membrane’s quality in relation to machinary’s parameters related to the extrusion, the cylinder’s cooling and the dimple’s form which has a relevant aspect in counting the final quality.

Automatic translation. We apologize for any inaccuracies. Original article in Italian.