PET spunbond for roofing membranes and underlays

What the carrier does in a roofing membrane

A bitumen roofing membrane is built around a carrier, also called the reinforcement. On the line, the carrier is unwound and pulled through hot bitumen, which coats and soaks it; the sheet is then surfaced, cooled and wound. In the finished membrane, the carrier gives the sheet its strength, holds it together while it is handled and laid, and helps it keep its shape as the roof heats up and cools down.

So the fabric has two jobs on your line: it must stay strong and flat while it is pulled through hot bitumen under tension, and it must let the bitumen wet it evenly so that the coating bonds well.

Why polyester

Polyester has a much higher melting point than polypropylene and keeps its strength and its dimensions when heated. That is why PET spunbond is a natural base for products that are coated, laminated or impregnated hot. A carrier that shrinks or stretches in the hot stages causes waves, uneven coating and sheets that do not lie flat.

Spunbond is made from continuous polyester filaments, laid into a web and bonded by heated calender rolls, so it is strong for its weight. It is also stiffer and more dimensionally stable than PP spunbond, and it takes up almost no moisture.

Roof underlays and building membranes

Underlays and other building membranes are usually made of several layers bonded together, for example a functional film or coating with a nonwoven layer on one or both sides. The nonwoven protects the functional layer, gives the sheet its strength and handling, and provides a surface that can be printed.

PET spunbond suits these products when the laminating or coating process runs hot, or when the finished membrane must stay stable in size. Its even surface takes PVC, PU and adhesive layers well.

Point bonded or flat bonded?

We make both bondings. Which one suits you depends on what your line does with the fabric.

• Point bonded: the filaments are fused only at small, regular dots. The fabric is softer, more flexible, more open and more porous, and it drapes and moulds well.
• Flat bonded: the whole web is pressed between smooth heated rolls. The fabric is thin, dense and smooth on both sides, with a closed surface that prints, coats and laminates evenly. It suits coating substrates and carriers.
• Not sure? Ask for samples of each and run them side by side on your line.

Made for your line

We supply PET spunbond from 15 to 150 gsm, in white, black or any colour matched to your requirement, as jumbo rolls or slit to your width, with clean, non-fraying edges. Tell us the weight, the roll width, length and core size your unwinder takes, and how the fabric runs on your line: bitumen or laminating temperature, line tension, and whether the fabric is coated, laminated or both.

If you are replacing a carrier you already use, its data sheet or a sample is the quickest starting point. The minimum order is one 20-foot container, and rolls are labelled and packed to your specification.