Effective Roof Sealing Through Coatings With Latex Impregnated Fleeces

Turning a flat roof into a waterproof roof, and keeping it tight for 20-30 years, is not necessarily an easy task. One of the most common solutions to create a waterproof barrier is to use polymer bitumen roofing membranes. These have been increasingly popular for years and are 'legitimate' successors to roofing felt thanks to their superior long-term performance.

Such roofing membranes essentially consist of two parts: a non-woven polyester fabric impregnated with latex, which is the actual carrier, and a top layer of bitumen for waterproofing. The bitumen also acts as a kind of adhesive to bond the fleece to the unprotected flat roof.

An important component of many of these polyester roofing membrane systems is synthetic latex to impregnate the fleece. The latex impregnation makes the fleece resistant to dimensional changes such as shrinkage and expansion (see DIN standard 18192) – which would otherwise lead to unwanted cracks and could destroy the waterproofing. These forces are caused by fluctuations in temperature, which vary between -40°C and +80°C due to the seasons and day and night cycles. A polymer-impregnated fleece is therefore much less susceptible to these dimensional changes. The latex also prevents water from penetrating the bitumen sheeting and thus prevents the sheeting from becoming delaminated – especially in frosty conditions. The cross-linking agent contained in the latex creates a three-dimensional link between the polymer chains before, during and after the evaporation of the water. This contributes to a balanced ratio of mechanical strength and hardness.

Advantages In Terms Of Environmental Compatibility – Reduction Of Formaldehyde Release

During the impregnation of nonwovens with typical chemical binders available on the market, formaldehyde is released by the cross-linking reaction. However, crosslinking is necessary – tantamount to the use of a polymer-impregnated nonwoven.

The latex also prevents water from penetrating into the bitumen sheeting and thus prevents the sheeting from becoming delaminated - especially in frosty conditions. The cross-linking agent contained in the latex creates a three-dimensional link between the polymer chains before, during and after the evaporation of the water. This contributes to a balanced ratio of mechanical strength and hardness.

Advantages in terms of environmental compatibility - reduction of formaldehyde release

During the impregnation of nonwovens with typical chemical binders available on the market, formaldehyde is released by the cross-linking reaction. However, crosslinking is necessary – as described – to achieve the required resistance and good thermal stability. New latex compounds are ammonia-free and do not contain formaldehyde-releasing crosslinkers.

Measurements show that the emission of the product not only meets the previous requirements of < 20 ppm/m3 exhaust air, but also stricter ones, such as the German Federal and State Working Group on Emission Control with 5 mg/m3 exhaust air (valid since February 2020).

In addition to a formulation that avoids the release of unwanted substances, modern polymers (such as the product 'Litex SkyShield') are also suitable for use as a 1 K system without thermoset resins. This leads to considerable cost savings, such as fewer logistics or reduced warehousing. Another advantage of the new polymer is that it allows the nonwoven to dry at much lower temperatures: The drying air can be reduced from typically 200°C to 170°C during the manufacturing process.

All this represents a significant economic benefit for the end-user compared to conventional technologies.

((From: nonwovens TRENDS 1/2020, authors: Michael Karnop, Andreas Gehr of Synthomer Deutschland GmbH, Marl/Germany))

Weserland can provide hands-on help in this area. We are looking forward to receiving your enquiries.

 

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