PUD-Based Waterproofing Membrane: A Waterproofing Solution for Roofs and Concrete Decks

Waterproofing membranes made with water-based polyurethane (PUD) are one option for creating a protective layer against water on surfaces such as roofs, terraces, and concrete decks.

Unlike standard decorative coatings, waterproofing membranes need to form a sufficiently thick and flexible film with low water uptake to help protect surfaces against water seepage.

For formulators and R&D teams, the challenge is not simply to create a layer that covers the surface. It is also about achieving the right combination of film properties for the intended application.

This makes binder selection an important part of waterproofing coating formulation.

What Makes Waterproofing Membranes Different from Standard Coatings?

Coatings can serve various purposes, from improving appearance and color to providing specific surface protection. Waterproofing membranes, on the other hand, are primarily designed to help protect substrates from water exposure.

These different requirements make film properties especially important.

A Thicker Film

Waterproofing membranes generally require a thicker layer than standard coatings. Film thickness helps create a protective layer that covers the surface more thoroughly.

The binder must therefore support the formation of a continuous film that meets the formulation’s target thickness.

Flexibility to Accommodate Substrate Movement

Roofs and concrete decks can experience small movements due to temperature changes and environmental conditions.

If the film is too rigid, these movements may increase the risk of cracking. A more flexible film can help accommodate small substrate movements without easily losing its continuity.

Protection Against Water

Ultimately, the main purpose of a waterproofing coating is to provide protection against water. Formulators therefore need to consider the film’s properties and its ability to maintain protective performance during use.

Why Are Flexibility and Low Water Uptake Important?

Two key properties to consider when developing a waterproofing membrane are flexibility and low water uptake.

Flexibility to Accommodate Substrate Movement

Roof and concrete deck surfaces can expand and contract as temperatures change.

Although these movements may be relatively small, they still need to be considered when designing a coating system. A film that is too rigid may be more prone to cracking as it responds to substrate movement.

In contrast, a flexible film can help accommodate these movements.

That is why high flexibility is a relevant property for roof and terrace waterproofing formulations.

Low Water Uptake for Long-Term Performance

In addition to flexibility, the amount of water absorbed into the film also needs to be considered.

When water is absorbed into a coating layer, it may affect the film’s properties and protective performance. This makes low water uptake a desirable characteristic in waterproofing membrane formulations.

By limiting water absorption into the film, the coating’s properties can be better maintained during use.

How Does PUD Work in Waterproofing Membranes?

In water-based waterproofing formulations, PUD can function as a binder that helps hold pigments and fillers together while forming a film on the surface.

After application, the water in the system evaporates during drying. The polyurethane particles then form a continuous and flexible film on the substrate.

For certain formulations, PUD can be used as the sole binder. It can also be combined with other water-based resins when needed, provided that compatibility testing is conducted beforehand.

For waterproofing applications, the focus is not on repeating every characteristic of PUD. Instead, it is on understanding how the binder’s properties can support the membrane’s key requirements: film formation, flexibility, and low water uptake.

Where Are PUD-Based Waterproofing Membranes Used?

One relevant application area is roofing and terraces, including surfaces that require a thick, flexible, pigmented waterproofing layer.

These formulations can be designed to create a thick, flexible, pigmented waterproofing membrane.

Some key considerations include:

• Continuous film formation
• Film flexibility
• Low water uptake
• Film thickness
• Substrate adhesion
• Surface appearance based on formulation requirements

PUD is also used in various other applications globally, such as disposable gloves and textile transfer printing. However, this article focuses on its use in waterproofing membranes for roofs, terraces, and concrete decks.

What Makes PUD Suitable for Waterproofing Membranes?

The following PUD characteristics are relevant to waterproofing formulation requirements:

However, binder properties alone do not determine whether a formulation will perform successfully. Substrate compatibility, compatibility with pigments, fillers, resins, and other formulation components, as well as application conditions, still need to be evaluated through trials.

Factors such as application method, drying conditions, and target film thickness should also be considered to ensure that the formulation meets the intended requirements.

Esacote PU 470: A Water-Based PU Binder for Waterproofing

Once the key requirements of a waterproofing membrane are understood, binder selection can be tailored to the desired film properties and formulation targets.

Esacote PU 470 is an anionic waterborne polyurethane dispersion based on aliphatic polyurethane. It can be used as a binder for waterproofing membrane formulations designed for roofs and terraces.

Key Product Information

One of the key characteristics of Esacote PU 470 is its combination of high flexibility and low water uptake, making it relevant for waterproofing membrane formulations that require a flexible film and water protection.

PU 470 can also be used in thick, pigmented membrane formulations and as a sole binder.

For formulations that combine PU 470 with other water-based resins, compatibility testing is still required to ensure that the system meets the desired formulation targets.

PU 470 Is Not Solvent-Free

It is important to note that Esacote PU 470 is not a solvent-free product.

PU 470 contains 4% NEP. Therefore, its solvent content should be considered during formulation development and when determining production requirements.

PU 470 should not automatically be treated as equivalent to other PUD grades with different characteristics or compositions.

FAQ: PUD for Waterproofing Membranes

What Is a PUD-Based Waterproofing Membrane?

A PUD-based waterproofing membrane is a waterproofing layer that uses Polyurethane Dispersion (PUD) as its binder.

After application, the water evaporates and the PUD forms a film that can be designed to provide flexibility and protection against water.

Why Is Flexibility Important for Waterproofing?

Roofs and concrete decks can experience small movements due to temperature changes. A flexible film can help accommodate these movements and reduce the risk of cracking caused by substrate movement.

Why Is Low Water Uptake Important?

Low water uptake helps limit the amount of water absorbed into the film. This characteristic can help maintain the coating’s function and properties during use.

Is Esacote PU 470 Solvent-Free?

No. Esacote PU 470 contains 4% NEP and therefore cannot be classified as solvent-free.

Can PU 470 Be Used as a Sole Binder?

Yes. Esacote PU 470 can be used as a sole binder in waterproofing formulations. However, the formulation still needs to be tested to ensure compatibility and performance meet the requirements of the intended application.

Looking for a PUD Binder for Your Waterproofing Formulation?

Developing a waterproofing membrane requires more than just a material that can form a film. Formulators need to consider how the film responds to substrate movement, interacts with water, performs at the target thickness, and remains compatible with other formulation components.

Esacote PU 470 is one PUD binder option for waterproofing membrane formulations used on roofs and terraces, offering high flexibility and low water uptake.

As a chemical distributor with 20 years of experience and a portfolio of more than 800 chemical product variants, PT Bahtera Adi Jaya also provides technical sales support to help evaluate material and formulation requirements.

Learn more about Bahtera Adi Jaya’s Coating & Construction solutions, or contact us to explore the right solution for your industry.