TECHNICAL BULLETIN | 0425TB01 | APRIL 2025

Dilution of solvent-based polyurethane membranes using Xylene

OVERVIEW

Xylene is a common solvent in the formulation of liquid waterproofing products, coatings, and membranes. It helps dissolve the polymeric resins, bitumen, or rubber compounds that form the chemical base of these products. By reducing the viscosity of the mixture, Xylene ensures easy workability and application.

Because of its versatility, it is also used to enhance the penetration of solvent-based waterproofing membranes into porous materials like concrete or wood. By helping the active waterproofing components penetrate deeply into surfaces, Xylene contributes to a more effective and durable waterproof barrier.

It is often used as a cleaning agent due to its strong solvent properties. It helps remove oils, adhesives, debris, dirt, and even old coatings, ensuring better adhesion of waterproofing materials to surfaces.

It can be used to reactivate existing solvent-based waterproofing membranes by softening and redistributing the existing coating, which allows for improved bonding and adhesion of additional layers or touch-ups.

THE ISSUES

Diluting a solvent-based waterproofing liquid membrane with Xylene can have several negative effects. Xylene is commonly used as a solvent, but excessive dilution can compromise the performance of the membrane. Here is the breakdown of potential issues:

  1. Reduced Effectiveness: The primary function of the waterproofing membrane is to form a durable and cohesive layer that prevents water infiltration. If the membrane is over-diluted, the coating may become too thin, reducing its ability to provide an effective barrier.
  2. Weakened Adhesion: The diluted membrane may have poor adhesion to the surface it's being applied to. This can lead to peeling, cracking, pin holing, or detachment of the coating over time, which will impair its ability to waterproof the surface.
  3. Faster Evaporation and Curing: Xylene is a volatile solvent, and if over-diluted, the drying process can become erratic. It might cause the membrane to evaporate too quickly, leading to uneven curing or incomplete curing, which affects its overall performance.
  4. Increased Toxicity: Xylene is a toxic solvent that can be harmful to health, especially when used in large amounts. Over-diluting the membrane could increase the overall release of toxic fumes, which can be a health hazard to those applying or exposed to the membrane during the curing process.
  5. Decreased Durability: The diluted mixture may result in a membrane that is less resistant to wear and tear, UV radiation, and other environmental factors. The membrane might break down more quickly, leading to a shorter lifespan of the waterproofing system.
  6. Appearance Issues: Over-dilution can cause the final membrane layer to be uneven or inconsistent in appearance. It may also result in a finish that is too glossy or too matte, depending on the dilution ratio.
  7. Increased Cost: If the waterproofing membrane does not perform as expected due to over-dilution, it may require reapplication, resulting in increased costs for materials and labour.

OUR RECOMMENDATIONS

PASCO Construction Solutions does not support the dilution of any of our solvent-based polyurethane membranes with Xylene.

Aquaproof 110 is formulated as a thixotropic product to be applied on both horizontal and vertical surfaces without any sag. Its specific rheology makes it extremely easy to apply and therefore does not need to be diluted.

The Aquaprorof 115UV has a self-leveling nature and therefore also doesn’t require diluting.

The Aquaproof 110UV being a topcoat is much thinner in viscosity and also doesn’t need to be diluted.

Excessive dilution of Xylene can potentially affect the chemistry of the product and in turn its performance characteristics, therefore Pasco is not in a position to warrant it.

Hence, Pasco Construction Solutions only allows the use of Xylene as a cleaning agent and to reactivate the existing cured solvent-based polyurethane waterproofing membrane surface prior to an additional coat of same material.

This technical bulletin has been prepared based on Pasco’s current knowledge and experience of Pasco’s products when properly stored, handled and applied under normal conditions. It only applies to the application and product referred to in this letter. In case of changes in the parameters of the application, such as changes in substrates etc., or in case of a different application, consult Pasco’s Technical prior to using Pasco’s products. The user of the product must test the product’s suitability for the intended application and purpose. Consult the current technical data sheet. Except as expressly stated in writing, Pasco’s warranty is governed exclusively by our current sales conditions. Pasco does not warrant the correct application of its product.