Blister & pinhole issues from hot humid midsummer? Two dehydrating additives for targeted fix.

Source: Publish Time:2026-08-11 16:47:37

Moisture Control Solution for Polyurethane Systems

Fast & Long-lasting

Right now, midsummer heat coincides with persistent high humidity. Colleagues formulating polyurethane coatings and sealants for wood, automotive, electronics and construction sectors are surely troubled by moisture issues. Moisture inherent in pigments, solvents and fillers stays trapped inside the coating system. Hot and stuffy warehouse conditions further build up water vapor. This in-can moisture triggers side reactions with isocyanates, directly causing drum bulging and caking, premature gelation of curing agents, drastically shortened shelf life, as well as coating defects such as pinholes and haze after spray application.

Isocyanate reacts with water:

For polyurethane systems require fast water scavenging and better storage stability.We’d like to recommend two Borchers® water scavengers: Additive TI™ and Additive OF. We will go through their respective advantages with performance data and practical test results.

Additive TI™ High-efficiency fast water scavenger

Core Advantages of the Product

Common molecular sieves on the market only trap moisture via physical adsorption. The water remains inside the system and is prone to releasing again under high temperature or long-term storage, which brings risks of gas bulging and pinholes. By contrast, Additive TI™ is a monofunctional, highly reactive low-viscosity isocyanate. It eliminates moisture through chemical reaction and fundamentally prevents moisture reversion.

Additive TI™ Moisture Removal Mechanism

• No additional catalyst required. It reacts rapidly with moisture and completes water scavenging within just a few minutes, significantly speeding up the overall production cycle.

• The reaction product is chemically stable. It will not undergo undesired side reactions with common coating solvents (esters and ketones) and does not interfere with the normal crosslinking and curing of the paint film.

• Compatible with both one-component and two-component polyurethane systems.

• When added separately into the curing agent for pre-treatment, it can extend the shelf life of the curing agent and prevent yellowing, caking and gelation during long-term storage

Test Results

1、Water Scavenging Rate Test

Monitored by FTIR spectroscopy, the intensity of the absorption peak corresponding to moisture in the system gradually decreases after adding Additive TI™. This indicates that Additive TI™ reacts with water extremely fast, and the reaction is nearly completed within just a few minutes.

2、High Temperature & High Humidity Anti-Bloating Test(50°C&98RH%)

Simulating hot and stuffy warehouse conditions in summer, samples were stored at 50 ℃ and 98% RH for 24 hours. The blank sample bag bulged obviously with gas generation, which proves that the curing agent reacted with water to produce carbon dioxide. In contrast, the sample with Additive TI™ remained stable throughout the test without bloating, as moisture had been scavenged by Additive TI™.

3、Long-Term Ambient Storage Test(23°C&50%RH)

After four months, the isocyanate in the blank sample had gelled. Under the same conditions, the isocyanate curing agent treated with Additive TI™ showed no obvious change and exhibited good storage stability.

4、Film Formation Test

Blank sample (left), sample with Additive TI™ (right)

Additive OF General Long-Life Water Scavenger

Core Advantages

• Additive OF is a low-viscosity, high-efficiency 100% active water scavenger. It is more suitable for long-term moisture protection and stabilization of finished products, with mild and non-irritating water scavenging reaction.

Reaction Equation of Additive OF with Water

• It undergoes an irreversible reaction with moisture without generating carbon dioxide throughout the process, fundamentally preventing secondary gas buildup and drum bulging. Moisture is converted into two liquid by-products: ethyl formate and ethanol, which will not release moisture back. In addition, ethyl formate can also improve the wettability of the system.

• It features excellent compatibility and can be added to both polyol and curing agent components. It is suitable for most solvent-borne PU coatings, adhesives and casting compounds on the market. Its reaction by-products are more environmentally friendly and will not cause surface defects such as haze, loss of gloss or discoloration of the paint film even after long-term storage.

• It can be used for pre-scavenging moisture of pigments and fillers in advance, or added at the finished product stage to keep the system dry and stable throughout.

1、High Temperature & High Humidity Anti-Bloating Test(50°C&98RH%)

After one day under high temperature and high humidity, the blank sample generated substantial gas and the container expanded and deformed. The sample with Additive OF showed no obvious change throughout the test. This demonstrates that Additive OF can effectively inhibit the reaction between moisture and isocyanate in the curing agent, greatly improving the storage stability of the curing agent and preventing container bulging.

2、Long-Term Ambient Storage Test（23℃）

Stored at ambient temperature for four months, the blank isocyanate system gelled completely and became unusable. The sample with Additive OF showed no obvious change, and its storage life was greatly extended.

Conclusion

You may select between these two products according to your requirements: choose Additive TI™ if you need to rapidly remove inherent moisture from raw materials on the production line for high-efficiency manufacturing. Select Additive OF for finished products requiring long-distance transportation and long-term storage, to avoid bloating and protect the film appearance.

The theoretical stoichiometric ratio of Additive TI™ is 12 g of Additive TI™ per 1 g of water. When the moisture content of the coating ranges from 0.05% to 0.30%, the recommended dosage is 0.5%–4.0% based on the total formula weight. Overdose is not recommended, as it may cause yellowing of the paint film.

The recommended dosage of Additive OF is 1–3% of the total coating weight. The exact dosage should be determined by testing and depends on the specific system.

*Moisture inherent in raw materials and atmospheric moisture introduced during application are two separate issues. The water scavengers introduced herein only consume residual moisture inside the coating formulation. High humidity from the workshop environment during application still needs to be controlled by ventilation, temperature adjustment and dehumidification.

Sample Service