Inquiries

Acrylic emulsion suitable for concrete substrate primer. Construction Materials Manufacturer K Company, Development Department

Silicone‑modified acrylic emulsion for self‑leveling primer applications 

Contributes to primer design considering low-temperature construction and durability!

Building & Construction
Adhesion, Bonding, and Tack Durability/stability

Mr. C(hereafter "C") from construction materials manufacturer K is in charge of developing flooring materials and primers in the development department. One day, the sales department approaches C for advice regarding a primer for large-scale concrete floor construction using self-leveling material (SL material).

* This is a hypothetical example posted as a reference for those with similar challenges

Challenges

It is necessary to optimize the primer used in the construction of self-leveling materials (SL materials)...

C participates in a meeting with the technical representative of a major client, the general contractor, along with the sales representative.

In recent years, there has been an increase in non-residential buildings such as office buildings, data centers, and shopping malls, which require large floor areas and high smoothness. In this context, the development of concrete flooring materials that are easy to construct and ensure durability is being advanced, and it has become particularly important to select the appropriate primer for SL (self-leveling) material substrates.

When installing SL material, insufficient adhesion at the interface with the underlying concrete can lead to issues such as bubbles, peeling, and uneven finishes. To improve this, it is common practice to apply a primer on the underlying concrete before the installation of SL material. The primer adjusts the water absorption behavior of the concrete surface, suppressing the rapid absorption of moisture from the SL material into the substrate. As a result, it stabilizes the moisture environment necessary for the hydration of cement and mitigates the effects of variability in the surface of the substrate.

C and the team consider the direction of primer design based on a meeting with the client. The roles required of this primer include adjusting the water absorption of the substrate, suppressing bubble formation when pouring self-leveling material (SL material), and improving adhesion between the substrate and SL material.

As for the main agents of primers, acrylic emulsion types are mainstream, along with SBR latex types and epoxy types. Among these, acrylic emulsion primers penetrate the surface layer of concrete substrates and, after forming a film, adjust the moisture absorption behavior during the application of self-leveling materials, optimizing moisture movement. Because they are water-based, they also excel in workability, making them the most widely adopted as substrate primers.

C and the team reconsider the acrylic emulsion that has been reliably used as a primer until now. As a result, depending on the specifications of the SL material and the underlying concrete, they find that using the conventional acrylic emulsion as a primer could lead to insufficient adaptability to volume changes in the mortar due to temperature fluctuations, resulting in interface delamination and, in some cases, a decrease in adhesion over the long term.

Furthermore, low-temperature applications also present challenges, where film formation deteriorates and adhesion strength decreases. Variations in ambient temperature, as well as differences in workload and working time among workers, also pose challenges to achieving consistent results.

As the deadline for submitting samples to the client approaches, C and the team are unable to identify a solution that balances workability and durability for the acrylic emulsion.

Key Challenges

  • A development engineer consulted C regarding a primer for substrate that can achieve both workability and durability for large-scale concrete floor construction using self-leveling materials (SL materials).

  • The roles required of a primer include regulating moisture absorption of the substrate, suppressing bubble formation when applying self-leveling materials (SL materials), and enhancing adhesion between the substrate and SL materials. The team focuses on an acrylic emulsion-based primer because of its excellent workability.

  • Conventional acrylic emulsions have issues such as insufficient followability leading to interfacial peeling, and a decrease in film-forming ability and adhesion strength during low-temperature applications, indicating the need for a new primer design that can accommodate variations in application conditions.

Solutions

Solution Summary

  • ACRYSET™ CE is an acrylic emulsion that utilizes a low Tg designed acrylic polymer as its main chain and incorporates a silicone-modified structure, making it suitable for use as a primer for concrete, with expected improvements in adhesion.

  • Due to the silicone cross-linking structure, it excels in water resistance, alkali resistance, and durability, and long-term stability of the floor structure can be expected.

  • The primer containing ACRYSET™ CE has good workability at low temperatures and also exhibits adhesion to base concrete and SL materials.

With a low Tg design, both workability and durability are ensured. The "silicone-modified acrylic emulsion" is the key to the solution.

Amidst a standstill in discussions, C decides to gather information again. He searches for information online about acrylic emulsion-based primers for civil engineering and construction.

He learns that Nippon Shokubai is introducing products called ACRYSET CE-518 and CE-553, which can be utilized as acrylic emulsions for concrete primers.

C promptly contacts Nippon Shokubai to hear a detailed explanation from the person in charge. This product is a silicone-modified acrylic emulsion, designed with low Tg values of -12°C and -21°C. This design improves interface followability with the underlying concrete and maintains adhesion even during volume changes in the curing of SL materials. Additionally, it excels in film formation in low-temperature environments during winter construction, allowing for the formation of a stable primer layer.

Furthermore, it is said that the introduction of silicone crosslinking due to silicone modification improves the water resistance, alkali resistance, and durability of low Tg polymers, which is expected to enhance long-term reliability.

C becomes interested in ACRYSET and decides to include the design of a primer using this emulsion in his considerations.

In practice, it was confirmed that using ACRYSET for trial and evaluation resulted in good workability at low temperatures, and adhesion to the underlying concrete and SL materials was also observed.

Furthermore, not only immediately after application but also excellent results in adhesion were obtained after conducting repeated temperature cycling tests intended for long-term use. C and the team are currently finalizing details to present a primer containing ACRYSET to their client.

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