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A water leakage is a major issue for builders to solve for prolonging the lifespan of a building and providing a comfortable place to live in. Gap sealing and painting were the usual finishing steps in building, preventing water penetration from the exterior through joints and gaps, more specifically, rainwater.

Over the years of research, various types of sealant technology were developed. The most common types of chemical types of sealants are namely silicone (SR), polyurethane (PU), polysulphide, and in more recent development, hybrid technology polymers. Scientists are now focusing their efforts onto greener and better performance materials.

Here at Kaneka, we have developed a latest hybrid polymer technology known as Kaneka MS Polymer®. Kaneka MS Polymer® has been growing exponentially for uses at the construction and automotive markets owing to Kaneka’s approach as a technical solution to the markets.  Kaneka MS Polymer® is more properly known as a silyl terminated polyether (STPE), where a polyether chain is end-capped with reactive silyl groups giving a more controlled crosslinking. The etymology of the term “hybrid technology” come from the fact that MS polymer is developed by combining advantages of SR and PU while overcoming their shortcomings, making Kaneka MS Polymer® an excellent choice of polymer as a sealant base.

Figure 1: Kaneka MS Polymer® resin

Kaneka MS Polymer® is a moisture-cured system, similar to PU and SR. At Kaneka, we produce a variety of MS polymer grades to meet different global standards in construction and automotive industries. Kaneka MS Polymer® grades are finely tuned by varying the polymer chain length and also branching points to produce MS polymers with mechanical properties for a wide range of applications. Kaneka MS Polymer ® can be used for various interior and exterior application such as gap filling sealants, structural sealants, and high tack adhesives.

Unlike PU and SR , Kaneka MS Polymer® provides solution to various sealants problems such as, UV resistance, paint compatibility, staining and dirt streaking problems, among others. MS polymer brings both the advantages of polyurethane and silicone together for a more versatile and greener material. Kaneka MS Polymer® is the future of construction sealants and adhesives that gives longevity to the buildings.

The main feature of Kaneka MS Polymer® in comparison to PU technology is that MS polymer eliminates the need of volatile isocyanate compounds as raw materials, which are toxic to human, thereby giving MS sealant low volatile organic compound (VOC) advantage. Polyurethane curing reaction produce carbon dioxide as a by-product.  Carbon dioxide release during the curing causes the polyurethane sealants to form hollow cavities (air bubbles) in the sealant body after curing. These cavities in the sealant reduces the tensile properties of the sealant.

Figure 2: Comparison of Kaneka MS Polymer versus PU sealant. Bubbling occurs in PU

Additionally, Kaneka MS Polymer® also has better UV resistance when compared to PU due to the polyether backbone being less susceptible to degradation than PU backbone which are made up by urea and urethane linkages. This gives Kaneka MS Polymer® advantage over PU on longer lasting performance.

When comparing to SR sealant, Kaneka MS Polymer® has inferior UV resistance. However, Kaneka MS Polymer® has more advantages than SR in that Kaneka MS Polymer® tackle the drawbacks silicone sealant poses. Kaneka MS Polymer® eliminates the use of silicone oil that can cause stain issues. Unlike SR sealant, Kaneka MS Polymer® sealants do not contain silicone oil that migrates out from sealant body to the surface overtime and cause staining on the joint and the substrate. As silicone oil is resistance to UV and thus does not decay under UV irradiation, the silicone oil will attract dust and cause staining which eventually flows down and cause reduction in building aesthetics. This phenomenon is sometimes known as dirt streaking, a major drawback for most SR sealant.

Figure 3: Comparison of Kaneka MS Polymer sealant versus SR sealant on dirt streaking (Kaneka internal outdoor exposure test)

Figure 4: Mechanism of dirt streaking by silicone oil in SR sealant

Figure 5: Comparison of Sealant durability

Another advantage of Kaneka MS Polymer® over SR is Kaneka MS Polymer® sealant can be painted over by water-based paints and coatings, SR sealants lack this feature due to presence of the hydrophobic silicone oil, deterring the painting over by water-based paints. Kaneka MS Polymer® do not contain hydrophobic silicone oil, so it is able to be painted over by water-based paints. This gives advantage to Kaneka MS Polymer® over SR in exterior application such as precast gap sealant and window perimeter sealant application, where paint over is needed.

Figure 6: Comparison of paintability of Kaneka MS Polymer® sealant versus SR sealant

A quick summary of the advantages of Kaneka MS Polymer ® over polyurethane and silicone can be found in Table 1*:

Property MS Polymer Polyurethane Silicone
Environmental friendliness 10 5 9
Non-bubbling 10 6 10
low temperature extrudability 10 8 10
Slump resistance 10 10 10
Quick cure 10 7 10
Storage stability 10 7 9
Body (tooling) 8 10 8
Weather resistance 8 6 10
Adhesion to various substrates 10 5 8
Mechanical properties 10 10 10
Heat resistance, mechanical stability 9 8 10
Non-dirt pickup 10 10 5
Stain resistance 8 8 5
Paintability with water-based paint 10 10 3

Table 1: Comparison between MS polymer, polyurethane, and silicone sealants.

In terms of adhesion, Kaneka MS Polymer® is balanced and fare better than PU and SR sealant. Except some thermoplastics such as PE, PP and Polysterene etc, MS are able to bond various susbtrate with good primer-less adhesion. In fact, MS adhesion grow over time, as compared to PU and SR. A comparison of adhesion over various substrates are shown below

Graph 1: Adhesion comparison between MS polymer, polyurethane, and silicone sealants.

Regardless the requirement of the target applications, Kaneka MS Polymer® is a versatile material with wide range of polymer grades that provide endless possibilities of finished products for a greener and cleaner future.

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*Hashimoto, K., “Silyl-Terminated Polyethers for Sealant Use: Performance Updates”, Adhesives Age, August 1998.