April 02, 2024

1. Source, type and current situation of MS sealant

Since MS sealant was launched in Japan in 1979, it has a development history of more than 40 years. It was only in 2010 that MS sealant entered the public consciousness in China. Now China has less than 5% market share, while in Japan, MS has a market share of about 30%. It can be seen that as long as it is applied properly, MS sealant will be able to gain popularity in China in the future. Rapid growth. Strictly speaking, most of the products now can only be called silane-modified resin, not MS resin. On the other hand, the structure of their products is completely different from that of Japan, and they are not the same thing.

The full name of "MS sealant" is modified silane polyether sealant. It is a new generation of building sealant developed after polysulfide sealant, silicone sealant and polyurethane sealant. At present, domestic "MS resin" includes: MS, STPE, SMP, STPU, SPU, etc. There are many types and models. What is the relationship between them?

1)       MS: Modified Silane(Silyl) Polymer (modified silane polymer)

MS Polymer® is a registered trademark of Kaneka Japan

2)       STPE: Silane Terminated Poly-Ether (silane-terminated polyether)

"Hybrid" STPE sealant, also known as silicone-modified polyether sealant and modified silicone sealant, is a high-performance elastic sealant from WACKER that uses silyl-terminated polyether as the base polymer.

3)       SMP: Silane Modified Polymer (silane modified polymer)

The silane-modified polymer launched by Dow Company under the brand name VORASIL™ SMP is a unique combination of polyether and silane end groups. It has the characteristics of low viscosity and rapid curing at room temperature.

The above three types all refer to resins using "silane-terminated polyether"; since they are the same, why do they have three names? Compared with MS resin, the latter is called SMP, which respects intellectual property rights; STPE has two meanings, one is the English abbreviation of "silane-terminated polyether", and the other is a "WACKER" resin, in 2014 Trial in China also respects the intellectual property rights of MS Polymer®!

But strictly speaking, modified silicone is not a modification of silicone. It is a non-silicone product. The main component is silane-terminated polyoxypropylene ether, which can be called modified polyether sealant, such as modified silane. It is completely wrong, but due to historical and standard reasons, "modified silicone" is more suitable, but Silicone Modified polyether (SMP) is commonly used in domestic papers.

4)       STPU: Silane Terminated PU

The so-called STPU refers to modified silane-terminated (STPU) resin/sealant, which is formed after connecting siloxane groups to both ends of the polyurethane chain. The polyurethane chain is the molecular skeleton and the siloxane is the end group. Molecular resin.

5)       SPU: Silane (modified) PU

SPU refers to silanized polyurethane. SPU is a material modified with polyurethane as the main chain through silane end-capping. In addition to retaining the advantages of the original PU sealant, this type of sealant has excellent heat resistance, aging resistance, and weather resistance. Great improvement, it has good bonding effect on common substrates such as metal, glass, PVC, etc., non-polluting cured exudate escapes, will not pollute the surface and surroundings of the adhered substrate, and is more in line with environmental protection requirements.

The latter two resins are quite different from the first three. They are basically closer to polyurethane, or just polyurethane.
 

2. Performance differences between silicone, MS sealant and SPU sealant

Add the familiar RTV silicone sealant (the main component is hydroxyl-terminated polydimethylsiloxane, referred to as 107 sealant) for comparison. The structural formula is as follows, and the related bond energy data: From the perspective of bond energy: the silicone main chain is composed of Si It is composed of -O bond with a bond energy of 444, which is greater than the energy of ultraviolet light of 399 (the energy of a photon of ultraviolet light with a wavelength of 300nm is about 399kJ/mol), so the weather resistance of silicone sealant is particularly good and it is not afraid of ultraviolet radiation.

From the reaction route: Japanese MS resin is synthesized by hydrosilation method. There is no C-N bond. It is mainly composed of C-C and C-O bonds. The bond energy is smaller than the Si-O bond, so the weather resistance is slightly worse than silicone, but it is still Quite good, but because the capped alkoxy group has low activity and stable storage, it requires chelated tin or a large amount of organic tin to catalyze the reaction. Generally, the surface still feels sticky after curing; while domestic SMP resins use polyether and isocyanate silane couplings. The coupling agent is used for reaction and end-capping, and no CNO group remains, but there will be C-N bonds at both ends. Due to the presence of C-N bonds, the capped alkoxy group has higher reactivity and the product cures quickly. However, due to the presence of C-N bonds at both ends, it is temperature resistant. The weather resistance is slightly worse than that of Japanese MS resin, and antioxidants and UV absorbers are generally needed to make up for the lack of performance.

As for STPU/SPU resin, the polymer is produced by the reaction polymerization of low-viscosity polyether and polyisocyanate. There are a large number of C-N bonds in the polymer main chain and at both ends. Because the bond energy of C-N bonds is only 284, which is much lower than the ultraviolet energy, so Sealant products of STPU and SPU resins containing a large number of C-N bonds in the main chain have poor temperature resistance and weather resistance. The colloid is prone to cracking and powdering after high temperature or ultraviolet irradiation. It is also difficult to add UV absorbers and antioxidants. To make up for its shortcomings, it is generally restricted from outdoor use.

The basic film-forming material of MS/SMP sealant products is MS/SMP resin, and the resin synthesis process and material costs are relatively high. In order to reduce costs, some manufacturers use polyurethane to replace the polyether main chain, and use ordinary aminosilane and NCO in polyurethane for sealing. End-alkylated and sold under the name of "MS sealant", the sealant is actually composed of STPU or SPU, so problems such as degumming, cracking, and powdering often occur when used outdoors. In addition, polyurethane generally contains a lot of NCO residues, which is very unfriendly to human health and the environment. Therefore, users should not be cheap when purchasing "MS sealant". In addition, the addition or non-addition of ultraviolet absorbers, light stabilizers, heat stabilizers, etc. to the sealants produced by domestic resins also has a considerable impact on the subsequent quality of the products. It is difficult to judge from aspects such as the tensile strength of the strips.