April 02, 2024

From time to time, people ask, what is MS glue? What is the difference between it and silicone glue?

1 Chemical structure and preparation of MS glue

In fact, MS glue is the abbreviation of modified silicone. It is called silane modified polyether glue in Chinese. It is a kind of prepolymer with macromolecular polyether bonds as the main chain and hydrolyzable siloxane groups as the end caps. Its molecular structure As shown below.

To prepare the above prepolymer, the most critical step is to first prepare a large molecular weight bisallyl polyether polyol. Then, silane-modified polyether (MS) resin is prepared through hydrosilane addition reaction between methyldimethoxysilane (MDMS) and large molecular weight bisallyl polyether polyol under the action of catalyst, as shown in the figure below:

2 Curing mechanism of MS glue

The curing mechanism of one-component MS glue is moisture curing like that of one-component silicone glue. At room temperature, under the combined action of appropriate moisture and catalysts, the siloxane groups at both ends of the macromolecular chain first undergo a hydrolysis reaction to generate silanol groups (Si-OH); then the Si- groups between the two macromolecular chains A condensation reaction occurs between OH and Si-OH or Si-OH and Si-OR, releasing water or alcohol substances to form a Si-O-Si structure, causing the molecules to cross-link to form an elastomer with a three-dimensional network structure.

3 Characteristics of MS glue

It can be seen from the molecular structure that the polymer backbone of MS glue is completely different from silicone glue. It is a new generation of building sealant developed after polysulfide glue, silicone glue and polyurethane glue.

Polysulfide sealants are gradually withdrawing from industrial use due to their slow low-temperature curing speed, easy aging and hardening, lack of durability, and strong irritating odor.

Polyurethane sealants (mainly used in industrial adhesives) have the characteristics of high strength, tear resistance, softness, wear resistance, puncture resistance, oil resistance, and medium corrosion resistance. However, ordinary polyurethane sealants often contain free isocyanate, which can be irritating during construction. It smells bad and is harmful to health. At the same time, carbon dioxide is released during the curing process and bubbles are easily generated, which affects the appearance and mechanical properties of the glue.

Silicone sealants (most glass glues and curtain wall glues on the market) have the characteristics of fast curing, no foaming, strong bonding with non-porous material surfaces, excellent resistance to moisture and heat, aging resistance, and good storage stability. However, It has low tear strength and is not puncture-resistant. The adhesive layer easily produces oily leachate that contaminates concrete, stone and other decorations. It has poor decorative properties and cannot be painted.

MS glue combines most of the advantages of silicone glue and polyurethane sealant, and its comprehensive performance is very outstanding:

1) Extensive adhesion to substrates: Due to the low surface energy and high penetration of silyl-terminated polyether, it has good wetting ability to most inorganic, metal and plastic substrates, thus producing good adhesion to the substrate. Adhesion.

2) Environmental protection: Silane-modified polyether is a long-chain structure of polyether terminated with siloxy groups, unlike polyurethane sealants that contain toxic isocyanate groups and free isocyanates. Silane-terminated polyether has low viscosity and good workability. There is no need to use organic solvents to adjust the process performance of the formula. Therefore, the volatile organic compound (VOC) content of silane-modified polyether glue is very low.

3) Paintability: The surface of ordinary silicone sealant cannot be painted and colored, and can only be adjusted to the color required by the user according to the user's needs; silane-modified polyether glue can be painted and colored, and has better paintability. Finishability.

4) The stain resistance is higher than that of silicone glue: it will not release oily molecules to contaminate the surface and joints of building materials, and maintain the beauty of the building for a long time. Silicone glue will precipitate small molecules, which together with rainwater and dust, will cause damage to the building. The appearance forms stains that are difficult to remove. More weather resistant than polyurethane sealant.

5) Weather resistance is stronger than polyurethane sealant: the entire three-dimensional network cross-linked structure is composed of the above-mentioned Si-O-Si chemical bonds and flexible polyether segments. The existence of Si-O-Si bonds makes MS sealant have good aging resistance and weather resistance, while the macromolecular flexible polyether chain segment gives MS glue good flexibility and high elongation.

Some researchers have made a systematic comparison of MS glue, silicone glue and polyurethane sealants, as shown in the following table:

Some of the contents in the table may be open to discussion, but overall it shows that silane-modified polyether sealant has very obvious comprehensive technical advantages.