Introduction to Silicone Modified Sealants

Cited from: https://pixabay.com/zh/photos/tools-construct-craft-repair-864983/

Cover Photo cited from :  https://pixabay.com/zh/photos/architect-plan-construction-3979490/

Sealant is the material that is used to fill the narrow, slots and other blanks of one or multiple layers of the same materials or different materials. During usage, it is one kind of flowing or squeezable material. It could inlay closure the narrows, it could also make the adhesion between materials to be tighter replying on the drying, change of temperatures, volatilization of solvents and chemical crosslinking processes. The filled materials will gradually to be formed as plastic solid or elasticity and becomes the sealing materials that have properties like waterproof, sealing, shock resistance and anti-corrision. It is economical and convenient to use the material to seal the parts and it also meets the requirement on functions. At present, sealant is widely used in constructions, industries and living consuming and the corresponding demand is increasing.

In China, the earliest type of sealant applied in constructions is the polysulfide type constructional structural sealant. Later on, the organic silicone, plyurethane and acrylic acid sealants are coming out, they are high-efficiency sealants and developed rapidly. The categories and numbers of sealants are more and more, and the organic silicone type sealant is the rapidest developing one and it is now the biggest sealant category.

Organic silicone sealants have been applied successfully for tens of years. Its heat resistance, low-temperature softness and outdoors weatherproof are all very excellent. Demands on the properties of sealants from different industries are getting higher but sometime they will also overstretch the proper functional ranges. Non organic silicone sealants are also applied in industrial sealing like small windows and small narrows for over two decades, its advantage is that its adhesion on the surface of common construction material is stable and the elasticity is great. It also has properties like tear resistance, abrasion resistance, penetration resistance and paintability, its color is stable and its durability is excellent. It has no corrosions on base materials and it has acid, alkaline and solvent resistance. The base material of organic silicone modified sealant is the organic silicone modified organic polymer. This polymer has the properties of organic silicone compounds and organic polymers. The sealants that contain it have good adhesion, good elasticity and aging resistance. Its properties are almost all better than organic polymer sealants and reach the level of organic silicone sealants and its cost is lower than organic silicone sealant. Thus, it becomes a very good new medium to high-end sealants.

Raw Materials of Organic Silicone Modified Sealants

The silicon modified polymer is liquid fluid, the solidification product that does not contain filler is the soft rubber form material. Its tension rate is lower and its cutting and tension strength are not high. Thus its direct application value is not high. However, by adding reinforcing agent, filler, plasticizer, light stabilizer, crosslinking accelerator and dehumidifier, the new designed sealant’s physical property will have evident changes. The function abilities are determined by the design, articrafting condition and selection of main components of sealants. The main components are the following ones:

1.      Base material. Silicone modified polymer is the base material of silicone modified sealant. To make full use of hydrolysis of silicone modified polymer endings, could make it to have solidification and to form the elastomers that has Si-O-Si bones to reach the effects of sealing and adhesion. The key of techniques are the selections of functional groups, main-chain structure and molecular quantity.

2.      Reinforcing filler. The main effect is to increase the strength and chemical resistance of sealants and to improve the viscous flow status. It could get the needed thixotropy and extrudability of construction sealing. It could also reduce the cost in some degree.

3.      Plasticizer. The plasticizer used in designing silicone modified sealability is mainly to improve constructability and physical properties. It could also adjust the hardness, viscosity, modulus and flame retardancy of sealant.

4.      Pigments. The pigments that added to silicone modified sealants are to make the sealant and the stick matter to have the same color or to allow the sealant and the coating to have the same color to improve the aesthetics. It is applicable to take any type of pigment or colorant.

5.      Catalyst. Catalyst is mainly used in the composition of pre-polymer and the acceleration of crosslinking and solidification of sealant.

6.      Thixotropic agents. It is to grant the ideal operability on sealants, thixotropic agent is applied.

7.      Stabilizer. Silicone modified sealants have aging problem; the main problems are thermal oxidation and light adding. Therefore, it is a must to add some antioxidants and light stabilizers. The antioxidants are mainly used to curb the thermal oxidation of sealants. Light stabilizers usually have two components, one is UV absorber and the other one is the hindered amines. When adding two together to the sealant, it will have a better light stability.

8.      Other auxiliaries. It is in order to increase its storage stability; it is a must to add some dehydrator and the solvents that could improve flowing ability like toluene.

These materials grant sealants many excellent properties. The storage stability is granted by the Si-C key on the endings of silicone modified sealants. The low unsaturated key amount in the molecular chains which is the unique property of silicone modified sealant pre-polymer gives the weatherproof. Also, it is since the crosslinking of siloxane and the chemical resistance of polymer chemical structure has synchronicity, and they have good hydrolysis resistance and chemical resistance. This could rapidly promote this sealant to be the ideal sealing materials that apply in many industries, transportation and automotive.

Summary

Sealant could be regarded as one of the largest consumable organic silicone products. It is sold by many small and medium manufacturers and almost every country has a large demand on it. So, it is one of the most hot selling organic silicone products that have great commercial value. Also, more and more people are studying and trying to develop new type of organic silicone sealants. This shows the high potential and the bright market future of the sealants.