Inorganic Adhesives and Application Overview (1)

Adhesives formulated with inorganic compounds are collectively referred to as inorganic adhesives. Examples of the inorganic compound as a binder include silicates, phosphates, sulfates, borates, magnesium oxychloride, aluminum oxide, lead oxide (lithium), sulfur, nitrides, low-melting-point alloys, and the like. The inorganic adhesive has the advantages of easy availability of raw materials, low price, convenient construction, durability, incombustibility and temperature resistance superior to organic adhesives and no pollution to the environment. Its application is not only cement (solid silicate) and gypsum used in large quantities in the construction industry, but also used in bonding of paper products, metals, ceramics, and glass.

Classification of inorganic adhesives can be divided into silicates, phosphates, borates, sulfates, etc. according to the main chemical components of the 1 base; 2 curing methods can be divided into air-dry, hydraulic, reactive and hot melt Type, but also according to room temperature or heating curing points; 3 other according to the strength of bonding, specific use and packaging and other classification. Most of the domestic classification is based on the chemical composition of the base materials, and foreign countries generally adopt the classification method of curing methods. The following is an introduction to the types of curing methods.

(1) Air dry type. This means that the moisture or solvent evaporates after being bonded to dry, cure, and form a certain bond strength. A typical adhesive is sodium silicate (water glass).

(2) hydraulic type. Water is used as a curing agent to make the adhesive chemically react with water and harden, such as cement, gypsum and so on.

(3) Reaction type. This is caused by a chemical reaction between the adhesive and chemical components other than water. Room temperature or warming reaction to cure, such as phosphates, silicates and so on.

(4) hot-melt type. The adhesive Liu is first heated to the melting point to melt it, and then it is applied to the adherend and then glued. The cooling is resumed to a solid state, that is, it has a bonding force. Such as sulfur, low melting point alloy (flux) and so on.

This article describes several inorganic adhesives by chemical composition.

1. Silicates

1.1. Portland Cement

It is a general term for highly alkaline silicate cement. It is commonly known as Portland cement in foreign countries. After adding water, sand, stones and other materials can be glued to form a solid stone. In the construction industry is a large amount of construction materials. Over 95% of cement varieties are Portland cement.

(1) Method of manufacture. Limestone and clay (aluminosilicate) are mixed in a prescribed ratio, ground, and calcined in a kiln at a high temperature of approximately 1720 K to obtain a cement clinker, which is then ground with a small amount of gypsum. The main components are tricalcium silicate (3CaO·SiO2) and dicalcium silicate (2Ca0·Si02), followed by tricalcium aluminate (3CaO·A1203) and tetracalcium aluminosilicate (4Ca0·A1203·Fe203), and A small amount of uncombined calcium oxide and magnesium oxide.

(2) Application process

1 with plastic. The general mortar ratio is cement: sand = 1:2.5. In the preparation, the dry materials are mixed in proportion according to the ratio, and then a suitable amount of water is mixed to form a mortar. When using concrete, 5 more stones should be added.

2 glued process

(a) Metal and concrete are glued together. First make a hole in the concrete, and then bury the metal bolt or embedded part at the end with a hook, and then fix it with mortar.

(b) Paste tiles, floor tiles, and mosaics. The mortar is applied to the back of the brick, and then it is affixed to the wall surface or the ground on which the mortar is previously applied, and is lightly tapped with a rubber mallet or a wood hammer, so that the paste is firmly and flattened, and is basically adhered one day. In order to improve the fastness of paste, 107% cement can be added to the mortar.

(c) floor. After spreading the mortar on the ground, it is compacted and smoothed with a wooden trowel or rubber roller. It is generally 20 mm thick. The mortar was pressed once on the surface when it was dry, slightly hard, and before solidification, and was calendered with a steel trowel. Continue curing for about 7 days.

(3) performance. The relative density of Portland cement is 3.1-3.2. The mixture of cement and water generates heat, which hardens and compresses for a certain period of time. It is a hydraulic adhesive. Ordinary cements, namely Portland cement, are commonly used in 325, 425, 525, and 625, and some high-strength and ultra-high-strength cements have a label of 1000 or more. The label is a numerical value indicating the compressive strength, and the larger the label, the higher the strength. For example, 425 cement, according to the national standard samples cured in water for 28 days measured the compressive strength of 425 ~ 524kg/cm2 (equivalent to 41.7 ~ 51.4MPa).

(4) Uses. Widely used in construction, roads, bridges, dams, cement parts such as poles, concrete floor tiles, railway sleepers and cement prefabricated parts.