Two-component polyurethane adhesive (2)

Effect of Distribution Ratio of Table A and B on Adhesive Strength*
A component: B component (mass fraction) 100:5 100:10 100:30 100:50 100:70 100:100
Shear strength, MPa 6.2 7.4 11.7 12.3 12.4 13.7
* The adhesive material is aluminum-aluminum alloy.

Adding a certain amount of filler to the adhesive can increase the hardness and heat resistance of the adhesive layer, and can also reduce the cost of the adhesive. The amount of filler added is generally 10% to 20% (parts by mass). It is required that the filler particle size be fine and can be uniformly dispersed in the adhesive. And it requires the filler to be dry and easy to be wetted by the adhesive. The influence of the amount of filler added on the aluminum-aluminum bond strength is shown in the table.

Filler (parts by mass) A component (parts by mass) B component (parts by mass) Aluminium-aluminum shear strength, MPa

Quartz powder, aluminum powder, iron powder, asbestos powder, and talcum powder can be used as fillers for general-purpose polyurethane adhesives.

(3) Coating and Curing When using a good glue solution for coating, use a paintbrush to apply the glue to the surface of the treated material. Place the glue for 5-10 minutes after the first application of the glue, and then apply it for a second time. 10-20min. Then, the surfaces of the materials to be bonded are attached together, and a pressure of 0.03-0.05 MPa is allowed to cure, and the pressing time is several minutes to 10 h. The adhesive bonding parts can be bonded at room temperature for a day and night to achieve a greater bonding strength. It takes 3-5 days to reach maximum intensity. Heating and curing can shorten the curing time, such as 2 hours at 100°C and 1 hour at 130°C, and the adhesive layer can reach the basic curing. Adhesives have a certain amount of adhesion before they cure, but do not use them in hot and humid places.

When the area of ​​the adhered material is large, the paint brush or the spray coating method can be used for sizing. The effect of the curing temperature on the bond strength is shown in the table, and the adhesion conditions of various adhered materials are shown in the table.
Effect of Table Curing Temperature on Adhesive Strength

A component: B component (mass fraction) Shear strength at 100°C for 2 hours, MPa Shear strength at room temperature for 1 day, MPa
100:10
100:50 7.3
12.2 6.5
11.1

4. Adhesive properties

The adhesive strength of general-purpose two-component polyurethane adhesives to various materials is shown in the table. The adhesive strength of the aluminum-aluminum alloy adhesive at various temperatures is shown in the table.

The hard PVC was bonded with a general-purpose two-component polyurethane adhesive and immersed in acid and alkaline solutions at different temperatures for 7 days respectively. The shear strength was measured as shown in the table. Immersed in sodium hydroxide solution, the adhesive film is in powder form, and immersed in hydrochloric acid is crisp.

The aluminum-aluminum bonded specimens were tested for oil resistance, hydrolysis resistance, and damp heat resistance. The changes in the adhesive properties are shown in the table. From the oil resistance test data, the gasoline soaked with the highest adhesion, cold water immersed second, therefore, can be used as a hydrolysis resistant adhesive, but not suitable for long-term use. However, after heat aging at 70°C, the adhesive strength was increased, which indicates that the polyurethane adhesive cures better under heating conditions.

5. Improved Universal Polyurethane Adhesive

In the production operation of the above-mentioned general-purpose two-component polyurethane adhesive, there is a problem that it is difficult to control the viscosity. If the index cannot be achieved, the initial adhesive strength of the adhesive is poor, which brings difficulties in use. In addition, general general purpose adhesives may produce crystals or floccules in winter, and may be used after being heated and melted, thus causing troubles for users. After the improvement of the preparation method and the adjustment of the structure of the polyester polyol, the above problems are solved, and a universal two-component polyurethane adhesive that is popular among users is obtained.

1. Preparation of A component glue by chain extension

Polyethylene adipate - ethylene glycol after vacuum dehydration, the moisture content of 0.06% or less. The molar ratio (R index) of toluene diisocyanate (80/20) to polyester polyol can be equal to 2.5, and the charge amount of TDI and polyester polyol can be calculated. The reaction temperature between TDI and polyester polyol is 90-95°C, and the reaction time is 2 hours. The chain extension reaction of diethylene glycol (diethylene glycol) chain extender and dibutyltin dilaurate catalyst are carried out according to the calculation to increase the molecular weight. (Viscosity) is further increased, and the addition amount of the solvent and the addition method are performed with reference to the above-described production method. The viscosity index of the component A glue prepared by the chain extension method is stable, and the viscosity index of the component A glue liquid can be controlled by adding the amount of the chain extender (diethylene glycol).

2. Low-temperature non-crystallized A component glue

The a-component glue prepared by using polyethylene adipate-ethylene glycol-propylene glycol instead of polyethylene adipate can be stored at room temperature and at a low temperature of about zero without crystals and floccules. Will crystallize. The molar ratio of ethylene glycol to propylene glycol in the polyester is 8:2 or 9:1.

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