Do you know about the adhesive strenght?

The adhesive strength of the adhesive is one of the important indicators to evaluate the quality of the adhesive. The adhesive strength is usually divided into shear strength, stretching strength, peeling strength and impact strength according to the force condition in the use of adhesives.

1. Definition of adhesion intensity

The adhesion intensity refers to the stress required to damage the adhesive and the adhesive interface or the neighbor of the adhesive under the action of external forces. The adhesive strength is also called the glue connection strength.

The adhesive intensity is the stress required when the adhesive system is destroyed. The size depends not only on the mechanical properties of the adhesive, the nature of the adhesive, the nature of the adhesion, and the adhesion process. Size, direction, frequency), environmental factors (temperature, humidity, pressure, medium) are related to test conditions, experimental technology, etc. It can be seen that the adhesion is only one of the important factors that determine the strength of the adhesion. Therefore, the adhesive strength and bonding force are two concepts with completely different meanings, and must not be mixed.

2. The form of force of adhesion joint

The force that the adhesive connector suffers can be summarized by four forms: shear, stretching, unevenly pulled and peeled off.

A. Cut.

The external force is equal and the direction is opposite. It is basically parallel to the adhesive surface and evenly distributed on the entire bonding surface.

B. Stretch.

It is also called uniformly pulled away, the effect of the opposite direction of the direction, vertically on the adhesive surface, and evenly distributed on the entire bonding surface.

C. Uniformly pull away.

It is also called splitting. Although the direction of the external force is also perpendicular to the adhesive surface, the distribution is uneven.

D. Dipping.

The direction and bonding surface of the external force form a certain angle. It is basically distributed in a straight line on the adhesive surface. The above four forces are likely to exist in the same adhesive system at the same time, but it is the main problem.

3. Classification of adhesion strength

Depending on the force of the adhesive joint, the bonding strength can be divided into shear strength, stretching strength, unevenness, peeling strength, compression strength, impact strength, bending strength, twist strength, fatigue strength, anti -creep, resisting creep, resistance to creep Change intensity, etc.

A, shear strength

The shear strength refers to the shear force that the unit adhesive surface can withstand when the adhesion is destroyed, and its unit is expressed by the unit (MPA). The shear intensity is divided into stretch shear, compressed shear, twisting shear, and bending shear strength according to testing.

Different properties of adhesives have different shear strengths. Generally, tough adhesives are greater than the shear strength of flexible adhesives. A large number of tests show that the thinner the thickness of the glue layer, the higher the shear strength.

The most impact of testing conditions is the ambient temperature and test speed. As the temperature increases the sharp shear strength, as the test speed slows down, the shear strength decreases, which shows that the temperature and speed have an equivalent relationship, that is, the improvement of the test temperature is equivalent to equivalent to equivalent Reduce loading speed.

B. Stretch strength

The stretching strength is also called uniformly lip -off strength and positive strength. It refers to the stretching force that the unit area is affected when the adhesion is damaged. Because stretching is much more powerful than shearing, the stretching strength of general adhesives is much higher than the shear. In actual measurement, under the action of external forces, the deformation of the adhesive is larger than that of the adhesive, and the different axis of the external force is likely to produce shear and horizontal compression. There may be breaks at the same time. If the length of the sample can be increased and the bonding area can be reduced, the effect of peeling during the disconnection can be reduced, and the distribution of stress effects can be more uniform. The effects of elastic modulus, glue layer thickness, test temperature, and loading speed on the stretch strength are basically similar to shear strength.

C. Dipping intensity

The peeing strength is the maximum load that the unit width can withstand when the specified divestiture is separated, and its unit is represented by Kn/M. There are many forms of peeling, which can generally be divided into L -shaped stripping, U -shaped stripping, T -shaped stripping and curved surface stripping.

With the change of the stripping angle, the form of divestiture also changes. When the peeling angle is less than or equal to 90 °, the L -shaped outbound, greater than 90 ° or equal to 180 °, is U -shaped. These two forms are suitable for the peeling of rigid materials and scratching materials. Type T is used for stripping when bonding of two deflection materials. Dipping intensity is affected by factors such as the width and thickness of the test parts, the thickness of the glue layer, the peeling strength, and the angle of stripping.

D. Uniformly pull away the intensity

Unexplained the maximum load that the adhesive joint can bear when the adhesive joint is unevenly lipped, because the load is mostly concentrated on the two or one edge of the rubber layer, so it is the unit length rather than the unit area of the unit area The unit is KN/M2.

E, impact strength

The impact intensity means that when the adhesive part is destroyed by the impact load, the maximum power consumed by the unit bonding area is KJ/M2. According to the different forms of the connector and the way of stress, the impact strength is divided into bending impact, compressed shear impact, stretch shear impact, twisting shear impact, and T -shaped stripping impact strength.

The impact intensity is affected by the toughness of the adhesive, the thickness of the adhesive, the type of adhesion, the size of the test parts, the impact angle, the environmental humidity, and the test temperature. The better the toughness of the adhesive, the higher the impact strength. When the amount of the adhesive is low, the impact strength increases with the thickness of the glue layer.

F. Specific intensity

The durable intensity is the maximum load that the unit bonding area can withstand after the long -term static load effect of the adhesive parts. The long -lasting intensity is affected by the loading stress and test temperature, and the durable strength of the loading stress and temperature decreases.

G, fatigue strength

Fatigue intensity refers to the maximum stress that repeats a certain load to the prescribed connector to the specified number of times. Generally, the fatigue intensity at 10 times is called the fatigue strength limit. Generally speaking, the tingling, bending, impact, etc. with high shear strength are always low; and the impact and curved strength of the peeling strength are high. Different types of adhesives have very different strength characteristics.