Time parameters in adhesives

The time parameters of adhesives are inextricably related to the production process and production beat, and have extremely important reference significance!

Today we're going to talk about time parameters in adhesives.

It generally refers to the time required for liquid resin or adhesive liquid to be transformed into a solid gel from a flowing liquid at a specified temperature; It is used to measure the active degree of reaction between resin and curing agent.

Measurement of gel time

(1) The effect of gel time on the temperature of the system is very sensitive, and the determination is carried out at constant temperature.

(2) It is usually measured at 100cm³ @ 25℃, which has an important relationship with the test temperature and sample volume.

(3) The simple test method is: after mixing the disposable cup with glue, the time that can stand up after inserting the skewer is estimated.

(4) Different resin and curing agent types have different gel times.

The applicable period refers to the time when the resin and curing agent are mixed and the mixed adhesive can be used for construction. Also known as "usable time", "operational time", "applicable time".

(1) The applicable period is directly related to the gel time, usually defined as 75% gel time.

(2) The application period is affected by the amount of mixed glue, and the amount of mixed glue can be short operation time.

(3) In actual operation, when the viscosity of the glue is felt to be too thick to be used again, it can no longer be applied.

(4) For single-component moisture-cured adhesives and sealants, the application period refers to the shortest time that it is extruded and exposed to the air for coating assembly.

(5) The application period of the two-component adhesive generally refers to the time when the viscosity is doubled.

(6) Different resin and curing agent types have different application periods.

(7) In some cases, the applicable period is also called "working time".

The opening time refers to the maximum time that the mixed resin and curing agent can be placed on the substrate before bonding. In general, gluing after a period of time still retains 80% of the final tension when gluing immediately after gluing, which can be calculated as the opening time.

(1) When the resin and curing agent are mixed, the viscosity changes and will continue to increase, which will affect the operation of gluing and also affect the effect of bonding.

(2) Opening hours are also affected by temperature.

The difference between application period and opening hours

The biggest difference between the two is that the application period is considered before the glue is coated to the substrate, and the opening time is considered after the substrate is coated.

The surface drying time usually refers to the time that a small PE sheet (approximately 2cm x5cm) is placed on the surface of the adhesive and no residual glue is left on the surface when removed. The adhesive itself is still sticky, but it will not leave traces on the PE sheet. Also known as "crust time" and "finger drying time".

(1) Surface drying time will be affected by temperature and humidity.

(2) For a single component moisture curing adhesive, the surface drying time is usually the applicable time.

Curing time refers to the time to achieve complete curing of the adhesive according to curing conditions.

However, the general adhesive to achieve the maximum strength, can carry out various types of performance testing time is recommended to be 3-7 days

6. Minimum curing time

The minimum curing time refers to the time required for the resin and curing agent to reach 80% of the final strength after mixing.

In terms of tensile shear strength, it is necessary to state the temperature point used for the test (e.g. 100°C or 25°C).

7. Processing intensity

Processing strength refers to the time after adhesive bonding to reach a certain strength, at which the bonding site can be moved without damaging the bonding structure, also known as "operational strength".

Therefore, if the adhesive structure is moved before the treatment strength is reached, it will cause adverse effects and cannot be remedied. The treatment strength is usually quantified as the time when the tensile shear strength reaches 1Mpa.

(1) The treatment intensity is also affected by temperature.

(2) The treatment strength is different from the initial strength.