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Time parameter in adhesive

Aug 02,2020 | Views: 642

1. Gel time


Generally, it refers to the time required for liquid resin or glue solution to change from liquid liquid to solid gel at specified temperature. It is used to measure the active degree of reaction between resin and curing agent.


The measurement of gel time


(1) Gel time is sensitive to the influence of system temperature, and the measurement is carried out under constant temperature.

(2) It is usually obtained under the condition of 100cm @25 , which is significantly related to the test temperature and the sample volume.

(3) The simplified test method is as follows: after the disposable cups are mixed with glue, the time that they can stand upright after being inserted with bamboo skewers is estimated.

(4) Different resin and curing agent types have different gelation time.


2. Applicable period Pot Life


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


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

(2) The applicable period is affected by the amount of mixed glue, and the amount of mixed glue is large, but the operation time is short.

(3) In the actual operation, when the glue viscosity has become too thick to be used again, unable to sizing is the applicable period.

(4) For single-component moisture curing adhesives and sealants, the applicable period refers to the shortest time it can be extruded and exposed to air for coating assembly.

(5) The application period of the two-component adhesive generally refers to the time when the viscosity increases by one time.

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

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


3. Open time


Opening time refers to the maximum time that a mixed resin and curing agent can be placed on the substrate before the substrate is bonded. Generally speaking, after gluing for a period of time and then gluing still retains 80% of the final tension force when gluing immediately after gluing, which can be calculated as the opening time.


(1) When the resin and curing agent are mixed, the viscosity will change and constantly improve, which will affect the operation of the adhesive, and also affect the bonding effect.

(2) The opening time is also affected by temperature.


Difference between applicable period and open time


The biggest difference between the two is that the application period considers the glue before it is applied to the substrate and the opening period considers the glue after it is applied to the substrate.


4. Skin over time/ time for Skin formation


Table drying time usually refers to the time for a single component of the moisture-cured adhesive to place a small PE sheet (approximately 2cm x5cm) on the surface of the adhesive and remove the surface without residual adhesive. Adhesive itself is still viscous, but will not leave traces on the PE sheet. Also known as "peeling time" "refers to dry time".


(1) Table dry time will be affected by temperature and humidity.

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



5. Cure Time


Curing time refers to the time for the adhesive to fully cure according to curing conditions.


But the general adhesive to the maximum strength, can carry out all kinds of performance testing time is recommended after 7 days.


6.Minimum cure Time


The minimum curing time is the time required to achieve 80% of the final strength after the resin is mixed with the curing agent.


LSS(Lap shear strength) is measured by specifying the temperature point (e.g., 100°C or 25°C) at which the test is to be performed.


7. Handling Strength


Treatment strength refers to the adhesive adhesion after the time to reach a certain strength, under this strength can let the adhesive parts move without destroying the structure of the adhesion, also known as "operating strength".


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


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

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

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