Adhesive products are very common in our daily life and in industrial production and are used in a wide range of applications.
Let's look at adhesives from the point of view of a number of technical parameters, which are specific to different product applications and substrates. We believe that after reading this article you will have a deeper understanding of adhesives.
1. Density
- Unit
The mass per unit volume of a substance is called the density of the substance. The main unit in the International System of Units is kg/m³, and the common unit of our products: g/ml.
- Density measurement and meaning
(1) Measurement method: density cup 5ml syringe (non-standard method, only for reference)
(2) Significance: physical constants, no special significance in electronic adhesives.
2. Viscosity
Definition of liquid in the flow, the nature of internal friction generated between its molecules, known as the viscosity of the liquid, the size of the viscosity expressed in viscosity. Liquid by the action of external forces and the relative movement of the liquid molecules produced between the resistance, so that the liquid can not carry out a smooth flow, the size of the resistance is called viscosity. Viscosity is divided into dynamic viscosity and kinematic viscosity.
- dynamic viscosity will be two boards with an area of 1 square meters immersed in liquid, the distance between the two boards for 1 meters, if you add 1N of shear stress, so that the relative rate between the two boards for 1m/s, then the viscosity of the liquid is 1Pa.s. In the International System of Units, the unit of dynamic viscosity is Pa.s, the viscosity is generally referred to as dynamic viscosity.
- the movement of viscosity power viscosity and the density of the same temperature ratio, said the liquid flow under gravity in the measure of internal friction; fluid shear stress and shear rate ratio. It is the measure of resistance to flow of this fluid under gravity; kinematic viscosity unit is ㎡ / S.
3. Curing reaction
The process of obtaining and improving properties such as adhesive bond strength through chemical reactions (polymerization, cross-linking, etc.). Curing is the key process to obtain good bonding properties, only fully cured, the strength will be the maximum.
Curing can be divided into initial curing, basic curing, post-curing.
Under certain temperature conditions, after a period of time to achieve a certain strength, the surface has been hardened, not sticky, but the curing did not end, this time is called the initial curing or gel. After a period of time, most of the reaction groups to participate in the reaction, to a certain degree of crosslinking, known as the basic curing.
After curing is in order to improve the adhesive properties or due to the needs of the process and the basic curing after the bonding parts of the treatment. Generally at a certain temperature, keep for a period of time, can supplement the curing, further improve the degree of curing, and can effectively eliminate internal stress, improve bond strength. In order to obtain a well-cured adhesive layer, the curing process must be carried out under appropriate conditions. Curing conditions include temperature, time, etc.
- Curing temperature
The temperature at which the adhesive reacts most vigorously. Adhesive curing requires a certain temperature, just different varieties of adhesives, curing temperature is different. Temperature is the main element of curing, not only to determine the degree of completion of curing, but also to determine the speed of the curing process. Appropriately increase the temperature will accelerate the curing process, but also can improve the bond strength.
- Curing time
Refers to a certain temperature, the adhesive curing time required. The length of the curing time is closely related to the curing temperature. Raise the temperature can shorten the curing time, lower the temperature can be appropriate to extend the curing time. Whether it is room temperature curing or heating curing, must ensure that sufficient curing time to cure completely, to obtain the maximum bond strength.
Curing time graph (DSC test) gel time is an important reference data to study the curing conditions of the adhesive, can be used as a test of the performance of the finished adhesive, to identify whether the formula is a simple and easy to implement method!
- Curing conditions
Curing temperature, curing time, gel time measured as a reference.
4. Storage period and application period
- Storage period
In the specified conditions, the adhesive can still maintain its operational performance and expected physical and chemical properties of the longest storage time. Generally speaking, if the viscosity does not change much during the storage period, its performance will not have a great change.
- Applicable period (Pot life)
In the specified conditions, the adhesive can still maintain its operational performance and the expected physical and chemical properties of the longest working time. In the ideal situation, the applicable period should be associated with the storage time at room temperature, but due to the operation of the environment temperature and humidity reasons, has been operating itself caused by some other factors (such as shear thinning, heat) and so on the impact of the applicable period will lead to a shorter period of time than the storage of the time at room temperature, the red adhesive by the impact of the larger, the specific operating time needs to be simulated to determine the use of the customer.
5. Shear strength
Tensile shear strength, adhesive tensile shear strength test is also often carried out at high or low temperature conditions. Is the main adhesive bonding strength indicators.
- On the adhesive head test piece of the adhesive layer to apply tensile shear load, to the joint destruction of the maximum load, divided by the value of the bonding area.
- That is, under the action of the load parallel to the adhesive layer, the bonding specimen destruction, the unit of the adhesive surface of the shear force endured, expressed in MPa.
6. Glass transition temperature
Glass transition is the amorphous polymer materials between the glass state and high elasticity state conversion.
- Taking the glass transition temperature as the boundary, polymers present different physical properties
- Below the glass transition temperature, polymers behave like plastics.
- Above the glass transition temperature, polymers behave like rubber.
Adhesive production line introduction
If you are interested in the production of adhesives, or you are preparing to run an adhesive production plant, you can contact us at any time, we will provide you with professional supply chain services. Click on the image to learn more.
