1. What is glue:
Glue is a substance that can bond two objects. Glue does not exist independently, it needs to be applied between two objects to play a bonding role.
2. Glue viscosity (cps):
The viscosity of the glue is measured with a Brookfield viscometer, and the unit is "cps centipoise". The reading of the viscosity of the glue is generally between 300 and 30000cps. In water-soluble adhesives, the solid content does not determine the viscosity of the glue, but the plasticizers, tackifiers, etc. in the glue formula affect the viscosity of the glue. Generally, the higher the ambient temperature is, the "viscosity↓" and "temperature↓viscosity↑". The viscosity of water at 27°C is "1".
3. Fluidity (rheology) of the glue :
Use low and high rotational force to measure its viscosity value and then take its ratio. Generally, the fluidity of the glue is 1.5-3. The viscosity of glue has a lot to do with its rheology. To glue "stir ↑ thinness ↓". Especially water-soluble glue, the more it is stirred, the thinner it becomes. The relationship between the coating characteristics of the glue and the rheology: less than 1 is the most difficult to coat; 0-1.5 turbid flow phenomenon; 1.5-3 is good coating property (the rheology is also better); greater than 3 is too thin;
4. Minimum film forming temperature (MFT):
At a certain temperature, after all the water in the adhesive volatilizes, it is the film-forming temperature in the critical state where it changes from liquid to solid. At this time, the dried glue layer is very brittle and has no cohesive force.
5. Film forming speed :
Effective bonding time from application of adhesive to formation of an adhesive film in two substrates. It is affected by the following factors;
The moisture dissipation time in the adhesive (short time and fast film formation).
High substrate porosity (large porosity and fast effective binding time).
The amount of adhesive applied (large amount, slow bonding time).
The formulation, solid content, etc. of the adhesive will affect the film forming speed.
6. The health preservation period of glue:
After the glue forms a film between the two substrates, it develops a bond over time. During this time period, the time of lowest bond formation is important. After the minimum binding force is formed, we can do other work, it will not affect the performance of the final product of the glue. With the increase of time, the formation of the bonding force of the glue is the most complete after a period of time, and the bonding force is stable, which is the highest bonding force. The time from the lowest binding force to the highest binding force is the curing period of the glue. The minimum binding force of general glue is 24 hours. The health preservation period is 1-7 days. The ambient temperature in use and different bonding materials will affect the curing period of the glue
7. Waterproof grade of glue:
The waterproof grade of glue is divided into four grades, and the waterproof grade of floor glue should be above grade 3.
Level 1: general waterproof;
Level 2: indoor weak waterproof;
Level 3: indoor strong waterproof;
Level 4: Waterproof for outdoor use. FDA standard: refers to the "international close to the human body pollution-free" standard.
8. Solvent resistance of glue:
Use "acetone" (the main ingredient in paint) to test how the glue reacts to acetone. After painting, the swelling rate of the solvent in the paint to the film. The bigger the glue the worse the quality. Poor quality glue in the presence of "acetone" in a high-temperature environment, the glue film of the glue will gradually turn black in about half an hour, and the cohesion of the film will decrease.
9. Does the color of the adhesive film affect the adhesive force of the adhesive?
The glue film is transparent or milky white, which is normal and will not affect the adhesive force of the glue (blackening, milky white swelling will affect the adhesive force of the glue). Generally speaking, after adding the water-blocking filler, the transparency of the glue film is poor, but it will not affect the effectiveness of the glue.
10. The bonding principle of water-soluble glue:
The chemical composition in the glue, in a water-based environment. Polymer body in the glue one of petroleum derivative (vinyl acetate in white glue be) is all rounded particle, and the radius of general particle is between 0.5～5 μm. Object bonding, it is simply to realize by the pulling force between the polymer body in glue. In glue, water is exactly the carrier of polymer body, and water loads polymer body and is immersed slowly in the tissue of object. After the moisture in the glue disappeared, the polymer body in the glue just relied on mutual pulling force, with two objects combining tightly. In the use of glue, too much glue will make the polymer bodies in the glue crowded together; good pulling force cannot be produced between the polymer bodies. The polymer bodies are crowded with each other, so that they cannot form a stronger attraction to each other. At the same time, the moisture between the polymer bodies is not easy to volatilize. Here it is why in bonding process " glued film is the thickest, reason that the bonding effect of glue is the poorest ". Glue-spread is too much, and what glue played greatly is " filling effect " rather than bonding effect, and what bonding between objects relies on is not the cohesive force of glue, but " cohesive force " of glue.
11. Commonly used and simple methods to identify the quality of glue:
★Pour the glue on the flat glass to observe its rheology, swing it left and right to observe its rheology.
Conclusion: The glue flows too fast, indicating that the glue is too thin. Poor fluidity, too thick is not conducive to bonding.
★Dip it with your hands to observe its viscosity.
Conclusion: It is better to be able to draw slowly, with a little stickiness.
★Pour it on a small piece of glass to observe its film-forming time.
Conclusion: The film forming time of the glue that can form a film on the surface of the glue is better in about 1 to 2 minutes.
★ After the glue is basically cured after film formation, dip your fingers in water and pour it out to observe its cohesion.
Conclusion: Glue melts quickly - poor cohesion. The glue is turbid after being purged - filler is added.
★Use two allegro boards to stick together after staggering, and measure the tension after 24 hours. Soak in water for a day and then dry to observe the color change.
Conclusion: If the tensile force of the glue changes little, it means that the glue has good water resistance. Otherwise it is very poor.
