What are the basic knowledge of environmentally friendly hot melt adhesives?

Hot melt adhesive is a plastic adhesive whose physical state changes with the temperature within a certain temperature range. When heated and melted to a certain temperature, it becomes a liquid that can flow and has a certain viscosity. The melted EVA hot melt adhesive is light brown or white. EVA hot melt adhesive is composed of basic resin, tackifier, viscosity modifier and antioxidant.

It is non-toxic and tasteless, and is an environmentally friendly chemical product. The basic common sense of hot melt adhesive is as follows:

1. softening point, the temperature at which a substance softens. Primarily it refers to the temperature at which the amorphous polymer begins to soften. It is not only related to the structure of the polymer, but also to the size of its molecular weight. There are many measurement methods.

Different measurement methods often result in inconsistent results. The more commonly used methods are the Vicat method and the globe method.

2. Viscosity: When a liquid is flowing, the property of internal friction between its molecules is called the viscosity of the liquid. The viscosity is expressed by viscosity, which is a resistance factor used to characterize the properties of the liquid. Viscosity is divided into dynamic viscosity, kinematic viscosity and conditional viscosity.

3. peel strength: The force required to peel a unit width from the contact surface of the materials stuck together. The angle of peeling is 90 degrees or 180 degrees, and the single is: Newton/meter (N/m).

4. Initial tack: When there is a brief contact between the object and the adhesive surface of the pressure-sensitive adhesive tape with a small pressure, the adhesion of the adhesive tape to the object is called the initial tack. Test principle, roll a steel ball over the sticky surface of the adhesive tape lying flat on the inclined plate.

According to the size of the steel ball that the sticky surface of the specified length can stick to,

5. Holding power, the ability of the adhesive tape to resist displacement when a weight with a specified weight is vertically suspended in the length direction of the pressure-sensitive adhesive tape pasted on the adherend. Use the test piece to move a certain distance of time or a certain time to move distance table.

6. The cohesion value is the mutual attraction between adjacent parts within the same substance, and this mutual attraction is the manifestation of molecular force between molecules of the same substance.

It is only shown when the molecules are very close together (less than 10e-6 cm).

7.tensile strength at break, in the tensile test, the tensile stress of the sample until it breaks is the tensile strength, which is called tensile strength in academia, and is often called tensile strength in engineering applications. strength.

8. Weather resistance refers to a series of aging phenomena such as discoloration and discoloration of plastic products due to the influence of sunlight, temperature changes, wind and rain and other external conditions. Among them, ultraviolet radiation is a key factor in promoting the aging of plastics.

9. Curing time: the shortest time for the glue to be pressed between the two substrates to form a firm bond, and the pressure holding time should not be less than the curing time to bond well.

10. Open time: refers to the time interval from when the glue is applied until the surface can still bond to the substrate. The glue has a good bonding effect within the open time. It is related to factors such as glue, temperature, substrate, and amount of glue.