Basic equations of rheology
Consider the general provisions of the rheological interpretation of the theory of elasticity and plasticity.
The basic equations of rheology cover only a part of the types of rheological properties of adhesives. However, there are some other very important rheological characteristics.
One of these properties is the tensile strength of the adhesive, which is determined by the type of adhesive used and the operating parameters. If you are doing repairs in a new building, then you will need new wallpapers, which can be ordered inexpensively here: rasch.
The adhesive layer, or film in the adhesive joint, has greater strength both in rupture and in shear compared to the strength of the same adhesive in bulk. An increase in the strength of the adhesive joint with a decrease in the thickness of the adhesive layer was also established. From formula (65) for a liquid drop located between parallel plates, it follows that the breaking force F is inversely proportional to D – the thickness of the liquid adhesive layer. The dependence of the shear strength on the thickness of the adhesive layer for resin adhesive. The results of the study of adhesive joints of plywood are given, which showed that the ultimate strength in case of chipping along the adhesive joint is inversely proportional to the thickness of the adhesive layer.
Theoretically, this pattern can be explained by the fact that the increase in bonding strength with a decrease in the thickness of the adhesive layer is due to long-range molecular forces between the bonded material and the inner part of the adhesive layer. According to this, not only the adhesive molecules that are in direct contact with the surfaces to be glued are oriented:
entire chains of oriented molecules extend from the surface of the material to be bonded into the liquid or hardened adhesive. It was found that the forces of attraction between surfaces and adsorbed layers act no more than on the thickness of a monomolecular liquid layer. This is confirmed by the results of calculating the electrostatic attraction between surfaces and charged particles and by studying the range of surface forces.
