What are the ways to increase the strength of glass?

The methods to improve the mechanical strength of glass are as follows:

1. Improve hardness. Cracks appear on the surface of the glass, and 90 percent of the cracks are scratches. Mechanical damage should be prevented during processing, but it is also important to have high hardness of high-temperature resistant glass.

2. Improve chemical stability. The second way to prevent surface cracks is to have a high chemical stability of high-temperature resistant glass. Sight glass is often subjected to a variety of environments that can cause chemical corrosion.

Therefore, the chemical stability of the glass is required to be at the level of water resistance. The surface of the glass with poor chemical stability will be eroded to produce microcracks, which will greatly reduce the mechanical strength of the glass, even to one-twentieth of the original, which is also an important reason why some bad glass products are fragile after forming.

3. Homogenize glass composition. The uneven composition of glass will cause its mechanical strength to drop significantly, and the macroscopic defects of glass appearance, such as stones, streaks and gas lines, are easy to find and difficult to eliminate in production, among which the greatest impact on strength is stones, which should be strictly controlled.

4. Reduce stress. Stress causes a decrease in mechanical strength, which mainly refers to the stress in the glass caused by the composition or temperature difference. This has a great impact on the strength of high-temperature resistant glass.

The internal stress caused by the temperature difference is related to the expansion coefficient of the glass, because the large high temperature glass should be processed repeatedly, in order to make the internal stress of the glass low, the glass with low expansion coefficient should be selected, and the annealing is good.

5. Improve appearance. The shape has a significant impact on the strength of high-temperature resistant glass, and the simple shape and uniform thickness can greatly improve the strength of the glass. In recent years, due to the great attention paid to safety performance requirements, the thickness of high-temperature glass has increased.

FRP strength enhancement method:

1.Use high-strength resin types;

2.Use high-quality reinforcing materials, reinforcing materials with alkali-free glass fibers;

3.To ensure that the curing degree of FRP products is in a reasonable range, generally speaking, if the curing degree of epoxy resin FRP material uses amine curing agent, its optimal curing degree range is about 135 degrees - 150 degrees, and polyester resin, Mohs hardness reaches about 60 It is very OK.

There are generally five methods of chemical toughening: high-temperature ion exchange method, low-temperature ion exchange method, dealkalizing method, surface crystallization method, and sodium silicate strengthening method.

1. High-temperature ion exchange method.

In the temperature region between the softening point and the transition point of the glass, the glass containing Na2O or K2O is invaded into the molten salt of lithium, so that the Na+ in the glass or the Li+ in the molten salt with their small radius are exchanged, and then cooled to room temperature, because the expansion coefficient of the surface layer containing Li+ is different from that of the inner layer containing Na+ or K+, the residual pressure on the surface is generated and strengthened, and at the same time; When the glass contains Al203, TiO2 and other components, through ion exchange, it can produce P-heclay (LiO, Al2O SiO2) crystals with very low expansion coefficient, and the surface of the cooled glass will generate great pressure, and the strength of the glass can be as high as 700MPa.

2. Low-temperature ion exchange method.

The low-temperature ion exchange method is a method to exchange monovalent cations (such as K+) with Na+ ions with a larger ionic radius than the surface base ions (such as Na+) in the temperature region lower than the strain point of the glass, so that K+ can enter the surface layer. For example, Na2O+CaO+SiO2 system glass can be impregnated in molten salt at 400 degrees for more than 10 hours. The low-temperature ion exchange method can easily obtain high strength, and has the characteristics of simple treatment method, no damage to the transparency of the glass surface, and no movement.

The chemically strengthened glass commonly used is manufactured by a low-temperature ion exchange process, and the so-called low-temperature system refers to the range of the exchange temperature not higher than the glass transition temperature, which is relative to the temperature range above the transition temperature and below the softening point compared to the high-temperature ion cross-fold transfer process.

3. Dealkalinization method.

The dealkalizing method uses PT catalyst to treat glass in a high-temperature atmosphere containing sulfurous acid gas and moisture, so that Na+ ions seep out of the glass surface layer and react with sulfurous acid, so that the surface layer becomes a SiO2-rich layer, and as a result, the surface layer becomes a low-expansion glass, and compressive stress occurs during cooling. Although the dealkalinization method can be used for Na2O+CaO+SiO2 glass, the effect is not so obvious.

4. Surface crystallization method.

The surface crystallization method is different from the high-temperature ion exchange method, but it is only strengthened by heat treatment to form microcrystals with a low coefficient of expansion on the surface. In this method, it is necessary to select the glass that precipitates the low-expansion micromirror body, and the system glass composed of Li2O+Al2O3+SiO2 is represented by it. However, it is difficult to form by melting, and it is easy to deform in the process of precipitating microcrystals.

5. Sodium silicate strengthening method.

The sodium silicate strengthening method is to process sodium silicate (sodium silicate) in an aqueous solution at several atmospheres above 100 degrees Celsius to obtain high-strength glass that is difficult to scratch the surface.

It is the heat treatment of glass to become tempered glass.

Tempered glass is obtained by cutting ordinary annealed glass to the required size, then heating to a close softening point, and then carrying out rapid and uniform cooling. After tempering, uniform compressive stress is formed on the surface of the glass, and tensile stress is formed inside, so that the bending and impact strength of the glass can be improved, and its strength is about four times more than that of ordinary annealed glass. After the tempered glass is broken, the fragments are uniform into small particles and there are no knife-like sharp corners, and the national standard requires that the fragments of tempered glass within any 50*50mm after crushing should be greater than 40 grains.

Therefore, it has a certain safety to use.

There are several main methods:

1.Choose the right glass composition, such as adding components with strong bonds and tight structure, adding components with high elastic modulus, and adding components with elastic bonds.

Improved process regimes such as very high temperature melting, vacuum and pressurized treatment to eliminate micro-inhomogeneities in the structure, accelerated cooling and pressurized cooling to prevent microscopic multiphase and structural normal order and visible and invisible crystallization.

Surface treatment, such as pickling, ion exchange, surface coating, etc.

Surface irradiation, such as irradiating glass with isotope components with thermal neutrons, produces new elements and nuclear reactions, because the radius of the ions and atomic radii of the elements produced are smaller than the original composition, and the glass structure is dense and enhanced; It can also be irradiated with R rays, such as the vertical window glass irradiated with R rays, the elastic modulus is increased, which is due to the diffusion of network adjusters, which occupy the defects in the structure, so that the structural defects are reduced and the strength is increased.

The following table compares the characteristics of the physical tempering method with the ion exchange method. Item Physical Tempering Chemical Reinforcement Compressive Stress Value Low (10 15) High (30 80) Compressive Stress Layer Depth Deep (about 1 6 of the plate thickness) Shallow (generally 10 300um) Tensile stress value High (about 1 2 of compressive stress) Low Processing time Short (5 10min) Long (30min 1 week) Change after treatment Slightly Almost no Glass thickness and shape Restricted No limit To obtain a deep enough compressive stress layer with practical value, the ion exchange method takes a long time, so the cost is much higher than that of the physical tempering method. However, the ion exchange method must be used for the following cases:

High strength is required; thin-walled or complex-shaped glass; Use small pieces that are not easy to fix when physically toughened; High size requirements and so on.

The stress distribution of ion exchange tempered glass is different from that of physical tempered glass, the compressive stress thickness of the surface layer of the former is small, and the internal tensile stress of the equilibrium is not large, which is the reason why the internal tensile stress layer of chemical tempered glass is not broken into small pieces like physical tempered glass when it is broken.

Due to the thinner ion exchange layer, the chemically tempered glass method is effective in reinforcing thin glass.