(1) Influencing factors
Factors affecting the chemical stability of glass packaging containers mainly include two aspects.
The nature, concentration, pH value and temperature of the filling material corrode the glass packaging container. Under the long-term action of acidic or alkaline solution, the glass surface will peel off in flakes and form flakes. For example HF, HCL, HpSO., HNO. Such as acidic solution, alkaline solution such as caustic soda, and the corrosion rate of alkaline solution is faster than that of acidic solution.
Some contents will deteriorate after exposure, so colored glass packaging containers are used, but colored glass is doped with iron oxide, manganese dioxide or some metal salts. Therefore, in addition to the alkali dissolution test for colored glass, a metal (such as iron) dissolution test is also required, which is often determined by atomic absorption method.
(2) Alkali resistance test
The alkali dissolution method is suitable for testing the alkali resistance of glass packaging containers, also known as the powder method. This test method has high sensitivity, good reproducibility, simple equipment and convenient operation. The specific test method is: weigh a certain amount of glass powder with a certain particle size, and under the action of pure water at 121°C, the alkali metal ions (including non-alkali metal ions) in the glass are leached out, making the original neutral or The acidic etchant is converted to alkaline. The amount of alkali leached from glass is obtained by direct titration of dilute sulfuric acid solution. The glass particles used in the test are 20-40 mesh, 10g sample, add 50ml distilled water, keep warm at (121±2)°C for 30min, use methyl red solution as indicator, titrate with sulfuric acid solution with a concentration of 0.01mol/L, and Calibrated by blank test.
(3) Dilute acid resistance test
① Reagent
These include distilled or deionized water, methyl red acid solution, and methyl red indicator. Unless otherwise stated, the test reagents are analytically pure grade reagents. Distilled water or deionized water should be boiled before use to remove carbon dioxide, and then cooled for use. The pH value is 5.5±0.1 (orange red with methyl red indicator), otherwise 0.02mol/L sodium hydroxide solution or 0.01 mol/L hydrochloric acid solution calibration. The concentration of methyl red indicator is 0.2%, which is prepared by dissolving 0.2g of methyl red indicator in 100mL of absolute ethanol. The preparation method of methyl red acidic solution is to take 0.7ml of 0.10mol/L hydrochloric acid solution and 5 drops of 0.2% methyl red indicator, add them to a 1000mL volumetric flask, and dilute to the scale value with distilled water or deionized water. It should be noted that the storage period of methyl red acidic solution should not exceed one week.
②Test method
The test was carried out in accordance with the national standard GB 4548 "Test method for corrosion resistance of glass bottles and jars to dilute acid". The specific test method is to first clean the glass bottles and jars that have not been used in other tests with water and distilled water, and then rinse them several times with methyl red acid solution. At room temperature, pour 90% methyl red acidic solution into the sample bottle, cover the mouth of the bottle with inert materials or boiled instrument glassware, and then heat it in a Water Bath. The sample bottle should not be in direct contact with the bottom and wall of the Water Bath, the liquid surface inside and outside the bottle should be kept basically the same, and the temperature of the solution in the bottle should reach (85 ± 2) °C within 10~15 minutes . After keeping warm for 30 minutes, observe the color of the solution in the bottle. If it is difficult to distinguish, add 2 drops of 0.2% methyl red indicator, and then observe its color. For dark vials, pour the solution into a clean beaker and observe. If the solution in the sample bottle is black and red, it is qualified, and if it is light yellow, it is unqualified.
