Compared to metals, special engineering plastics from Pres have the greatest advantages of chemical compatibility, chemical resistance, and corrosion resistance. By selecting the right plastic series products, even in the harshest environmental conditions, no additional protective measures such as surface treatment, painting, or cathodic protection are required. In our product line, you can find specific acid resistant materials, alkali resistant plastics, and solvent resistant plastics, such as those that are resistant to hot water and steam. Based on various end applications, users can find chemically resistant plastics that comprehensively balance their needs.
In most cases, insufficient chemical resistance is manifested through material expansion or softening, which may lead to a decrease in mechanical properties and directly affect the usability of the material. During this process, molecules in the medium diffuse into the gaps between polymer chains and separate them. Due to the fact that most diffusion processes are temperature dependent, chemical resistance should always be considered based on the temperature specified in the testing conditions. Users should pay special attention when using non crystalline plastics in the presence of chemical substances, as the material may experience stress cracks or local deformation. At the beginning, small cracks will appear on the material, and under the action of mechanical stress, large cracks will eventually form.
The impact of inorganic chemicals
Water and inorganic substances such as acids, bases, and salts dissolved in water will not significantly erode thermoplastic materials. But there are exceptions, such as PVDF materials that come into contact with a specific concentration of alkali at a specific temperature, which can cause stress cracks in the material; And oxidative media can also cause stress cracking in PP and PE materials. The color change that may occur when in contact with chemical substances indicates a change in the chemical resistance of plastics.
The impact of organic chemicals
The effect of organic media on thermoplastic is different from that of inorganic media. The molecular chains of organic chemicals and thermoplastic plastics can interact with each other. This means that besides showing signs of true dissolution (such as when dichloromethane comes into contact with PVC material), the material is likely to expand. Expansion (widening the distance between molecular chains) is a change in the volume and shape of a solid under the influence of liquid, vapor, or gas.
Polymer chains can also be encapsulated by certain specific solvents. It should be pointed out that in this case, the stress generated by expansion comes from changes in length, and most of this type of expansion can be eliminated through subsequent drying.
The impact of mixed chemicals
When thermoplastic materials come into contact with mixed chemicals, it is generally impossible to reliably predict whether the material will be subjected to chemical erosion, as unknown secondary effects may occur in many cases. For example, concentrated hydrochloric acid is mixed with nitric acid in a ratio of 3:1 to form aqua regia, which is one of the most corrosive media currently available. Although many thermoplastic materials have resistance to any of their components individually, only PVDF material can be used in this medium for a long time at 20 ℃.
When testing the chemical resistance of substances, the temperature, concentration, testing time, and load of the solution are all very important parameters. The following table illustrates the resistance of various engineering plastics to different chemicals. All standard tests are conducted in an environment of 23 ℃ and 50% humidity according to DIN 50014.
These data represent the knowledge we have acquired and only provide some information on the chemical resistance of our products and their uses. We do not assume any legal responsibility for the chemical resistance of materials and their suitability for certain specific applications. In the application, certain commercial property rights also need to be considered.
If you have any questions about the required medium, chemical concentration or temperature, or whether there are any mixtures for special engineering plastics. We strongly recommend that you conduct separate testing on the material to examine its performance under actual application conditions and any unforeseen interactions that may occur.
