Shanghai Xinfan Bio: Electrophoresis principle and electrophoresis equipment requirements - Database & Sql Blog Articles

**Principle of Electrophoresis** Electrophoretic coating is a sophisticated process that involves the application of an electric field to deposit paint onto a conductive surface. The water-soluble resin used in anodic electrophoresis is typically a high acid value carboxylate, which dissolves in water and exists in a state of molecular and ionic equilibrium under a direct current (DC) electric field. When the system is energized, ions move directionally due to the potential difference between the two electrodes. Anions are deposited on the anode, while cations are reduced at the cathode, leading to a complex electrochemical reaction involving four simultaneous processes: electrophoresis, electrolysis, electrodeposition, and electroosmosis. 1. **Electrophoresis**: Charged colloidal particles suspended in a medium move toward the electrode with the opposite charge under the influence of an electric field. 2. **Electrodeposition**: Anion resins deposit on the anode, forming a water-insoluble paint film. 3. **Electroosmosis**: This is the reverse process of electrophoresis, where the medium moves through the deposited paint film from the anode back into the paint solution. 4. **Electrolysis**: As current flows through the paint bath, hydrogen gas is released at the cathode, and oxygen is emitted at the anode. **Electrophoretic Coating Types** There are three generations of electrophoretic coatings. The first generation uses epoxy resins, commonly applied to automotive chassis. The second generation features acrylic resins, widely used for their versatility and good adhesion. The third generation includes polyurethane coatings, often used in specialized applications such as jewelry finishing. Acrylic resins are particularly popular due to their ability to form uniform films when cross-linked with amine-based curing agents. The resin structure usually contains carboxyl groups trapped internally and amine groups on the surface, allowing it to become water-soluble through the presence of -COONHR groups. **Painting Process Overview** The electrophoretic painting process consists of several key steps: 1. **Degreasing**: Typically done using alkaline solutions like Na₂CO₃ and NaOH, this step removes oils and contaminants from the surface. 2. **Washing**: Tap water is used to rinse away any residual chemicals from the previous stage. 3. **Etching**: Alkaline etching can slightly reduce surface brightness but is necessary for proper adhesion. 4. **Two Washes**: Additional rinsing ensures thorough cleaning, especially after chemical treatments. 5. **Ash Removal**: Nitric acid is effective, followed by multiple rinses to prevent contamination. 6. **Oxidation**: Sulfuric acid is commonly used, with oxidation times around 20 minutes to achieve a 9µm oxide layer. 7. **Coloring**: Tin or nickel salts are used to color the surface, ensuring consistency to avoid color differences post-painting. 8. **Hot Pure Water Washing**: Required to maintain low conductivity and pH, typically around 70–80°C and pH 4–6. 9. **Final Rinse**: A final pure water rinse ensures the surface is clean before electrophoretic coating. **Electrophoresis Equipment** The electrophoresis system includes various components: - **Electrophoresis Tank**: Usually lined with PVC or glass-reinforced plastic to prevent corrosion. - **Overflow Tank**: Controls paint level and removes foam, typically one-fifth the size of the main tank. - **Stirring System**: Ensures even distribution of paint; circulation rate should be 4–6 cycles per hour. - **Electrodes**: Cathode plates are typically made of 316 stainless steel, with careful attention to area ratios for safety. - **Power Supply**: Most modern systems offer ripple factors below 6%, with options for constant voltage or current control. - **Deionized Water Unit**: Produces high-purity water, often using electrodialysis or ion exchange. - **Resin Towers**: Cation and anion exchange towers help purify the paint solution during operation. - **Ultrafiltration/Reverse Osmosis**: Used to recover paint and reduce waste, each with distinct mechanisms and pressures. - **Oven**: Convection heating is most common, with strict temperature control to ensure even drying. **ELISA and Related Products** In addition to industrial coating technologies, the document also mentions biological testing kits such as ELISA kits, including SOD, IgG, and IgM assays. These are essential tools in immunological research and diagnostics. Companies like GIBCO and AMRESCO provide high-quality reagents and equipment for experiments ranging from Western Blotting to Immunohistochemistry. Free test samples and experimental support are often available to researchers. This comprehensive guide covers both industrial and scientific applications, offering detailed insights into electrophoretic coating techniques and related laboratory procedures.

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