Tablet coating is vital in making tablets more appealing, protecting the ingredients, and ensuring they release correctly in the body. However, issues like blooming, orange peel effect, cracking, and peeling can sometimes arise, affecting the quality of the tablets. Here’s a look at these common defects, their causes, and how they can be resolved.
Introduction to Tablet Coating Defects
Defects in tablet coating often result from incorrect processes or materials. When problems like blooming or peeling occur, they can impact not only the look of the tablet but also its effectiveness. By understanding these issues and their causes, manufacturers can ensure better product quality.
Blooming
What it is:
Blooming is when the tablet’s coating becomes dull or hazy, often due to prolonged exposure to high temperatures or the use of low-grade plasticizers that migrate to the surface over time.
Image source：colorcon
Solutions:
· Choose higher-quality plasticizers to prevent them from moving to the surface.
· Store the tablets in cool, dry places to reduce the chance of blooming.
Orange Peel Effect
What it is:
This defect gives the tablet a rough texture, resembling the skin of an orange. It often happens when the coating liquid isn’t spreading smoothly before drying. This can result from high-viscosity coating solutions, quick drying, or improper atomization.
Image source：colorcon
Solutions:
· Thin out the coating solution to make it less viscous and allow it to spread more easily.
· Lower the drying temperature and adjust the spray rate to ensure the coating has time to settle evenly.
· Increase atomizing air pressure to create finer droplets, which helps achieve a smoother coating.
Additional Defects: Cracking and Peeling
Cracking:
Cracking happens when the coating film breaks due to internal stress. This usually results from a rigid coating that doesn’t flex well with the tablet core’s movements.
Image source：colorcon
· Solution: Use flexible plasticizers to make the coating less brittle and choose coating materials that align well with the tablet core’s properties.
Peeling:
Peeling occurs when the coating layer separates from the tablet, often due to poor adhesion or inadequate drying.
Image source：colorcon
· Solution: Improve adhesion by using a more adhesive coating formulation and ensuring that the tablets are dried thoroughly to help the coating stick better.
Preventive Measures and Best Practices
To avoid these defects, consider implementing these best practices:
· Regular Equipment Checks: Ensure that spray nozzles and pans are well-maintained and calibrated, which helps keep coating consistent.
· Control the Environment: Keep the coating area’s temperature and humidity stable, as fluctuations can cause problems like blooming or peeling.
· Use Appropriate Formulations: Adjust coating formulations based on the tablet’s composition to ensure that the coating adheres properly and doesn’t crack under pressure.
By following these steps, manufacturers can produce high-quality coated tablets with minimal defects, ensuring they are visually appealing, durable, and effective.