2023-03-01 Technology Sharing
How to solve the problem of uncoated spots during the application of hydrophilic coatings?
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According to the feedback from peer partners and jMedtech coating cooperation customers, a problem may be encountered during the production and processing of medical coatings: the product coating area has spot-like and flake-like abnormalities without coating, and some engineers will It is defined as bubbles, patterns or spots, etc. When these abnormal areas are inspected under an optical microscope, they can be easily seen, showing that they are not so bright or reflective.

Under the light microscope, the boundary of the abnormal area is clear; usually after testing with friction equipment, there will be no peeling phenomenon; after the coating is stained with Congo red, the abnormal area cannot be dyed, but it is relatively easy to touch by hand Obvious grainy, not smooth.

1. What is the impact 

For the above problems of uncoated spots or uncoated blocks, will it affect the use of device products?

After the research of jMedtech coating engineers, it is concluded that this problem is not absolute and requires specific analysis of specific products.

On balloon catheters, PE dilatation tubing, or loach guidewires, if there are only a few uncoated spots, this usually does not affect the hydrophilic coating performance and we can consider it acceptable. However, if there are a large number of continuous large-scale uncoated areas, this may affect the lubrication uniformity of the hydrophilic coating, and when the product is stored for a long time in a large area without coating, the coating edge may Peeling will occur and, therefore, should be considered a non-conforming product.  

2. Cause Analysis 

So, how do we solve the problem of no coating in tiny areas?

First of all, we need to analyze its causes. Commonly used interventional device substrates are usually polymer materials such as pebax, TPU, PA and PE. The common feature of such polymer materials is strong hydrophobicity. Therefore, during the process of hydrophilic coating, if the primer is applied The entire section of the catheter is not completely wetted, which will result in partial areas of the hydrophilic coating primer not being coated, which will affect the coating effect of the surface coating and produce no coating points.

3. Solution 

Based on the long-term coating research and application experience, jMedtech coating engineers have summarized the following methods to improve or solve such problems.

First, plasma treatment is performed on the substrate to reduce the hydrophobicity of the substrate, which can solve such problems well, and at the same time, plasma treatment can also increase the firmness of the coating.

Second, change the absolute ethanol used to wipe the catheter before coating to a more polar organic solvent, such as n-hexane, acetone or isopropanol, etc. This method is equivalent to cleaning the catheter surface Doing a hydrophilic treatment is simpler than plasma treatment, but its effect is not as obvious as plasma treatment.

Third is to reduce the probability of non-coating points by reducing the temperature when the equipment is cured.

Coating cured coating products requires more attention to the process and details. For the above solutions to deal with "no coating point", I hope it will be helpful to your coating process. If you want to know more relevant information, or have other questions, you can continue to pay attention to the official account of jMedtech Coating, or consult jMedtech technical engineers.