Whether you are manufacturing silicone kitchen utensils, medical tubing, or industrial seals, cleaning methods will directly affect the product compliance and the repeat purchase rate. Below, we will provide a detailed introduction to the industrial-level cleaning methods, verification tests, and certification requirements applicable to you.
Why Do Different Silicone Items Need Different Cleaning Methods?
As is well known, silicone products are applied in various industries and are mainly classified into industrial grade, food grade and medical grade. Different grades of silicone products correspond to different cleaning standards and residue limits.
When cleaning different grades of silicone products, you should choose suitable cleaning methods according to grade requirements. This ensures the products meet the application needs and relevant compliance standards.
The table below lists the specific applications and key compliance requirements corresponding to different grades of silicone products:
| Grade | Typical Applications | Key Compliance Requirements |
| Food Grade | Kitchen utensils, baking molds, baby bottle nipples | Passes FDA 21 CFR 177.2600 extraction test; non-volatile residues ≤ 0.5%; no migration of harmful substances, no odor contamination |
| Medical Grade | Catheters, implants, seals for medical devices | Complies with ISO 10993 biocompatibility testing; extremely low extractables and volatile residues; suitable for repeated autoclaving |
| Industrial Grade | Seals, gaskets, automotive components | Most cleaning standards specified by the customer; generally requires removal of oil, grease and dust |
Cleaning Methods for Different Silicone Products
Food Grade Silicone Products
If you are involved in the food grade silicone industry, it is crucial to clean the silicone products before shipping them out. Your customers are usually end consumers. If the product is not clean, it will directly affect the reputation of your brand.
So, the main goal of cleaning silicone products is to ensure that no harmful substances remain after cleaning, and that the smell and taste of the products remain unchanged, meeting the standards of FDA or LFGB.
The following is the batch production and pre-shipment cleaning process provided for you:
- Perform pre-rinsing. Rinse the surface of your product with pure water or deionized water. This will quickly remove the loose particles remaining from the production process, laying the foundation for subsequent cleaning.
- You can choose the appropriate method based on the size of the product. If you are producing small-sized but large-quantity baby nipple products, you can use ultrasonic cleaning by setting the appropriate frequency. We recommend a water temperature of 40–60°C, combined with a water-based neutral cleaning agent.
- If you are producing larger items such as kitchen utensils, then choose the automatic spray cleaning method. Using the rotating nozzle, apply food-grade weak alkaline solution to thoroughly clean the surface.
- After cleaning, rinse thoroughly. We recommend performing at least two rounds of pure water rinsing to ensure that no cleaning agents remain on your product, which could affect its safety.
- For the drying process, you can use clean hot air drying or sterile air blowing to dry the product, in order to prevent water stains from remaining from the previous steps and affecting the appearance and quality of the product.
- If you have stricter hygiene requirements for the product, you can add disinfection steps. We recommend using food-grade hydrogen peroxide spray or ultraviolet irradiation.
Industrial Grade Silicone Products
If you are cleaning industrial-grade silicone products, the main purpose is to remove surface release agents, oil stains and dust. These factors will reduce the flexibility, adhesion or other functional properties of the silicone, thereby affecting the subsequent assembly and usage performance of the product.
Here are the commonly used cleaning methods for industrial silicone products that we have compiled for you:
- Dry ice cleaning. If your product has complex shapes or you want to clean the molds, this method can be used. This enables you to not have to worry about generating secondary waste or damaging the product surface.
- If you need to remove oil stains and release agents, you can use IPA(isopropyl alcohol) for wiping or soaking. We generally recommend using an IPA concentration of 70%. However, after cleaning, you need to ensure that it has completely evaporated. As a precautionary measure, it is recommended to rinse it thoroughly with pure water.
- It is common to have residual un-solidified silicone gel during the production process. In this case, you need to use a special silicone solvent. After spraying, let it remain for 5 minutes, then wipe it clean with a soft cloth and blow dry it.
- If you find solidified silicone residue remaining on the equipment or mold, you can soften it by heating and then remove it with a soft scraper. The key point of this step is to remain patient and avoid scratching the metal surface.
- If you need to clean a large quantity of silicone seals and gaskets, it is recommended to use an alkaline cleaning agent in combination with ultrasonic cleaning. We recommend that the pH value of the cleaning agent be between 10 and 12, the water temperature be between 50-70℃, and the cleaning time be between 10 and 30 minutes.
- Don’t forget to perform neutralization rinsing after cleaning to ensure there are no residues left.
Medical Grade Silicone Products
Medical grade silicone products have very strict requirements for cleaning and must be processed in a clean environment. So, after you have completed the cleaning of the medical-grade silicone products, make sure that the products meet the medical-grade compliance standards.
Below is the cleaning procedure for the medical grade silicone products we have provided for you:
- Let’s start with the pre-washing process. It’s best to use WFI (Water for Injection) to pre-wash the product. Pure water can also be used, which can remove loose impurities on the surface.
- Then perform a thorough cleaning. If your main products are precision tubes and seals, we recommend using SCD(Supercritical CO₂ Cleaning). This method involves extracting low-molecular-weight siloxanes and organic residues from the supercritical CO₂ without affecting the mechanical properties of the product.
- You can also use multi-slot ultrasonic cleaning, combined with medical-grade cleaning agents. After setting the frequency, heat the water temperature to 50–70°C to achieve deep cleaning.
- If your product needs to undergo bonding or coating treatment in the future, plasma cleaning can be used to remove organic contaminants. This method can enhance the compatibility of subsequent processes.
- After the thorough cleaning process is completed, rinsing is also necessary. We recommend using WFI(Water for Injection) for repeated rinsing until the test results are satisfactory, ensuring that no cleaning agents or contaminants remain.
- When you reach the drying stage, remember to use HEPA-filtered hot air drying or vacuum drying.
- The final sterilization process is extremely important for medical-grade silicone products. However, it needs to be packaged first before being sterilized. You can choose from options such as high-pressure steam sterilization, EO sterilization, or gamma irradiation based on your specific needs.
Verification and Testing After Silicone Cleaning
After cleaning silicone products, you must conduct a test. This is the main criterion for verifying whether your cleaning process is successful. We will introduce various methods to suit different scenarios and detection requirements for you:
If you are conducting a preliminary screening and detecting visible contaminants, you can use visual inspection. You need to observe the uniformity of surface reflection under white light or ultraviolet light, and use a 10x magnifying glass to check the gaps.
When you need to determine the types and quantities of residues, you can do so by using a swab to wipe the selected area and then conducting extraction analysis. If you want to conduct rapid biological contamination detection, the commonly used method is ATP bioluminescence detection. This method also involves swabbing and then measuring the RLU value.
It is efficient for you to test, as the results can usually be obtained within 15 seconds. For silicone products, if they are of medical grade, the RLU requirement is less than 200; for industrial grade ones, it is less than 500.
Contact angle measurement can help you assess changes in surface energy. It measures the contact angle of water droplets on the material surface and the detection sensitivity is very high.
The clean silicone surface is usually hydrophobic, with a contact angle of approximately 100°- 110°. If you notice a significant discrepancy between the measured contact angle value and this, it might be due to the presence of contaminants.
When you need to detect organic contamination, we recommend using FTIR infrared spectroscopy. It identifies the residual organic substances through characteristic absorption peaks.
If you find it difficult to conduct the testing of complex-structured silicone products, you can use the weight analysis method. However, it is only applicable in cases of severe pollution. By weighing before and after cleaning, you can calculate the residual contaminants.
The following is the specific application and cost level of the detection methods listed for you:
| Applications | Recommended Method | Cost Range |
| Pre-Sterilization Testing of Medical Devices | ATP + Contact Angle Measurement | Medium |
| Cleaning Acceptance of Electronic Devices | Ion Contamination Test + Visual Inspection | High |
| Batch Quality Inspection of Auto Parts | Gravimetric Method + White Light Imaging | Low |
| Inspection of Food Equipment | ATP Test + Colony Culture | Medium |
Common Mistakes in Cleaning Silicone
Use an Abrasive Cleaning Pad
Although silicone can withstand physical pressure, if you use rough tools such as steel wool, it may scratch its surface or affect its smoothness.
We recommend using soft fabrics, sponges or brushes with nylon bristles. When cleaning complex or textured silicone products, you can use a soft-bristled toothbrush or compressed air to clean the hard-to-reach areas.
Choose the Wrong Cleaning Agent
Silicone usually has tolerance to various cleaning agents, but not all cleaning agents can be used. If you use acetone, strong acids or petroleum-based solvents, it may damage the material of the silicone and cause it to change color.
You should choose the cleaning solution based on the type and severity of the pollutant. For mild cleaning, we recommend using warm water combined with mild soap or detergent. For stubborn stains, we recommend using IPA to remove oil stains, adhesives, and it will not damage the silicone.
Not Completely Dried
If you fail to completely dry or blow dry the silicone after the washing process is completed, not only will water stains appear, but mold may also grow and unpleasant odors may develop. You can use a lint-free cloth for wiping, or place the components in a clean environment to air-dry, ensuring they are in a usable condition.
FAQ
What Are the Differences in Cleaning Between Platinum-Cured Silicone and Peroxide-Cured Silicone?
Because platinum-cured silicone undergoes a more complete cross-linking process compared to peroxide-cured silicone, it contains fewer soluble substances. In this way, its cleaning intensity is lower, making it easier for you to achieve low residue during the cleaning process.
Therefore, medical-grade silicone products and food-grade silicone products mostly use platinum-cured silicone.
Can Chlorine Bleach Be Used to Clean Silicone Products?
No. First, due to the prolonged use of high-concentration chlorine, it will damage the molecular structure of the silica gel, thereby accelerating the aging and even cracking of the silica gel products.
Second, the bleach will leave white spots on your product, affecting its appearance. Moreover, the silicone will absorb the chlorine smell and it is very difficult to remove.
How to Package Cleaned Silicone Products to Maintain Cleanliness?
You can use dust-free PE bags, PP bags, clean composite films, etc. in a clean environment and seal them for packaging. For silicone products in the electronics industry, it is best to use anti-static bags; for medical grade silicone products, they need to be processed in a sterile environment.
Final Thoughts
Legensilico is a company that has been deeply engaged in the manufacturing of silicone products for over 20 years. We can provide you with professional silicone cleaning solutions. If you want to know more about our silicone products or have any preferences, please feel free to contact us at any time.
