Last updated on 30 January 2020
Somos® BioClear is the material for printing clear guides and models with peace of mind. It is ideal for customized, non-implantable limited body contact (<24hr) medical and dental applications. Somos® BioClear has passed stringent ISO 10993-5 Cytotoxicity, ISO 10993-10 Irritation & Sensitization and USP Class VI testing, after following the validated cleaning procedure.
Download the technical data sheet here.
|Ec||C 11.5 mJ/cm²||[critical exposure]|
|Dp||6.50 mils||[slope of cure-depth vs. In (E) curve]|
Please adhere to the following guidelines:
We recommend the following room conditions:
When replacing material, make sure you clean the vat thoroughly, dispose of used material and cleaning products (solvents, paper towels, etc.) properly and follow vat installation procedures.
Contact your equipment supplier for up-to-date technical support for your equipment. Below are a few common checks that will help you build parts successfully.
Covestro has conducted sterilization tests for the 3D printed materials developed for healthcare purposes. These studies give indications on material changes that can occur during the sterilization process. It remains the responsibility of the device manufacturers to determine the fitness of device in their application.
The most commonly used methods of sterilizing a medical device are steam autoclave, irradiation, ethylene oxide and hydrogen peroxide gas plasma.
Steam autoclaving is a widely used, and available as sterilization technique for dental, and medical devices. It is fast, reliable, inexpensive and all healthcare agencies recommend using steam autoclaving whenever possible.
Disadvantage of this sterilization method in combination with polymer materials is the high temperature, and moisture levels that can lead to deformations during the process. Changes in mechanical properties occur during, and right after the process. Mechanical properties are regained to about 80% in 2hrs. Parts should also be allowed to cool to room temperature, without adding any forces on it after the autoclave cycle to avoid accidentally bending or breaking the part. Thin walls or unsupported areas can deform under its own weight, thicker parts are more stable. In the designs parts can be optimized to prevent these deformations.
Cycle times necessary to achieve sterility vary depending on the items that are being sterilized and the sterilization vessel being used. Generally, cycle times for flash cycles is 3-5 min or 15 to 30 minutes for standard cycles at temperatures ranging between 121°to 135°Celsius.
Moisture uptake might take place during sterilization, therefore a post-oven treatment under low temperature or keeping the part in a well ventilated room is advised.
Sterilization with autoclave is known to influence biocompatibility of the material extra biocompatibility testing after sterilization is recommended
This low-temperature sterilization process utilizes a concentrated solution of hydrogen peroxide that is injected into a chamber under vacuum. The gas can diffuse throughout the chamber for a period before an electromagnetic field is introduced that creates a gas plasma. The gas plasma breaks down hydrogen peroxide to form free radicals, as well as UV-energy. The free radicals and UV-energy destroy pathogens on the device. Once the plasma begins to lose energy, oxygen and water are formed as by-products. The process can be repeated as necessary to achieve desired sterility on a given device. After the final cycle, the chamber is vented to remove oxygen and moisture.
It should be noted that this type of sterilization may have limitations with certain metals and smaller diameter lumens. Materials must also be dry for this process and must be packaged in gas-permeable packages.
Hydrogen peroxide gas plasma sterilization can be used with some polymer materials due to the lower temperatures than autoclave.
Irradiation is the use of either an electron beam or gamma rays to sterilize materials. It is especially useful for sterilizing large, bulk-quantities of disposable items. Dosage or exposure commonly used for irradiation ranges between 20 to 55 kiloGrays (kGy). This method is suitable for some 3D printed polymers, although mechanical properties and color can change during the process.
Color change is a very common occurrence, but will not necessarily cause problems for the final application. It has been found that even low dose irradiation can cause significant color changes. Clear 3d printed materials tend to change color from clear to green or pink, while white materials tend to change from white to tan or brown.
Mechanical property changes are common for plastics during irradiation. Often the changes are negligible and sometimes beneficial. Irradiation tends to increase both Young’s Modulus and percent elongation at break, while keeping Izod impact unchanged and in some cases increasing impact strength.
Polymers can be sensitive to heat, and high moisture environments. Ethylene oxide (EO) is often used to sterilize these materials. EO is an extremely toxic gas and alkylating agent. It works to sterilize materials by disrupting the proteins, DNA and RNA of pathogens, destroying them or interfering with their ability to replicate, and can inactivate all microorganisms.
Items to be sterilized by EO must be completely dry. EO sterilization may require about 12 hours of cycle time, and materials must be packaged in gas-permeable packages. ETO is absorbed by many materials, finding the right aeration parameters is crucial, and depends on material, and geometry of the parts.
Mechanical properties can be moderately affected. The surface of some materials can react with the EO gas leading to toxic residues, therefore careful testing to get the right setting is needed.
If EO sterilization is used, it is recommended that the parts be thermally post-treated, coated or dyed to create a surface barrier to the reactive EO environment.
ISO 10993-5 has been passed using the following sterilization method:
Depending on the viscosity range of the material you want to test, use the appropriate-sized cup, based on Zahn Cups guidelines. You will also need a long-stem thermometer that mounts onto the Zahn cup handle and a stop watch.
Remember: Whenever you have material in your machine, measure and record its viscosity once a week.
|Seconds||Approximate Viscosity (CPS)|
In some areas, partially cured or uncured waste UV material may be classified as hazardous waste, and requires special packaging.
Contact the governmental or other body that regulates waste disposal in your area to determine the disposal protocols.
Packaging-Transportation-Disposal methods must prevent any form of human contact with the waste UV material, even if it is classified as nonhazardous or unregulated. This therefore precludes the use of disposal methods that might result in groundwater or surface water contamination.
Solvents should be isolated in a sealed, marked container and disposed of as “hazardous waste” in accordance with all applicable laws and regulations.
Soiled clothing, empty containers, etc., should be disposed of in accordance with the applicable “hazardous waste” guidelines. If any of these items contain uncured or partially cured UV-curable materials, the disposal method used must prevent any form of human contact, including any that could result in groundwater or surface water contamination.
Below are some examples of common issues and troubleshooting solutions. Consult this part of the guide if you are having difficulties and do not hesitate to contact our Tech Support.
Delamination occurs on the bottom layer of parts at the corners or on part edges.
Solution: Check Blade
Have the physical gap on your re-coating blade checked.
The top surface of the part is not smooth and level.
Solution: Check Re-coating Blade
This condition is somewhat common and arises due to the viscosity of the material and the presence of debris that may become suspended in it.
Check the re-coating blade to make sure the bottom surface is clean and filter debris from the vat.
It is very important that you maintain the correct material viscosity in your stereolithography machine. The viscosity can increase over time, and this can cause problems in building parts. If the viscosity increase is severe enough, the material may have to be replaced, resulting in significant expense and lost production time.
If increasing viscosity is identified early, the material can, in most cases, be saved. Regularly measuring resin viscosity can provide an early indication of the problem. This must be done even if the machine is not used often, as resin viscosity can change even when the machine is idle.
Contact our experts to discuss how Covestro can help you tap into the full potential of additive manufacturing.