Clear or opaque? Applying different grades of Eastman Tritan™ copolyester
Selecting the right material for your next medical device can be a complicated process. Whether you’re building a fluid management component, blood contact device, or electronic medical device housing, you’ll want to choose a polymer that has the right properties for your application.
 
Each medical grade of Eastman Tritan copolyester offers a different combination of superior strengths that help optimize performance for specific medical applications. Depending on the needs of your device, you may need a clear or opaque material.
 

Clear applications
If your device is clear, such as fluid management and IV components, renal devices, or dialyzer housings, you’ll need a material with the following properties:
 
  • Glasslike clarity for an unobstructed view of fluid levels, foreign substances, and the ability to detect air bubbles, clots, or blood leakage during treatment
  • Durability and toughness to withstand the applied stress of handling, connecting, and fabricating
  • Chemical resistance to endure aggressive cleaning and bonding agents as well as harsh drugs and their carriers
  • Color stability after sterilization
  • Biocompatibility with FDA/ISO 10993 and USP Class VI biological evaluation
  • Heat resistance
  • Specific rigidity requirements to comply with ISO 80369 (required in some connectors)
 
Eastman Tritan™ MX711, MX731, or MX811 copolyesters are clear material grades that meet these needs. They have high impact strength and toughness, excellent clarity, elevated chemical resistance, and good color stabilization upon sterilization.
 
Opaque applications
Opaque medical housings and hardware  require a different set of properties than clear applications. For an opaque application, you’ll need a material that can deliver:
  • Superior chemical resistance and impact strength to resist cracking, breaking, and premature device failure during rigorous daily use and disinfection
  • Ability to retain finish after repeated applications of bleach and alcohol
  • Color stability and matching of brand standards
  • Less noise in devices where sound reduction is valued
  • Processability—moldability and resistance to solvents 
  • Flame resistance
Eastman Tritan™ MX121 copolyester is an opaque material that can add value to opaque handheld or medical diagnostic and electronic devices. It has excellent inherent toughness and enhanced chemical resistance, hydrolytic stability, fast cycle and drying times, heat resistance, melt flowability, color matching ability, improved processability over traditional copolyesters, and is made without BPA, halogens, antimony, or ortho-phthalate plasticizers.
Find more information here about the advantages of Tritan for a wide range of medical applications. Eastman also provides technical expertise and support to help determine your best material option. Contact us for help bringing your product to market quickly and efficiently.
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This Old Mold 1 - Cooling
Tips for optimizing existing molds to run Eastman Tritan copolyester
 

The success of Eastman Tritan copolyester—especially in medical devices—makes more brand owners want to try it. One challenge to even

greater success has been how to use molds designed for other plastics. Sometimes it works fine - sometimes not so much.

Successful molding of any polymer depends on the ability to fill the part, cool the mold, and “freeze” the melted resin. Failure to do

so can cause sticking and ejection molding difficulty—which can limit the number of parts per hour and the quality of the parts.

 

Since most competitive materials freeze off at a higher temperature than Tritan, the mold may now need to cool more efficiently and

quickly than the original design. Engineering solutions that are straightforward when a customer builds a new mold for a different resin

can become challenges when a molder wants to produce high-quality Tritan parts by optimizing “this old mold.”

 

 The basics

  1. The suggested mold temperature for running Tritan is 38°–66°C (100°–150°F).
  2. Uniform temperature throughout the mold helps ensure even heat transfer from both wall surfaces, which decreases residual stress and warpage and reduces cycle time. When optimizing an existing mold, keep this in mind so upgrades do not upset existing dynamics. 
  3. Tower water may be adequate, but we strongly recommend using chillers to ensure a proper supply of cool water to the molds. Properly sized pumps and supply lines are also critical.    

Typical modifications
Here are the most common actions required when optimizing existing molds to run Tritan. 

1. Cooling the cavity walls
  • Consider the theramal conductivity of the mold material. This is one variable you can't change, so it's important to factor it into all changes you can make.
  • Evaluate the current cooling line layout, and make sure all changes are made to achieve uniform cooling.
  • Make sure you have a turbulent water flow in the lines—laminar flow only has ½ the cooling efficiency of turbulent flow. Changing flow dynamics may be more cost-effective than changing diameter of the coolant channel.
2. Cooling the cores
  • Use baffles or bubblers to achieve proper core cooling.
  • Consider circular cooling channels around the cavity and core inserts.
3. Cooling the gates
  • Injection molding gates typically have the highest heat load in an injection mold
  • Increased cooling efficiency here can pay big dividends.
4. Cooling around the sprues
  • Consider adding cooling lines adjacent to sprues.
  • Spiral cooling sprue inserts or high-conductivity sprue bushings can be cost-effective retrofits.
5. Don't forget venting.
  • Poor venting can result in incomplete fill, increased pressure heat, and bum marks.

 No old mold is typical
Every combination of existing mold properties and molding requirements is different. Because your needs are unique, we recommend involving Eastman as early in the planning as possible. Contact the Tritan Experts.

Eastman can review your tooling drawings and help you plan for uniform mold cooling. The Tritan experts can also help you evaluate the results of optimizing your old mold.

 

 

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Thank You for Asking:
 
“What are Eastman’s recommendations for sonic welding of thin-walled parts?”    

In general, small thick-walled parts made with Eastman Tritan copolyester can be ultrasonically welded by
following the welder’s recommendations for other amorphous thermoplastics.

 

Like all ultrasonic welding applications, those involving Tritan may require some optimization to achieve
successful welds. In particular, larger diameter, thin-walled parts may require
additional consideration of part design and welding  operation.


Tips for ultrasonic welding of thin-walled parts
 
Ultrasonic welder
     •  Thin-walled applications using Tritan may require a minimum of 72 microns for 20 kHz or 96 
         microns for 15 kHz of amplitude to weld (converter x booster x horn).
       •  Power output may vary depending on part size and wall thickness—2000- to 4000-watt generator is
          suggested.
        •  Sonic welder must be capable of fine tuning adjustments such as amplitude profiling and time or
            energy mode capability. 
Feedback recording is critical for optimizing weld strength.
 
Joint/part design
•  Use a tongue-and-groove or step joint with 60° energy director.
•  Preferred placement for the energy director is on the horn side.
•  Texturing the mating surface (opposite the energy director) may improve weld strength up to 3 times—and may reduce flash and particulatematter and lower total energy requirements.
•  Near-field welding is critical—distance between the ultrasonic horn and the weld joint should be 0.25 in. (6.35 mm) or less.
•  Additional weld joint designs may be necessary for a given application. Details on
specific weld joint options are available from Brett Jones and his team.

Stabilization
•  Parts must be locked into the equipment to ensure proper alignment and prevent vibration.
•  A vibrating part leads to both poor energy transfer and the potential for the part to move out of alignment.
•  Stabilization should be accomplished with a split-fixture clamping system (modified toggle clamp), which:
  • Prevents movement of the outer section of the part
  • Accommodates faster cycle time
  • Prevents part marring
  • Fixture devices can be fabricated using any rigid material, such as aluminum.
 

 



 
Mold design—critical factor #5
Tips for a clean release 

Tips for clean releaseThe coefficient of friction of copolyesters such as Eastman Tritan™ copolyester is at its highest near the heat deflection temperature (HDT) of the material—and competitive materials generally freeze at a higher temperature than Tritan. Keep this in mind if you’re repurposing a mold that was originally designed for the cooling temperature of another plastic. Parts molded with Tritan must be adequately cooled to withstand ejection forces during demolding.  

Three mold design and maintenance factors can also help ensure a clean and efficient release: 

Draft—Part design features with minimal draft, such as long cores and deep ribs, often result in high ejection forces. The Eastman Design Services team recommends that all wall​ surfaces have a minimum draft angle of 1° in the direction of draw. 

Polish—Polishing mold cavity features in the direction of draw will reduce the coefficient of friction and result in lower ejection forces required. 

Mold steel coatings—Several mold steel coatings have been successfully used to reduce the coefficient of friction and required ejection force. Ask Eastman Design Services for a description of these coatings. 

NOTE: A textured surface may affect all three factors and should be considered when you’re designing the mold. Working with Eastman Design Services early in the process can help reduce frustration and cost later. 

TMI Tip




 
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Designing Disinfectant-Ready Medical Devices
Are the devices you design ready for aggressive medical disinfectants? 

The designer is the point where innovative creativity crashes head-on into the real-world needs of durable functionality in a health care environment.
 
Unfortunately, many device housings and hardware designed just a few years ago were made with materials that lack the right combination of impact strength and chemical resistance. They crack, craze, and ultimately fail when challenged by the increased use of aggressive medical disinfectants—combined with the applied stress of greater portability. 
 
Connecting the dots between design flexibility, chemical resistance, and impact strength is critical for selecting the best material for reliable clear and opaque medical devices. That’s why Eastman created a 60-minute webinar to provide new information about: 

Patient safety and HAI prevention
      •  The cost of device failure
      •  The relationship between chemical resistance and impact strength
      •  A practical new 4-step testing protocol for comparing suitability of different material 

                                                

Use this valuable information to identify material liabilities earlier in the development process. It can help you make design adjustments before you bring a new device to market—and be more confident of its reliability and safety in the future. 






 
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