Case Study: Self-Lubricated Polyisoprene for Medical Septum Applications
Develop a system that reduces the needle drag and piercing resistance of the septum and injection site materials to increase product performance.
Chemists developed a family of self-lubricated polyisoprene materials that have been manufactured with a proprietary lubricant system and show a minimal reduction of physical and mechanical properties.
By Saman Nanayakkara and Shu Peng
Due to its availability as an ISO 10993 medical grade compound, polyisoprene rubber, which has a unique set of combined mechanical and chemical properties, has been widely used in medical device applications. The material is ideal for septums and injection sites for medical fluid transfer applications. Medical grade polyisoprene compounds have high tear strength and high elastic resilience. These characteristics can provide the desired resealability properties of the septum or injection site after piercing one or more times with a needle.
Medical device manufacturers have long sought a reduction in needle drag or piercing resistance of septum and injection site materials to increase product performance. Post molding surface treatment to modify coefficient of friction is the conventional approach taken to reduce tackiness for improved part handling. This process, however, is a surface treatment for reducing surface friction and does not effectively reduce needle drag, which is caused largely by friction within the septum and injection site materials. Furthermore, this secondary surface treatment adds additional cost to the component.
Can electrically conductive plastics really replace traditional metal electronics enclosures? The answer is a resounding yes! There are very effective electrically conductive plastics available today that provide excellent electromechanical properties that help shield portable electronics from the electromagnetic interference (EMI) noise that is proliferating our daily life. Smart phones, Bluetooth, Wi-Fi, radio, even your television are all susceptible to EMI. So here are the key points you may want to consider when evaluating electrically conductive plastics for your application:
#1: Shielding Effectiveness
Every day we encounter EMI, and sometimes it happens at the most inopportune time. Maybe you’ve been put on hold for an hour and just when the customer service agent gets back to you, your cell phone drops the signal. Or perhaps you’re blasting the car radio listening to your favorite song, and just when the chorus comes on, static noise drowns out the tunes as you drive under high tension power lines. These are all examples of EMI interfering with our daily life, and electrically conductive plastics can help shield our portable devices from these interruptions.
Reduce Exhaust Leakage in Heavy Duty Engines by 80 Percent with an Air Duct Seal
Increased emission restrictions are requiring engine manufacturers to conform to Euro 6 and Tier IV regulations to reduce exhaust leakage 80% or more. In order to achieve these new standards, engines with extreme temperatures coupled with a high amount of vibrational movement, need to have highly engineered sealing solutions. Applications with predetermined mating components cannot always be changed, so the need for a sealing solution with a similar coefficient of thermal expansion is needed.
What is the problem in existing exhaust applications?
Most heavy duty diesel engines can reach exhaust gas temperatures upwards of 1292°F(700°C) while subjected to constant vibrations. These engine vibrations can cause havoc when a seal needs to be maintained on the exhaust line. Vibrations from the engine cause rotation, cavity offsets, pivoting, and reciprocation which become difficult to seal against. Movement, pressure cycling and thermal cycling require an engineered solution to maintain a seal under extreme application conditions. With the use of custom engineering and advanced analysis techniques, Parker is able to create custom solutions for our customers’ most difficult applications.
Semiconductor FFKM Offers Low Particle Generation AND Extreme Etch Resistance
In the world of semiconductor manufacturing, performance requirements are driving circuit sizes smaller and smaller, causing increased sensitivity to wafer defects. In parallel, the number of manufacturing steps has also increased driving a need for improved tool utilization and leaving more opportunity for these defects to be introduced. Identifying and eliminating the sources of defects is a tedious but necessary process to improve wafer yield.
What impact does seal contamination make?
One very distinct source of defects are the seals within a fab’s tool. Plasmas involved in both deposition, etch and cleaning processes utilize aggressive chemistries that put even high-functioning perfluorinated sealing compounds to the test. Much room for improvement has been left in this industry with many seal materials still posing significant threats to defectivity or downtime despite being designed for low particle generation or etch resistance.
How can Parker ULTRA™ change the industry?
Parker’s UltraTM FF302 Perfluorelastomer has proven success in CVD and etch applications, putting this material at the top of its class. Typically, seal materials for semiconductor applications are optimized for low particulation or extreme etch resistance, however, Ultra FF302 provides both attributes in one material. Laboratory testing shows Ultra FF302 has lower erosion in aggressive plasma chemistries even when compared to today’s leading elastomeric materials (Figure 1 below shows comparison erosion levels of various etch resistant perfluoroelastmers after exposure to O2 plasma).
Custom Environmental Seal Solutions: When Unique Requirements Throw a Curveball
When it comes to the topic of utilizing elastomeric seals, it’s stereotypical to consider environmental sealing as one of the simpler categories of applications. Near-ambient pressure and temperature conditions and a lack of exotic or aggressive chemistries are the kinds of details that typically come to mind. However, throw in a curveball or two and suddenly the challenges posed can make finding a solution seem reasonably more intricate.
Unique conditions call for custom design expertise
For instance, consider the potential challenges of sealing off a battery enclosure or other kind of electrical component. While this may seem like a simple issue of finding a material that seals against moisture or fluids found in open-air conditions, manufacturability also needs to be taken into consideration. Many electrical enclosures have particular spatial requirements, including those which involve seal housings that require low closure force or those with sharp corners that could damage more conventional seal designs like solid-profile O-rings. These kinds of conditions are becoming more and more frequent, especially considering the automotive market and its increasing share of electric vehicles, which involve a larger proportion of electrical components in a more compact arrangement for reduced weight. Add to this the fact that these batteries and other electrical components are becoming more elaborate and more expensive as a result, and the need for highly-effective protective sealing design becomes imperative. This is where Parker engineers can design products like picture frames gaskets and hollow profiles that are customized to unique requirements.
A Guide to Proper Storage and Cleaning of Elastomer Seals
Elastomer seals from Parker Prädifa meet the most exacting demands in a wide range of applications. Aside from the appropriate seal designs, the material properties of the seal compounds are crucial to ensuring that seals deliver the desired performance.
A key criterion for the storage period of elastomers is the time at which the product was vulcanized. Parker indicates the date of manufacture on the packaging bags: “1Qxx” stands for parts produced in the first quarter of the year 20xx. The recommended maximum storage period depends on the type of elastomer.
Omega Seal Profile: A More Robust PSA-Backed Sealing Solution
Customers often call with various sealing challenges. But sometimes their dilemmas can be solved with more robust solutions instead of direct replacements. For example, when a customer is having issues with a PSA-backed hollow seal that keeps peeling away from the bottom surface.
If you need to seal a box with a lid, you may need a 4-corner gasket to seal the contents from dirt and moisture. If you use a solid gasket, the compression force may be too great to effectively close the lid. Using a hollow seal reduces the compression force by orders of magnitude, but it comes with its own set of challenges.
A hollow seal for a box will most often seal between two flat surfaces. The bottom surface will be flat for adhesion to the box, while the top surface is curved to engage the lid as it is seated on top of the seal. However, the disadvantage of this design is the tendency of the flat portion to lift off the bottom surface. Figure 1 illustrates this phenomenon with standard Parfab profile D015.
TetraSeal: An Alternate Sealing Solution When an O-Ring Isn’t Working
Our applications engineering team takes more than a few calls each month where the O-ring is leaking, either immediately or after just a short time in service. Once we drill down to the details, we learn the failure mode is an improperly sized groove and O-ring. It isn’t all that uncommon for a groove to be cut in a flange and a novice designer learns the hard way that standard O-rings cannot fit in just any groove geometry. For hardware that has already been machined, frustration ensues as the caller learns the O-ring solution requires tooling. Tooling can have a lead time of at least a month to cut and can cost thousands of dollars. Parker offers a TetraSeal® solution, which often does not require tooling and can be made of many of the same materials used for O-rings.
Benefits of TetraSeals
The TetraSeal is a circular precision-cut seal with a square cross-section. Unlike O-rings which require a unique mold for each material family and size, TetraSeals are extruded, cured and machine cut to the target thickness. Our manufacturing facilities in both Spartanburg, South Carolina and Goshen, Indiana are tooled in a variety of interchangeable extrusion dies, making this type of seal an easily sourced seal solution without the lead time and cost of a custom molded O-ring.
Avoid Leakage and Support a More Accurate System There are many applications in industrial settings where fluid must be sealed and released in calibrated quantities. Some examples include pressure regulators, relief values, fuel nozzles, or gas metering. Specifically a demand flow regulator is designed for use with various industrial instruments and uses a pump to draw the calibration of gas. It is crucial that there is no leakage of the fluid for the system to operate properly.
Parker Composite Sealing Systems Division designs different poppets to help control leakage in flow control applications. Our poppet is used to help keep the demand flow regulators in the “closed” position. And when the user “demands” gas flow, a diaphragm pushes down on the seat stem of the Poppet to help monitor the flow of gas.
One of the decisions equipment designers need to make when installing O-ring seals in their applications is how much the O-ring will be squeezed by its mating hardware to create an effective seal.
What is O-ring squeeze
Squeeze is a ratio of the amount of deformation applied to the seal expressed as a percentage of the free-state cross-sectional thickness. Deforming the seal cross-section “energizes” the elastomer matrix much like compressing a spring; the inherent elasticity of the rubber material causes it to push back against the mating components. This contact force blocks the passage of liquids, gases and dry powders, preventing them from flowing between the rubber seal and the mating hardware.
The greater the squeeze, the more force is applied against the hardware and the tighter the seal. But that doesn’t necessarily mean that designers should always specify the most squeeze (assuming they knew what that level was or why it was “the most”). There are a number of factors to consider, which include: