Sealing and Shielding

Parker Chomerics has recently released THERM-A-GAP™ GEL 75, a 7.5 W/m-K thermal conductivity, single-component, dispensable thermal interface material. THERM-A-GAP GEL 75 is the latest from the THERM-A-GAP family of dispensable thermal materials from Parker Chomerics to be released to the market. 

When applied to a heat generating component, THERM-A-GAP GEL 75 provides minimal stress and pressure due to its low compression force. It is form stable in horizontal or vertical applications and allows for lower assembly costs when compared to multiple thermal gap pads in higher volume applications.

THERM-A-GAP GEL 75 represents the highest thermal conductivity dispensable available from Parker Chomerics. With a flow rate of 30 grams per second, it is nearly 3x faster than the next closest performing material in the THERM-A-GAP family. 

The gel-like consistency enables superior performance and long-term thermal stability and is designed to be dispensed in applications requiring low compressive forces and minimal thermal resistance for maximal thermal performance.  

Parker Chomerics has conducted a detailed examination of the thermal reliability of this high-performance gap filler after being subjected to long-term environmental aging under dry heat, heat and humidity conditions, and temperature cycling from -40°C to 125°C. 

The thermal performance of THERM-A-GAP GEL 75 was examined, and the findings were reported in the THERM-A-GAP GEL 75 Reliability Report TR1104. After being subjected to multiple environmental stress tests, the thermal impedance of the aged samples did not experience a significant increase after any of the treatments studied.  

After a 1,000-hour dwell at 125°C, 1,000 hours at 85°C/85% relative humidity, and 1,000 temperature cycles from -40°C to 125°C, there was no statistically significant increase in impedance according to one-way ANOVA with the Tukey method for multiple comparisons.  

The National Aeronautics and Space Administration (NASA) criteria for low-volatility materials limits the total mass loss (TML) to 1.0% and collected volatile condensable material (CVCM) to 0.10%. Outgassing results for GEL 75 are 0.18% TML and 0.05% CVCM. Independent laboratory results indicate THERM-A-GAP GEL 75 passes the NASA outgassing criteria for low-volatility material. 

Based on these results, THERM-A-GAP GEL 75 demonstrates the ability to withstand long-term aging without a reduction in thermal performance. THERM-A-GAP GEL 75 is best suited for high volume, automated production, specifically found in telecommunication applications, base stations, power supplies, and memory and power modules.

Learn more about THERM-A-GAP GEL 75 and receive a free product sample.

This blog post was contributed by Jarrod Cohen, marketing communications for Parker Chomerics. 

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In the Oil & Gas industry, the need for elastomers to seal higher pressures for sustained periods of time with minimal damage is abounding. Applications such as drilling tools, completions equipment, blow out preventers, and subsea pressure control systems now routinely require or exceed 15,000 psi with both liquid and gas media for functional testing and qualification. Parker meets this challenge, providing a best-in-class extrusion and rapid gas decompression resistant hydrogenated nitrile (HNBR) compound called KB292.

One of the most common failure modes for seals utilized in high pressure applications is known as extrusion or nibbling.  This failure method emerges when the seal material is forced into a clearance gap that is present between the mating substrates and gradually can be cut, nicked, or chewed away.  Typical applications which can see this transpire include dynamic reciprocating cylinders and/or vessels where pressure fluctuations cause clearance gap to open and close trapping the seal between mating surfaces.  The higher the pressure or the larger the clearance gap that is present, the more likely extrusion or nibbling is to occur.  Once a mass of the material is removed from the seal geometry it is inevitable that a leak will eventually form which normally results in failure of the system.  Section 10 of the Parker O-Ring Handbook highlights extrusion and nibbling as well as includes several suggestions for prevention.

Another failure mode which can be seen for high pressure gaseous applications is known as Rapid Gas Decompression (RGD), also referred to as Explosive Decompression (ED). This damage arises after a period of service under high pressure gas, when pressure is reduced too rapidly, the gas trapped within the internal structure of the seal expands rapidly, causing small ruptures or fissures to develop. There are many Oil and Gas industry standard tests which have been developed to determine whether compounds are RGD resistant. Parker routinely tests and acquires certificates for these standards which can be supplied upon request for end user documentation.  Our Oil & Gas Reference Guide outlines our numerous materials, temperature ranges, recommended uses, and a list of approved certifications by material. 
 

To combat seal damage and the typical failures in high pressure applications, Parker has developed material KB292. This hydrogenated nitrile (HNBR) based material has been formulated with physical properties which allow it to withstand exposure to the highest-pressure environments with extreme extrusion resistance. With hardness of 95 +/- 5 Shore A points, KB292 is one of the hardest elastomers in the Parker OES material offering. The extreme extrusion resistance is also identified with a modulus value of 2500psi at 50% elongation as well as excellent abrasion and tear resistance. The material offers good compression set and chemical resistance that is expected from all Parker HNBR’s used in the O&G industry. Additionally, Parker's KB292 has been tested to and passes the requirements of ISO 23936-2 RGD which shows excellent resistance to explosive decompression for high pressure gas applications.  

For more information about the KB292 compound, reference Parker’s OES 7003 technical bulletin or chat live with an applications engineer by visiting our website.  

Nathaniel Sowder, business development engineer, Parker Hannifin O-Ring & Engineered Seals Division

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Robotic surgery systems or robot-assisted surgery, offer immense patient benefits -- from shorter recovery time, to better surgeon visualization, which leads to a more precise, effective and successful surgery. Robot systems are used for various surgical procedures, including urologic, gynecologic, cardiothoracic, general, and head and neck surgeries. Manufacturers and designers of these surgical systems are now focusing on robot specialization instead of all-encompassing surgical systems.

This means there will be more specialized systems developed to perform specific surgeries, and the breadth of those procedures is expanding too. General surgery uses are increasing the fastest, followed by gynecology and urology uses. In 2017, there were 877,000 robotic surgeries performed in the US alone. That number is expected to rise exponentially in the years to come.

Robotic surgery system manufacturers and engineers consider EMI shielding when designing their systems. EMI shielding prevents equipment failure and keeps manufacturers compliant with federal regulations. Understanding EMI and taking steps to prevent it is paramount, as the resultant issues could cause robots to behave unexpectedly, such as requiring frequent restarts, showing a limited radio frequency range, moving unintentionally or affecting other nearby robots.

Remember, EMI is when electromagnetic emissions from a device or natural source interfere with another device or system. EMI might occur if the following three factors are present — the source of EMI, a coupling path and a receptor.

The coupling path from the source to the receptor can be either an electric current, magnetic field or an electromagnetic field. The EMI source can be a natural source, such as lightning. It can also come from devices such as radios, computers, wireless networks, cell phones or any electric device designed to transmit signals.

Robotic surgery systems are computer controlled, and therefore sensitive electronic components must be shielded from electromagnetic interference (EMI) and generated heat must be effectively dissipated from various integrated circuits (ICs). On top of these stringent requirements, components must be able to withstand high heat sterilization, and resist damage caused by harsh chemical cleaning agents in the hospital environment.

1. Electronics generate heat. Thermal interface materials are used to dissipate heat away from the heat generating component onto a heatsink. This task is completed by using a thermal interface material (TIM). Popular TIMs include thermal gap pads and thermal dispensable compounds. Parker Chomerics manufactures thermally conductive gap filler pads which offer excellent thermal properties and the highest conformability at low clamping forces. There are a variety of thermal performances available from 1-6.5 W/m-K thermal conductivity.
    
2. Electrically conductive elastomers are reliable over the life of the equipment, and the same gasket is both an EMI shield and an environmental seal. Electrically conductive elastomer are available in many different conductive filler and binder options, in virtually any size or shape you can design.
    
3. Electrically conductive plastics provide "immunity" for sensitive components from incoming electromagnetic interference (EMI) and/or prevent excessive emissions of EMI to other susceptible equipment. Available in a variety of available options.
    
4. Electrically conductive paints and coatings are available in a variety of options, designed for high levels of EMI shielding on plastic or composite substrates.

With proven solutions in EMI shielding and critical thermal management, Parker Chomerics gives you a wealth of integrated, multi technology systems and components that meet or exceed your specifications and expectations.

This blog post was contributed by Jarrod Cohen, marketing communications for Parker Chomerics.

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Have you been frustrated with going through multiple design iterations when rubber components are failing due to high stresses or your device has been leaking due to insufficient compression? Have you lost months and months of precious time having to recut tools and make design changes?

Finite element analysis (FEA) is an effective tool used in design iterations. It allows for different design ideas, options, and alterations to be quickly, effectively, and precisely compared. 

Using FEA can improve both the speed and quality of product design as well as reduce the overall cost. Rubber parts, such as silicone diaphragms, septums, seals, valves, tubing, and balloons are critical components in today’s medical devices that can benefit from the use of FEA. It can be an excellent design tool to improve the functional performance of these devices. FEA for rubber products is actually far more complex than for metal or plastic products. It requires sophisticated nonlinear FEA software  - such as MSC Marc - as well as a good understanding of the material behavior, material modeling, and testing requirements.

Rubber is highly stretchable, flexible, and durable. This blend of elastic properties differentiates rubber from other materials and makes it one of the best choices for many components in medical devices. However, it’s important to note that rubber materials are not 100 percent elastic because they can develop compression sets and force decay, causing eventual performance degradation and shorter useful life.

Normally, there are three types of nonlinearities encountered: kinematic nonlinearity, material nonlinearity, and boundary nonlinearity. Additionally, rubber products are often subject to large deformations. Whenever material experiences large deformations at least two kinds of nonlinearity - kinematic and material - are involved.

Commonly used nonlinear material models in FEA are elastoplastic models for metals and plastics and hyperelastic models for rubber. in addition, the boundary nonlinearity is usually associated with large deformations.

What are the best test modes to use? One basic engineering rule should apply: always design and perform tests that most closely simulate the actual application conditions that the finished component or device will experience. 

In general, rubber materials are considered nearly incompressible, simply because their volume change is negligible for most applications as a result of that their bulk modulus (105 psi) being several orders larger than their shear modulus (102 psi). The rubber material is actually much more compressible than metal in a confined state (the bulk modulus of typical steel is 107 psi). This understanding is very important to the design considerations of elastomeric products, especially when thermal expansion, limited groove space, or compression of high aspect ratio parts are involved.

Many factors affect the accuracy and reliability of FEA results,  such as material modeling, geometry simplification, and numerical methods. FEA is mostly used in design iterations for which relative comparison is sufficient in the majority of instances. When analysis results are interpreted in a relative sense, different design ideas, options, or modifications can be compared effectively and accurately, and most importantly, rapidly. Furthermore, some tested cases may already exist and can be used as references.

FEA is a powerful tool for the development of rubber components for medical devices. The proper use of FEA can minimize physical prototyping and provide for concurrent engineering. It greatly improves both the speed and the quality of product design, as well as provides cost savings.

Parker has more than 20 years of testing experience with FEA. For more information on Parker‘s use of FEA watch our detailed video - Accelerating Your Launch: Reducing Design Iterations with FEA.

Check out all of our Sealing solutions for Life Science applications including featured applications for Diabetes Care, Surgical, Respiratory, Drug Delivery Systems, and more! 

This post was contributed by Albena Ammann, life science development engineer, Engineered Materials Group, Parker Hannifin.

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In our recent webinar about electrically conductive sealants and adhesives, our experts covered many topics from electrically conductive filler packages to the physical properties of the materials like adhesive strength, flexibility and working life. Did you miss Introduction to Electrically Conductive Sealants and Adhesives? Watch it now.

The viewer learned the difference between an electrically conductive sealant and an electrically conductive adhesive, why you’d choose one over the other, and the design considerations you need to take now.

During the Q&A portion of the webinar, our experts fielded your excellent questions, so we’ve rounded up our eight top favorites for you below.

1. Are there any major chemical incompatibilities that may cause issues with applying an electrically conductive sealant with a non-conductive sealant on apart simultaneously?
   
   With platinum cured silicone systems, sulfur is one contaminant that's known to kill the cure of these materials. There are other materials that kill the cure of silicone materials such as fatty acids. You must be careful when you're using two different types of polymer systems, each with different types of cure systems on the same part. It is something that you want to make sure that there's no interaction between the two systems.
    
2. Can you describe the difference between flame, corona and plasma treatments?
   
   A flame treatment is the use of actual a gas flame right against the surface of the of the part. Flame treatments, corona treatments and plasma treatments all aim to accomplish the same thing: increase the surface energy of the part and improve adhesion. 
   
   Plasma treatment usually requires a high energy gas in a vacuum type environment. It's more of a batch process, but that's also very effective in increasing the surface energy of plastics. Corona treatment is the application of an electrical arc on the material. These treatments are usually done right before you intend to cure the material into the part. You want to apply the electrically conductive sealants or adhesive right after these surface treatments, because over time, the surface energy will decrease. And the advantage of the gains that you get by using these surface treatments will be reduced.
    
3. Do electrical properties vary with cure temperature?
   
   The higher the cure temperature, the greater both the mechanical and electrical properties are. With these cross-linking systems, you typically get a more dense and tighter cross-link at the higher cure temperatures, and that's what gives you the better mechanical and electrical properties. 
    
4. Is a silver-aluminum filled electrically conductive sealant silver-over-aluminum or aluminum-over-silver?
   
   A silver-plated aluminum particle is on the outside. In many electrically conductive fillers, the outside is either silver or nickel plating over an aluminum particle, a glass sphere, potentially a copper or a graphite particle.
    
5. Over time, is there degradation of conductivity due to oxidation of particles?
   
   With silver-plated copper materials, there can be some degradation over time in oxidation, especially in higher temperature applications. Be sure to note the high temperature limit of the material you’re interested in. Some of our silver-plated copper particles have an organic coating or other stabilizing surface treatment which helps to reduce the oxidation over time. While it is true that there are some silver copper particles that may show degradation or oxidation over time, especially at higher temperatures, specifically, there are other silver-copper fillers that that we offer that don't show that same degradation. It's specific to the filler itself.
    
6. How do you spec an electrically conductive fillers for particle size, shape, and surface area?
   
   For particle size, shape and surface area, we use a Microtrac to characterize the particle size distribution, because most of these particles are not one size. There’s usually a particle distribution for different conductor fillers. The shape of the filler particle also has a huge impact on how it's going to perform in an adhesive or in a sealant. Over years and years of testing and analysis of our conductive fillers, we found out that you don't want to design in a spherical particle for any application where you might see a lot of vibration, like a rotorcraft or aerospace type application, because typically when you vibrate conductive particles that are spherical shape, the electrical performance of the shielding will degrade.
    
7. My products are exposed to terrible conditions such as salt fog, jet fuel, low pressures, high temperature swings, mold, vibration and 30-year lifetime. Any suggestions for keeping our RF covers in place?
   
   Combining electrically conductive sealants or adhesives with an electrically conductive coating will help with these requirements as described above. An electrically conductive coating may help in terms of sealing surfaces and providing a longer field life. Additionally, using an electrically conductive elastomer gasket against fuel splash and salt fog may help protect the internal components, as conductive elastomers are designed for both harsh environments and long field life.
    
8. What effect does a high number of thermal cycles have on RF performance of electrically conductive sealants and adhesives? Specifically, I need performance from 1 - 40 GHz and hundreds of cycles from - 55°C to 105°C.
   
   Our materials are run through thermal cycle testing and we test EMI shielding before and after various thermal cycles. It usually has a lot to do with the type of material and the substrate the material will be applied to. Also, how it will perform after thermal cycling will deepened on how closely the coefficient of thermal expansion is between the compound and the substrate that you're applying the compound to. Other things can influence EMI shielding performance following thermal cycling, like particle size and shape and filler loading of the material. It is important test to the specific substrate that you're going to put these materials on in thermal cycling to determine the outcome.

Did you miss this webinar, or maybe want to watch it again? Watch it for free on-demand now.  And so you don’t ever miss another, be sure to sign up for our upcoming webinars.

This blog was contributed by Jarrod Cohen, marketing communications manager, Parker Chomerics.

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Improvements to a drug delivery system (DDS) can control the consistency and increase the quality of drug delivery. Parker’s self-sealing polyisoprene is designed to improve on existing systems available in the market. Parker’s USP <381> self-sealing polyisoprene elastomers demonstrate exceptional self-sealing capabilities, even with needles as large as 16-gauge. Due to the minimal force required for piercing, our material is ideal for seals and septa used in infusion systems and insulin pumps. Using our USP <381> polyisoprene material may improve septum performance and user safety for doctors, nurses, and patients.

A needle, as large as 16-gauge, can pierce the polyisoprene septa as many as 20 times with no trace of leaks. Good self-sealing properties ensure that when the needle comes out, the drug stays in. Our self-sealing polyisoprene is non-coring. After piercing, there is no visible fragmentation and therefore no tiny pieces to clog the system or contaminate the fluid. This is important to maintaining the purity of the drug throughout the delivery process and ensuring a safe transfer to the patient.

Parker’s self-sealing polyisoprene meets USP <381> standards for the functional testing of closures intended to be pierced by a needle. It also meets biological testing as defined by USP <88> and USP <87> for in vitro and in vivo testing, respectively. Our self-sealing polyisoprene passed the biological reactivity and systemic injection tests. The material is biocompatible and has shown no harmful reactions or toxic effects.

Using Parker’s self-sealing polyisoprene for seals and septa in insulin pumps and infusion systems provides improved performance, ease of use, and increased safety due to elimination of leaks and reduction of blockages. This pioneering material allows medical staff to have seals and septa that can be pierced multiple times during use with no leaks. The development of this new product is an exciting prospect for the drug delivery market.

Our facilities are located near major cities to enable easy distribution. Contact us for more information on how we can improve reliability with your drug delivery system. 

This article was contributed by Saman Nanayakkara, Engineering Manager, Parker Hannifin Composite Sealing Systems Division.

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