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Fabricating Extrusion Dies and Tooling using Wire EDM Technology
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For nearly 50 years, Jehbco Silicones has been at the forefront of silicone extrusion, amassing an impressive library of over 2,600 extrusion dies and a wealth of knowledge to ensure the delivery of perfect silicone products to their customers. One of the critical elements contributing to our sustained excellence and innovative edge is the use of advanced machining technologies for tool and extrusion die making at Jehbco, such as our Excetek V400G Wire Electrical Discharge Machine (Wire EDM). 

Figure 1. Excetek V400G Wire EDM Machine used for cutting extrusion dies and tooling at Jehbco.

What is Wire EDM? 

Wire EDM is a non-conventional machining process that uses a thin wire as an electrode to cut intricate shapes and fine details in hard materials. The Excetek V400G model employed by Jehbco Silicones stands out due to its precision, reliability, and ability to produce complex geometries with exceptional accuracy. The WEDM process works by generating a series of electrical discharges (sparks) between the wire and the workpiece. These sparks erode the material, creating the desired shape. The wire, typically made of brass or a similar conductive material, does not make physical contact with the workpiece, which allows for precise cutting without the wear and tear associated with traditional machining tools. This technology operates in a submerged environment, which helps to control the temperature and remove debris, further enhancing the precision of the cuts [1][2]. 

Figure 2. Diagram of wire EDM cutting process [3].

Advantages of Wire EDM Over Traditional Machining Methods 

Unparalleled Accuracy: Wire EDM machines, like the Excetek V400G, achieve a level of precision that is difficult to match with traditional machining methods. The accuracy of the Wire EDM process can reach tolerances within microns, making it ideal for producing intricate extrusion dies required in silicone product manufacturing. This precision ensures that the final product adheres to exact specifications, reducing waste and enhancing product quality​ [1][2]. 

Ability to Machine Intricate Geometries: Traditional machining methods often struggle with creating complex shapes and fine details, especially in hard materials. Wire EDM excels in this regard, as it can effortlessly cut intricate geometries, including sharp corners, thin walls, and delicate features. This capability is particularly beneficial for Jehbco Silicones, where the design of extrusion dies often demands intricate patterns to meet specific customer requirements​ [1][4]. 

Figure 3. Extrusion dies with intricate profiles cut using wire EDM.

Material Versatility: Wire EDM machines can cut a wide range of conductive materials, from common metals like steel and aluminium to exotic alloys and hardened tool steels. This versatility allows Jehbco to fabricate extrusion dies and tools from materials best suited to the specific demands of silicone extrusion [2][6]. 

Enhanced Surface Finish: The Wire EDM process produces a high-quality surface finish, often eliminating the need for additional finishing operations. This is crucial for extrusion dies, where a smooth surface ensures consistent flow through the extrusion die and reduces the likelihood of defects such as streaks in the final silicone product [2][6]. 

Automation and Efficiency: Modern Wire EDM machines like the Excetek V400G are equipped with advanced automation features, including CNC controls and automatic wire threading. These features enhance operational efficiency, reduce setup times, and allow for unattended machining. For Jehbco Silicones, this means faster production cycles and the ability to meet tight deadlines without compromising quality​ [2][5]. 

Jehbco’s Expertise and Experience 

With five decades of experience in silicone extrusion, and a library of over 2600 dies and extrusions at Jehbco, there is a wealth of knowledge and data to draw from. This experience and expertise, combined with the precision of our Excetek wire EDM machine, enables Jehbco to fabricate high quality extrusion dies with which to produce the perfect silicone products tailored specifically for our customers. The integration of Wire EDM technology has allowed Jehbco to push the boundaries of what is possible in silicone extrusion, offering innovative solutions and products that set industry standards. 

Overall, the adoption of the Excetek V400G Wire EDM machine at Jehbco Silicones underscores the company’s commitment to precision, innovation, and quality. By leveraging the advantages of Wire EDM, Jehbco continues to lead in the silicone extrusion industry, delivering products that consistently exceed customer expectations. The combination of advanced technology and extensive experience positions Jehbco as a trusted partner for those seeking high-quality silicone extrusion solutions. 

References 

  1. Wire EDM: Guide to EDM Wirecut Machine, Process & Uses – Fine Metalworking.
    https://finemetalworking.com/wire-edm 
  2. Wire EDM: Components, Types, Applications, and Advantages – IQS Directory.
     https://www.iqsdirectory.com/articles/edm/wire-edm.html 
  3. Wire EDM – Manufacturing Guide Sweden
    https://www.manufacturingguide.com/en/wire-edm 
  4. What’s Wire EDM Machining? Techniques, Benefits, and Uses – Rapid Direct.
    https://www.rapiddirect.com/blog/what-is-wire-edm/ 
  5. Wire EDM Explained: Everything You Need to Know – Union Fab.
    https://www.unionfab.com/blog/2023/10/wire-edm 
  6. All About Wire EDM Machining: Definition, Application, and Materials – Xometry.
     https://www.xometry.com/resources/machining/wire-edm-machining/ 

 

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Low Compression Set in Silicone Rubber and its Application in Seals
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Silicone rubber is well known for its excellent elastomeric properties, exhibiting outstanding elongation at break values and rebound resilience. Due to these properties, silicone is an ideal material for producing a wide variety of seals and gaskets which readily form stable and durable mechanical seals upon applying pressure.  

A crucial parameter in the sealing performance of silicone is the compression set. In a sealing application, mechanical force is applied on the silicone seal to compress it between two surfaces. The elastomeric properties of the silicone causes it to bounce back to its original shape, and tightly forms a seal against the two surfaces that obstructs any flow of liquids and gasses. However, upon long-term compression, the silicone can lose a fraction of its shape memory, becoming permanently deformed and will no longer fully bounce back to its original shape. This permanent deformation after prolonged mechanical stress is applied and then released is known as the compression set. If a material has a high (poor) compression set, a large proportion of its original shape memory will be lost upon prolonged compression, which can cause sealing failure. Thus, compression set is a crucial property in sealing design as it indicates the ability of the seal to maintain its shape and sealing properties over extended periods of time. 

Compression set of silicone elastomers is typically measured using conventional standards such as ISO 815-1 B and ASTM D395 B. In these standards, standardised samples of silicone are placed between two metal plates which are then compressed, using gauge blocks to calibrate a fixed deformation distance, which is typically 75% of its original height. The entire apparatus is then placed in elevated temperatures to promote accelerated ageing, and compression set is provided at the testing values. For silicone rubber, a compression set testing period of 22 h at 175°C is often used. For related materials such as silicone sponge, separate testing samples and test durations are outlined in ASTM D1056.  

Solid silicone rubber exhibits excellent compression set values, typically between 10 – 30 % depending on the hardness and grade used, which is significantly lower than other elastomers such as EPDM or neoprene. In addition to an excellent low compression set, silicone is a chemically inert material, has outstanding heat resistance, and is safe for use in contact with food, and is thus the material of choice for sealing applications in high temperature environments, and food and medical grade industries. More information on silicone seals, mechanical properties and elastomeric behaviour is available on our articles page.  

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Post Curing of Silicone Tubing
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Post Curing is the process of heating up the silicone tubing in an oven at a given temperature for certain amount of time.  The lowest and highest temperatures used in Jehbco for post curing is 160˚C and 200˚C. Post curing process helps to remove the volatiles from the manufactured products. 

As the name indicates, post curing is the secondary curing process in the silicone manufacturing. The Post curing helps to further cross link the polymer chains to enhance mechanical properties, thermal and chemical resistance. Post curing of silicone helps to improve the physical characteristics of the material. All silicone elastomers go through a peroxide silicone curing using peroxide-based chemicals or a platinum cure using a catalyst.  Even though the rubber is in a finished product format, it is still not a stable state. Few by products /volatiles from the chemical process is left with the silicone after the initial cure. These volatiles will be removed during the post curing process. Inadequate or poor post-cure may cause bubbling, delamination and unappealing sticky surface deposits. 

In a typical post curing process, the temperature is adjusted between 160˚C and 200˚C for a period of 2-6 hours. The time and temperature may be altered depending on the application. Post-curing ensures the product remains dimensionally stable. Post Curing also helps to reduce /eliminate the outgassing process. The main reduction in mechanical properties of the silicone occurs in the first couple of hours at a service temperature. Post-curing brings the silicone to a state where its degradation rate is minimized, ensuring long-lasting performance with consistent quality. 

Apart from all the advantages mentioned above, post curing also helps to enhance the thermal stability of silicone rubber. Allowing it to maintain its properties at higher temperatures without degrading. For silicone products that come into contact with high-temperature surfaces, undergoing the post-curing process is highly beneficial as it posts curing will produce a highly thermal resistant product.  

By completing the cross-linking process, post-curing improves the silicone’s resistance to chemicals and solvents. This is particularly important in environments where the material is exposed to aggressive substances, such as in pharmaceutical or food processing equipment. Current manufacturers recommendation from Jehbco’s supplier is to post cure at 200 degrees Celsius for 4 hours for pharmaceutical and food applications.

Oven temeprature records which shows the temeprature distribution in different locations of the oven

Jehbco is dedicated to meeting customer silicone requirements despite the costliness of post curing. The company employs oven curing or all post curing needs, a process involving placing manufactured goods in an oven under carefully controlled temperature and time conditions. Jehbco utilizes two new ovens from Steridium for this purpose, ensuring efficient post curing operations. One oven is exclusively used for platinum curing, while the other is dedicated to peroxide curing. This segregation guarantees that there is no cross contamination during the post curing stage at Jehbco.  The Airflow specification for Jehbco’s new ovens is 20,000 liters/minute. Thermocouples are positioned in nine locations on both sides of the oven to monitor and ensure even heat distribution throughout. The oven requires only 30 minutes to reach the desired temperature. Customers may request post curing of silicone from Jehbco if needed. Jehbco will monitor the temperature readings from the ovens to ensure the post curing process is executed effectively. Committed to delivering top-quality products, Jehbco prioritizes maintaining customer trust and satisfaction. The oven picture and the sample temperature records are added in the annex section of the article. 

References 

  1. https://rdabbott.com/wp-content/uploads/2017/08/Dow-Corning-Post-Curing-Silicone-Elastomers.pdf 
  2. https://shorehoses.com/news/importance-of-post-curing-of-silicone-products/ 
  3. https://www.adhesivesmag.com/articles/99586-post-cure-advantages-for-silicone-elastomers-and-adhesives 
  4. https://www.wacker.com/h/medias/7562-E-0323-final.pdf 
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Silicone products for pharmaceutical industry

Silicone products for pharmaceutical industry
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Silicone tubing is widely used in pharmaceutical and biomedical industries. This article will detail the specific reasons why silicone tubing is preferred in numerous pharmaceutical applications.

Silicone tubing’s are well known for its flexibility, durability, and chemical inertness which makes it ideal to be used for pharmaceutical applications. Silicone is one among the very few biocompatible materials available in the industry. Silicone is also odourless, tasteless and heat resistant.

Biocompatibility

Silicone rubber is known for its biocompatible nature. Silicones are biocompatible because they do not support microbiological growth and they do not interact with microbiomes. Silicone materials is formed by a highly strong and stable chemical bond and so the binding energy between siloxane bonds are stronger than that of carbon bonds. The stronger binding energy in silicone polymer makes it durable, chemically and thermally stable. Due to the strong binding energy, silicone bonds can’t be broken and thus it is insoluble in body fluids and chemicals. The chemically inert nature of silicone is crucial for the pharmaceutical industry, where product purity is paramount.  The intermolecular force between silicone bonds is low, which makes gives it high elasticity and compressibility.

Thermal & chemical stability

Due to the high binding energy of siloxane bonds, these bonds cannot be broken even at 200 degrees Celsius. Properly cured silicone rubber is also stable This strong binding energy also contributes to the chemical stability of silicone products, as chemicals are unable to react with them since the siloxane bonds remain intact. The capability to resist a wide range of temperatures, from extreme cold to intense heat, without degradation, is vital for sustaining the integrity of sensitive pharmaceutical products. The thermal, chemical and electrical insulation properties of silicone make it ideal to be used in pharmaceutical manufacturing and research laboratories.

Non – Porous Sterile nature

Along with biocompatibility, silicone rubber is also non-porous, making it impermeable to water and easier to clean this will also eliminate the chances of bacteria growing up in the products. Silicone materials are easy to be cleaned/sterilized as it is heat, cold and chemical resistant. Various heat sterilization options are widely used for cleaning silicone products as they are heat resistant.

Flexibility

The improved flexibility of silicone products makes it ideal for various fluid transfer applications in pharmaceutical industry. Furthermore, the translucency of silicone tubes helps in monitoring of fluid flow, which is vital in various pharmaceutical applications.

Durability

The lifecycle of a silicone product may vary based on the way it is cured and the environment it is being used. Based on the curing process, there are products that can last up to 40-45 years. The durability is crucial in pharmaceutical applications as they are primarily focused on human lives.

Why Choose Jehbco?

Platinum-cured hospital-grade silicone manufactured by Jehbco is biocompatible and non-porous. With proper curing and post-curing, Jehbco’s platinum hospital-grade silicone can be used for food contact applications and complies with the Recommendation “XV. Silicones” of the BfR and FDA 21 CFR §177.2600 “Rubber Articles Intended for Repeated Use,” considering any given limitations on extractable and volatile substances. The raw material used by Jehbco for hospital-grade tubing also come with a statement from the supplier regarding biocompatibility, in accordance with USP<88> Class VI and selected tests of ISO 10993.

Some common applications in pharmaceutical industry

Peristaltic Pumps: Contamination free fluid transport

Laboratory Research: For the management sensitive biological samples, where cleanliness and non-toxicity are crucial.

Sterile Filling: Essential in the aseptic filling of pharmaceutical products.

Drug Delivery Systems: Precise and contamination free drug delivery.

 

References 

  1. https://fluidbiosolutions.com.au/the-ultimate-guide-to-silicone-tubing-in-pharmaceutical-applications/#:~:text=Silicone%20tubing%20is%20extensively%20used,precision%20and%20purity%20are%20critical.
  2. https://globalsilicones.org/explore-silicones/benefits-uses/healthcare/#:~:text=Their%20chemical%20stability%2C%20durability%2C%20and,tension%2C%20and%20ease%20of%20sterilization.
  3. https://www.vikingextrusions.co.uk/blog/how-silicone-is-used-in-medical-pharma/https://www.sciencedirect.com/topics/engineering/silicone-material#:~:text=Silicone%20materials%20consist%20of%20repeating,and%20insoluble%20in%20body%20fluids.
  4. https://www.shinetsusilicone-global.com/catalog/pdf/rubber_e.pdfhttps://www.xometry.com/resources/materials/properties-of-silicone/
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Optical Comparator Technology at Jehbco Silicones: Revolutionising Dimensional Accuracy

Optical Comparator Technology at Jehbco Silicones: Revolutionising Dimensional Accuracy
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At Jehbco Silicones, precision and accuracy in product dimensions are paramount. To achieve this, the company employs an advanced optical comparator, the Starrett Precision Optical VB400 model. This tool represents a significant advancement over traditional measuring methods such as the Vernier caliper, especially in handling the delicate and intricate profiles of silicone extrusions.

What is an Optical Comparator?

An optical comparator is a device used in manufacturing and laboratory settings to magnify the silhouette of a part onto a screen to compare it against a set scale or the design drawing. It combines optics, mechanics, and electronics to offer non-contact measurement, which is crucial for materials that are easily deformed or damaged. The Starrett VB400 at Jehbco Silicones utilizes high-quality optics to project a shadow of the silicone profile onto a screen at precise magnifications, allowing for meticulous inspection and measurement.

Starett VB400 optical comparator used at Jehbco

Figure 1. Starett VB400 optical comparator used at Jehbco

How It Works 

The process begins by placing a silicone extrusion profile on the stage of the optical comparator. Light is projected onto the object, casting a shadow which is magnified and projected onto a screen. This shadow clearly displays the profile’s dimensions and geometry against predefined scales or overlays. Engineers at Jehbco can then visually compare and measure each dimension against the profile drawings or utilize digital tools integrated into the VB400 model to capture and analyse these measurements automatically.[1] [2]  

Measurement Capabilities 

The Starrett VB400 optical comparator boasts a high degree of accuracy, thanks to its advanced features. It is equipped with linear encoder scales that offer a resolution of 0.1 microns (0.000004 inches), which ensures precise measurements. Furthermore, the VB400 is particularly adept at handling complex profiles and dimensions that are difficult to measure with traditional tools. This high resolution facilitates the examination of complex and detailed part geometries, making the VB400 a robust tool for quality assurance at Jehbco where precision is critical​. It can accurately define radius, diameter, clearances, and angular dimensions, which are often critical in the high-quality silicone products manufactured by Jehbco. This precision is facilitated by features such as high-resolution cameras and digital displays, enhancing the ease and accuracy of the measurement process.[3] [4]  

A silicone extrusion sample is placed on a glass platform above a light source, projecting a silhouette for accurate, non-contact measurement.

Figure 2. A silicone extrusion sample is placed on a glass platform above a light source, projecting a silhouette for accurate, non-contact measurement.

Advantages Over Traditional Methods of Measurement 

Optical comparators offer several advantages over traditional measuring tools like Vernier callipers. Firstly, they provide a non-contact measurement method, thereby preventing any deformation during measurement. This is particularly advantageous for soft materials like silicone which deform under physical contact. Using an optical comparator ensures that the integrity of the part remains intact during inspection. Additionally, the magnification ability of the optical comparator allows for the detection of minute defects and ensures compliance with tight tolerances that might be missed by the naked eye. 

Measuring an extrusion sample using Vernier calllipers. Inaccurate measurement due to deformation of the soft silicone rubber.

Figure 3. Measuring an extrusion sample using Vernier calllipers. Inaccurate measurement due to deformation of the soft silicone rubber.

Moreover, with features like digital readouts and automated data collection, the VB400 speeds up the measurement process and reduces the potential for human error, enhancing the overall efficiency of quality control at Jehbco. [1] [3]  

Conclusion 

The investment and use of the Starrett Precision Optical VB400 at Jehbco Silicones highlights the company’s commitment to quality and precision in the manufacture of silicone extrusion profiles. By adopting such advanced metrology tools, Jehbco ensures that each product not only meets but exceeds customer expectations and industry standards, reaffirming our position as a leader in the silicone manufacturing industry. 

References 

  1. Higher Precision Blog: How an Optical Comparator Works
     https://www.higherprecision.com/blog/what-is-an-optical-comparator 
  2. VisionX Inc: What Is an Optical Comparator and How Does It Work?
    https://www.visionxinc.com/what-is-an-optical-comparator 
  3. Starrett Metrology: Starrett Optical Comparators
    https://au.starrett.com/product-detail/VB400 
  4. Crescent Gage & Tool: Starrett VB400
    https://crescentgage.com/gaging-equipment-sales/starrett/vertical/starrett-vb400/ 
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Unveiling the Elasticity Dynamics: A Deep Dive into Silicone Rubber’s Rebound Resilience
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When any elastic material is exposed to an impact load, it will initially deform before bouncing back to its original shape. When this occurs, part of the initial energy delivered by the impact is returned as mechanical energy, and a certain portion is dissipated as heat. From this, the rebound resilience is defined as the ratio of mechanical energy returned to the initial mechanical energy exerted from the impact. Higher rebound resilience indicates stronger elasticity, resistance to deformation and a stronger capacity to bear impact loads. However, for some applications such as vibration dampening, lower rebound resilience may be more beneficial.

Testing for this property is typically performed by dropping a standardized pendulum at a set height and speed onto a material sample, as described by standards including ISO 4662 and DIN 53512. After the pendulum impacts the rubber, the rubber will deform before pushing back against the pendulum, returning mechanical energy. Here, the rebound resilience can be quantified by the ratio of the pendulum rebound height to the initial release height.

Compared to other elastomers silicone rubber exhibits intermediate rebound resilience values, typically between 30 and 70 %. Typically this is better than some elastomer families such as butyl or styrene-butadiene rubber, but worse than elastomers such as natural rubber or polyurethane. Notably, silicone rubber can be produced to have high rebound resilience in a range of hardness values. Thus, depending on the application, silicone rubber can be an excellent choice for dampening applications or dynamic applications where higher rebound resilience is more important.

While rebound resilience is one method of quantifying material elasticity, another complementary parameter that characterizes a material elasticity is the material’s compression set. This property describes how readily the shape of a material is permanently affected when subject to prolonged deformation. More information on silicone’s outstanding compression set is available on our articles page.

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Carbon-based vs Silver-based Electrically Conductive

Carbon-based vs Silver-based Electrically Conductive Silicone
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Standard silicone elastomers are electrically insulating, however with the right chemistry and speciality materials they can be made electrically conductive. 

The most common ways of making electrically conductive silicone is by combining it with reinforcing filler materials with strong electrical conductivity. These can include silver coated glass/graphite/nickel/copper/etc, pure silver nanoparticles, or more commonly conductive carbon black. Silver based conductive filler provides extremely low electrical resistivity profiles up to 0.002 Ohm/cm and provides electromagnetic pulse (EMP) shielding properties for highly specialized applications. However, these silver-based conductive silicone components cannot be produced via extrusion and cannot be directly produced at Jehbco. 

 

Conductive Component Pros Cons
Silver or Metal Based Nanoparticles
  • Excellent EMP shielding capabilities
  • Extremely high electrical conductivity (resistance ~ 0.002 Ohm/cm)
  • Excellent temperature stability (-50 to 200 °C)
  • Extremely expensive
  • Poor mechanical strength 
  • Cannot be produced via extrusion
  • High density (~ 3 g/cm3)
Conductive Carbon Black
  • High electrical conductivity (resistance ~ 2 Ohm/cm)
  • Good mechanical properties
  • Producible via extrusion
  • Low cost compared to other conductive grades
  • Excellent temperature stability (-50 to 200 °C)
  • Standard silicone density
  • Intrinsically flame retardant
  • Weaker EMP shielding capabilities
  • Conductivity still high, but not as good as silicone with silver based conductive components

 

For extrusion silicone materials, conductive carbon black is commonly used to create highly conductive silicone materials. Conductive carbon black is a speciality grade of carbon that is manufactured entirely differently from carbon blacks used in pigmentation, which provides it with extremely useful properties including high electrical conductivity. Interestingly, the use of carbon black necessitates the use of more resourceful chemistry to facilitate processing. High loadings of carbon black typically interfere with standard peroxide silicone curing systems, due to incompatibility with the most common catalyst used in extrusion processing (2,4 dichlorobenzoyl peroxide). Thus, platinum curing systems must be used in all carbon loaded electrically conductive silicone articles processed via extrusion. 

 

By utilizing elevated quantities of reinforcing and electrically conductive carbon black, extremely low electrical resistivity of < 2 Ohm/cm are commonly achieved, while maintaining excellent mechanical integrity. In addition to providing electrical conductivity, the addition of conductive carbon black provides increased fire retardant properties without requiring supplementary fire retardant additives. Carbon black conductive silicone components find frequent application in sensors and electrical components, and can also be used as anti-static materials including sleeving to discharge static build-up.

 

At Jehbco, we offer electrically conductive silicone in from 50 to 70 ShA hardness exhibiting extremely low electrical resistance (<2 Ohm/cm), and can be formulated to other hardness grades based on customer requirements. All Jehbsil conductive silicone is jet black in colour. For another article comparing conductive silicone to standard silicone, see: https://jehbco.com.au/silicone-electircally-conductive-silicone/

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RoHS: “Restriction of Hazardous Substances” in Silicone Parts for Electrical Products
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The RoHS (Restriction of Hazardous Substances) regulation derives from the European community joint efforts to regulate and restrict the use of hazardous substances in electrical and electronic products to protect the environment and human health.

The directive adopted on July 1 of 2006 has undergone updates until the most recent RoHS 3 – directive 2015/863 – where was established that all electrical or electronic products, manufactured or distributed within the European community, should not exceed the maximum concentration for each substance on the table below:

 

Restricted Substance Maximum Level allowed
Cadmium (Cd):  < 100 ppm     (0.01%)
Lead (Pb):  < 1000 ppm   (0.1%)
Mercury (Hg):  < 1000 ppm   (0.1%)
Hexavalent Chromium (Cr VI):  < 1000 ppm   (0.1%)
Polybrominated Biphenyls (PBB):  < 1000 ppm   (0.1%)
Polybrominated Diphenyl Ethers (PBDE):  < 1000 ppm   (0.1%)
Bis(2-Ethylhexyl) phthalate (DEHP):  < 1000 ppm   (0.1%)
Benzyl butyl phthalate (BBP):  < 1000 ppm   (0.1%)
Dibutyl phthalate (DBP):  < 1000 ppm   (0.1%)
Diisobutyl phthalate (DIBP):  < 1000 ppm   (0.1%)

Last update July 22nd, 2021.

 

The substances above can be carcinogenic, mutagenic, toxic and bio accumulative for the human body. In addition, they can produce highly toxic transformation products when mixed with other components during disposal or recycling.

Electrical products that are in contact with food and beverages should comply with the RoHS directive. Not only because people will consume the items inside but also because they can be in use daily. Microwaves, refrigerators, blenders are examples of appliances where silicone gaskets should comply with RoHS.

Similarly, electrical appliances in constant contact with water for example, washing machines or heaters, should not introduce harmful chemicals such as lead, mercury or cadmium into pipes or drainage systems to avoid contamination of water sources and other negative impacts on the environment. In those cases, silicone tubing and door gaskets should also comply with RoHS.

The silicone products manufactured at Jehbco have countless applications within the electrical and electronic industry, most recently providing the manufacture of medical devices and electrical appliances with silicone gaskets, washers and membranes. That is why Jehbco remains in constant communication with raw material suppliers who provide the company with the RoHS declarations and the corresponding raw materials composition.

Whether they contain RoHS, limited or prohibited substances, Jehbco identifies the current requirements of the applicable regulations and will be happy to provide their customers with the necessary declarations.

 

References

https://ec.europa.eu/environment/topics/waste-and-recycling/rohs-directive_en

https://www.env-health.org/IMG/pdf/Joint_NGO_Position_RoHS.pdf

https://rohsguide.com/rohs-substances.htm

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Adhesive Peel Strength Testing for Silicone Adhesives
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At Jehbco, we are constantly finding innovative ways to use the products we produce to suit your needs. The application of silicone elastomer profiles can be extended in combination with adhesives for applications across many industries.

 

Adhesive peel testing can assist in selecting the right silicone adhesive for your application. Comparing peel adhesion, tensile strength, and shear resistance provide a comprehensive answer to how suitable an adhesive is to a certain application. If the adhesive strength is lower than the requirement, the bond may wear away and lose adhesion.

 

Adhesive peel strength is determined through the constant load per unit width required to separate the adhesive and substrate in kilonewtons/metre. This force is applied to an edge of the adherend and the substrate and is determined from the average value of the flat portion of the force-extension curve [1].

 

A simple qualitative test can be done by hand is the ‘pull test’, which is to pull the silicone with reasonable strength. For a more detailed quantitative result, standardized adhesive peel tests may be conducted on clean, contaminant free substrates to determine the force required to separate the substrate and the adherend[2]. The most typically used tests are:

  1. The T shaped peel test (ASTM D1876[3]) is the most widely used peel test for thin-gauge metal adherends.
  2. The 180-degree peel test (ASTM D903 [4]) requires flexible adherends that may be bent 90 degrees without breaking or cracking.
  3. The 90-degree peel test (ASTM 6382 [5]), which also required flexible adherends.

 

At Jehbco, we have the capability to conduct tests according to ASTM 6382. The testing rig is illustrated below. The use of a machine ensures controlled peel rates that reduce scattering and lead to more accurate results [4].

 

Major factors that affect the measurement of adhesion are [5]:

  • Selection of the peel test
  • Pull speed
  • Temperature and humidity conditions
  • Substrates and adherend material, interfacial characteristics, and thickness
  • Adhesive choice
  • Aging condition (typically 4hrs, 7 days, and 14 days)

 

References

  1. B. Duncan, “Developments in testing adhesive joints,” in Advances in Structural Adhesive Bonding, Woodhead Publishing Series in Welding and Other Joining Technologies, 2010, pp. 389-436.
  2.  tesa, “What’s the deal with peel (peel adhesion, that is)?,” 2016. [Online]. Available: https://www.tesa.com/en-au/wikitapia/what-s-the-deal-with-peel-peel-adhesion-that-is.html.
  3. ASTM International, “ASTM D1976: Standard Test Method for Peel Resistance of Adhesives (T-Peel Test),” ASTM, West Conshohocken, PA, USA, 2015.
  4. ASTM International, “Standard Test Method for Peel or Stripping Strength of Adhesive Bonds,” ASTM International, West Conshohocken, PA, United States, 2017.
  5. ASTM International, “Standard Test Method for 90 Degree Peel Resistance of Adhesives,” ASTM International, West Conshohocken, PA, USA, 2003.
  6. T. S. J.K. Dennis, “Physical and mechanical properties of electrodeposits and methods of determination,” Nickel and Chromium Plating (Third Edition), 1993.
  7. S. R. Meyer, “Adhesion – Considerations, Testing and Interpretation,” 3M, Minnesota USA, 2015.
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Flame Retardant Silicone Products for Railway Industry

EN 45545-2_R22 European standard
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EN 45545 is a European standard that specifies the “fire performance requirements for materials and product used on railway vehicles”[1] in order to protect passenger and staff in railway vehicles in the event of a developing fire on board[2]. The part of the standard that applies to Jehbco products is R22 which has a section about the requirements for interior seals[3]. This standard section is now used in replacement of BS 6853 which was a smoke safety standard for the rail industry[4].

The methods to perform testing are detailed in the standard. It consists of 3 tests that are used to establish product performance versus these product requirements: 

  1. Oxygen index (EN ISO 4589-2): this test determines the burning behaviour at ambient temperature[5]. It is defining the minimum concentration of oxygen in a mixture of oxygen/nitrogen that will support flaming combustion.
  2. Smoke density (ISO 5659-2): this test measures the smoke production from the exposed surface of materials or composites[6].
  3. Smoke toxicity (NF X70-100): this test quantitively determines the thermal decomposition and combustion of materials decisive for the toxicity of the fire environment[7]. 

The standard defines three hazard levels: HL 1, HL 2 and HL 3; HL1 being the lowest requirement and HL 3 the highest.  The performance requirements on EN 45545-2 for each of these tests is summarized below:

Table 1: Summary of test methods

Test Method Parameter Unit Maximum or minimum HL 1 HL 2 HL 3

Oxygen Index 

(EN ISO 4589-2: OI)

 Oxygen content % Minimum 28 28 32

Smoke Density

(EN ISO 5659-2: 25 kWm-2)

Ds max

dimensionless

 Maximum 600 300 150
Smoke Toxicity

(NF X 70-100-1 & -2 600°C)

 CITNLP dimensionless Maximum 1.2 0.9 0.75

 

Ds max is the maximum optical density in the test chamber

CITNLP is the conventional index of toxicity for non- listed product

 

Jehbco is proud to inform that their Jehbsil black flame retardant products with hardnessess going from 30 to 90 Sh A have successfully met the requirements of the PN  EN45545 2 + A1:2015 standard for R22 and R23 at the HL 1, HL 2 and HL 3 hazard levels in November 2020.

 

References

  1.  European Committee for standardization. EN 45545-2:2020 standard. “Railway applications – Fire protection on railway vehicles – Part 2: Requirements for fire behavior of materials and components”, August 2020
  2. European Standard. “Set DIN 45545-1-7- Fire protection on railway vehicles”. Viewed on 31st March 2021https://www.en-standard.eu/set-din-en-45545-1-7-fire-protection-on-railway-vehicles/
  3. DGE smart speciality chemicals, “EN 45545-2 European railway standard for fire safety”, viewed on 31st March 2021. https://dge-europe.com/en-45545-european-railway-standard-fire-safety/
  4.  Nathan White, CSIRO , “Fire Performance of Passenger Trains”, FPA Australia, viewed on 31st March 2021. fpaa.com.au/media/229521/d1-fse-p5-white.ppt.pdf  
  5. International Standard Organisation, “ISO 4589-2:2017(en). Plastics — Determination of burning behaviour by oxygen index — Part 2: Ambient-temperature test”. Viewed on 31st March 2021.https://www.iso.org/obp/ui/#iso:std:iso:4589:-2:ed-2:v1:en 
  6. International Standard Organisation, “ISO 5659-2:2017 Plastics — Smoke generation — Part 2: Determination of optical density by a single-chamber test”, viewed on 31st March 2021. https://www.iso.org/standard/65243.html
  7. Sychta laboratorium, “the toxicity test for thermal decomposition and combustion products of materials with methods according to NF X70-100-1, NF X70-100-2 and PN-EN 45545-2”. viewed on 31st March 2021. http://www.sychta.eu/en/nf-x70-100-1.html
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