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Silicone vs SBR
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Jehbco Silicones is an industry leader, manufacturing high quality silicone extrusions in Australia. Whilst silicone and Styrene Butadiene (SBR) share some similarities in their characteristics and chemical resistance levels, their physical properties vary, which depending on the conditions of application, a justified material selection can be made.

 

SBR Silicone
-45° to 100° C -50° to 230° C
Great compression set Excellent compression set
Fair weather resistance Excellent weather resistance
Approx. tensile strength 18 MPa Approx. tensile strength 5 MPa
Excellent abrasion resistance Poor abrasion resistance
Not compatible with: alphatic hydrocarbon solvents, aromatic hydrocarbon solvents, petroleum products Not compatible with: hydrocarbon fuels, alkalis and acids, steam over 121 °C, trichloroethylene, aromatic hydrocarbons.
Compatible with: acids, alcohols, oxygenated solvents, oils, alkali, hot and cold water, salt water Compatible with: oils, brake fluids, hot and cold water, salt water, high molecular weight chlorinated hydrocarbons, fire resistant hydraulic fluid, ozone.

 

Silicone and SBR can both withstand temperatures as low as approximately -40° C, making them both considerable for low temperature applications. However, silicone rubber offers a significantly higher heat resistance making it an ideal material for high temperature applications.

Very similar to natural rubber, SBR has an excellent abrasion resistance which make an ideal material choice for dynamical applications involving a large amount of physical demand. This is not the case with silicone, which with its low abrasion resistance is much better suited for high-temperature static applications. The tensile strength of SBR is much higher at 18 MPa which also make it an ideal candidate for applications with high dynamical loading and force.

Both materials exhibit the same degree of compression set allowing both materials being acceptable for applications that demand high durability.

In general, silicone is an ideal material for static and high-temperature applications whereas SBR is a common elastomer for applications requiring a high resistance to dynamical load and friction. The ideal material for your application highly depends on your requirements. To help guide you in choosing the right material for your application, please contact us.

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use-of-silicone-in-food-processing

The Strengths & Common Use of Silicone in Food Processing
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Silicone rubber is widely used in food processing from home to industrial-scale cooking. The properties of silicone make this polymer material ideal for food applications. Silicone combines the following properties:

  • The ability to withstand extremely high and low temperatures (from -60°C to + 200°C) for extended periods of time
  • Chemical resistance and compatibility
  • Suitability for contact with dry, aqueous and fatty foods
  • High quality and long-lasting product
  • Safety, as the levels of volatiles and extractable particles rejected are low

Jehbco Silicones has provided custom made silicone solutions for the last 40 years and aims to keep providing high-quality products to the food industry. All food-grade silicone produced by Jehbco uses U.S. Food and Drug Administration (FDA) approved materials and follows FDA standards. All food grade products made by Jehbco are thoroughly post-cured to further decrease levels of extractables.

Additionally, Jehbco can make silicone food grade heat stable products using a specially designed additive. This increases the extreme temperatures that silicone can withstand from 200°C to 300°C.

 

Jehbco extrudes any shape, cuts to any particular length and bonds to form a variety of inner-diameter sizes.

Jehbco extrudes any shape, cuts to any particular length and bonds to form a variety of inner-diameter sizes.

 

Furthermore, Jehbco has recently researched and developed a platinum sponge which meets food grade requirements of FDA. Platinum food grade sponge made by Jehbco has the following advantages:

  • The ability to withstand extreme high and low temperatures (from -40°C to + 200°C)
  • Low density (400-650 kg m-3)
  • Low compression deflection (92.4 kPa, 13.4 psi)
  • Low hardness (20 Shore A)
  • Excellent compressibility (9%)

Food grade silicone products are used by a wide range of industries including oven/refrigeration, milk and dairy, meat processing, powder containment/transport, beverages, and food packaging etc. For example, some of Jehbco’s products are used in-line for some of their processes such as conveyors and others are used in batch processes such as fermentation vats.

Similarly, a wide range of food-grade silicone products can be produced:

  • Seals: commonly used for ovens, refrigeration units, powder containment/hoppers, and blenders. The majority of seals sold by Jehbco are corner-joined or butt-joined for sealing application, but Jehbco can also provide custom made O-rings for sealing applications.
  • Inflatable gaskets: used for a number of applications, from sealing of machinery to in-line support of food products (e.g. some of Jehbco’ inflatable gaskets are used to hold ice-cream cones in place during production).
  • Sheets:  often used for heat/vibratory insulation
  • Tubing: often used for fluid transfer, pumping application

If you would like to learn more about how silicone can be used in food applications please see our applications page or contact us.

 

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Silicone Extrusion Cut Quality

Silicone Extrusion Cut Quality
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At Jehbco, silicone rubber extrusions are cut accurately to our customers desired lengths. Using our state-of-the art cutting machine we are able to produce precise and clean straight cuts. Our in-house cutting capability reduces the lead-time and cost for our customers.

 

Silicone Extrusion Cut Quality

Silicone Extrusion Cut Quality

 

Having a high quality cut is significant for not only the appearance but also the intended function of the extrudates. We design and develop in-house cutting tools and accessories to cut not only tubes and cords but also complicated profiles of various hardness. The right blade shape is determined based on our research.  We have extended our cutting capabilities to include silicone sponge extrusions which exhibit a high degree of difficulty in handling due to their low stiffness and hardness.

The cutting machine uses a flying knife type blade which ensures a uniform cut as the adjustable blade speed allows Jehbco to cut extrusions with a wall thickness of less than 0.1mm.

We also have the option of using stainless steel cutting blades for pharmaceuticals and food-grade applications. Moreover, the static from the cut pieces are removed using static-removal instruments to ensure dust and other air-borne particles don’t adhere to the surface of the extrudates.

With our R&D we have optimized the cutting operations for high consistency and reliability thus meeting strict cut length tolerances. The tolerances adhere to our ISO 3302-1:2014 Rubber tolerance standard. Periodic calibrations are carried out and machine data is maintained as part of Jehbco’s quality control processes. This is then audited yearly as part of our ISO 9001:2015 accreditation.

 

2.5mm dia chord, cut length 17.8 mm

2.5mm dia chord, cut length 17.8 mm

10.9 OD tubes, cut length 1000 mm

10.9 OD tubes, cut length 1000 mm

 

Our straight cut extrusions make sure the butt-joints in our gaskets are of the highest quality. We are currently studying and developing alternate cutting methods using ultrasonic blades for cuts that are not perpendicular to the length of the extrusion. For example, 45 degree cut for corner joint gaskets. Our use of cutting jigs makes sure the process is highly efficient and the cut lengths are error free.

Jehbco makes every effort to ensure our product fits your application. To match our products with your application, please see our applications page and contact us if you have any silicone queries.

 

References

  1. Yarra, S., Gordaninejad, F., Behrooz, M. and Pekcan, G. (2018). Performance of natural rubber and silicone-based magnetorheological elastomers under large-strain combined axial and shear loading. Journal of Intelligent Material Systems and Structures, 30(2), pp.228-242.
  2. Yarra, S., Gordaninejad, F., Behrooz, M. and Pekcan, G. (2018). Performance of natural rubber and silicone-based magnetorheological elastomers under large-strain combined axial and shear loading. Journal of Intelligent Material Systems and Structures, 30(2), pp.228-242.
  3. https://www.gillardcutting.com/technical/faqs/which-knife-blade-should-i-use

 

 

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Eliminating Volatile Organic Compounds (VOCs) and Leachables from Silicone Rubber Using Thorough Post-curing Processes
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Silicones are widely used in food, medical and pharmaceutical industries due to their excellent stability over a wide range of temperatures, mechanical strength, elastic properties and non-toxic material characteristics. However, such industries who typically use silicone for sensitive applications have extremely strict tolerances on leachables and volatile organic compounds (VOCs). Without a dedicated post-curing process, outgassing of silicone elastomers can occur under high temperature and low pressure environments1. At Jehbco, silicone items are subject to a thorough post-curing process to ensure that leachable substances present in the extrusions are eradicated.

 

Figure 1: Silicone tubing being prepared for post-curing.

Figure 1: Silicone tubing being prepared for post-curing.

 

Without post-curing, there are two major constituents that can be present in the silicone rubber. The first category encompasses volatile organic compounds2. These carbon containing compounds are typically only present in silicones cured with a peroxide catalyst. During the extrusion process, the peroxide catalyst facilitates cross-linking of silicone by joining methyl and vinyl groups between silicone chains. However, when the elastomer is fully cross-linked, the organic peroxide migrates to the surface of the extrusion. This process is extremely slow, and is accelerated at higher temperatures. The residual peroxide and peroxide by-products form the majority of VOC content found in silicone rubber. These are eliminated by using a platinum catalyst. Here, the platinum catalyst stays is embedded strongly in the rubber without forming any volatile compounds, and does not leach into its surroundings. The only VOCs found in platinum are derived from degradation of carbon based side-groups on the siloxane chains.

The second category of leachables are uncrosslinked low molecular weight siloxanes. Silicone rubber consists of long-chain molecules made by repeating units of methylsiloxanes and methylvinylsiloxanes2. While most of these are cross-linked completely, some short-chain molecules are not crosslinked, and their small molecular size means they are free to move within the silicone bulk. Thus under the proper conditions, these molecules can leach into their surroundings. Typically, more low molecular weight compounds are found in platinum curing materials due to the curing mechanism requiring a Si-H containing siloxane to be added in excess, as such these compounds do not fully cure into the material. It should be noted that although present, low molecular weight siloxnaes have no known negative biological effects2. Low molecular weight siloxanes are present in both peroxide and platinum catalysed compounds, which is why even platinum compounds require thorough post-curing to facilitate to pass strict regulations required for products used in sensitive industries. A rough quantitative analysis of the extractables in non post-cured silicone can be found in Table 1.

 

Table 1: Quantitative analysis of extractables found in platinum and peroxide cured silicone2

Platinum Cured Silicone
(50° ShA)		 Peroxide Cured Silicone
(50° ShA)
Organic Carbon 2.63 62.73
Low Mw Siloxanes 10241 3837

 

Typical guidelines for post-curing processes specify 4 hours at 200°C3 or for the product to be post-cured at least 10°C above the specified operating conditions for 4 hours4. The first method ensures that all of the possible leachables are extracted, whereas the second method ensures that only compounds that are likely to leach into the environment under standard operating conditions are removed. In addition to specified post-curing temperatures, post-curing also requires a high airflow to ensure that the leachables are properly vented3,4. To ensure peace of mind for our customers, all of our products are post-cured at 200°C for 4 hours (excluding heating up and cooling down time) to ensure all of the leachables are eradicated from our silicone profiles. This process has some small effects on the mechanical properties of the silicone, typically raising the hardness while lowering the material’s elastic properties5. The compression set of the material is typically improved by this process5. At Jehbco, platinum and peroxide products are never post-cured in the same unit, to avoid the peroxide leachables damaging the platinum cured silicone3.

Due to our thorough extraction process, Jehbco silicone products exhibit extremely low levels of leachables, far lower than required under food grade standards such as FDA 21 CFR 177.2600 Rubber Articles intended for repeated use. The extraction tests specified in this standard require leachable levels below 4 mg/in2 after 2 hours of continuous extraction in hexane at reflux temperature, or 1 mg/in2 after 2 hours of continuous extraction in water at reflux temperature. These are in addition to further limits at different time intervals. Jehbco products sent for leachable testing have returned results significantly lower than required, a testament to our processing capabilities.

If you would like to learn more please contact us or browse our articles.

 

References

  1. Rothka, J., Studd, R., Tate, K. and Timpe, D. (2002). Outgassing of Silicone Elastomers. ISC, pp.1-9.
  2. Malczewsk, R., Jahn, D. and Schoenherr, W. (2003). Peroxide or Platinum? Cure System Considerations for Silicone Tubing Applications. Dow Corning Healthcare.
  3. Wacker Chemie AG (2016). SOLID AND LIQUID SILICONE RUBBER MATERIAL AND PROCESSING GUIDELINES. Munich, pp.66-67.
  4. Xiameter (2009). Fabricating with XIAMETER High Consistency Silicone Rubber. USA, pp.45-47.
  5. Inman, W. (2016). Post-Curing of Silicone Elastomers: When is it Necessary?. Technical Service & Development Silicone Elastomers.

 

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Rubber Burn Tests
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It is often a challenging task identifying an unknown rubber compound, as they can look and feel very similar to one another. At Jehbco Silicones, we regularly provide 100% silicone alternatives to original equipment manufacturer (OEM) parts, and as such need to know what material the original part was supplied in.

There are multiple methods of determining what type of rubber is used in a product, but methods such as elemental analysis are costly, require specialised equipment, and is not practical in the field. One tried and tested method that we use regularly at Jehbco is a burn test, in which a small sample of the rubber material is combusted. The characteristic burning pattern, smell, smoke colour, and mode of extinguishing are all indicators that can be used to identify what the composition of the burned sample is.

The table below is a basic guide that outlines the main components of the burn test:

 

Material Burning Pattern Smell Smoke Colour Extinguishing Mode
Natural Rubber Continuous burning Burning rubber Dark black smoke Material melts and leaves sticky residue
Nitrile Rubber Continuous burning with minor cracking Acrylic smell Dark smoke with black soot Leaves a tacky residue
EPDM Continuous burning Chemical smell Dark black smoke Material melts and leaves a tack and charred residue
Silicone Difficult to ignite, infrequent burning Little to no smell White smoke Self-extinguishing, produces a white ash

 

There have been numerous cases where customers have thought they were purchasing one type of material, but in actuality they have been supplying an inferior grade of material or a different material altogether. We recently had a case where one of our customers wanted to replace what they thought was a nitrile O-Ring, but when we conducted a burn test on the material it melted and had a distinct burning rubber smell, which was indicative of a natural rubber material. Luckily for the customer, they were not using the O-Ring for a sensitive application, but this uncertainty in material could have had catastrophic consequences in a more critical or sensitive application.

Even within the niche area of silicone materials, some manufactures opt to add fillers to reduce costs, at the expense of inferior mechanical and chemical properties. We have conducted burn tests on many silicone parts made overseas, and an alarming amount of these parts did not behave as expected during the burn test (no white ash produced, black smoke) which suggests that fillers have been added.

At Jehbco, we only produce 100% pure silicone products for your guaranteed peace of mind. If you have any doubt about the quality of your existing rubber products, or want to manufacture a custom solution that you can be confident with, feel free to consult our applications page and contact us with any questions.

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Agile, Lean and Design Thinking
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Agile ‘philosophy’ was developed in attempt to develop products in a simple, fast and efficient manner. The process brings together a multidisciplinary team, thus facilitating productive interactions. As part of the process, it is necessary to include the customer as a lens for realising and validating decisions. This approach initially started within technology companies and has now made its way to manufacturers customer contacts the company directly, the factory is notified, and the manufacturing process begins within hours. Each product is customer-built, and all necessary quality testing is carried within one day. Overall, the customer receives his customised product in less than 5 days1. This approach does not only provide a customer-focused product design, but also facilitates higher levels of cooperation within supply chains, ensuring that production reaches its full potential.

 

Intersection of Agile Philosophy, Lean Manufacturing and Design Thinking Diagram – Jehbco Silicones Manufacturing

Intersection of Agile Philosophy, Lean Manufacturing and Design Thinking Diagram – Jehbco Silicones Manufacturing

Lean manufacturing is based on the principle of eliminating unnecessary work, with the aim to combine flexibility, quality and low costs2. It focuses on the elimination of waste, maximising value addition, and reducing the essential support in an organisation’s processes.

Design thinking puts the customer at the core of operations, thus making products intuitive for the customers to use. The formalised process of design thinking is to discover, define, develop and deliver. Teams are encouraged to go broadly research in both the ‘discover’ and ‘develop’ phases. This process facilitates innovation and results in products that provides ultimate user-experiences.

Combining ‘Agile’, ‘Lean’, and ‘Design Thinking’ results in an efficient, sustainable, and highly-responsive business that puts its customers at the heart of their operations.

Jehbco always puts the customer first; when a customer asks about a silicone rubber through the sales department, our multi-disciplinary team of specialists are notified. The team assess the suitability of the product range for the application of interest. Jehbco works closely with the customer to achieve the best possible choice. At times, the specialists provide custom-built silicone rubber products for customers with unique applications.

In principle, Jehbco is adopting best business methodologies to provide customers with high-quality, low-cost, and customised silicone rubber products.

References

  1. Agile Manufacturing – Case Studies Available from: http://agilemanufacturing.weebly.com/case-studies.html.
  2. Idea. Lean Production. 2009; Available from: https://www.economist.com/news/2009/10/19/lean-production.
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Quality Assurance at Jehbco
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At Jehbco, quality assurance is one of our most important departments. We want to provide all of our customers, distributors and business partners guaranteed piece of mind. With this in mind, Jehbco has implemented and is maintaining a quality management system that meets the requirements of ISO 9001:2015.

ISO 9001 is an international standard that specifies the requirements for a quality management system1. This is a standard that has been chosen and implemented by a wide range of companies around the world. The purpose of this standard is to make sure that our company has a system that aims to meet and improve customer satisfaction as well as providing conformed products2.

Jehbco’s quality management system is assessed every year by an external accredited organisation which certified our company. Our last certification was obtained on the 18th May 2018 for the “manufacture and supply of silicon rubber extruded products including gaskets, mouldings and sheetings”, see Figure. This certification remains valid until 12th May 2021 but it will be subject to yearly satisfactory surveillance audits.

 

ISO 9001:2015 SGS Quality Management System Certification – Jehbco Silicones.

ISO 9001:2015 SGS Quality Management System Certification – Jehbco Silicones.

 

Jehbco has been ISO 9001 certified for more than 20 years. Our quality management system is a collection of documented procedures, forms, policies, records and quality plans. We regularly internally audit our different departments to make sure that all our procedures are revised and followed in order to maintain high levels and consistencies in the services and products we supply to our customers.

Jehbco aims to provide the highest quality whilst manufacturing. That is why different quality controls are placed through the process. Any raw materials that come into the company are rigorously inspected according to our procedures. During the production step, our operators carefully monitor the manufacturing process using different procedures, checklists and controls. This ensures that there are no defects and little variation in our products. All our products are also inspected before dispatch, as just another step in ensuring that our final products are exactly as our customers ordered. As well, our suppliers and subcontractors are assessed and their quality of product is controlled through incoming inspection procedure at the management review.

Any non-conformances are taken very seriously by the team at Jehbco. A process improvement book was created aiming to tackle any issues that arise at any stage of the manufacturing process, as Jehbco strives to provide the outstanding products and services to our partners.  Jehbco continuously works toward the open communication between our customers and our team in the pursuit of the constant improvement of products and services, as we develop tailor-made silicone solutions for the Australian and international market.

References

  1. https://www.iso.org/iso-9001-quality-management.html. Visited on 21st November 2018
  2. Poksinska, Bozena; Dahlgaard, Jens Jörn; Antoni, Marc (2002). “The state of ISO 9000 certification: A study of Swedish organizations”. The TQM Magazine. 14 (5): 297. doi:10.1108/09544780210439734
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Corrosion Prevention for Marine Applications
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Corrosion is the process in which a material, normally a metal deteriorates as a result of chemical reactions. The corrosion of metallic compounds is accelerated by moisture and salt; therefore, marine-related industries are especially susceptible to the effects of corrosion. One US-based study revealed that the negative effects of corrosion cost the United States Navy an estimated $8.63 billion USD in maintenance expenditure [1] during the 2016 fiscal year alone. As a result of this, many marine-based businesses have been investing in methods to reduce the effects of corrosion on their equipment.

 

 

Rust – The result of corroding iron alloys

Rust – The result of corroding iron alloys

 

 

Silicone is a material that has gained a lot of traction in the corrosion-prevention industry, due to its superior resistance to saltwater and UV radiation, low compression set, and wide operating temperature range. Many companies have incorporated silicone seals and O-Rings into their designs to protect metallic components and sensitive electronics from the environment. With this in mind, there are many engineering standards in place to ensure that a silicone seal can withstand given environmental conditions. Examples of these standards include the Ingress protection (IP) rating system, and the MIL-STD-810G Environmental Engineering Considerations standard. Silicone seals have been used to produce products with an IP rating of IP-68 and above, and thus the seal has complete protection against dust, and continuous submersion in water. This means that components protected by an IP-68 rated seal would be heavily protected from the effects of corrosion. Similarly, silicone seals have been used to pass testing under the rigorous MIL-STD-810G standards of testing in categories such as Humidity, Solar Radiation, Salt Fog, and Extreme Temperatures.

At Jehbco Manufacturing, we produce custom engineered silicone extrusions, which are used in all forms of sealing and corrosion-prevention applications. Our staff can provide expert consultation on what solution can be applied to achieve a certain standard, whether it be an IP rating, Military standard, or otherwise. For help selecting a material for your application, consult our applications page and contact us with any questions.

 

References

  1. Herzberg, E., Chan, T., Guo, S., Morris, A., Stevenson, A. and Stroh, R. (2018). Estimated Impact of Corrosion on Cost and Availability of DoD Weapon Systems. [online] Corrdefense.org. Available at: https://www.corrdefense.org/static/media/content/11393.000.00T1-March2018-Ecopy.pdf [Accessed 16 Nov. 2018].
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Simulations on Hyperelastic Materials

Simulations on Hyperelastic Materials
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Finite Element Analysis (FEA) is extensively used at Jehbco to simulate and develop seals. We currently hold over 2600 extrusion designs which have been developed over our four-decades of operations in the silicones industry. Jehbco can both modify our existing designs to suit your application or engineer a new design for you. Our expertise in non-linear multi body contact problems help us develop virtual gland-seal interactions in our software and check for operational validity.

 

 

Hyperelastic simulation of a facade joint seal

Hyperelastic simulation of a facade joint seal

 

Hyperelastic models are used to represent silicone rubber models in simulations. To develop numerical models of elastomers various physical tests are carried out such as uniaxial and biaxial tension tests in order to experimentally determine certain parameters for the numerical models. These tests help to incorporate the mechanical properties and thus the behavior of the elastomer in the model.

The boundary conditions of the problem are defined from the customer’s input. These include the operating conditions, loading and movements. These are given as problem-constraints and the model behaves accordingly.

Iterations of various designs are simulated to understand how the seal or gasket behaves under different loads and constraints. Then, the most optimum design is chosen and dies are manufactured to its exact dimensions.

Some of the innovative applications for which we have run simulations include seals for building facades, pressure vessels, washing chambers, panel joining, and gasket compressions.

References

  1. V. V. Mozgalev and N. R. Prokopchuk, \The choice of best-fit mathematical models of the
    behaviour of rubber compounds for finite element analysis,” Kauchuk i Rezina, vol. 1, pp.
    32{34, 2014.
  2. ANSYS, \Hyperelasticity,” Tech. Rep.
  3. \Nonlinear finite element analysis of elastomers,” Tech. Rep. 4, 2010. [Online]. Available:
    http://linkinghub.elsevier.com/retrieve/pii/0045794987900162
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Jehbco’s closed cell silicone sponge in a variety of profiles.

What is Jehbco’s closed cell silicone sponge, and why is it so popular?
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Silicone sponge is one of Jehbco’s most unique materials, finding applications in a variety of industrial applications from lighting gaskets to dry seals and oven manufacturing. The most important feature of a closed-cell silicone sponge is its extreme compressibility, which allows it to form airtight seals with very low sealing loads. This feature combined with silicone’s naturally ability to withstand high and low temperatures (-60°C to 200°C) and the increased insulating properties of sponge rubber makes silicone sponge an exceptionally versatile elastomer suitable for many different applications.

 

Jehbco’s closed cell silicone sponge in a variety of profiles.

Jehbco’s closed cell silicone sponge in a variety of profiles.

 

Silicone sponge is what is known as an expanded elastomer. Many elastomers can be formulated into a kind of sponge by incorporating air into the bulk of the elastomer during the manufacturing process. Typically, this air is visible on the final product as well-dispersed bubbles, which can vary in size depending on the cell structure. This incorporation of air increases the softness and compressibility of the elastomer while simultaneously lowering its density. The amount of air and overall consistency of the air inclusions determines the cell structure of the sponge, which has significant impact on the mechanical properties of the final sponge.

Two different kinds of sponge rubber can be made depending on the cell structure of the sponge itself. The first is called an open-cell sponge, which is the same kind of cell structure as the sponges used for dishwashing. In an open-cell sponge, all the inclusions of air are connected by channels, which allows fluids to flow through the sponge. This is crucial when the absorption or passage of fluids through the sponge is required for the desired application. Open-cell sponges can be very heavily compressed upon the application of pressure and will expand back readily as air can easily flow back into the air pockets of the material. However, open-cell sponge is not suitable for the formation of air-tight seals.

In a closed-cell silicone sponge, all the inclusions of air are completely enclosed by rubber. This means that the air inclusions are completely inaccessible to any fluids or microorganisms. These air pockets can still be deformed by the application of pressure, in the same fashion as a rubber ball can be compressed, providing significantly improved compressibility over solid silicone. This allows air-tight seals to be easily formed. To maximise compressibility and also improve the appearance of the sponge, smaller, more consistently shaped and dispersed air inclusions will form a higher quality sponge rubber. In accordance with ASTM D1056, a closed cell sponge must not absorb more than 5% of its weight in water, while a sponge that absorbs more than this value is classified as open-cell.

Typically, closed-cell sponge rubber is made using a chemical blowing agent, which decomposes during the curing process to produce gas, which mechanically expands to form small inclusions in the bulk rubber. Over time, air slowly through the bulk of the silicone, replacing these gasses with air. However, due to the unique chemistry and processing temperatures of silicone rubber, many traditional blowing agents are chemically incompatible with silicones. Typically, silicone sponge employs a peroxide curing system together with a carefully formulated mix of additives and blowing agents to produce a high quality closed-cell silicone sponge with a low density and a consistent cell structure. As can be expected, the blowing process causes severe expansion of the silicone profile, so it is extremely difficult to manufacture specific profiles. Jehbco is one of few silicone manufacturers that have dedicated extensive amounts of research and resources to perfecting the sponge making process so that even the most intricate custom profiles can be made. Jehbco’s sponge can be made into a wide range of profiles, or custom-made to suit your requirements, and is available in three softness grades (soft, medium and firm) depending on your preferences.

Ultimately, if you are looking for a soft, low-density material with excellent compressibility and extreme chemical and heat stability, enquire about our closed-cell silicone sponge. Jehbco has spent many years formulating and developing closed-cell silicone sponge and have consistently impressed our customers with our high-quality sponge rubber. For help selecting a material for your application, consult our applications page and contact us with any questions.

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