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A moulded silicone keypad that utilises electrically conductive silicone

Silicone vs Electrically Conductive Silicone
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Whether it be designing a new product, or improving an existing piece of equipment, the choice of material is extremely important. It can be overwhelming picking the right material when there are so many options available on the market. We at Jehbco are often asked to help consult our customers on what elastomer is the right choice for their application. 

 

In this article, we’ll explore the different properties of silicone and electrically conductive silicone (ECS), and what applications each material would be best suited for. Silicone and ECS are both silicone-based products, but ECS is normally impregnated with electrically conductive particles which changes the physical properties of the material. While both elastomers may be used to create similar products, the specific application and environment will ultimately determine whether silicone or ECS will be the better choice for you. The table below summarises some of the key differences between the two materials

 

Electrically Conductive Silicone Silicone
-60 °C to 170 °C -50 °C to 230 °C
Excellent compression set Excellent compression set
Average weather resistance Excellent weather resistance
Approx. tensile strength 8 MPa Approx. tensile strength 9 MPa
Poor abrasion resistance Poor abrasion resistance
Not compatible with: hydrocarbon fuels, alkalis and acids, steam over 121 °C, halogenated solvents Not compatible with: hydrocarbon fuels, alkalis and acids, steam over 121 °C, trichloroethylene, aromatic hydrocarbons.
Compatible with: oils, brake fluids, hot and cold water, salt water, fire resistant hydraulic fluid, ozone. Compatible with: oils, brake fluids, hot and cold water, salt water, high molecular weight chlorinated hydrocarbons, fire resistant hydraulic fluid, ozone.

 

It is no surprise that the mechanical properties of silicone and ECS are similar, as they are both silicone-based products. The loading of conductive particles in the ECS material framework is normally not enough to cause any major changes to the fundamental elastic physical properties (tensile strength, compression set, and abrasion resistance) compared to a standard silicone material. However, the conductive particles impregnated within the ECS material provide ECS with a number of different properties that make it very useful for niche applications.

 

As the name suggests, ECS is electrically conductive, which makes it ideal for use in the electronics industry. ECS can be used a conductor, as well as anti-static and electromagnetic shielding (EMS) applications. This is in stark contrast to standard silicone material, which generally conducts a lot of static and does not provide any EMS capabilities.

 

Another benefit of ECS is that the conductive particles also increase in the thermal conductivity of the material. ECS can been used in heat exchange components as a heat transfer medium in semiconductor applications. Conversely, standard silicone has good insulative properties and can be used as a heat shield/protective cover for fluid transfer systems.

It is clear to see that there is merit in using either silicone or ECS, depending on the specific application you require and the operational environment.  For help selecting a material consult our applications page and contact us with any questions.

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Grey silicone being mixed in a milling machine

Filler/Extender filled Silicone vs 100% Pure Silicone Rubber
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Jehbco silicones specialises in 100% pure silicone rubber. Jehbsil silicone is not adulterated with any cheap fillers or non-reinforcing extenders. In the past, many customers have been unhappy with their existing silicone products as they were highly filled with cheap fillers, resulting in frequently breakage, leaking and in some cases, total product failure. This is particularly true for extremely cheap silicone materials, who can offer a cheaper price by using extenders or fillers to lower their production costs. By purchasing 100% pure Jehbsil silicone products, you can have guaranteed peace of mind that your products will be significantly stronger, more durable and less likely to break than cheaper, low quality products that may contain significant amounts of cost-cutting filler.

 

Fillers and extenders are bulk materials that can be easily mixed into a silicone matrix. Some fillers with good compatibility with silicone can be loaded to exceptionally high loadings, even up to 60% while retaining some processability. By diluting the silicone with high loadings of cheap non-reinforcing fillers, the overall material cost can be dramatically reduced. The most common filler used in silicone rubber is ground quartz rock. Other extenders include talc, clay and calcium carbonate. These are extremely cheap materials and all of them have a high compatibility with silicone, however high loadings can severely impact the mechanical properties of the final product. Excess filler usually causes a severe reduction in elasticity, tensile strength, elongation to break and tear strength properties.

 

Table 1: Mechanical properties of 100% Pure Silicone vs Extender Filled Silicone. Extender filled silicone has significantly worse mechanical strength.

100% Pure High Quality Silicone Filler/Extender Loaded Low Quality Silicone
Tensile Strength (MPa) 11.0 6.0
Elongation to Break (%) 460 270
Tear Strength (KN/m) 25 16

 

This severe worsening of material strength can easily lead to product failure in a variety of situations. Depending on the application, seal, tubing or gasket failure could be catastrophic.

 

While fillers are mostly used as a cost cutting measure, reinforcing fillers do exist which provide benefits to mechanical properties or impart special properties on the material. A good example is fumed silica, a very high surface area silica form of silica. This material is characteristically present in the base silicone rubber, and can increase the hardness and tensile strength when added in excess (to a point). Other useful fillers include conductive carbon black and silver nanoparticles, which render the silicone electrically conductive and provide shielding from electromagnetic interference. Adding any of these fillers typically increases the total cost of the material, rather than decreasing it as extenders do.

 

Cheap silicone products are available, but come with the price of reduced strength and durability. By purchasing 100% pure silicone rubber extrusions from Jehbco Silicones you can be assured that your product will last longer and perform better than cheaper, lower quality silicone products on the market.

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Silicone vs Polyurethane

Silicone vs Polyurethane
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Silicone and polyurethane are both commonly used materials for o-rings, gaskets, seals, tubing and membranes. While both elastomers may be used to create similar products, the specific application and environment will ultimately determine whether polyurethane or silicone will be the better choice for you. 

 

The table below summarises some of the key differences between the two materials.

Polyurethane Silicone
-50 °C to 80 °C -50 °C to 230 °C
Very good compression set Excellent compression set
Good weather resistance Excellent weather resistance
Approx. tensile strength 25 MPa Approx. tensile strength 5 MPa
Excellent abrasion resistance Poor abrasion resistance
Not compatible with: alkalis and acids, aromatic and oxygenated solvents, brake fluids, alcohols. Not compatible with: hydrocarbon fuels, alkalis and acids, steam over 121 °C, trichloroethylene, aromatic hydrocarbons.
Compatible with: most oils and fuels, cold water, salt water, metal salts. Compatible with: oils, brake fluids, hot and cold water, salt water, high molecular weight chlorinated hydrocarbons, fire resistant hydraulic fluid, ozone.

 

Both polyurethane and silicone can operate at extremely low temperatures, although silicone is the far better option in high temperature environments. Silicone can resist intermittent temperatures of up to 230°C, or up to 280°C if a heat stabiliser is added into the raw material. In contrast, polyurethane will start to degrade at 80°C which is not ideal for any high-temperature environments.

 

Polyurethane has an excellent tensile strength and great abrasion resistance, whereas silicone has good tensile strength, but poor abrasion resistance. For dynamic applications subject to friction and wear, polyurethane would most likely be a better option. The durability of polyurethane parts is why it is the industry standard for skateboard and forklift wheels. With this being said, silicone can be formulated to have improved tear strength, making it an ideal choice for applications such as vacuum sheeting and peristaltic pumps. Silicone also has the superior compression set, which makes it a better choice for applications requiring a long lasting, reusable seal, especially in high temperature environments.

 

While silicone has an excellent resistance to ozone and UV, polyurethane does not have the best resistance to ozone and UV, making silicone the more viable for most outdoor applications. However, polyurethane is resistant to most forms of fuels and oils, whereas silicone is not compatible with a lot of hydrocarbon fuels. With this in mind, polyurethane would be the superior choice for the automotive industry, although fluorosilicone compounds can be a good fuel-resistant alternative if a silicone-based material is required. 

 

It is clear to see that there is merit in using either polyurethane and silicone, depending on what physical properties you require and the operational environment. For help selecting a material for your application, consult our applications page and contact us with any questions.

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Shore Hardness and Sealing
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Selection of right rubber hardness is critical to the sealing application. The shape and size of extrusion profile and sealing pressure factors in while deciding on the right hardness of silicone. 

Shore Hardness

Shore A hardness is tested using a durometer. The Shore A hardness measurement is often referred “duro” or “durometer”. The hardness test is performed on cured rubber as per ASTM D2240.

The device consists of a hardened steel rod with a truncated cone at the tip. The steel rod is spring-loaded and actuates a dial with a scale of 0 to 100. The test specimen (a silicone extrusion) is placed directly underneath the truncated cone, and the device is pressed down onto the part until the flat metal plate on the bottom is flush with the rubber specimen  as shown below[1].

 

Testing hardness on a Shore durometer – Jehbco Silicones

Fig 1.0 Testing hardness on a Shore durometer

 

The more the cone deforms the rubber material, the lower the hardness measurement. The less the cone deforms the rubber material, the higher the hardness measurement.

Gaskets

Gaskets are made from joining lengths of extrusion in a closed or open loop arrangement.  Gaskets could be used for simple contact prevention between two parts or sealing. In the latter case they could be referred as seals.

askets (joined extrusions) are designed for deformation. Where extrusion undergoes one-time deformation – such as façade joint seals, the extrusion is designed to stay in place and form a seal after being compressed by the gland or gap initially. Where extrusion undergoes cyclic deformation – such as in oven door seals, extrusion is designed for withstanding alternating loading and unloading over a period of time.

Seal failure can be predominantly attributed to loss of compression resistance or tear[2].  Our engineers are mindful of the magnitude of deformation every application requires. The proportions of the extrusions are designed keeping in mind the hardness – for critical applications Jehbco has in-house ability to carry out hyperelastic simulations to find the right extrusion profile dimensions in relation to the hardness or vice-versa. Alternately, Jehbco provides an option of making test samples of various hardness upon request.

O-rings

O-rings are extensively used across mechanical sealing application involving any cylindrical geometry of parts. An effective seal is made by creating a zero clearance between parts that blocks fluid or gas[3]. Figures 2, 3 and 4 illustrate how a half model section of an O-ring looks before any application of pressure and how it reaches maximum deformation. If the customer provides us with the sealing pressure or the minimum and maximum clearance to be maintained between the faces, we would be able to find the right hardness for a given diameter of the o-ring.

 

O-ring at zero compression – Jehbco Silicones

Fig 2.0 Initial state at zero compression

 

O-ring at 50 percent compression – Jehbco Silicones

Fig 3.0 50% compression

 

O-ring at 100 percent compression – Jehbco Silicones

Fig 4.0 100% compression


If you would like to learn more about Jehbco’s o-ring design and hyperelastic simulations please click here.

For any further enquiries please contact us.

References

  1. http://blog.parker.com/why-is-shore-a-hardness-important?src=Twitter&cm_mmc=Twitter-_-Enterprise_Social_EMG_OES-_-Blog-_-number4_most_popular_blog
  2. https://www.prepol.com/solutions/why-do-o-rings-fail-a-brief-guide-to-o-ring-failure-modes
  3. https://promo.parker.com/promotionsite/oring-ehandbook/us/ehome/ci.How-an-O%E2%80%93Ring-Works,EN.EN
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Silicone burning with very little visible smoke production

Silicone Performance in Smoke Toxicity Tests (BS 6853, EN 45545, AS 1530.3)
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As a common flame retardant material, silicone is one such material that can conform to the most stringent requirements of smoke toxicity tests in a variety of industries. 

When fires break out, it’s often not burns from the fires that cause the most harm, but the resulting smoke. In many instances of deadly fires, it has been the resulting smoke that causes more deaths than the fire itself. The dangers of smoke are widely recognised and strict standards have been constructed within a variety of industries that aim to minimise high quantity production of toxic smoke in cases of fire. 

Inhalation of toxic smoke has disastrous effects on the human body. Immediate effects of smoke inhalation include extreme shortness of breath, cough, headache and nausea. For some toxic compounds, smoke inhalation can also cause disorientation, panic, loss of mental function and fainting, as well as skin, eye and lung damage. Simple asphyxiation in conjunction with incapacitating side effects can lead to an excruciating death. Toxic smoke is frequently produced by burning organic elastomers, which results in many seals and gaskets constituting a fire safety risk.

 

Silicone Burn Test at Jehbco Silicones

Figure 1: Silicone burning with very little visible smoke production

 

Smoke is not only toxic, but in many cases also obscures light and obstructs visibility. This reduction in visibility makes it more difficult for persons to walk around obstacles, or find their way to a safe location. Additionally, this slowing of movement due to visibility means that people are more exposed to hazardous conditions and inhale more potentially toxic smoke. While smoke toxicity is a severe immediate threat to human safety, visual impairment for smoke can similarly lead to increased harm or death in a catastrophic fire. 

Silicone materials do not ignite until fairly high temperatures (>400°C). While burning, silicone products primarily decompose into silica (SiO2) and carbon oxides. The silica is a solid material which deposits on the surface of the material. The carbon oxides at this temperature are usually transparent, and do not significantly impact visibility. As silicones do not contain harmful sulphur or halogen containing substances, their decomposition by-products are largely non-toxic. Fire resistance, including smoke mitigation, can be enhanced by the use of flame retardant silicone grades which have been researched and developed by Jehbco to reach and exceed customer requirements. 

At Jehbco, products have been tested to a variety of smoke toxicity and visibility standards including BS 6853 and EN 45545 for the rail industry, and other testing standards including AS 1530.3 and ISO 5660. The results of all tests performed on silicone rubber have shown outstandingly low toxicity and good visibility results. For BS 6853 Annex B, the weighted R rating 0.27, significantly below the most stringent requirement, R ≤1. Other testing performed were all significantly below required specifications, as expected based on the exceptional material properties and flame retardance, including receiving a HL3 rating under EN 45545-2 R22/R23 testing. 

Before devastating fires have a chance to break out, every design should be carefully assessed to ensure all possible measures to minimise dangers to human safety have been implemented. The replacement of toxic smoke producing elastomers with flame retardant silicones is one such measure that can significantly reduce risk in cases of fire.

 

For more information on silicones and silicone flame retardance, please browse through our website or contact us.

 

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ISO 45001:2018 Work, Health and Safety
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ISO 45001:2018 is an international standard providing requirements for an effective occupational health and safety (OH&S) management system[1]. The standard focuses on providing safe and healthy working conditions. This is proactively performed by identifying risks and opportunities, carrying out hazard identification and risk assessments and adding different controls. These actions result in a reduction of risk and hence in an improvement in work, health and safety. ISO 45001:2018 is based on earlier international standards in this area (e.g. OHSAS 18001 or the International Labour Organisation’s ILO-OHS Guidelines etc.)[2].

The standard is suitable for all types and sizes of organisation[3]. It uses a high level structure (see Figure 1) which is similar to other ISO standards and in particular the quality management system (ISO 9001:2015) that Jehbco has been holding for the last 20 years. In addition, ISO 45001:2018 closely follows ISO 14001:2015 which is an environmental management system standard that Jehbco is currently implementing. Thus, ISO 45001 can be easily integrated into our existing quality management system and business processes.

The implementation of an OH&S management system brings many benefits to  an organisation. For example, it helps companies to proactively protect the health and safety of their employees and visitors by measuring and reducing OH&S risks. This leads to  less workplace incidents, decreased absenteeism and increased productivity. It would also increase the safety awareness of every employee by encouraging them to take an active role in their own OH&S system and reinforce the commitment of management to proactively improve OH&S performance.

Finally, having an OH&S management system improves the ability of a company to meet legal and regulatory requirements. Furthermore, ISO 45001 certification can open organisation access to new markets through competitive advantage[4].

Jehbco is currently developing and implementing an occupational health and safety management system which will be integrated into its certified quality management system (ISO 9001:2015). Jehbco aims to get its OH&S management system certified in parallel with its environmental management system by the end of 2020.

High Level structure diagram for the implementation of ISO 45001:2018 – Jehbco Silicones

High Level structure diagram for the implementation of ISO 45001:2018 – Jehbco Silicones

To find out more about quality assurance at Jehbco, please read this article.

To know more about ISO environmental certification (ISO 14001:2015), please click here.

 

References

  1. ISO 45001:2018 standard, November 2019
  2. International Organization for standardization , ‘ISO 45001 occupational health and safety’, viewed on 20th November 2019, https://www.iso.org/iso-45001-occupational-health-and-safety.htmlhttps://www.globalspec.com/learnmore/flow_control_fluid_transfer/pipe_tubing_hose_fittings_accessories/medical_tubing (accessed 31st October 2019)
  3. International Organization for standardization, ‘Occupational health and safety ISO 45001’, viewed on 20th November 2019, https://www.iso.org/files/live/sites/isoorg/files/store/en/PUB100427.pdf 
  4.  Interlek, ‘ISO 45001 – Occupational Health & Safety Management Systems Certification’, viewed on 20th November 2019, https://www.intertek.com/assurance/aus-nz-iso45001/
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Jehbco’s Silicone Tubing for Medical Industry

Jehbco’s Silicone Tubing for the Medical Industry
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The medical industry requires tubing that meets stringent standards for a variety of medical or pharmaceutical related applications, such as peristaltic pumps and biopharmaceutical laboratory equipment. This tubing frequently needs to pass biological tests to ensure it is safe for medical applications, with USP Class VI certification being the most common requirement.

USP Class VI is a standard of biocompatibility for materials used in medical applications[1]. This certification is put in place by the United States Pharmacopeia (USP) to test for toxicity, biochemical compatibility, leaching, and inertness of the material[2]. USP Class VI is considered the most stringent, which consequently makes it the most useful for medical applications[1].

Aside from USP Class VI certification, some medical applications also require tubing to be certified by the Food and Drug Administration (FDA). The applicable standard is FDA CFR 21 177.2600 Rubber Articles.

 

Jehbco’s Silicone Tubing for Medical Industry

Figure 1: Jehbco’s Silicone Tubing for Medical Industry

 

Silicone is one of the few materials that could meet both standards. On top of that, using tubes made of silicone offers numerous advantages[3][4]:

  • Physiologically inert
  • Odourless and tasteless
  • Excellent mechanical properties over a very wide temperature range, and
  • Excellent weatherability.

 

This is why silicone is an ideal material for some medical applications, such as peristaltic pumps. In peristaltic pump application, the tubing must be able to withstand numerous squeeze repetitions and not reactive to the fluid being pumped.

With more than 45 years of experience manufacturing custom-made silicone products, Jehbco Silicones is an experienced supplier of tubing for the medical industry. Jehbco is able to manufacture tubing that are certified by both USP Class VI and FDA CFR 21 177.2600 Rubber Articles.

In addition, Jehbco’s products are subject to a thorough post-curing process to eliminate the leachable substances and volatile organic compounds (VOCs). Because of our thorough process, our products exhibit minuscule amount of leachables, even far lower than what is required by the FDA CFR 21 177.2600 Rubber Articles standard.

Aside from that, Jehbco is also able to manufacture tubing tailored to each customer’s requirement. Jehbco is able to manufacture tubing in various diameter, cut-length and wall thickness, and in wide range of colours (from translucent, pigmented translucent to solid pigmented). Jehbco can colour match its products to customers’ needs, which sometimes could be crucial to customers especially when they are using various sizes of tubing.

For further information about Jehbco’s silicone products for medical applications, please do not hesitate to contact us.

 

References

  1. Foster Biomedical Polymers and Compounds, ‘USP Class VI’. Foster Corporation, n.d. https://www.fostercomp.com/stewardship/usp-class-vi/ (accessed 31st October 2019)
  2. Engineering 360, ‘Medical Tubing Information’. IEEE GLobalSPec, n.d. https://www.globalspec.com/learnmore/flow_control_fluid_transfer/pipe_tubing_hose_fittings_accessories/medical_tubing (accessed 31st October 2019)
  3. Wacker Chemie AG, ‘Solid and Liquid Silicone Rubber: Material and Processing Guidelines’. Wacker Chemie AG, n.d.
  4. Shin-Etsu Chemical Co. Ltd., ‘Characteristic Properties of Silicone Rubber Compounds’. Shin-Etsu Chemical Co. Ltd., August 2016.
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Quickjoint by Jehbsil
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Jehbco’s QUICKJOINT by JEHBSIL is our line of products specifically tailored to meeting Australia’s demand for façade seal and expansion joint seals in the building and construction industry. Solid silicone extrusions offer a substantially more convenient and cost effective replace ‘wet silicone’ that is traditionally used to seal between composite façade panels. Wet sealants are chemically hazardous, have a notorious reputation for being tedious and difficult to install, and frequently have rough and inconsistent finishes. Quickjoint offers many benefits over wet silicone from its temperature and weather resistance, ease of installation, and its ability to be customised to strict specifications. Jehbco is able to customise Quickjoint to any width, any depth, and any colour.

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Dry Gap Sealing Compared With Wet Silicone Sealing
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Wet silicone can be difficult to apply, can be messy with high wastage, and if it is not used correctly, it can contribute to poor sealing quality and performance issues in the medium and longer terms. In this video, we have compared Jehbco Dry gap sealing with wet silicone sealing.

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Jehbco Silicone Extrusion Adhesion Procedure
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This instructional video is provided to you by Jehbco Silicone experts to help with the application of silicone adhesives. In this video Jehbco Silicone extrusion adhesion procedure are compared with easy to use self-adhesive backing.

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