What does the new set-up look like?

Paul and Adam have stepped back to the role of shareholders and maintain an oversight as Chairs of the Board. They have handed over the day-to-day running of the business to Martin Candy, Laurent Watremetz and Dave Hamer. The new Directorship team have all been working with the company for many years in the roles of Head of Sales, Business Intelligence Manager and Finance Manager, respectively.

What will you notice?

Hopefully nothing, aside from the continued improvements that the existing Senior Management Team are already working on. Each of the Directors have experience that they bring to their new roles and are excited to take on the challenge of leading the business, guiding us through further growth and development as we take on the challenges of SME engineering life in 2025 and beyond.

As far as working with us, it will be business as usual for our customer-facing and manufacturing teams. If you have any questions, please get in touch on the usual channels.

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Some fantastic rubber materials are already on the market and work perfectly for many industrial applications. Buna-N has been around for nearly a century and pulls its weight as a veteran of materials. But it’s important to understand what a material is good at and why. 

If you’re looking for a rubber compound that is suitable for contact with hydrocarbons and that will provide great heat resistance and stability, Buna-N is likely to be at the top of your list.

Is Buna-N the same as Nitrile?

Buna N is a trade name for nitrile butadiene rubber (NBR), and BASF owned the name Buna N during the twentieth century up until the nineteen eighties. Buna-S was simultaneously developed in the US during the 1930s and is fundamentally the same compound, designed as a synthetic alternative to natural rubber. Nitrile rubber, or NBR, as it is most commonly known, became one of the most popular rubbers in circulation (notwithstanding natural rubber, used globally for tyre manufacture).

Why is Buna-N rubber so popular?

Buna-N’s chemical compatibility is its most valued property, widely favoured for its resistance to oils and fuels. It is the elastomer of choice for many automotive and mechanical aerospace applications – not only is it a practical rubber grade for fuel resistance, but it also offers good heat stability. It will withstand temperatures up to 100˚C or 120˚C in hot air applications. In aerospace and other industries, nitrile rubber is often found in automotive applications. It is popular for oil-resistant seals and diaphragms, fuel lines and other components that may come into contact with hydrocarbons.

Why is Buna-N resistant to hydrocarbons?

Due to the presence of acrylonitrile (ACN) in the polymer backbone, nitrile rubber (NBR) provides resistance to non-polar fluids such as hydraulic oil or petrol/diesel fuels. The level of acrylonitrile can vary in different grades, and the higher the ACN content, the poorer the low-temperature resistance and flexibility. However, those grades with the highest ACN content allow the highest resistance to swelling in hydrocarbon fluids.

Weaknesses of Buna-N

No rubber can excel at everything; to provide resistance or strength in one area, it is almost inevitable that another property will be compromised due to the careful chemical balance that must be maintained within rubber compounds. Due to its chemical structure, NBR has poor resistance to UV, ozone or weathering. This can be improved by using the saturated version of NBR, hydrogenated nitrile butadiene rubber (HNBR) – though this comes with a higher price tag.

Blends and Alternatives

Blends with PVC can be used for improved resistance to UV; however, this comes at the expense of elastic return, so it is not recommended for many sealing applications. The introduction of PVC into the NBR structure increases the material’s stiffness while lowering the elongation-to-break. 

The benefit of this blend is the additional resistance provided by PVC, allowing for high-gloss cosmetic finishes and increased UV and ozone resistance without compromising oil and fuel resistance. PVC also significantly increases the range of applications for using NBR in cabling, allowing the NBR-PVC material to operate at higher temperatures. However, PVC is becoming increasingly regulated, so it now has a relatively high administrative burden.

If the level of oil resistance required is relatively modest, but the need for UV resistance is high, then neoprene can be a good alternative where mechanical properties are not critical; neoprene has the equivalent of a low-level ACN NBR, but HNBR would generally be considered a better alternative.

Availability of Nitrile Butadiene

Nitrile rubber (NBR) is one of the materials we use most commonly at Martins Rubber. Over a quarter of our rubber mouldings are manufactured in either NBR or HNBR. NBR is now readily available without the issue of material shortages.

Nitrile for Rubber Moulding

Nitrile rubber (NBR) can be used for all three of our moulding types – compression, injection, and transfer – without any difficulties. It is also widely used by our aerospace and motorsport customer base. 

Nitrile butadiene rubber is one of the most useful general-purpose compounds in circulation for applications where hydrocarbons are in contact. It has weaknesses, and these can be addressed by using HNBR or by considering a more bespoke compound that may offer a more specific range of properties. 

But, if you select NBR as your material of choice, you’ll be in good company. You’ll be choosing a compound that is great for moulding and will provide you with a product that can be manufactured consistently and reliably.

Contact Us

For all your rubber moulding needs, trust Martin’s Rubber to deliver the best results for your application. Explore our technical articles and case studies for more information on Buna-N vs Nitrile. If you have any questions about our rubber services, be sure to contact us; a team member will be happy to help.

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Bianca’s background lies in customer service, with a career starting in South Africa in the hospitality industry and then moving to the UK and into B2B work in the manufacturing/assembly sector. The theme that runs through Bianca’s working life, she says, is her enjoyment of building relationships with customers, acting as the ‘middle man’ for that customer and making sure their needs are represented. We have a wide range of customers at Martin’s, each facing different technical challenges and presenting us with differing service requirements – but, as Bianca says, that’s what keeps things interesting!

She says her biggest challenge in the time that she has been with Martin’s has been the move to a business where everything is bespoke, and where we manufacture from raw material, in house. This creates a steep learning curve, alongside the challenge of learning new systems and processes; Bianca handles enquiries from the initial point of contact, through the quotation and sales process, and beyond that to ensure that projects run smoothly – she says she loves being this involved, it keeps the job interesting and creates constant opportunities for learning.

I asked Bianca what she is enjoying most about her new role, and her answer was simple: the people. She said, “Everyone is so helpful and so friendly, it’s just been such an easy transition for me to be part of the company. The one thing I really loved was the dinner with all the staff.” She was referring to the fact that we usually hold a company BBQ in the summer but because of difficulties getting everyone together during the daytime, we moved it to an evening meal, ”That was really, really nice. I’ve never experienced anything like that. It’s just so great that we can get to know each other at work and work together really well, and then you also have time outside of work where the company wants you to familiarize yourself with everyone and get along and enjoy being with the people around you.”

When I asked Bianca what she is looking forward to at Martin’s, her answer was based around building the confidence and knowledge to work independently as she gets to know our products, systems and processes better and can manage customer accounts without the levels of support she’s currently needing from the team. This learning curve is one that each member of our team has been through due to the complexities of the business and our services, but Bianca is keen to get through this learning process and become more independent. She said she’d love to one day have enough skills and knowledge to become a Sales Manager – and I’ve no doubt that, with the drive and tenacity that she’s already showing, this is entirely within her reach.

Author: Claire Clarke, Marketing Manager

Take a look at our current job vacancies here, or find out what it’s like to work with us.

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What do we mean by ‘high temperature resistant’?

The first thing to clarify is that high temperature resistance in rubber is not the same as fire retardancy; the requirements are very different and therefore the additives used in the compounds are also different. Fire retardancy in rubber means that the material will not release noxious chemicals when alight, and is designed primarily for the health and safety of those in the vicinity of a fire. High temperature resistant rubber are those which will not deform or degrade when exposed to temperatures in which standard rubbers may not maintain structural integrity.

How high is ‘high’ when we talk about temperature resistance in rubbers?

As with all things, the term ‘high’ is relative and will depend on the type of elastomer and application in question; high temperatures for elastomers can be considered to be anything over ambient or room temperature – for natural rubber, a high temperature could be +70°C, whereas for fluorinated rubber high temperature could be 230°C. High operating temperatures for elastomers are often low in comparison to other materials. Above temperatures of 175°C, the only available options for elastomers are silicone, which will manage temperatures in excess of 200°C, and fluorinated elastomers, which can withstand temperatures of up to 315°C.

All elastomers have an operating temperature range and each has a blend of properties and performance, and the balance that you opt for when selecting a rubber material will depend on the application in question and the priorities in terms of operating conditions.

What enables high temperature resistant rubbers to perform outside of standard elastomer operating temperatures?

The upper temperature limit of organic elastomers – those with a carbon backbone – is determined by the bond strengths of the constituents in the polymer and the curing mechanism used. Specialist grades of elastomer, such as fluorinated polymers (FKM), can resist temperatures over 200°C.

Fully fluorinated elastomers, known as perfluoroelastomers (FFKM), when compounded and cured correctly, can withstand temperatures up to 316°C. The reason for the specific temperature ceiling is that beyond this, the elastomer begins a de-fluorination process and will eventually thermally decompose; the material may be able to cope with short periods above this threshold but in turn its service life will be significantly reduced.

Inorganic elastomers such as silicone have a temperature stable siloxane backbone that can resist temperatures in excess of 200°C, and the thermal degradation process can be stabilised further still to achieve resistance to temperatures up to 300°C.

Each elastomer material will have an upper temperature limit, and by use of specific curing mechanisms or compounding ingredients such as stabilisers, the upper limit may be slightly extended or the performance at elevated temperature can be improved.

Implications of opting for temperature resistance in rubber

The application of a rubber component is critical in specifying a suitable material. Silicone is often the go-to high temperature rubber but it must have oxygen present in order to sustain its structure – and the higher the operating temperature, the more important this is. Thermal degradation softens the rubber, whilst oxygenation increases the hardness, and silicone rubber requires a careful balance between these two processes to maintain its properties for extended periods at elevated temperatures. If you exposed a silicone component to 200°C in the absence of oxygen, you would find yourself with a puddle, which is why you won’t find silicone used in an environment where saturated steam is present.

Similarly, the curing systems used in FFKM have an impact on the temperature range that the material will withstand, but the application is what drives that decision on curing system. The curing system in a rubber compound enables crosslinks to be created during the vulcanisation process, but because they are chemical additives, they don’t necessarily respond well to some environments. For example, a peroxide curing system in FFKM is good for applications where water and steam are present, but will only withstand 230°C. A bisphenol cure system will provide a working temperature of 280°C but is poor in acids. Triazine, the most effective in terms of temperature resistance – offering up to 316°C – is very poor in water and steam.

The intended application for any rubber component is crucial when looking at which compound to use for the temperature range in question. When elastomers are subject to compression (for example, a seal under load), the objective is for that component to return to its original cross section when the load is removed. This is known as compression set, and this is the property of rubber which is most affected by temperature. Therefore, when considering a rubber for a sealing application at high temperatures, careful consideration needs to be given to material selection.

In terms of monetary cost, high temperature resistant elastomers such as silicone rubber and FFKM may cost more than other elastomers due to the specialist nature of the compound and the more complicated polymerisation process. To add to a material’s low temperature flexibility in addition to its high temperature resistance can significantly increase the material cost even further.

How to select the right elastomer for your high temperature application

The process of selecting a suitable material, as outlined above, is not as simple as looking at the service temperature that your product will experience. Alongside this, the environment and application are also critical, alongside the curative selection and the consistency of temperature during the product’s service life.

Our team includes technical specialists with experience in material selection as well as finite element analysis tools to fully understand how a component will perform within a particular application when moulded from a specific rubber compound. If you are developing a product that will be required to perform in extreme environments, including high temperatures, it is always better to seek advice from the outset to ensure that the compound and component design will behave as you intend.

Contact us to chat to one of our expert about your high temperature application.

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With a greater focus on risk-based thinking, AS/EN9100 forces the business to focus on areas of weakness, strengthening them and slowly pushing all parts of the business to perform with greater consistency and at a higher level. Internal auditing prioritises high-risk areas, with a requirement for an improvement plan and then more regular assessments. Goals for improvement are challenging but achievable, with targets that are stretched as they are met, ensuring continuous improvement. Unlike ISO9001 which selects just a few areas to audit on each external auditor’s visit, AS9100 auditors look at every area of the business and its processes each year.

If you’re thinking that this sounds arduous and like a lot more work than ISO9001, in a way you would be right. However, the increased workload, for us, has shown more than a relative improvement for the business. We’ll take a look below at some of the ways in which AS/EN9100 has benefited our customers, how it has improved our own business practices, and then look at the cost implications for those who are considering starting out on this journey.

How our customers benefit

• Consistency of service. As a manufacturer we have always had processes in place for making things. However, the introduction of AS/EN9100 has made us look much more closely at the processes outside of the manufacturing areas:
  • Quotation calculation and creation now has a much more stringent process, ensuring that our costs are likely to be both more accurate and more consistent.
  • Sales order loading processes have been updated, demonstrably reducing administrative and system errors.
  • Packing and shipping processes are now much more uniform so that we provide a more effective and more streamlined shipping service.
  • Overall contract review is much more robust. This means that we ensure from the outset that we understand customers’ needs fully, document what, when and how we’re agreeing to fulfill the solution, and then deliver to our promise.
• A uniform approach. We now have a much more consistent level of service throughout the business; best practice is based on quantitative data to demonstrate effectiveness and then rolled out across all personnel and all teams.

It may sound obvious that all these things are important, but it’s easy within a growing business to have departmental differences in approach, and the people within those teams creating a methodology that suits them, rather than one that is best for customers. Without a really stringent set of processes, customer experience can vary from order to order, and that’s the area in which we’re really seeing change happen.

How we’ve benefited

• Consistency of operation and methodology. Processes throughout the business are better controlled and documented. A much wider set of work instructions create a more uniform
  

  Zygi Navickaite, Quality Manager

  approach, which not only helps control consistency but also makes it much easier to train people. And in a business where we need people to be multi-skilled, and where many of our products are custom-made, the more uniformity we can achieve, the better for our customers and for our own bottom line.

• Everyone is held accountable. AS/EN9100 is designed so that not only are the Quality Team responsible for quality of service and product, but so is each person within the business. Our company now has a noticeably more positive quality culture, one where everybody understands its importance and is actively engaging with the process of developing and maintaining those standards.
• Empowerment for resolution. Where issues arise – either as a customer complaint (let’s be honest, we all have them!) or a problem with an internal process – the improved quality culture means that people are much more empowered to find a solution not just for the short-term, but also to prevent a recurrence.
• Process changes are much more widely understood and considered. Whilst updating or amending a process in one area may apparently solve the issue, unless impacts on other departments and their processes are considered, there may be an unintentional knock-on effect elsewhere. AS9100 has led to a much better appreciation of the broader impact of process change throughout our teams.
• Reduced scrap rates through consistency of manufacture. Rubber manufacture inevitably produces a level of scrap and this is accepted across industry. However, AS/EN9100 encouraged us to look at scrap rates from new angles, and has already resulted in further improvements to both profitability and our environmental footprint.
• Improved customer service. The benefits of the improved service outlined in the previous section really speak for themselves; a stronger order book and repeat business are the cornerstone of any company, SME or otherwise.

But what about the investment?

Time and commitment. It’s true, AS/EN9100 shouldn’t be taken on casually; it’s a big project from the get-go and needs proper support from throughout an SME, with the risk of failure creating a stress-point in what is often an already stretched team. Added to that, as an ongoing commitment there is the requirement for 5 external audit days per year (vs the two for ISO9001), where all processes will be audited. Suffice to say, AS9100 isn’t a quality management system for those who just want to pay lip service and get a tick in the box.

The initial preparation to ready ourselves for the initial AS/EN9100 audit took a year or so – and involved every departmental manager and their team, lead by a Quality Manager who has experience in working with the AS9100 standard. We were lucky enough to have a senior management team who were keen to drive the project forward and understood the likely benefits to the business.

Open to inspection. AS9100 approved businesses must sign up to an open database called Oasis – a portal that logs your performance across all areas, including any failures or non-conformities. Depending on your size and place in the supply chain you can see all or some of this information about your customers, suppliers and competitors – so AS/EN9100 is not for the faint hearted as you have to be willing to be completely open about any areas of weakness, and be seen to be addressing them.

Measurement and accountability. AS/EN9100 requires every business to measure key processes. You need to have the means to measure, record and improve on each of those areas consistently. Our core areas, which each have two KPIs against them, are:

• Sales: Turnaround time for quotations, accuracy of information
• Technical support: number of internal complaints raised, speed of quotation process
• Purchasing: supplier delivery to promise, supplier concerns raised
• Manufacturing: scrap rate, completion of orders on time and in full
• Despatch: number of internal complaints raised, shipping of stock on time

Any regrets?

The subsequent culture of honest debate and teamwork created by the implementation of AS/EN9100 has led to a stronger and more robust foundation for Martin’s Rubber to operate upon.

As pointed out by our Quality Manager, Zygimante Navickaite, AS9100 doesn’t necessarily have to add extra work and administrative burden to every team; if people are willing to be creative and find new ways of approaching a problem, often the result can be a more streamlined and effective way of doing things – but it does mean allowing people the time and space to think things through and be open to alternative ways of working.

Overall, is AS/EN9100 working for us? Absolutely. In our experience, ISO9001 works well for quality departments, but AS/EN9100 improves the business overall.  When we set out on this journey, we knew we wanted to improve our operations to make it a more robust, more efficient and more sustainable company to allow for growth, whilst also providing our customers with a better service. We chose to benchmark ourselves against a standard that holds us accountable to that ethos, but the mindset was already in place and that may just have been the key to success.

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Michelle has joined the team at Martin’s Rubber that looks after our aerospace and defence customer base, working alongside Sales Managers Steve Rubery and Martyn Johnson. She is responsible for providing internal sales support, working with clients across these industries as a key point of contact and to help deliver projects. She started working with us in November, and says of her time so far ‘There is a lot to learn with so many diverse customers and products, but the scope of work is really interesting and I’m enjoying getting stuck in.’

Michelle chose to join Martin’s Rubber, she says, because ‘the business has been around for a long time; it is stable, sustainable and is investing in the future.’ She also felt that the company values matched her own, and that was an important factor in choosing where to work.

Michelle is always looking for self-development opportunities and has said that she wants to future-proof herself, upskilling and gaining knowledge through her time at Martin’s. When not knee-deep in rubber, Michelle dons her wellies for music festivals and is looking towards Glasto for her next trip.

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Material supply issues are impacting our service levels and lead times to an extent that we can no longer absorb into our own processes. Therefore we intend to do three things: 1. Provide some clarity around where the delays are being caused, 2. Explain what we are doing to mitigate these challenges and 3. Explain what you can do to help us to help you.

What are the reasons for the supply issues?

• Sanctions on Russia

Oil and gas is a feedstock of many polymers, and carbon black is a critical component of many rubber compounds. Russia is responsible for roughly 30% of the world’s supply of both. This means that current sanctions placed on Russia have created a squeeze on these important raw materials – resulting in both material shortages and price hikes.

• Force majeure declared by 3M

3M are a key part of the global rubber supply chain and the recent forced closure of one of their European sites has resulted in a shortage of key ingredients used in FKM and FFKM (perfluoroelastomers). They have also terminated supply from one of their Russian plants, severing material availability from that source. 3M have, as a result of these events, declared a force majeure event.

• Competition with other markets

R142b gas is a critical component of FKM, and challenges in the scaling up of production (largely in China) combined with a huge increase in demand for the manufacture of lithium batteries for vehicle electrification has resulted in supply shortages and price increases.

Similarly, an increase in demand by the automotive and oil & gas industries has led to a deficit of the HNBR compound; key global producers do not intend to increase capacity but there is hope that the demand will abate in Q4 of this year.

• Energy crisis in China

China is in the midst of an energy crisis which has led to the introduction of rolling blackouts for their most energy-intensive industries. The majority of the world’s silicone feedstock comes from China, and with plants running at reduced capacity we are seeing shortages of all silicone compounds as a result.

• Impacts of Covid

Personnel absence as a result of Covid is still impacting staffing levels on many production lines and, as a result, some suppliers are choosing to consolidate production runs or stop specific lines. The impact further down the supply chain is in much longer lead times on some constituent ingredients. Added to this, the port of Shanghai is currently closed due to a city-wide lockdown, meaning that containers of already limited silicone supplies are unable to leave for export.

In all, there are 90 ingredients that go into the compounds we purchase which are currently all but impossible to get hold of by our own suppliers, regardless of the price that we or our customers are willing to pay.

What are we doing?

We are holding increased stocks of our most commonly used compounds. However, raw rubber materials have a limited lifespan (some last just weeks, others 6-12 months), which means that we have to be realistic about balancing material stocks against known demand.

Due to this limitation on shelf life we are actively creating forward order call-off schedules on our key suppliers for our materials in most regular use, to help our suppliers in turn better manage their own forecasts and production schedules.

We are also expanding our supply chain and qualifying new suppliers; however, we already have excellent relationships with our key, approved long-term compound suppliers and, given that this is a global supply shortage, a wider supply base is unlikely to have much of an impact on material availability.

What is likely to happen during the coming months?

Supply: Whilst the supply issues with some types of compound may ease as production opens up due to Covid impacts coming under control, in the vast majority of cases the supply chain issues have other origins and are likely to remain for at least the rest of this year. We cannot influence those shortages or provide any guarantee of when or where they will occur.

Pricing: The rubber compounding industry has seen some significant price rises over the past 12 months and those are likely to continue to increase – erratically in some cases – particularly where we are competing with other industries for ingredients, in combination with basic shortages.

What can you do?

Hold stock: Given that we cannot guarantee to hold prices, nor to supply within your usual expected timeframe, carrying a buffer stock of finished goods may provide you with a backup. Whilst raw rubber compound has a shelf life of weeks or months, vulcanised rubber will last at least 5-7 years, much longer in many cases. Please see our guide to the recommended storage conditions for cured rubber products.

Place a scheduled order: If you are unable to hold stock but can forecast with reasonable certainty, you could provide us with a bulk order to be delivered to schedule. This will allow us to purchase scheduled material in bulk now, to be manufactured for delivery as you need it and at the current cost base.

Allow longer lead-times: For materials where force majeure has been declared (FKM and FFKM materials), then all bets are off and we can only source materials as they become available. However, for other raw materials where the delays are due to temporary reduced availability, the best action you can take is to provide longer delivery windows for us. We would advise 10 weeks where possible.

Pre-warn your customers of delays: If you’re unable to take any of the actions above because you can only respond to demand as it arises, then we urge you to warn your customers of likely delays and look to them to respond to some of the calls to action above.

The current mix of complex social, economic and political challenges facing the global supply chain are unprecedented in our experience. The only thing we can currently be certain of is that there will be disruption to deliveries of our raw material – and therefore your finished product – over the next 12 months at least. Let us help you by working with you on the best route to success; speak with our service team so that we can find a solution that works for you and your customers’ needs.

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What do we mean by rubber quality?

Before we look at how to test the quality of rubber, we need a clear understanding of the term ‘rubber quality’. Ensuring that you are working with the right quality of rubber might best be described as the process of ensuring that the product or material you choose is most suitable for the application you need it to perform. In other words, does it do the right job when it is brand new, and will it continue to perform at an acceptable level for as long as you want it to? 

This analysis can be broken down into two areas: firstly, whether the mechanical design is correct, ensuring the product is functional and reliable, and secondly, whether the rubber type and grade are suitable for the conditions in which it will operate. 

If the product’s design is sound and proven, which we can assess even before manufacture using non-linear finite element analysis, then we can begin to focus on whether the rubber quality is right for your product. To answer this question, we would need to know about the operating environment of the rubber part, as this affects the choices you should make in terms of the polymer type and the grade of that polymer to provide the performance and service life that you need within a specific budget. 

One of the essential points to remember about ‘rubber quality’ is that it isn’t necessarily true that the highest grade, most expensive material available will be the best solution; instead, we recommend that you aim to use the most cost-effective and sustainable solution for the application, and it can often be the case that a lower cost, lower grade of material will perform perfectly well in meeting the design requirement and service life needed.

What is the difference between a commercial rubber and a specified grade of rubber?

Within the rubber family are many different polymer types, ranging from natural rubber that is tapped from rubber trees to synthetic rubbers derived from crude oil and other chemicals. They all have different strengths and weaknesses, and no single ‘magic rubber’ does everything optimally, so it is vital to understand the best polymer type for any given application. 

Once the polymer type has been identified, the required operational parameters may dictate whether its performance needs to be formally defined as part of a specification. For example, if a particular level of chemical or temperature resistance is required or a tensile strength value must be met, this aspect of the ‘rubber quality’ will be designed to meet those targets, and if tested against those requirements, it becomes known as a ‘specification grade’. Such a rubber spec may be unique to a customer or meet an industry or international standard such as ISO, DIN, ASTM, etc.

Alternatively, the polymer choice’s general purpose—or commercial grade—may be suitable for the application. In this respect, properties such as chemical resistance, compression set, and tensile strength will be lower, but in many cases, will provide a suitable rubber quality for many products.

How do you know what quality of rubber is most suitable for your product/application?

Rubber technology is a wide-ranging topic with many subtle aspects; a slight change in the constituents in a rubber compound can dramatically affect the properties of the rubber products made from that grade, either to enhance or detract from performance. 

General guidance on the typical strengths and weaknesses of the family of rubber types is readily available, but it is really important to fully understand the environment that a product will be working in; using the garden hose o-ring example, most o-rings on general sale are commercial grade NBR, rather than EPDM, which is the material best suited to the application due to its operating environment. 

The level to which a rubber product is required to perform will then dictate whether a commercial grade of a rubber compound will be suitable or whether a higher grade of material, to a known and provable specification, is needed. That way, the rubber quality will be suited to your application and product needs.

How to test the quality of rubber 

We are sometimes contacted by businesses receiving rubber components from other sources that are failing or underperforming where they were previously acceptable. This could be caused either by a change in the operating conditions or environment or by a reduced rubber quality due to a change in the rubber composition or the manufacturing process used for the part.

It can be challenging to perform rubber testing of quality on a range of finished parts or analyse why components begin to fail when historically they have performed well, but there are steps that you can take: 

• Physical properties such as hardness and tensile strength can be checked if regulation size and shape samples can be created.
• Soak testing can be done to check fluid resistance.
• A TGA process can test the components to identify the chemical constituents destructively.
• Gas Chromatography can, if needed, provide further insights into the chemical constituents. 

These laboratory tests on the quality of rubber are not routinely done unless a comprehensive failure mode analysis is required once a full review of the traceability with the supply chain has been done, along with a series of process checks and validations. 

Unfortunately, it is all too easy within a global supply chain to provide documentation that does not reflect reality, and for safety-critical components, reliable, trustworthy suppliers and high-confidence processes are essential to ensure the product supplied is as it should be and continues to meet your specifications. Rubber moulding compound can be impacted when the supply chain has changed the composition to include higher proportions of lower-cost materials to ostensibly produce the same rubber quality.

Rubber tests we offer at Martins Rubber

• Hardness (Shore A and IRHD)
• Compression Set
• Load deflection
• Rheology (MDR)
• TGA
• Tensile stress-strain
• Peel
• Fluid Swell
• Vibration analysis
• Thermal Conductivity
• Radiation Resistance

Ensure Consistent Rubber Quality With Martins Rubber

To combat the issue of changes within compound make-up and to ensure that you have the confidence that there is adequate control over supply chains, choose a rubber manufacturer who only buys materials from credible, long-term suppliers and who can demonstrate robust quality systems and proven laboratory facilities to continuously monitor the adherence to the specification of the materials used. 

Whether our rubber moulding compounds are specification or commercial grade, we only use highly competent and trustworthy suppliers based in Western Europe, where we have the confidence and track record to assure us that what we receive and process meets expectations. We have in-house testing of the cure profile of any material batch via our MDR, and we undertake hardness and compression set testing routinely to ensure that our finished products meet the rubber quality standard required of any given material or product.

If you are concerned about the quality of rubber for your future projects or would like to discuss how to test the quality of rubber parts you have had manufactured elsewhere, be sure to contact us, and our expert team will be able to guide and support you in finding the most suitable way forward.

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Here at Martins Rubber, we look at how to find rubber’s tensile strength, which factors influence it, and how it relates to FEA simulation. 

Why is the tensile strength of rubber important?  

Tensile strength is the property of a material that quantifies the maximum load it can withstand before fracturing. It applies to stiff materials such as metals, composites and natural materials like timber and stone just as much as it does to rubber. When a load that is less than the tensile strength of a material is applied, that material may deform or stretch but should return fully or mostly to its original size and shape. As the tensile strength approaches its maximum load, the material may begin to ‘neck’, showing a permanent deformation. As the load increases further, the neck will ultimately snap. 

The tensile strength of rubber is unique to its chemical composition and structure. This particular property is important precisely because rubber’s elastic element is often the reason why it is the chosen material for an application—if you want a rubber seal surface to remain in contact with a shaft, a strap to retain its grip, or an AV mount to deliver long-term reliable support without snapping, then rubber provides the ideal solution.

How does the tensile strength of rubber impact product performance? 

If your application requires support, grip, flexibility, or sealing, rubber is often the ideal material for the job. Therefore, it is important to consider how the rubber might fail under your specific operating conditions and what is required of the material to operate reliably.

Applications and environments can vary widely, and factors such as whether the rubber will be in compression or tension could be critical; a static pad that simply takes a long-term load may not need much tensile strength but will need good compression set properties, whereas an AV mount that could see both tension and compression cycles, as well as vibration, will need a much higher tensile strength threshold.

How to find the tensile strength of rubber?

A standardised industry-wide test is generally used to obtain a rubber material’s tensile strength. A standard-thickness sheet has a piece of rubber shaped like a dumbbell cut out using set dimensions. This dumbbell sample is then gradually stretched apart until it breaks. The force applied and the resultant elongation are plotted, and this stress/strain curve derives the Young’s modulus of the material. 

This test also provides the ultimate measure of elongation at the point at which the material breaks; this informs us how much a given rubber will stretch before failure. Although this ‘elongation at break’ figure doesn’t relate directly to the material’s tensile strength, it is still a key value when calculating likely performance.

How does the tensile strength of rubber vary between different types of rubber? 

A rubber’s tensile strength can vary widely depending on the compound in question; the differences in the structures of the polymer chains and their crosslinks give a broad range of tensile strength values and elongation at break values. As ever with rubber, there is an almost infinite mix of variable properties that need to be considered for the best performance in any given application, of which tensile strength is only one – which may not be the most important material property for some applications.

Can you alter the tensile strength of rubber to suit the application?

It can influence rubber’s tensile strength by selecting the optimum polymer type, cure system, and fillers. However, the tensile strength of a rubber may need to be compromised to ensure that a requirement relating to another property, such as hardness, temperature, or chemical resistance, is met.

How do you test the tensile strength of rubber for an existing product?

To understand the tensile strength of an existing rubber component, a test piece in the actual material used to manufacture that product would have to be created. This can be done by moulding a sample sheet under the correct cure conditions from the correct compound, and then a set of dumbbell test pieces are made and put through the test process described above. 

It is not possible to establish information about this property from a non-standard shape, although empirical comparative testing could potentially indicate better or worse performance.

How does tensile strength relate to FEA?

FEA is used to simulate the performance of a component in situ, analysing likely failure points and providing the ability to improve a rubber product design before rubber manufacturers create it. One of the key pieces of data required for FEA is tensile strength; without knowing the tensile strength value of the rubber material intended for manufacture, it is impossible to calculate the failure point of a model being analysed under FEA. This is true of FEA for both linear and non-linear materials. Still, non-linear analysis needs additional information, such as a fully representative stress-strain curve and the type of failure mode – of which tensile stress failure is only one.

Find rubber strength solutions here at Martins Rubber

If you would like to know more about the tensile strength of rubber materials that you are considering working with or are considering likely failure points of a rubber component, be sure to get in touch. Whether it’s rubber development you need or expertise in non-linear FEA, we will be able to support you in finding the right material for your application. 

Be sure to explore our technical articles and case studies for more information on finding rubber tensile strength. If you have any questions about our rubber services, be sure to contact us, and a member of our team will be happy to help.

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