It can be overwhelming when looking for a rubber part. That’s why we tried to simplify the process by answering some questions you should consider the next time your application needs the best seal it can get. From exposure and temperature to hardness and production method, read ahead to find the information you need.
Q1: What Will the Rubber Part Be Exposed to?
All rubber parts will deal with exposure, but the key is knowing exactly what the rubber will be exposed to so you can maximize its effectiveness. Will the rubber be involved with petroleum oil, bases, chemicals, or acids? What about outdoor weather or natural elements like sunlight, rain, ozone, or snow? Does the environment where the rubber part will experience abrasion or movement? Pressure or vibration? Weather can be unpredictable, so choosing a part that can withstand and thrive in elements frequently experienced by the application it will be involved in is crucial. Also, will the part be continuously exposed or only have intermittent exposure?
Q2: What Temperature Range Will the Part Need?
Rubber will be exposed to temperatures that regular people cannot withstand. Knowing the regular operating temperature that the part will experience daily is different from the maximum and minimum spikes and dips, but all of these need to be kept in mind. Many types of rubber can withstand both heat and cold in the triple digits. The normal operating temperature also needs to be considered.
Q3: What Mechanical Forces Will the Part Experience?
Rubber deforms under load, and selecting the incorrect material for an operation can lead to permanent deformation, catastrophic component failure, or premature tearing. In the mechanical field, rubber can also undergo tension (pulling or stretching), shear (sliding across a part in opposite directions), compression (squeezing), and torsion (experiencing twisting forces). Mechanical forces also include shock or impact, both of which can be high-energy and intense.
Q4: How Long Does the Rubber Part Need to Last?
Different rubber types last for different amounts of time. When specifying a part, determining how long it will need to be in service is important. When you’re using the part in an application, does it need to be replaced within a lower amount of years (3–5) or can it go even longer (such as 20) without maintenance or needing to be changed?
Shelf life is another factor, although this one is dependent on if the seal is not being used right away. It focuses on the storage period prior to seal installation into hardware components. You can follow guidelines from the Aerospace Standard (AS) 5316 which, although focuses on the shelf life of aerospace-related seals, can be used as a general guideline and recommended practice for industrial- and commercial-grade elastomers. It lists the following as ideal storage conditions: ambient temperatures not exceeding 100ºF; exclusion of air (oxygen), light (especially ultraviolet), and ozone; and controlled relative humidity.
Q5: What Type of Rubber is Appropriate for the Application?
Not all rubber is similar in its resistance and the applications and conditions it can tolerate. For instance, if a seal is being used in a fuel system, it should be strong against oil; a seal for an air conditioning system needs excellent resistance to ozone and weathering. Whether your application is exterior- or interior-based, involves chemicals or oils, or needs outstanding physical toughness, knowing the specific capabilities of your material, as well as what it cannot handle, is key.
Q6: What Hardness Does the Part Need?
Each material has a different rubber hardness, or “durometer.” A higher durometer provides resistance against abrasion and deformation, as well as supporting heavy structural loads; a medium durometer can dampen well and maintain its structure against vibration and shock; and a lower durometer can flex and conform to surfaces while having great sealing ability. Choosing a part with the incorrect hardness for your application is a path to sealing failure that you can avoid.
Q7: What Dimensional Tolerances Are Actually Required?
Tolerances are the allotted variation in a part’s properties, like its dimensions. It’s not viable to try and pinpoint the exact amount a part will change, so defining a range of acceptable dimensions is the best course. If the tolerances are too loose because of too much variation, its sealing effectiveness will be poor. If the tolerances are tighter than they should be, it can lead to higher scrap rates. Thus, knowing the necessary tolerances for your application is important.
Q8: What Regulatory or Industry Requirements Apply?
This is an important question, especially if your part is being used domestically or internationally. Knowing these standards for the country you’re operating in helps ensure safety and effectiveness. For example, the European Union has the Restriction of Hazardous Substances (RoHs), which means that components need to be tested for the presence of lead, cadmium, mercury, hexavalent chromium, and polybrominated biphenyls, among others, because these substances create pollution and exposure manufacturers to health dangers.
Certain industries have their own regulations as well. Aerospace has AS9100/ISO 9001 as its quality standards. The medical field uses the Food and Drug Administration (FDA), United States Pharmacopeia (USP) Class VI standards, and ISO 10993 test protocols to ensure the biocompatibility and safety of materials used in medical applications. Making sure that the rubber manufacturer you are ordering from has their parts meeting these standards is key to part success. At Apple Rubber, we meet these requirements and more, including the American Society for Testing and Materials (ASTM) D2000, which, despite its focus on the automotive industry, can also apply to the aerospace, medical and industrial sectors as they all benefit from this standard.
Q9: What Quantity and Production Method Make Sense?
For simple, high-strength parts that are available with the widest selection of sizes and intermediate precision, compression molding is your choice. Transfer molding is great for design flexibility and high cavity counts for seals with complex geometries. For quick, high-volume production of parts, choose injection molding; it also makes seals with varying sizes, complexity, and shapes.
The amount of seals you’ll need is another consideration. Check if where you’re ordering from has a minimum order quantity, and if they do, whether it’s much more than what you’re looking for. Ordering more parts than you need means those excess seals can eventually decay and reduce in their effectiveness if they have to be stored, and if those storage conditions are not suitable to that specific part. Low-volume orders can be more expensive per part and you have less risk of aging since they’re more likely to be used; high-volume orders are lower in per-part-cost but the chance of aging and decay increases.
Q10: What Does Success with the Rubber Part and Its Application Look Like?
Is it properly dampening vibration? Is it able to remain stationary or can it be effective in dynamic settings? Can the part endure for as long as you need it to last for? Does it retain its sealing ability after coming into contact with chemicals or oils? Knowing these questions and their answers can help you determine what specific material you’ll need.
One More Question
If you’re ready for the next step, visit our O-Ring Material Selection Guide to find the best material suitable for your application. Already know what you need and want to request a quote? We’ll get back to you as soon as we can.