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Rubber material testing evaluates the properties and characteristics of elastomers, polymers that have both viscosity and elasticity (viscoelasticity). The applications for rubber materials are numerous and range from automotive parts to medical devices to components used by the oil and gas industry.  To ensure the quality and reliability of the rubber that engineers can select, testing is critical.

This article from MACH Rubber examines some common types of rubber material testing. Keep reading to learn more, or request a quote if you’re ready to order standard or custommoulded rubber products made from materials such as natural rubber, SBR, butyl, EDPM, nitrile, Hydrin®, neoprene, Hypalon, urethane, polysulfide, silicone, fluorosilicones, or fluoroelastomers.

Tensile Testing

Tensile testing determines the tensile strength, elongation, and modulus of elasticity of a rubber material. This information is important in determining an elastomer’s ability to withstand deformation and stress. Tensile testing applies force to a material sample to determine the residual deformation. ASTM D412 contains standard test methods for vulcanized rubber. 

Compression Testing

Compression testing is used to determine compressive strength and deformation. This type of rubber material testing is important in determining an elastomer’s ability to withstand pressure and compression. ASTM D575 is a testing specification that determines the compression-deflection characteristics of rubber compounds.

Hardness Testing

Hardness testing measures the resistance of a rubber material to indentation and, in turn, its ability to resist abrasion and wear. There are at least seven scales of rubber hardness, including A and D. Shore A measures the hardness of flexible moulded rubbers and Shore D measures the hardness of hard rubbers.  ASTM D2240 is a testing specification for measuring the hardness of rubber materials.

Aging Testing

Aging testing is used to determine the performance and durability of rubber materials over time and in response to different environmental conditions, such as heat and light. Rubber aging is a long and continuous process, but accelerated aging tests are performed under laboratory conditions. ASTM D573 contains a standardized procedure for heat aging in an air oven.      

Tear Resistance Testing

Tear resistance testing is a method of measuring a rubber material’s ability to withstand tearing forces. This type of testing is important for moulded rubber products such as hoses, gaskets, and seals, which may be subjected to tearing forces during regular use. ASTM D470 contains a tongue tear test for rubber products.

Chemical Resistance Testing

Chemical resistance testing is used to determine a rubber material’s chemical compatibility and to evaluate the elastomer’s durability and fatigue life. There are many different standards for rubber material testing for chemicals. For example, ASTM D6284 measures the effect of aqueous solutions with available chlorine and chloramine on rubber properties.

Compression Set Testing

Compression set testing measures a rubber material’s ability to return to its original thickness after the removal of prolonged compressive stresses at a given temperature and deflection. The results of compression set tests are reported as a percentage, and a lower percentage indicates greater resistance to permanent deformation. ASTM D395, Test Method B is commonly used.   

Rubber Moulding and Rubber Material Testing

Do you have questions about rubber material testing, or do you need help choosing the right rubber compounds for moulded products? MACH Rubber uses a moving die rheometer to ensure batch-to-batch consistency so that all of your moulded rubber parts have the material and performance properties you expect. Contact us for quality rubber moulding.

Rubber moulding processes uses heat and pressure to mould raw rubber into the specific shape and size of a desired part. Examples of moulded rubber products include seals, gaskets, O-rings, tubing, and bellows – just to name a few. Today, there are three main types of rubber moulding processes: compression moulding, transfer moulding, and injection moulding. Each has its own advantages and applications.

This article from MACH Rubber explains the differences between all three rubber moulding methods. Keep reading to find out which process you need, or request a quote if you’re ready to order standard or custom moulded rubber products. MACH Rubber offers all three processes at our Barnsley, South Yorkshire location and we’re ISO 9001:2015 certified.

#1 Compression Moulding

Compression moulding is the oldest, most basic, and most cost-effective rubber moulding process. It begins by placing a pre-measured amount of raw rubber into a mould cavity. This pre-measured amount, the pre-form, is compressed under high pressure and heat until the rubber fills the entire cavity. The pressure and heat cause the rubber to flow and take on the shape of the mould while it cures.

Compression moulding is best suited for producing simple shapes and low to medium volumes of rubber products such as seals, gaskets, and simple O-rings. The process is relatively simple, and it requires less machinery than either transfer or injection moulding. All of this makes compression moulding a popular choice for prototyping and small-scale production.

#2 Transfer Moulding

Transfer moulding is more complex than compression moulding but less complex than injection moulding. With transfer moulding, raw rubber material is heated in a chamber. As the press closes, the material is transferred to a mould cavity through a sprue or channel. The mould is then closed and compressed, and the rubber cures in the cavity.

Transfer moulding is best suited for producing complex shapes and higher volumes of rubber products. Often, it’s used to produce electrical connectors, diaphragms, and O-rings with intricate designs. Because it allows for precise control over the amount of material in the mould, transfer moulding creates a higher-quality product. It also minimizes material waste and reduces the need for post-production trimming.  

#3 Injection Moulding

Injection moulding is the most advanced and the most precise rubber moulding process. It’s also highly automated, which allows for faster production times and lower costs. Injection moulding involves melting the raw rubber material in a heated barrel and then injecting it into a closed mould cavity under high pressure. The pressure and heat cause the rubber to flow and take on the shape of the mould.

Rubber injection moulding is best suited for producing high volumes of parts that have complex shapes and tight tolerances. Often, it’s used with seals, O-rings, and gaskets for automotive and aerospace applications. The injection moulding process allows for precise control over the amount of material injected into the mould, resulting in high-quality finished products with minimal post-production trimming required.

MACH Rubber v Transfer Moulding

As you’ve learned, each rubber moulding process has its own advantages and applications. Compression moulding is ideal for producing simple shapes and low to medium volumes of rubber products, while injection moulding is recommended for producing complex shapes with tight tolerances and in high volumes. MACH Rubber does not provide transfer moulding services as we consider this to be less efficient.

Rubber material selection is critical for ensuring the optimal performance, durability, and safety of your moulded parts and products. Rubber is used in a wide range of applications, from medical devices and industrial equipment to aerospace assemblies and by the oil and gas industry. By fully understanding your requirements, you can choose the right rubber material for either standard products or custom products.  

Here are some of the key factors to consider when selecting rubber materials.

• Physical Properties
• Chemical Resistance
• Temperature Range
• Environmental Factors
• Rubber Material Cost
• Industry Standards and Regulations

The following sections explain.

Physical Properties

The physical properties of elastomers, such as hardness, tensile strength, elongation, and compression set, are all important to consider during rubber material selection. For example, a rubber with high tensile strength is ideal for applications that require high durability, while a material with high elongation is better suited for applications that require flexibility.

Chemical Resistance

The chemical resistance of rubber materials is also a key consideration. Depending on your application, you may need to choose an elastomer that can withstand exposure to chemicals, oils, solvents, or other substances. By selecting a rubber with the chemical compatibility that’s requried, you can help to ensure the optimal performance and longevity of your moulded rubber products.

Temperature Range

The application’s temperature range is also a critical factor during rubber material selection. Different materials have different temperature ranges, and selecting a rubber that can withstand the temperature extremes of your application can help to prevent cracking, degradation, and other types of damage. In addition to minimum and maximum temperatures, you may need to account for temperature cycling.

Environmental Factors

Environmental factors, such as exposure to ultraviolet (UV) light, humidity, and ozone can also affect the performance and durability of moulded rubber products. If the carbon bonds in the backbone of a polymer begin to break down, degradation and failure can occur. That’s why choosing a rubber material that is resistant to environmental factors in your application is so important.

Rubber Material Cost

Cost is also a key consideration during rubber material selection. Different materials can have very different costs, and commodity-grade rubber is generally less expensive than specialty elastomers. For moulded rubber products, it’s important to select a material that is cost-effective but that can still meet performance specifications and requirements.  

Get Help with Rubber Material Selection

Selecting the right rubber material requires careful consideration of physical properties, chemical resistance, temperature range, environmental factors, rubber material cost, and industry standards and regulations. With the right approach, you can choose a rubber material that promotes performance, durability, and safety while meeting specifications and requirements.

Engineering design reviews are critical to the success of any product, especially those involving moulded rubber parts. Rubber moulding supports a variety of applications and can produce parts ranging from simple seals to complex components for demanding environments. To ensure part quality and reliability, rubber moulders need to conduct thorough engineering design reviews

Engineering Design Reviews at MACH Rubber

MACH Rubber uses a design review process in which our engineering and quality teams work with a customer’s stakeholders to examine a product’s design and specifications in detail. The goal of this process is to identify any potential design flaws, performance issues, or manufacturing challenges that could affect product quality and functionality.

Four Factors and Additional Considerations

During our design review process, the team evaluates a number of different factors, including:

• Material selection
• Product design
• Manufacturing process
• Testing and evaluation

The following sections explain.

Material Selection

Selecting the right type of rubber material is critical for the performance and durability of your product. The team will evaluate factors such as temperature resistance, chemical resistance, and mechanical properties to ensure that the chosen material is suitable for the intended application. There are many different types of elastomers, including solid, sponge, and foam rubber.

Product Design

The design of a product must be evaluated carefully to ensure that it meets functional requirements and can be manufactured in an efficient and cost-effective manner. During an engineering design review, the team will examine factors such as geometry, moulding tolerances, and surface finish to ensure that a product will perform as intended.

Manufacturing Process

The manufacturing process for rubber parts can be complex and many involve variety of different techniques, such as injection, compression, and transfer moulding. During an engineering design review, the team will evaluate the manufacturing process to ensure that it is capable of producing parts that meet the required specifications and quality standards.

Testing and Validation

To ensure the quality and reliability of moulded rubber products, the design review team will evaluate testing and validation procedures to ensure that they are sufficient for determining the performance and durability of the product. With medical rubber moulding, MACH Rubber can perform process validation to ensure that every batch of moulded medical parts meets your specifications.

Additional Considerations

In addition to these four factors, the engineering design review process can evaluate the cost of the product and the feasibility of the manufacturing process itself. This can help to identify opportunities for cost savings and process improvements that benefit the customer.

The Value of Engineering Design Reviews

Engineering design reviews are critical to the success of moulded rubber parts and can help to ensure that a product meets the required specifications and quality standards. By carefully evaluating the material selection, product design, manufacturing process, and testing and validation procedures, the design review team can identify potential issues and make necessary adjustments to ensure that the final product is of the highest quality.

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