The differences between TPE and TPR

What are the differences between TPE and TPR?

Both TPE and TPR belong to the family of Thermoplastic Elastomers. To learn more about these materials, read our guide and discover our TPE and TPR product ranges.

To learn more about other materials used in injection molding, see our guides:

LDPE vs HDPE
EPDM vs Silicone
PVC vs TPE

In this article we cover:

TPE vs TPR
Differences between TPE and TPR
What are TPE groups?
The Shore durometer scale
What is TPE material?
What is TPR material?
A comparison: TPR and TPE chemical resistance
Differences between TPR and TPE

 

TPE vs TPR

On the surface, their characteristics appear to be the same:

TPE	TPR
High-flexural fatigue resistance	High-flexural fatigue resistance
Resistant to tears and abrasions	Resistant to tears and abrasions
High-impact strength	High-impact strength
Good dielectric properties	Good dielectric properties
Excellent weather and chemical resistance	Excellent weather and chemical resistance
Recyclable	Recyclable
Temperature range: -22°F to 284°F (30°C to 140°C)	Temperature range: -22°F to 284°F (-30°C to 140°C)

View our TPE and TPR products

Difference between TPE and TPR

TPE (thermoplastic elastomer) and TPR (thermoplastic rubber) definitely offer some differences, which really comes down to their base materials. TPE (thermoplastic elastomers) is modified from SEBS base material and TPR (thermoplastic rubber) is often modified from SBS.

To better understand the difference in the manufacturing processes behind TPE and TPR, we must first break down the meaning of SEBS base material and SBS.

What are SEBS and SBS?

Styrene Ethylene Butylene Styrene Block Copolymer (SEBS) is the product of hydrogenated SBS. But what exactly is SBS? It’s styrene-butadiene-styrene block copolymer, which offers soft-touch characteristics utilised extensively by designers – especially in hand tools.

What does this mean in relation to SEBS? It’s the act of introducing molecular hydrogen to unsaturated molecules in special reaction conditions. What this does is ensure the molecular structure becomes saturated, which offers anti-aging properties, as well as resistance to yellowing. On top of this, it also ensures higher heat and corrosion resistance than SBS, therefore resulting in a higher performance output of TPE over TPR.

What are TPE groups?

There’s a lot to choose from, with TPE groups available, including:

• Polyolefin blends (TPE-O)
• Styrenic block copolymers (TPE-S)
• Elastomeric alloys
• Thermoplastic polyurethanes (TPE-U)
• Thermoplastic polyamides (TPE-A)
• Thermoplastic co-polyesters (TPE-E)

With the flexibility of plastics and rubber, both TPE and TPR are used widely in engineering, but for different applications. In TPR, specifically, its unsaturated molecular structure is similar to that of rubber, which gives it its elastic feel.

The Shore durometer scale

Thermoplastic elastomers are certainly thermoplastic, but they still offer similar elasticity to their cross-linked rubber counterpart. This is determined by its softness or hardness, which is monitored on a scale known as the Shore durometer.

Available as soft gel materials – from 20 Shore OO up to 90 Shore AA – TPEs possess similar qualities to crosslinked rubber. After reaching 90 Shore AA, they are introduced to the Shore D scale, which means they can be formulated to achieve a hardness of up to 85 Shore D.

TPRs are available in a wide range of durometers, from 20 Shore OO to 85 Shore D – again, this aligns with TPE.

What is TPE material?

Made up of soft and hard domains, TPEs are multiphase materials in their solid state. Some engineers may wonder why they’re rubbery – and there’s a very good reason for this.

The temperature range and unique design of a TPE is determined by its glass transition temperature during the rubbery phase, as well as the melt temperature or glass transition during the hard phase of its manufacture.

Containing more than one type of polymer – an elastomer which is responsible for giving a material its elastic properties – TPE compounds, or TPE-S, as it's sometimes known, can be used for a variety of purposes in the world of engineering. TPE materials are mostly used in medical devices, hardware tools, electronic appliances, sports equipment, toy products,, auto parts, most of the medical products and communication instruments. TPE material has a nice high temperature resistance (but TPR has better high temperature resistance) and weather resistance but its advantages are not limited with that.

Advantages of TPE

• Weather resistance
• High temperature resistance
• Fatigue resistance
• Helps to reduce costs

What is TPR material?

TPR material has qualities that combine the physical properties of rubber with the injection molding capabilities of thermoplastics. This material is a kind of thermoplastic soft rubber material and can be directly processed. Think of custom-fitted floor mats in cars, for example. TPR is also standard material for truck-bed liners.

Characteristics of thermoplastic rubber material:

• Holds its shape
• It comes in varying levels of flexibility
• Flexibility can be increased by adding more rubber to the chemical makeup
• Can be formulated so the rubber smell is not noticeable
• Lightweight
• Can be coloured to your requirements

TPR is used in applications which require gluing, such as footwear and toys, while TPE doesn't react well to adhesives. You'll also find thermoplastic rubber at work in:

• Tubing
• Wire and cable
• Sealants
• Bitumen additives
• Automotive trim
• Gaskets
• Packaging
• Film and sheet
• Injection molding

Similar to TPE, TPR incorporates the flexibility of rubber and plastics – and in terms of combustion, TPR emits thicker and darker smoke when burning, as opposed to TPE. When using thermoplastic elastomers, engineers are able to stretch them to moderate elongations. They can then be returned to the original shape; what this does is offer a much longer life. On top of this, the fact that the TPR material provides a better physical range than TPE material and others is also a big draw.

TPE material is matte and has a smooth appearance. It has a light astigmatism, too. It feels smoothly and comfortable. In contrast, TPR is somewhat more viscous, especially when the temperature is around 30˚ to 40˚C/ 86˚ - 104˚. On the other hand, as disadvantages, TPR is not a good at tensile strength aging resistance and mechanical properties.

Advantages of TPR

• Good chemical resistance
• Ability to be used in injection molding process
• Ability to be used in blow molding
• Good fatigue resistance

A comparison: TPR and TPE chemical resistance

TPR and TPE are resistant to some chemical properties. For example, TPE has good UV resistance and TPR is a good chemical resistant. In the chart below, you can check their resistance to the materials.

	TPE	TPR
Dilute Acid	Excellent	Excellent
Dilute Alkalis	Excellent	Excellent
Oils and Greases	Excellent	Excellent
Aliphatic Hydrocarbons	Excellent	Excellent
Aromatic Hydrocarbons	Moderate	Good
Halogenated Hydrocarbons	Moderate	Moderate
Alcohols	Excellent	Good

TPR and TPE in manufacturing

Thermoplastic elastomers can offer significant cost savings – and the reason for this is they can be processed on plastics machinery, therefore reducing the overall price per project. Combining the aesthetics of conventional thermoplastic rubber with the ease of processing which comes with manufacturing them, TPEs are suitable for high-volume injection molding.

With shorter processing times, TPE (thermoplastic elastomer) – like TPR – is also 100% recyclable. They can be used up to five times each, although different grades may vary. This consistency ensures engineers can rely on thermoplastic elastomer for their project. Energy saving and requiring less man power overall, TPEs are lightweight and can be blow-moulded or thermoformed.

Often, the cost can come down to the number of cavities that can be fabricated for each stage of the production process, with the TPE process needing around four cavity moulds on a 30-second injection moulding cycle. With four cavities needed on a 30-second cycle, eight parts per minute can mean 480 are required per hour.

The rubber process can mean twice as many cavities are needed. But engineers are advised not to be put off. The reason is that the TPE process will probably still offer benefits in terms of cost.

TPRs combine the look, feel, and elasticity of thermoset rubber with the processability of plastic. Which brings us right back to where we started – the qualities TPR and TPE have in common. TPR can also be used in injection molding. It, too, can be blow moulded and thermoformed. Because it's so malleable, it's ideal as a custom injection molding material.

It is thought that rubber materials offer improved tensile strength and that TPE materials are still deemed ‘inferior' in terms of their physical properties. You should judge the project and its components on their merits, using the right tools and kit for the job and ensuring plenty of forward-planning is in place.

Differences between TPR and TPE

You've been given the long version. If you're still confused, then think of it this way: TPE material is essentially a softer version of TPR. TPE is used when a bit more flexibility and softness is what you're after. Below you can find some othe differences between TPR and TPE.

At a glance:

Thermo-plastic Elastomer Type	Manufacturing Process and differences	Pros	Cons	Applications
TPE	Modified from SEBS base material Its surface is matte with light astigmatism	Flexibility of plastics and rubber It’s smooth and comfortable	Emits thinner smoke when burning	Food products, Medical and healthcare, sealing rings, cap and closure liners
TPR	Modified from SBS Its particles have a reflective, glossy surface	Flexibility of plastics and rubber Reflection is more apparent	Emits thicker, darker smoke when burning	Products which need gluing with adhesives, or which require a glossy surface or colouring

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