Thermoplastic Elastomer Injection Molding

Thermoplastic Elastomer, as the name suggests is a combination of both, thermoplastics and elastomers. TPEs are a mix of plastics and rubber (elastomers) thus, they exhibit a combination of physical properties. For example, TPEs combine the flexibility of the rubber with the toughness of the thermoplastics. 

TPE can be customized in order to reflect the properties required for the project. For instance, if a company requires to manufacture a particular type of plastic casing that exhibits toughness, and high wear resistance with a certain amount of elasticity then, TPE can be customized to meet these specific properties. It is thus, one of the most versatile injection molding materials. In this article, we describe TPE properties, their types, applications, and how they can be customized.

Table of Contents

What are Thermoplastic Elastomers (TPE)?

A thermoplastic elastomer, abbreviated for TPE, is a type of polymer material with the physical and chemical characteristics of elastomers and thermoplastics. TPEs exhibit high elasticity of thermoset rubber at room temperature and they demonstrate excellent processability of thermoplastics at slightly elevated temperatures (150–210℃ / 302–410℉).

TPEs are basically polymers that exhibit thermoplastic characteristics above their melt temperatures. This property enables them to be shaped while possessing elastomeric behavior without cross-linking during fabrication. This process is also reversible which means that the product can be reprocessed and remolded.

TPEs are popular because it’s easy to achieve outstanding properties by simply varying the blend compositions, the viscosity of the components, and compounding ingredients. 

A typical TPE must fulfill the following characteristics:

  • It should fulfill the ability to stretch moderate elongations and, return to its original shape upon the removal of stress. 
  • It should be processable between 150–210℃ / 302–410℉.
  • There should be no significant amount of creep. Creep resistance or sensitivity is the factor that determines a material’s tendency to withstand or slowly deform under high levels of prolonged stress. 

Chemical Structure of TPE

All TPEs include crystalline and amorphous segments. These can be either physical blends or a chemical mixture of crystalline and amorphous domains in the polymer chain of the block copolymers. 

thermoplastic elastomer structure

The hard blocks are responsible for easy processing, temperature resistance, adhesion, and material properties such as tear and tensile strength or chemical resistance. The soft blocks are responsible for the elastic properties. They also determine the hardness and flexibility of the material. 

TPE Categories

TPEs are divided into two distinct categories: Blend and block copolymers. 

TPE chemical morphology

This distinction is based on the structural composition. Let’s understand these types, more in detail: 

Blend Copolymer TPEs

You must note that the polymer system of TPEs has both crystalline and amorphous domains. Blend Copolymer TPEs are achieved by a mechanical mixture of semi-crystalline and amorphous polymers.

Block copolymer TPEs

Block copolymer TPEs are based on polymers that have hard and soft blocks along the backbone of the polymer chain. The crystalline domains that are formed into hard blocks during the melt give the characteristic thermoplastic behavior whereas the amorphous domains that form elastomeric bridges give an elastomeric behavior.

TPEs Position in Polymeric Group

A polymer is a large molecule made of repeating chemical units. They are classified according to their formation ability.

Thermoplastic elastomers belong to the synthetic elastomer class. The following diagram depicts its position in the polymeric group: 

TPE on polymer table

TPE Properties

  • Mechanical Properties – TPEs exhibit excellent mechanical properties such as abrasion, hardness, stiffness, compression, and tear resistance. 
  • Flexibility – The elastic soft phase of TPEs generate rubber-like properties of elongation, flexure, low-temperature performance, dynamic properties, and tensile strength.
  • Electrical Properties – Electrical insulation properties are dependent on the level of polarity that is present in the TPE. Nonpolar olefinic TPO, TPV, and SEBS TPE display excellent electrical insulation properties.
  • Chemical Resistance – The chemical resistance of TPE is determined by its morphology. You should note that nonpolar amorphous TPE materials have limited chemical resistance to a broad range of solvents.
  • UV Stability – Thermoplastic elastomers are widely susceptible to the effects of high-energy UV radiation.

Advantages and Disadvantages

When should I use TPEs

  • TPE is 100% recyclable. It can be recycled and reused like plastics. They can be ground and turned into 3D printing filaments. 
  • It exhibits excellent material properties such as flexural fatigue resistance, good electrical properties, strong tear, and abrasion resistance, high impact strength and elongation, a low specific gravity, excellent resistance to weathering and chemicals, and a low compression set.
  • It’s easier to process. TPEs do not require large amounts of energy to produce and need very little compounding. They also do not require any reinforcing agents or stabilizer systems. 
  • There is no static crosslinking process. 
  • The cycle time is shorter with less energy consumption.
  • It can be colored and exhibits good coloring.  They are easily colored by most dyes, leading to a wide range of uses. 
  • TPEs can also be co-injected and co-extruded with certain engineering plastics to customize a desirable property. 
  • TPEs are resistant to low and high temperatures (-30°C to +150°C) / (-22°F to +320°F), providing good thermal properties and material stability at a range of temperatures. 
  • It can be processed via blow molding, injection molding, thermoforming, and heat welding.

When not to use TPEs

  • Despite the good temperature resistance, TPEs melt above 150°C / 320°F thus, this limits their use in high-temperature applications. 
  • Most thermoplastic materials require drying before processing, a step that is almost never undertaken on conventional rubber materials. 
  • TPEs are more expensive than other plastics. 
  • The processing temperature needs to be optimum in order for TPE to maintain its rubbery properties.
  • They don’t exhibit a high creep resistance. TPEs can move and deform under the influence of sustained stress, such as that caused by pressure or temperature.

Types of Thermoplastic Elastomers

Styrene Block Copolymers (SBCs)

SBCs are multi-phase compounds in which the phases are chemically bonded through block polymerization. SBCs are in a poly (styrene-b-elastomer-b-styrene) structure. 

Styrenics are most commonly used among the basic TPE categories because styrenic block copolymers can successfully blend with many materials including fillers, extenders, additives, and other resins.

Styrene Ethylene Butylene Styrene (SEBS)

The soft phase in SEBS is ethylene butylene, which is produced by hydrogenating SBS. Due to  the lack of double bonds in their structures, they have very good heat, UV, oil, and chemical resistance. 

Types of TPE

Thermoplastic vulcanizates (TPV)

Thermoplastic vulcanizates are formed through the homogeneous dispersion of crosslinked rubber parts in the thermoplastic phase through dynamic vulcanization. 

In this case, two polymer phases (elastomer and plastic) are required for dynamic vulcanization. Dynamic vulcanization is a process of crosslinking a polymer while mixing another polymer in the molten state. 

Most commercial TPVs are based on a mixture of Ethylene Propylene Diene Monomer (EPDM) and Polypropylene (PP). PP is used because it has a high melting point and crystallinity, therefore it imparts good properties at high temperatures. EPDM is used because it has a high temperature, oxygen, and ozone stability and thus, it enables the production of TPVs with good heat oxidation and ozone resistance.

Thermoplastic Polyolefins (TPO)

Thermoplastic polyolefins are obtained by mixing uncrosslinked amorphous rubbers and semi-crystalline polyolefin thermoplastics in a molten state. The production processes of TPO do not include a vulcanization step. TPOs are impact and chemical-resistant. 

Natural Rubber Versus TPE

It is imperative to understand the type of elastomer that is right for your project! A weak elastomer could damage the product or cause safety hazards whereas an excessively strong rubber could render the products extra rigid to fit the requirements of your project. 


You should consider factors such as the project’s temperature range, the substance resistance of the material, and the industry it needs to be applied to. It is recommended to choose an elastomer that will be compliant with your chosen industry. 

There are prominent differences between Natural rubber and TPE. Natural rubber exhibits great resilience and excellent elastic properties. They however have poor chemical resistance and are not so great in terms of processability. TPE, on the other hand, is extremely brittle but is great when it comes to processability. 

Let’s understand more about the similarities and differences between Natural rubber and TPE: 

What is Natural Rubber?

Natural rubber is an organic compound and a type of elastomer. It is an isoprene polymer that is derived from natural sources such as Hevea brasiliensis, rubber fig, and Pará rubber trees. These trees contain a milky, sap-like substance that is collected by making incisions in the bark of the trees. This substance is known as Latex and is processed for various applications. 

Latex rubber
image credit:

Now, do we understand what Natural rubber is? Let’s understand how it is different from synthetic elastomers. Natural rubber consists of isoprene monomers that are loosely held together. They can be pulled apart and altered but they have the ability to always revert back to their original shape. This property gives rubber its primary property of natural flexibility and elasticity. Synthetic elastomers, on the other hand, have long, randomized polymer chains that when pulled apart do not always revert back to the same shape. 

Natural rubber is softer than synthetic elastomers, making it an ideal choice for manufacturing anti-vibration components, springs, automotive parts, shoe soles, and medical tubing. Natural rubber is also strong and heat resistant which is why it is used very popularly to manufacture high-performance tires. 

Benefits and Limitations of Natural Rubber

Benefits of Natural Rubber

Natural rubber offers various benefits. It makes an optimal choice for various applications due to the following reasons: 

  • Biodegradable:  As it is plant-derived, natural rubber is biodegradable. It can be safely decomposed through natural means. You should note, however, that any additives or curing will render it non-organic. Natural rubber is also sustainable as it is organic and renewable. 
  • Flexibility: Natural rubber is known for its flexibility. It has a high resistance to tearing and its ability to return to its natural form is what makes it one of the most popular rubbers. 
  • Adhesive property: Natural rubber is an excellent choice for Adhesives as Latex is naturally sticky. 
  • It’s non-reactive: In its natural state, Rubber is chemically simpler than TPE and other synthetic elastomers. It is thus, less reactive to many fluids, gases, and chemicals.
  • Consistency: Natural rubber is derived from latex which has a consistent set of monomers that do not vary as much as some synthetic elastomers might. 

Limitations of Natural Rubber

Though natural rubber has various advantages, it may not always be the best fit for every application. Like every plastic or injection molding material has disadvantages, natural rubber also has limitations. Let’s take a look at its disadvantages: 

  • Temperature Monitoring: It’s crucial to monitor the temperature with natural rubber. It’s easily influenced towards being pliable at a very high temperature whereas if the temperature is too cold, natural rubber would crystallize and become too rigid.
  • Cost and Availability: Latex cannot be manufactured and thus, natural rubber is dependent upon availability thus, the production cost also tends to fluctuate.
  • Weak Substance-resistance: Natural rubber has weak resistance to grease, fats, and oils. 
  • Latex Allergy: Although latex allergy is rare, its reactions can be quite harsh. Some of the symptoms include rashes, tightening of the chest, and itching.

TPEs in comparison to Natural Rubber

TPEs, when heated flow freely, and when cooled almost regain their original structure but not as well as Natural rubber. 

Natural Rubber exhibits physical properties such as excellent tensile, elongation, and, tear resistance. Additionally, it exhibits good abrasion resistance but poor resistance to ozone, oxygen, sunlight, and heat. TPE, on the other hand, exhibits great resistance to sunlight, and heat and is UV-resistant. 

It also exhibits excellent low-temperature flexibility. The temperature range for Natural rubber is -55° C to +82° C / -67° F to +180° F whereas TPE is 150–210℃ / 302–410℉. 

Let’s take a look at some of its pros and cons in comparison to Natural rubber. 

Rubber vs TPE

Pros / Benefits

  • Comparatively Cost-Effective: Since TPE is synthetic, its production is not dependent upon natural resources, thus, its comparatively cost-effective. 
  • TPE is Non-Allergic: TPE is a known alternative to latex i.e. it possesses similar properties to latex but is chemically safe to use as it does not cause allergies. 
  • Durability: TPE is durable over a long period of time as opposed to natural rubber which tends to dry over time. 
  • TPE is UV-Resistant: TPE is also better at resisting the effects of UV radiation than natural rubber.

Cons / Limitations

  • Less Elasticity: TPEs do not exhibit the same elasticity as natural rubber. Since TPEs are a mixture of elastomers and plastic, they do not retain their shape or elasticity, as natural rubbers do. 
  • Non-Biodegradable: TPEs aren’t biodegradable as natural rubbers are. 

Additionally, there are some more TPE properties to consider. We have listed these below: 

  • Temperature: The temperature range for TPE is (150–210℃ / 302–410℉). If the temperature is too cold, TPEs tend to get either brittle or extremely rigid. If the temperature is too hot, it is unusable as it undergoes permanent chemical changes. 
  • Disposal: TPEs are not biodegradable, unlike natural rubber. Recycled rubber can be  repurposed but the addition of additives into TPE makes it toxic for organic decomposition. 
  • Fluid compatibility: Most TPEs vary in their compatibility with chemicals and oils thus, it’s important to ensure that fluid compatibility is considered.

TPEs Versus Thermosets and TPR

What is the difference between Thermoplastic elastomers and Thermosets?

The principal difference between thermoset and thermoplastic elastomers is due to crosslinking bonds in their structures. Crosslinking is a structural component that is critical for imparting polymers with highly elastic properties. 

TPEs and Thermosets are both polymers, but they behave differently when exposed to heat. At high temperatures, thermoplastics can melt under heat after curing while thermosets can retain their form. Thermosets, unlike TPEs, stay solid once cured.

Thermoplastics have a low melting point, and they are thus ideal for applications that use recycled materials. Thermosets, on the other hand, are able to withstand high temperatures without losing their shape, making them more durable and suitable for high-temperature application projects.

What’s the difference between Thermoplastic elastomers and Thermoplastic rubber?

TPR is interchangeably referred to as TPE since they both exhibit rubber-like appearance but they are different polymers and extremely distinct in their characteristics from each other. 

As described earlier, TPE is abbreviated for Thermoplastic Elastomer. Elastomers are commonly referred to as rubber thus, they are often regarded as the same types of polymers. However, they are both modified versions of different materials. TPR is synthesized using block copolymers such as Styrene-Butadiene-Styrene (SBS) polymer whereas TPEs are manufactured using Styrene-Ethylene-Butadiene-Styrene (SEBS) polymer. SEBS has a molecular formula in a saturated state, and its aging, yellowing, high-temperature, and corrosion resistance are better than SBS. Thus, they both exhibit different properties and cannot be regarded as the same. 

You should note that TPE and TPR both have the ductility of plastic and vulcanized rubber, but TPR has an unsaturated fatty molecular formula (similar to vulcanized rubber), thus, it has the tactile sensation and resilience of vulcanized rubber. 

Let’s take a look at some more similarities and differences between Thermoplastic elastomers and Thermoplastic rubber: 


You can read about TPR materials in-depth here.

What to consider for TPE Material Selection

One of the most critical stages in any manufacturing process is ‘material selection’. It determines the development of the final plastic part. There is a wide range of TPEs available, and we have listed below, a TPE material checklist to help you simplify the process. Let’s take a look at some of the most common factors that you should consider for TPE material: 

Application Purpose of TPE

It is imperative to understand the application requirements in order to achieve the product requirements. The manufacturer should not only understand the extent of the application requirements but also whether it’s an existing or a novice application. If it’s a new application, you might need a new TPE grade, and if it’s an existing application, the same TPE can be used. 

Additionally, the following factors should be considered: 

  • Maximum and minimum exposure temperature
  • UV-exposure 
  • Chemical Exposure 
  • Expected life-expectancy of the product

Material Requirements

TPEs can be formulated from the standard variations to meet a specific requirement. TPEs are popular injection molding materials because they can be customized to include a specific physical or chemical property to fit the product design and requirements. Today, there are various TPE formulations available. We have listed some of the most important material requirements to help you evaluate your application. These requirements are listed below: 

  • Abrasion Resistance and Adhesion
  • Clarity and Colorability
  • Elasticity, Bounce-back, Elongation
  • Hardness and Tensile Strength
  • Rheology (Deformation measurement) 
  • Durability

Environmental Factors

TPEs are versatile and they exhibit excellent chemical resistance. They also demonstrate exceptional thermal properties and material stability.

Thermoplastic Elastomer Industry Requirements

It is also essential to understand the industry type as that will influence various requirements. For instance: 

  • The automotive industry may require specific OEM (Original equipment manufacturer) material specifications. 
  • The medical industry requires critical FDA regulations. 
  • The food industry in the EU may require REACH  (Registration, evaluation, authorization, and restriction of chemicals), RoHS (Restriction of Hazardous Substances), and EU-restricted substances compliance. 

Production Costs

It is important to understand what the production costs are. There are various types of TPEs available and with that, the resin prices vary. It is thus essential to factor in the production costs. 

Thermoplastic Elastomer Applications

Thermoplastic elastomers have unique properties that have made them a popular injection molding material. They are today, applied to manufacture a wide range of products in various industries. Let’s take a look at some of its popular applications:


TPE is widely used for automotive applications due to its flexibility, excellent wear, chemical, and electrical resistance, and UV stability. Examples of its application in the automotive industry include weather seals, bumpers, exterior & interior parts, instrument panels, air ducts, pipe grommets, glass encapsulation, drive belts, high/low-pressure pipes, and mats for motor scooters.

tpe plastic applications
image credit:

Medical Industry

TPE is flexible, biocompatible, lightweight, and chemically resilient. This makes it useful for breathing tubes, syringe seals, masks, and catheters. 

Electronics Industry

Due to its electrical resistance and ability to be molded, TPE is very popularly used in the electronics industry to manufacture mobile phone components, sheaths for condensers, plugs and loose sockets, and cables.


Its durability and flexibility make it the perfect choice for extruded weather seals for doors and windows, glazing, and pipe seals. 

Sporting Goods

Due to its flexibility, wear resistance, and UV stability, TPE is applied to manufacture items for diving (flippers, snorkels, masks) and skiing (ski pole handles, ski boots).

Consumer Industry

TPE exhibits durability, flexibility, ease of molding, and chemical resistance which are desirable properties for manufacturing various consumer goods such as remote control covers and mobile phone cases. TPEs are also applied to manufacture magnetic seals for refrigerators, push-button panels, and shock-absorbing protections for vacuum cleaners. 

TPE phone case
Contact Us for TPE Injection Molding

Thermoplastic elastomers have unique properties as they combine thermoplastics with rubbers. TPE technologies can also be further customized to offer a wide range of mechanical properties that are diverse. It is thus applied to various applications. 

VEM Tooling has the expertise for your TPE injection molding project. To better understand how VEM tooling can provide you with the expertise and serve you for your TPE injection molding project, contact us or request a quote today.

TPR Frequently Asked Questions (FAQ)

TPEs are manufactured by combining a hard and soft material that typically forms its crystalline and amorphous domains

TPEs are non-allergic and they are considered to be safe. Various grades of TPEs are often used in the medical and food industry. Some TPEs are also categorized in FDA’s GRAS (Generally Recognized as Safe) category.

Yes, TPEs are water-proof. They can also be blended with additives to make them extremely waterproof which is why they are often applied in water-proof electronic applications.

TPEs are naturally white or cream in color which is why they can be easily colored. There is no limitation when we talk about dyeing TPEs.

TPEs technically don’t melt! They get softer upon heating after which the material tends to freely flow. You should note that TPEs don’t transform to a liquid state and this ability to freely flow in a near-melted state, allows TPEs to be easily molded in the required shape.

There are various differences between TPEs and general plastic. The primary difference is that TPEs exhibit excellent resilience, low brittleness, and deformation under room temperature over general plastics.