Thermoplastic Elastomer (TPE): Properties, Types, Application

Thermoplastic elastomer (TPE) is a type of polymer mix or combination that, when heated beyond its melting point, can be molded into various shapes like a typical thermoplastic material. Within its intended temperature range, it shows elastic properties without requiring any cross-linking process during shaping. Several plastic production techniques, including injection molding, extrusion, and blow molding, are used to process thermoplastic elastomers. Advanced processing techniques like overmolding and two-shot molding can be applied to a TPE. It can also be subjected to secondary processes like welding and bonding to different materials.

Thermoplastic elastomer material is a popular option for product developers, processors, and designers because it combines the benefits of plastics, such as recyclability and processing advantages, with the characteristics of rubber. TPE is a material that can have many of the mechanical and physical characteristics of both plastic and rubber, giving it an alternate option for a variety of uses.

What is Thermoplastic Elastomer (TPE)?

Thermoplastic elastomers (TPEs) are a class of polymers that combine the characteristics of both thermoplastics and elastomers. These materials exhibit thermoplastic behavior, meaning they can be melted and reshaped multiple times without undergoing chemical degradation. At the same time, they also possess elastomeric properties, allowing them to stretch and return to their original shape after deformation, similar to rubber.

• TPEs are usually made by combining different polymers or changing the molecular structure of one polymer in order to get the required results. TPEs don’t require a curing or cross-linking procedure during fabrication, in contrast to thermoset elastomers like vulcanized rubber. Due to their ability to be blown, extruded, or injection molded like traditional thermoplastics, they become more affordable and easier to work with.
• Conventional plastics processing methods, such extrusion and injection molding, can be used to handle thermoplastic elastomers; excess material can be recycled. The characteristics of thermoplastic elastomers are typically inferior to those of traditional vulcanized rubbers at higher temperatures.
• Six fundamental types of thermoplastic elastomers can be distinguished: ionomers, graft copolymers, hard polymer-elastomer combinations, multiblock copolymers, styrenic thermoplastic elastomers, and core-shell morphologies.
• The versatility of TPEs makes them suitable for a wide range of applications across industries such as automotive, consumer goods, medical devices, and electronics. They are used in products like seals, gaskets, grips, and soft-touch components due to their excellent flexibility, durability, and resistance to chemicals and weathering.

Characteristics of Thermoplastic Elastomers

• Elasticity and Flexibility: TPEs exhibit rubber-like flexibility and elasticity, allowing them to be stretched and then return to their original shape.
• Thermoplastic Processability: Injection molding, extrusion, and blow molding are a few of the standard plastic manufacturing processes that can be used to them. Their capacity to harden when cold and soften when heated is the reason behind this.
• Recyclability: TPEs can be recycled and reprocessed, which is an advantage over traditional thermoset rubbers that cannot be remelted once cured.
• Chemical Resistance: They can be used in a variety of applications due to their strong resistance to a wide range of chemicals, oils, and solvents.
• Durability: TPEs offer good abrasion resistance and durability, contributing to their long life span in various applications.
• Low Temperature Performance: Unlike many polymers that can break easily at low temperatures, they keep their pliability and functionality at these levels.
• Biocompatibility: Because some TPEs are biocompatible, they can be used in healthcare and medical settings.
• Varied Hardness: They can be formulated to have a wide range of hardness, from very soft and gel-like to rigid and hard.
• Colorability: TPEs can be easily colored, allowing for aesthetic flexibility in product design.
• Weather Resistance: A lot of TPEs are appropriate for outdoor applications because of their strong resistance to UV rays and weathering.
• Lightweight: TPEs are generally lighter than traditional rubbers, which can be beneficial for applications where weight is a critical factor.
• Cost-Effective: The ability to use standard plastic processing techniques and the recyclability of TPEs can lead to cost savings in manufacturing.

Properties of Thermoplastic Elastomer

• Elasticity and Flexibility
  • TPEs exhibit high elasticity similar to that of conventional vulcanized rubber, allowing them to stretch significantly and return to their original shape without permanent deformation.
  • They are appropriate for applications requiring repetitive motion or flexing because they are flexible and quickly bend or flex.
• Thermoplastic Behavior
  • TPEs are reprocessable and can be melted, unlike typical elastomers. Because they harden when cold and soften when heated, common thermoplastic molding processes like extrusion and injection molding can be easily used to process them.
  • This thermoplastic nature also means they can be recycled and reshaped, contributing to material efficiency and sustainability.
• Chemical Resistance
  • TPEs typically show good resistance to a wide range of substances, including solvents, oils, and different environmental elements. Because of this, they can be used in abrasive situations and come into contact with different materials.
  • Specific TPE formulations can be tailored to enhance resistance to particular chemicals as needed for specialized applications.
• Durability and strength
  • Rubber’s elasticity and plastic’s mechanical strength are combined in these materials. They are perfect for situations where a blend of hardness and elasticity is needed since they are strong and resistant to severe wear and tear.
  • TPEs maintain their properties over a wide range of temperatures and environmental conditions.
• Aesthetic and Surface Properties
  • For many consumer applications, including grips, handles, and soft-touch coatings, TPEs can be made with a smooth, rubber-like surface texture. They offer diversity in appearance and design and are easily colored. They are also available in different degrees of transparency or opacity.
• Low-Temperature Performance
  • Many TPEs function well in cold climates, holding onto their flexibility and resistance to impact. Because of this, they can be used in outdoor or chilled environments.
• Processing Efficiency
  • The thermoplastic nature of TPEs allows for rapid processing cycles, which can enhance manufacturing efficiency and reduce production costs.
  • The manufacturing process can be further streamlined by processing them with standard thermoplastic machinery without the need for vulcanization or curing.
• Softness and Comfort
  • TPEs are frequently utilized in products that come into direct touch with the skin, such as ergonomic grips, medical devices, and personal care products, since they may be tailored to create a soft, comforting feel. To fit particular uses, the formulation can be changed to change the softness.
• Adhesion to Other Materials
  • TPEs can be co-molded or overmoulded with other materials, such as rigid plastics, to create composite parts with varied properties. This allows for the integration of hard and soft components in a single product.
  • Their ability to bond well with a variety of substrates expands their use in multi-material assemblies.
• Environmental and Regulatory Compliance
  • Many TPEs are designed to be free of dangerous ingredients like heavy metals and phthalates, adhering to different safety and environmental effects regulations. They are frequently used for applications where adherence to environmental laws and standards is crucial.

Types of Thermoplastic Elastomer

Styrenic Block Copolymers (TPE-S)

TPE-S materials, also referred to as styrene block copolymer thermoplastic elastomers, are derived from SBS or SEBS, which are briefly explained below:

• Styrene Butadiene Styrene (SBS): This kind of TPE has a molecular structure made up of butadiene and styrene units that are repeated and have styrene end caps. Styrene hard blocks and butadiene soft blocks are produced by this structure. The most popular TPE is SBS.
• Styrene Ethylene Butylene Styrene (SEBS): By hydrogenating SBS, butane mid-block is broken down into ethylene butadiene, which is then used to make SEBS. Through this procedure, the TPE obtains enhanced resistance to heat and chemicals, as well as improved weathering and UV and ozone protection. SEBS and other thermoplastics can form bonds. For outdoor uses, it is perfect.

Properties of TPE-S

• Insulating from electricity
• Wide range of hardness
• Strong resistance to abrasion
• Colorless and translucent,
• Resistant against ozone and UV

Application of TPE-S

• Glues
• agents that alter asphalt
• Shoes Poor-quality sealing

Thermoplastic Polyolefins (TPE-O or TPO)

Thermoplastic olefins (TPO) are a type of thermoplastic elastomer made by combining polypropylene or polyethylene with elastomers like EPDM, EPR, EO, or EB. These elastomers are typically uncross-linked, and the components are blended mechanically. TPO materials are known for their excellent thermal and chemical resistance, though they exhibit fewer elastomeric properties and have a relatively high hardness, typically around 80 Shore A. They are used in scenarios where standard polypropylene lacks sufficient toughness. TPO can be processed through various methods, including injection molding, extrusion, and blow molding.

Properties of TPO

• resistant to flames
• Exceptional resistance to weather
• Strong resistance to chemicals
• More durable than copolymers of polypropylene

Application of TPO

• Bumpers for cars
• Dashboards
• Airbag shields
• mudguards

Thermoplastic Vulcanisates (TPE-V or TPV)

Similar to TPOs, TPVs (Thermoplastic Vulcanisates) are composed of a blend of EPDM and polypropylene. Here, though, compounding causes the EPDM to vulcanize. The hardness range of TPVs is broader. In comparison to TPOs, they also have superior elastomeric qualities. Since they can withstand temperatures as high as 120°C, TPVs are frequently found in car engine chambers. Injection molding and other common melt-processing methods can be used to create TPV materials.

Properties of TPV

• Resistance to temperatures as high as 120°C
• Set low compression.
• The 45A to 45D hardness range is resistant to chemicals and weather.

Application of TPV

• Bellows
• Hoses
• Pipe seals
• Automotive seals

Thermoplastic Polyurethanes (TPE-U or TPU)

Thermoplastic polyurethane (TPU) is created by reacting diisocyanates with polyester or polyether polyols. In this process, diisocyanates produce the hard segments, while polyethers or polyesters form the soft segments. The properties of TPU can be easily adjusted by varying the polyol and diisocyanate mixture. TPU is commonly processed using injection molding, extrusion, and blow molding.

Properties of TPU

• Superior resistance to abrasion
• Increased tensile strength
• Considerable range of elastic elongation
• Superior tearing strength resistant to oils and fuels derived from petroleum

Application of TPU

• Caster wheels
• Power tool grips
• Tubes and hoses
• Drive belts

Thermoplastic Copolyesters (TPE-E or COPE or TEEE)

With the benefit of being melt-processible, thermoplastic copolyesters, or TPE-Es, are high-performance thermoplastic elastomers that have many characteristics with thermosetting elastomer polymers. TPE-Es are block copolymers that usually have soft segments derived from different polyesters and hard segments made from polybutylene terephthalate. The medical field makes extensive use of TPE-E.

Properties of TPE-E

• Resistant to compression sets and creep
• Outstanding long-term tolerance to 165 degree Celcius temperatures
• Resistant to greases and oils
• Insulating from electricity
• Steady in terms of dimensions

Application of TPE-E

• Air ducts in vehicles
• Bags for ventilators
• Boots for dust
• Belt conveyors

Melt Processable Rubber (MPR)

MPR, a cross-linked halogenated polyolefin combined with plasticizers and stabilizers, is an alternative to vulcanized rubber. The main goal of MPR is to use thermoplastic processing technology to manufacture parts that resemble rubber. At working temperatures below 120 degree Celcius, MPR performs better than many other rubbers.

Properties of MPR

• UV-resistant
• increased coefficient of friction
• resistant to oil and gasoline

Application of MPR

• Weather strips for cars
• Boats that are inflatable
• Goggles for Seals
• Handholds

Thermoplastic Polyether Block Amides (TPE-A)

TPE-As are composed of hard segments made of polyamide and soft segments made of polyester or polyether. One can employ a variety of polyamides, including polycarbonate-esteramide (PCEA), polyesteramide (PEA), and polyether ester amide (PEEA). The kind of polyamide used has a significant impact on each TPE-A’s characteristics. It is possible to bond thermoplastic polyamides to TPE-A.

Properties of TPE-A

• Outstanding resistance to temperatures up to 170C
• Strong resistance to solvents
• Strong resistance to impacts
• Pliable in cold weather
• Strong resistance to wear

Application of TPE-A

• Aerospace components
• Cable jacketing

Application of Thermoplastic Elastomer

• Automotive Industry
  • Sealing Systems: TPEs are widely used in automotive sealing systems, including door seals, window seals, and trunk seals. Their flexibility and durability provide excellent sealing properties, reducing noise and preventing water ingress.
  • Interior Components: Airbag covers, door knobs, dashboards, and other interior components all use TPEs. They feel soft to the touch and are easily molded into complicated forms.
  • Exterior Components: They are also utilized in exterior components such as weatherstrips and bumper coverings, where their resilience to impact and tolerance of environmental elements including UV rays and temperature changes are essential.
• Medical and Healthcare
  • Medical Devices: TPEs are used in medical devices such as tubing, catheters, and syringe plungers. Their biocompatibility and ability to be sterilized make them suitable for these critical applications.
  • Wearable Technology: TPEs are utilized in wearable technology, including fitness trackers and medical monitoring systems, in the healthcare industry. The wearer’s comfort is ensured by their skin-friendly characteristics and flexibility.
• Consumer Goods
  • Sporting Goods: TPEs are used in the manufacturing of sporting goods such as grips for tennis rackets, golf clubs, and bicycle handles. Their ability to provide a comfortable grip and resistance to sweat makes them ideal for these applications.
  • Household Goods: TPEs are utilized in household goods, which include toothbrushes, culinary utensils, and remote control buttons. Their soft-touch and non-slip qualities improve product usability and user comfort.
  • Toys: TPEs are safe for use in toys due to their non-toxic nature and compliance with safety standards. They are used in making various types of toys, including flexible figurines and soft play items.
• Construction
  • Sealants and Gaskets: TPEs are employed in construction for sealants and gaskets. Their elasticity and resistance to weathering ensure long-lasting seals in windows, doors, and other structural elements.
  • Roofing Membranes: They offer strong, weather-resistant solutions that can tolerate high temperatures and UV radiation. They are also utilized in roofing membranes.

Advantages of Thermoplastic Elastomer

• Ease of Processing
  • Injection Molding and Extrusion: TPEs can be processed using standard thermoplastic equipment like injection molding and extrusion machines, facilitating high-speed production and complex part geometries.
  • Recyclability: TPEs may be melted, warmed up again, and processed again, which lowers waste and encourages environmentally friendly production methods.
  • Shorter fabrication periods, which also result in less expensive final parts. The offered equipment is much more productive because TPE molding cycles usually last several seconds as opposed to minutes for thermoset rubbers.
  • TPEs are processed utilizing thermoplastic techniques, which are generally more effective and much less expensive, resulting in simpler and fewer steps in the final product’s cost.
• Design Flexibility
  • Customizable Properties: TPEs offer a broad range of hardness, elasticity, and resilience and can be tuned to individual performance requirements by varying the ratio of hard to soft segments.
  • Color & Aesthetics: TPEs are readily colored, offering a wide range of design possibilities to satisfy aesthetic standards without sacrificing material qualities.
• Mechanical Properties
  • Elasticity and Flexibility: TPEs have outstanding elastic recovery, which makes them perfect for uses like flexible joints, gaskets, and seals that call for strong, flexible materials.
  • Resistance to Tearing and Abrasion: A lot of TPEs have a strong resistance to tearing and abrasion, which increases the longevity and durability of items.
• Chemical and Environmental Resistance
  • Chemical Stability: TPEs resist a wide range of chemicals, oils, and solvents, making them suitable for harsh chemical environments.
  • Weatherability: These materials demonstrate good resistance to UV light and ozone, preventing degradation over time when exposed to outdoor conditions.
• Comfort and Safety
  • Soft Touch and Hold: TPEs are perfect for consumer products including grips, handles, and sporting goods because they offer a secure hold and a comfortable touch.
  • Biocompatibility: A few TPEs satisfy regulatory requirements and are biocompatible, making them suitable for usage in healthcare items and medical devices.
• Thermal Properties
  • Broad Temperature Range: TPEs function in both high- and low-temperature situations by sustaining performance across a wide temperature range.
  • Low-Temperature Flexibility: TPEs are essential for applications in frigid or cold locations because they maintain their flexibility at low temperatures.
• Economic and Environmental Benefits
  • Cost-Effectiveness: The ease of processing and ability to reuse TPE scrap significantly reduce manufacturing costs compared to traditional rubber materials. The volume cost of TPEs is frequently less than that of traditional rubber compounds since they typically have lower densities.
  • Reduced Waste: Recyclability contributes to lower production waste and supports environmentally-friendly manufacturing practices. the potential to reuse scrap in a similar way as thermoplastics. It is common practice to dispose the scrap from thermoset rubbers. In certain situations, its generated amount might be equivalent to the weight of the molded part. The TPE scrap can be recycled into regrind, which often yields materials with characteristics identical to those of a virgin material.
• Adhesion and Overmolding Capabilities
  • Bonding with Other Materials: TPEs may be overmolded onto stiff thermoplastics to provide a robust bond without the need for adhesives, which is useful when making parts made of many materials.

Disadvantages of Thermoplastic Elastomer

• Limited High-Temperature Performance
  • Thermal Stability: TPEs generally have lower thermal stability compared to thermoset elastomers. They may soften or deform at high temperatures, limiting their use in high-heat applications.
  • Melting at high temperatures: Because of this intrinsic characteristic, TPE components can only be used at temperatures much below their melting points. A rubber that is thermoset would most likely be appropriate for a brief exposure at that temperature. A growing variety of TPE materials that can be employed at temperatures of up to 150 °C have been developed recently.
• Mechanical Strength
  • Lower Mechanical Properties: Compared to some thermoset rubbers, TPEs usually have lower mechanical strength, tensile strength, and resistance to deformation under stress, despite their good elasticity and flexibility.
• Cost of Raw Materials
  • Greater Material Cost: Compared to traditional rubbers, some TPE varieties may require more expensive raw materials, which could raise the end product’s cost overall.
• Chemical Resistance
  • Selective Resistance: While TPEs resist many chemicals, oils, and solvents, they may not be suitable for all chemical environments, particularly those involving aggressive chemicals or prolonged exposure.
• Hygroscopic Nature
  • Moisture Absorption: Due to their hygroscopic nature, certain TPEs can absorb moisture from the surrounding air, which may have an impact on how they process and function. Before processing, proper drying is frequently required.
• Elasticity Over Time
  • Permanent Deformation: When continuously stressed or strained, TPEs may display permanent deformation (compression set), which may have an impact on their long-term performance in specific applications.
• Limited hardness range
  • Shore Hardness: The whole range of hardness that thermoset rubbers can provide may not be covered by TPEs, which could limit their use in applications that call for exceptionally soft or hard materials.
  • Limited supply of TPEs with low hardness. Many TPEs are offered with hardnesses of 80 Durometer A or above. There are now a lot more materials that are softer than 50 Durometer A, and some of them even resemble gel.
  • Most TPE materials must be dried before being processed. This process is frequently employed in the production of thermoplastics overall, although it is seldom ever utilized for traditional rubber products.

Video on Thermoplastic elastomer (TPE)

References

• Geoffrey Holden, Thermoplastic Elastomers. Applied Plastics Engineering Handbook, https://doi.org/10.1016/B978-1-4377-3514-7.10006-6
• https://omnexus.specialchem.com/selection-guide/thermoplastic-elastomer
• https://www.starthermoplastics.com/products/what-is-tpe/
• https://www.bpf.co.uk/plastipedia/polymers/Thermoplastic_Elastomers.aspx
• https://www.kraiburg-tpe.com/en/thermoplastic-elastomers
• https://www.xometry.com/resources/materials/types-of-thermoplastic-elastomers/