Email: keenhu@lztooling.com | Whatsapp/Wechat/Phone: +86 134 1694 6882
Email: keenhu@lztooling.com | Whatsapp/Wechat/Phone: +86 134 1694 6882
Custom TPE injection molding with LTC Plastic, with design and engineering support, DFM, OEM, ODM, mold making, post-finishing, and shipment support.
Thermoplastic elastomers (TPEs) have become a key material in modern manufacturing, offering the elasticity of rubber with the easy processing of a thermoplastic. Their flexibility, durability, and soft-touch feel make them ideal for automotive components, consumer products, medical devices, electronics, and countless industrial applications.
Among the available production methods, TPE injection molding—also known as thermoplastic elastomer injection molding—is the most efficient and scalable way to create consistent, high-quality elastomeric parts.
Using an injection molding process, TPE material is heated, plasticized, and injected into a mold using a standard molding machine, allowing manufacturers to produce soft, ergonomic, and complex geometries with excellent repeatability. The TPE molding process is highly adaptable, enabling precise control over part hardness, surface feel, and performance.
This guide provides a clear overview of TPE injection molding, covering material fundamentals, tooling requirements, injection parameters, design considerations, benefits, and common challenges. Whether you work in engineering, procurement, or product development, it will help you understand how to optimise TPE injection molding for reliable, cost-effective production of high-performance plastic components.
TPE injection molding is a manufacturing method where molten thermoplastic elastomer (TPE) material is injected into a mold cavity under controlled pressure to create a finished molded part. As a polymer, TPE combines the elasticity of rubber with the processing ease of a thermoplastic, allowing it to be shaped using standard plastic injection equipment.
Unlike traditional rubber, TPEs—including popular grades such as TPU—melt and re-melt without requiring vulcanisation, making the process far more efficient.
Because TPE material flows smoothly when heated and solidifies quickly when cooled, manufacturers gain shorter cycle times, lower production costs, and improved consistency. These advantages make TPE injection molding especially valuable in industries where performance and efficiency matter—such as automotive, consumer goods, medical components, electronics, and industrial products.
With excellent durability, flexibility, and soft-touch characteristics, TPEs continue to expand their role in modern product design and high-volume manufacturing.
To fully understand plastic injection molding for elastomeric components, it’s essential to know how TPE material properties influence processing.
Thermoplastic elastomers (TPEs) are versatile polymers that combine rubber-like flexibility with the reprocessability of thermoplastics. Their Shore hardness TPE range and various TPE durometer levels make them suitable for soft-touch, elastic, and durable injection molded parts. Because TPEs melt and flow like plastic, they can be shaped using standard injection molding machines, providing excellent efficiency and recyclability.
Each TPE category behaves differently in a plastic mold, influencing key factors such as TPE melt temperature, TPE melt flow index, and TPE molding shrinkage rate.
SBS/SEBS (Styrenic Block Copolymers)
Soft-touch feel
Great clarity options
Used in consumer grips, wearable items
Easy flow and forgiving TPE injection molding parameters
TPO (Thermoplastic Polyolefins)
Good weather resistance
Ideal for automotive exterior parts
Requires a higher mold temperature for a proper surface finish
TPV (Thermoplastic Vulcanizates)
High elasticity and chemical resistance
Often replaces EPDM rubber
Moderate shrinkage and stable processing
TPU (Thermoplastic Polyurethane)
Excellent abrasion resistance
Strong and flexible
Sensitive to moisture; requires strict drying before molding
COPE (Copolyester Elastomers)
High resilience and heat resistance
Used for engineering components and moving parts
COC/Other Specialty TPEs
Excellent chemical resistance
Common in automotive, medical, and industrial applications
Understanding the differences between these TPE materials helps engineers optimise mold design, improve surface quality, and ensure consistent production during plastic injection molding.
Thermoplastic elastomers (TPEs) possess a unique combination of elasticity, durability, and processability that makes them highly suitable for TPE injection molding. Their rubber-like flexibility with a wide range of hardness (0 Shore A to 60 Shore D) allows the production of soft-touch TPE grips, ergonomic handles, cushioning components, and TPE sealing gaskets for industrial or consumer applications.
Fast Processing Cycles
Unlike traditional rubber, TPEs do not require curing, resulting in shorter cycle times. Optimized injection speed ensures consistent quality for thin-walled parts, complex geometries, or TPE waterproof components. These traits are crucial for high-volume applications, including automotive TPE parts, TPE for consumer products, medical-grade TPE molding, and food-grade TPE injection molding.
Excellent Moldability and Bonding
TPEs flow well into molds and can be co-molded with other plastics such as PP, ABS, PC, or Nylon, enabling TPE overmolding applications and co-injection TPE techniques. This capability allows the creation of soft-touch surfaces on rigid substrates or multi-material assemblies.
Chemical, Weather, and Heat Resistance
TPE grades vary in UV stability, chemical and oil resistance, and temperature tolerance, supporting uses in medical devices, electronics, or outdoor automotive components. Comparison with thermoplastic polyurethane (TPU) and other elastomers like TPR highlights differences in durability, flexibility, and abrasion resistance. Reinforced TPE compounds further enhance strength for demanding applications like TPE for footwear soles.
Overall, TPE’s combination of process efficiency, flexibility, and functional performance makes it a versatile choice across consumer, industrial, and medical applications.
The TPE injection molding process follows the principles of standard plastic injection molding but requires adjustments to accommodate the elastic and soft nature of TPE parts. Careful attention to TPE mold design, gating for TPE, and venting for TPE molds ensures consistent quality and minimal defects.
Step 1: Material Preparation
Most types of TPE do not require extensive drying, except for TPU or specialty grades. When necessary, drying at 80–100°C for 2–3 hours removes moisture that can cause bubbles, splay marks, or compromised mechanical properties. Proper preparation is critical, particularly for overmolding TPE onto plastic or two-shot molding TPE processes.
Step 2: Melting and Plasticising
TPE pellets are fed into the barrel and gradually melted. The melting point depends on the type of TPE, typically between 170–240°C. Controlled heating prevents degradation and preserves elasticity, ensuring excellent TPE adhesion and bonding in multi-material applications.
Step 3: Injection
Molten TPE is injected into the mold cavity under moderate injection pressure (30–80 MPa). Use of hot runner TPE systems or cold runner TPE tooling allows precise flow control. TPE color matching and surface finish considerations—matte vs glossy TPE finish—are incorporated during this step to meet design requirements.
Step 4: Cooling
TPE solidifies faster than rigid plastics. Cooling times range from 5–30 seconds, depending on part thickness and mold configuration. Controlled cooling maintains shape and surface integrity for functional or cosmetic plastic parts.
Step 5: Ejection
Due to the elasticity of TPE, parts may stick or deform. Proper draft angles, textured mold surfaces, or air-assisted ejection help prevent defects. Attention to TPE surface finish options ensures high-quality final products suitable for applications ranging from soft-touch grips to liquid silicone or liquid silicone rubber overmolds.
This process ensures the parts are durable, visually appealing, and meet precise specifications for a wide range of industries.
Below is a recommended processing window:
| Parameter | Recommended Range |
|---|---|
| Drying temperature (if required) | 80–100°C |
| Drying time | 2–3 hours |
| Melt temperature | 170–240°C |
| Mold temperature | 20–60°C |
| Injection pressure | 30–80 MPa |
| Holding pressure | 30–60% of injection pressure |
| Back pressure | 2–8 MPa |
| Screw speed | 20–60 rpm |
| Cooling time | 5–30 seconds |
| Cycle time | 10–45 seconds |
These values vary based on:
TPE type
Hardness
Part thickness
Mold design
TPEs require specialized mold design due to their softness, flexibility, and unique mechanical properties. Proper tooling ensures consistent quality for injection molding services producing consumer goods, automotive components, or industrial parts.
Steel Selection
Although less demanding than thermoplastic vulcanizates or rigid plastics, durable mold steel is recommended:
P20 for general molds
H13 or S136 for high-volume or complex molds
Good steel selection supports long-term recyclability and maintains heat resistance under repeated cycles.
Gate Design
Since TPE flows easily when molten, common gate types include: fan, tab, pin, and submarine gates. Proper sizing reduces shrinkage, flow lines, and weld lines, ensuring high-quality molded products.
Venting
TPE’s viscosity requires efficient venting to prevent trapped air. Recommended vent depth: 0.01–0.03 mm. Venting supports TPE cooling and solidification and avoids surface blemishes.
Draft Angles
Soft thermoplastic rubbers can stick in molds; increasing draft angles to 1–5° and adding textures improves part release. Mold release agents for TPE can further enhance ejection.
Undercuts and Part Geometry
TPE tolerates undercuts better than rigid plastics, enabling snap-fit and flexible designs. Careful screw design for TPE processing optimizes flow into complex features.
Cooling System Design
Efficient cooling is critical for TPE cycle time optimization and part consistency. Proper channel layout reduces cycle times, preserves abrasion resistance, and maintains compatibility with other rubber and plastic materials in multi-component assemblies.
These considerations ensure TPE parts meet performance, aesthetic, and functional requirements across diverse applications.
A major advantage of molding thermoplastic elastomers is their compatibility with overmolding. TPE can be molded directly onto plastics such as PP, ABS, PC, or special PA grades, enabling the creation of ergonomic, soft-touch, and functional components.
Benefits of Overmolding TPE
Overmolding improves comfort, provides a rubber-like grip, enhances surface finish, and adds shock absorption or sealing functionality. It also reduces assembly costs by integrating multiple materials in a single process.
Examples include toothbrush handles, automotive knobs, power tool grips, and medical grips or seals. Selecting the right TPE processing window—including low-temperature TPE grades, high-temperature TPE grades, or UV-stable TPE formulations—ensures consistent flow, proper viscosity, and optimal adhesion to the substrate.
Two-Shot Injection Molding
This process involves first injecting a rigid substrate, then overmolding TPE in the same machine. Flame-retardant TPE molding can also be incorporated for safety-critical parts. Two-shot molding improves bonding strength, reduces cycle times, and supports sustainable production through TPE recycling and sustainability initiatives.
Monitoring molding conditions carefully helps avoid defects, and knowledge of troubleshooting TPE molding defects ensures high-quality outcomes. These techniques allow manufacturers to produce multifunctional parts with superior aesthetics, performance, and efficiency across a range of specific applications.
TPE injection molding offers multiple benefits over traditional thermoset rubber molding and other plastics, making it ideal for modern manufacturing of precision TPE components.
Faster Production
Unlike rubber, which requires long curing or compression cycles, TPE can be processed rapidly in standard injection machines. This reduces cycle times and improves efficiency for high-volume production.
Lower Cost
Shorter cycles, lower energy consumption, and reduced labor make TPE molding cost-effective. Additionally, mold scrap can be recycled, supporting sustainable manufacturing practices.
Greater Design Flexibility
TPE’s softness and flow characteristics allow thin walls, non-linear shapes, tactile and ergonomic TPE parts, soft-touch textures, and other complex geometries that are difficult to achieve with rigid plastics or thermosets.
Consistent Quality
Injection molding ensures tight TPE molded part tolerances across the cavity, enabling uniformity and high repeatability, critical for functional and aesthetic components.
Environmental Advantages
TPEs are recyclable, produce low VOC emissions, and support eco-friendly processing.
Strong Adhesion to Plastics and Overmolding
TPE is ideal for overmolding onto plastics, providing excellent bonding while maintaining hardness, chemical resistance, and high temperature performance where needed.
These advantages make TPE injection molding a preferred method for creating durable, ergonomic, and high-quality elastomeric components across automotive, medical, consumer, and industrial applications.
A comparison of common elastomeric materials helps select the right option for your production process, including insert molding with TPE or other multi-material applications. Key considerations include temperature resistance, chemical stability, and processing requirements.
| Material | Elasticity | Cost | Heat Resistance | Chemical Resistance | Processing / Notes |
|---|---|---|---|---|---|
| TPE | High | Low | Medium | Medium | Easy injection molding, supports valve gate vs edge gate for TPE, TPE mold flow analysis, and fast cycles. Suitable for quality control for TPE parts and efficient TPE post-processing and finishing. |
| TPU | High | Medium | Medium | High | Requires drying; sensitive to moisture; precise holding pressure needed for injection. |
| Silicone (LSR) | Very High | High | Very High | Very High | Slow, requires curing; often used for high-performance seals or medical applications; blow molding possible for certain shapes. |
| Rubber (EPDM, NBR) | High | Low | Medium | High | Slow vulcanisation; limited recyclability; suitable for heavy-duty sealing and vibration-damping parts. |
When to choose TPE:
Soft-touch surfaces and ergonomic grips
Fast production cycles
Recyclable and cost-effective material
Applications requiring consistent quality control
When not to choose TPE:
Very high-temperature environments
Aggressive chemical exposure
TPE’s versatility, ease of processing, and compatibility with insert molding make it ideal for a wide range of industrial, automotive, and consumer applications.
Achieving high-quality TPE plastic parts depends on understanding specific TPE material properties and selecting the right material for the application.
1. Choose the Right TPE Type
Select TPE based on hardness, chemical resistance, temperature range, and bonding requirements. Use raw material specifications and TPE pellets with suitable properties of rubber or thermoset elastomers for optimal performance.
2. Ensure Material Compatibility in Overmolding
When using thermoplastic for overmolding TPE, check manufacturer compatibility charts to avoid delamination.
3. Avoid Sharp Corners
Minimize stress concentrations to reduce cracking or warpage in flexible parts.
4. Maintain Uniform Wall Thickness
Even wall thickness helps maintain the quality of TPE, prevents deformation, and ensures consistent injection pressure for TPE.
5. Control Cooling
Soft TPE plastic parts can deform if cooled too rapidly. Balanced cooling supports dimensional stability for transparent TPE molding or flexible TPE tubing molding.
6. Use Textured Surfaces
Texturing improves surface finish, enhances aesthetics, and simplifies demolding.
7. Increase Draft Angles
Larger draft angles help high-pressure parts release cleanly from molds.
8. Minimise Shear and Avoid High Temperatures
Excessive shear or heat can degrade the material, impacting product design, production efficiency, and overall TPE viscosity control.
Following these tips ensures reliable, consistent, and high-performance TPE molded parts for automotive, consumer, medical, and industrial applications.
TPE injection molding has emerged as a key technology for producing high-performance, thermoplastic and elastomeric components across various applications. Compared with traditional rubber, it offers faster processing methods, shorter cooling process times, and greater design flexibility, making it ideal for plastic products in consumer, automotive, medical, and industrial sectors.
Careful material choice—including biocompatible TPE materials—combined with optimized mold manufacturing, mold release, and tooling ensures high-quality TPE parts with consistent dimensional accuracy and durability. Attention to the TPE supply chain and sourcing guarantees reliable raw materials for production, while design tips for TPE injection molded parts help maximize functionality, ergonomics, and aesthetic appeal.
By integrating injection molding and extrusion techniques, manufacturers can achieve superior adhesion, complex geometries, and scalable production. TPE injection molding enables the creation of soft-touch grips, seals, gaskets, wearable devices, electronic components, and industrial parts with consistent performance.
Overall, TPE injection molding provides a versatile, efficient, and sustainable solution, combining cost-effectiveness, repeatable quality, and adaptability for various applications across modern manufacturing.
