Arch Support Shell Materials Compared: How to Choose the Right Material for Insoles

Choosing the right arch support shell material depends on more than stiffness alone. TPU, PP, Nylon, PA11/PA12, carbon composites and EVA each offer different trade-offs in flexibility, weight, thickness, durability and manufacturability.

The key is to match material + shell geometry + thickness + manufacturing process to the intended application, whether the insole is designed for orthotic, sports, work or everyday use.

This guide compares the most common arch support shell materials and explains how to choose the right option based on performance needs, product design and production requirements.

An arch support shell is the structural portion of an insole designed to resist or control deformation around the medial arch, heel and midfoot.

Depending on the product, it may contribute to:

• Medial arch support
• Heel and midfoot stability
• Torsional control
• Motion control
• Pressure distribution
• Shape retention
• Overall insole stiffness.

The shell may cover only the arch and heel or extend further toward the forefoot depending on the design objective.

It is important to distinguish the structural shell from the cushioning system.

A PU foam, EVA foam, PORON®, gel pad or other cushioning component primarily manages comfort, pressure or impact. A structural shell typically provides greater resistance to deformation and helps maintain the intended geometry of the insole.

That distinction is not absolute. EVA, for example, can be shaped into supportive structures and variable-stiffness arch constructions. Research has evaluated custom arch supports using EVA at different Shore A hardness levels.

However, EVA produces support differently from a thin PP, Nylon or carbon-composite shell. The distinction is also visible in manufacturing practice. Datong & Bangni current material system separates structural arch-shell materials such as TPU, Nylon, carbon fiber and PP - based materials from cushioning components such as gel, silicone, PORON® and shock-absorbing foams. This is why selecting a shell should begin with the intended mechanical function not simply the material name.

There is no single material suitable for every arch-support product. A systematic review of clinical trials involving custom-made foot orthoses found polypropylene shells in four studies, EVA in two, and other constructions including carbon-graphite composites. Today, digital manufacturing has expanded the options further to TPU, PA11, PA12 and reinforced polymers.

TPU is useful when a shell requires a combination of controlled flexibility, resilience and structural support.

Compared with highly rigid materials, TPU can allow more deformation during movement, making it useful for products where the design needs to support the arch without creating an excessively rigid platform.

Common manufacturing routes include injection molding and, depending on the grade, additive manufacturing.

Typical considerations include:

• Hardness
• All thickness
• Arch geometry
• Rib design
• Material grade
• Molding conditions.

TPU can therefore work particularly well for sports or everyday support designs where dynamic flexibility is part of the product objective.

Polypropylene is one of the most established thermoplastics in orthotic fabrication.

Its combination of relatively low weight, structural rigidity, durability and formability has made it common in semi-rigid and rigid orthoses.

Its long history does not mean all PP shells perform the same way. Research into polypropylene orthoses has shown that fabrication practices, material grade and thickness can influence the mechanical characteristics of the final device.

PP is therefore a practical option when the design needs:

• Predictable structural support
• Moderate weight
• Established processing methods
• Cost control
• Semi-rigid to rigid construction.

Nylon can offer a useful balance of strength, toughness and controlled flexibility.

For injection-molded support structures, it can provide more structural resistance than softer TPU constructions while maintaining greater toughness than highly rigid composite solutions.

PA6 and PA66 should not be treated as one universal material specification. Performance varies with polymer grade, moisture condition, wall thickness and reinforcement.

This makes Nylon particularly relevant to:

• Performance sports insoles
• Midfoot support structures
• Thin structural shells
• Products exposed to repeated flexing.

Adding glass fiber to Nylon can substantially increase structural stiffness and make thinner, more rigid components possible.

For example, BASF lists an injection-molding PA6 grade reinforced with glass fiber at a tensile modulus of 9,640 MPa in the dry condition. This is a grade-specific example rather than a universal value for all GF-Nylon, but it demonstrates the level of structural reinforcement possible through fiber modification.

The trade-off is that increasing reinforcement can reduce flexibility and alter impact behavior, flow, shrinkage and mold design requirements.

GF-Nylon is therefore particularly interesting when a product needs:
higher stiffness than conventional Nylon without immediately moving to a carbon-fiber composite.

PA11 and PA12 have become increasingly relevant as digital orthotic manufacturing expands.

Both are widely used in powder-bed additive manufacturing such as SLS or MJF.

PA11 tends to be valued where ductility and impact resistance are important. EOS describes its PA11 materials as durable and particularly suited to parts requiring high material strength or impact resistance.

PA12 is one of the most established additive-manufacturing polymers and is valued for dimensional stability, durability, chemical resistance and versatility.

Their ability to be digitally manufactured also enables designers to change:

• Shell thickness
• Lattice structures
• Reinforcement zones
• Arch geometry
• Local flexibility

Without relying on conventional tooling for every individual geometry.

Carbon-fiber composites are attractive when the design requires high stiffness at a low profile.

They are particularly relevant when:

• Shoe space is limited
• Ưeight must be minimized
• High structural rigidity is required
• Torsional control is a major performance target.

However, “carbon fiber” does not describe one fixed stiffness.

Performance depends on factors including:

• Fiber type
• Fiber orientation
• Number of layers
• Resin system
• Layup
• Shell geometry
• Thickness.

Research on commercial carbon-composite orthotic devices demonstrates this variation clearly. Thirteen carbon-composite AFOs tested under the same methodology showed sagittal stiffness ranging from 0.58 to 3.66 N·m/degree, despite all belonging to the broader carbon-composite category. These were ankle-foot orthoses rather than insole shells, but the finding reinforces an important principle: a material label alone does not define the stiffness of the finished structure.

EVA is more commonly associated with the cushioning or body layer of an insole, but it can also provide supportive geometry depending on its hardness, density and thickness.

Compared with thin rigid shells, EVA generally requires more material volume to generate structural resistance.

This can be useful for:

• Comfort-focused products
• Full-foot contoured insoles
• Variable-density constructions
• Products where cushioning and moderate support need to be integrated.

Research has used EVA in both custom arch supports and orthotic constructions, confirming that it should not simply be classified as “cushioning only.”

The table below summarizes typical material tendencies, not fixed engineering values. Actual performance varies by grade, formulation, reinforcement, geometry, thickness and manufacturing method.

A running product and a rigid clinical orthotic may both require medial arch support, but they should not automatically use the same shell.

Material selection becomes much easier once the product application is defined.

The following combinations should be treated as starting points for development, not universal prescriptions.

Sports insoles need enough structure to improve stability without overly restricting foot movement. The preferred material depends on the sport, footwear volume and required stiffness.

• Running Insoles: Nylon / TPU
• Football Insoles: Nylon / GF-Nylon / Carbon Fiber
• Cycling Insoles: GF-Nylon / Carbon Fiber
• Court Sport Insoles: Nylon / TPU / GF-Nylon

TPU and Nylon are useful where controlled flexibility is important, while GF-Nylon and Carbon Fiber are better suited to applications requiring greater stiffness, torsional control or a thinner structural profile.

Work and outdoor insoles generally prioritize long-term stability, durability and structural support under repeated loading.

• Hiking Insoles: Nylon / GF-Nylon / PP
• Work Insoles: PP / Nylon / GF-Nylon
• Comfort / Everyday Insoles: EVA / TPU

PP, Nylon and GF-Nylon are practical when stronger structural control is required, while EVA and TPU are better suited to products that need a softer balance between support and everyday comfort.

Orthotic insoles require more precise material selection because support needs can vary from controlled flexibility to highly rigid correction.

• Orthotic Insoles: PP / PA11 / PA12 / Carbon Composite

PP is a practical choice for semi-rigid support, PA11 and PA12 are well suited to digitally customized shell geometries, and Carbon Composite is better for thin, high-stiffness structures when stronger control is required.

Material selection should ultimately follow the intended clinical function, required support level and shell geometry rather than stiffness alone.

Material selection is only part of arch support design. The final performance of a shell also depends heavily on its thickness, geometry, coverage and structural reinforcement.

Material Properties + Thickness + Geometry + Reinforcement = Final Shell Performance

Even shells made from the same material can behave very differently. In a published PA11 foot orthosis study, increasing shell thickness from 2.6 mm to 3.0 mm increased medial arch stiffness from 10.90 to 15.39 N/mm. More importantly, structural changes—including forefoot-rearfoot posts and a 6° medial wedge—produced a much greater increase in overall stiffness.

For insole development, this means that simply choosing a “stiffer” material is not always the best solution. Engineers can adjust shell thickness, arch geometry, trim lines, coverage and reinforcement ribs to achieve the required support while balancing weight, flexibility and shoe space

For buyers and brands, the key takeaway is: Don’t specify the material alone—specify the performance you need.

Choosing the right arch support shell material should start with the application and required support level, not with the material itself. An orthotic, running, football, cycling, hiking, work or everyday insole will place different demands on stiffness, flexibility, durability and weight. Product teams should first define whether the shell needs to be flexible, semi-rigid or rigid, while avoiding the assumption that a stiffer shell automatically provides better support.

Footwear space is another important constraint. A shell may perform well mechanically but still create problems if it raises the heel, reduces internal shoe volume or creates excessive pressure around the arch. Low-profile applications may therefore require a thinner, higher-stiffness material, while products with more available space may use thicker polymer structures to achieve the required support.

Weight, production volume and cost should also be evaluated together. Sports products may prioritize low mass, while work or orthotic applications may accept additional weight for greater durability or control. Custom or small-batch orthotic programs may favor digitally manufactured PA11 or PA12, while higher-volume products can justify injection molding with TPU, Nylon or GF-Nylon. Carbon composites may be appropriate when a thin, lightweight and highly rigid shell is required, although they usually involve higher material and processing costs.

The commercial decision should therefore consider more than raw-material price. Tooling, cycle time, scrap, assembly, testing, expected production volume and redesign risk all contribute to the true cost of the shell.

Before mass production, brands should also define measurable acceptance criteria such as hardness, thickness, dimensional tolerance, shell weight, bending or flex behavior, fatigue performance, bonding and finished-insole fit. This helps ensure that the approved prototype can be reproduced consistently at scale.

The right shell is ultimately a combination of material, geometry, stiffness, thickness and manufacturing process. At Datong & Bangni, we support arch support shell development from material selection and 2D/3D design to prototyping, injection molding, 3D printing, testing and mass production.

Need help choosing the right shell material for your insole project? Our engineering team can evaluate the most suitable combination of support, thickness, manufacturability and cost based on your target application.