How to Choose the Right Engineering Resin for Your Application: Strength, Cost, & Processability

There’s no single “best” plastic—but there is a best one for your part

As a quality compliance manager at Toray, I review material specifications for hundreds of industrial projects every year. If you’re reading this, you’re probably trying to nail down one specific number, or compare two materials you’re not sure about. You might be asking:

• “What’s the tensile strength of Toray T300 carbon fiber?” (It’s 3,530 MPa, by the way—that’s a standard spec we certify per batch.)
• “What’s the tensile strength of TPU?”
• “Is epoxy resin thermoplastic or thermosetting?”
• “Can I get plastic balls made from a resin that won’t crack under load?”

The honest answer is: it depends on your application. There’s no universal winner across all categories. What works for a durable automotive bracket won’t work for a transparent, flexible tube. What works for a high-temperature electrical component won’t work for a low-cost disposable part.

Instead of giving you one generic recommendation, I’ll walk through three common industrial scenarios. Each has different requirements for strength, flexibility, and processing method. You’ll find your scenario, and I’ll tell you exactly which Toray resin or compound fits best—and why.

Scenario A: High strength & stiffness for load-bearing parts

If your part needs to hold a load without deforming, you care about tensile strength and modulus. This is typical for structural brackets, frames, housings, or components that replace metal.

What to look for

You want a material with high tensile strength (above 60 MPa for unfilled plastics) and a high flexural modulus (above 2.5 GPa). The material should resist creep over time. Processing method usually involves injection molding or compression molding for short-fiber reinforced compounds.

Best options from Toray

• Toray T300 Carbon Fiber (for composites): Tensile strength of 3,530 MPa and modulus of 230 GPa. This is a standard, reliable high-performance fiber. It’s not the absolute top of our line, but it’s the workhorse for industrial applications where you need predictable, certifiable performance. We supply it both as continuous fiber for prepreg and as chopped fiber for injection moldable compounds.
• Toray PC (Polycarbonate) compounds: Standard polycarbonate offers tensile strength around 65-70 MPa with excellent impact resistance. Our glass-filled PC compounds (like Toray PC-GF20) push tensile strength to 90+ MPa. If your part needs both stiffness and toughness, this is a strong contender.
• Toray PA (Nylon) 6/6 compounds: Unfilled PA66 has tensile strength around 75 MPa. With 30% glass fill, it reaches 160+ MPa. Nylon has excellent fatigue resistance, making it ideal for parts that see repeated load cycles (brackets, gears, clips).

What to avoid

Don’t choose TPU for this scenario. TPU (thermoplastic polyurethane) has tensile strength typically between 25-50 MPa depending on hardness. It’s an elastomer—it stretches. If you need stiffness, TPU is not the answer, even though it’s incredibly tough and abrasion-resistant (which we’ll cover in Scenario B).

Also avoid unfilled polypropylene for load-bearing parts. PP has a low modulus (around 1.0-1.5 GPa) and creeps under sustained load. We do offer glass-reinforced PP (Toray PP-GF30), which boosts modulus to 4-5 GPa, but it still can’t match PA or PC in strength-to-weight ratio.

Scenario B: Flexibility & toughness for dynamic, high-wear parts

If your part bends, flexes, or experiences repeated impact, you need a material with high elongation at break and good tear strength. This is common for hoses, seals, bumpers, gaskets, and some consumer goods.

What to look for

You want high elongation at break (200-500%), good tear resistance, and excellent abrasion resistance. Processing method is typically extrusion or injection molding, often at lower melt temperatures.

Best options from Toray

• Toray TPU (Thermoplastic Polyurethane): This is the star player for flexibility. Depending on the hardness grade (Shore A 70 to Shore D 60), tensile strength ranges from 30 to 50 MPa, but elongation at break can exceed 400%. It has outstanding abrasion resistance (Taber abrasion loss typically < 50 mg). Toray supplies TPU in both polyether and polyester grades—polyether for hydrolysis resistance, polyester for higher mechanical strength.
• Toray TPO (Thermoplastic Olefin) compounds: If you need a softer feel with moderate impact resistance, our TPOs offer a balance of flexibility and moldability at lower cost than TPU. They’re common for automotive interior skins and exterior trim.

What to avoid

Don’t choose rigid engineering resins like PC or PA for highly flexible parts. They will crack or fatigue under repeated bending. I’ve seen engineers try to use a glass-filled nylon for a clip that needed to snap repeatedly. It worked for about 100 cycles, then failed. The material was simply too stiff (modulus 8 GPa) for the application.

A note on ‘plastic balls’

If you’re sourcing plastic balls (for ball valves, check valves, or other rolling elements), the material choice depends on the fluid and pressure. For most industrial ball valves, we recommend Toray PTFE (Polytetrafluoroethylene) or Toray POM (Polyoxymethylene, Acetal). PTFE offers chemical inertness and low friction, while POM gives better dimensional stability and creep resistance. For high-pressure applications, consider glass-reinforced POM.

Scenario C: Heat resistance, chemical resistance, or thin-wall flow

If your part lives in a hot environment, contacts aggressive chemicals, or needs to fill a very thin mold (like a connector housing), you need a material with specific thermal or chemical properties.

What to look for

- Heat: Look at continuous use temperature (UL RTI) and heat deflection temperature (HDT).
- Chemical resistance: Check against specific fluids.
- Flow: Melt flow rate (MFR) indicates how easily the material fills a thin cavity.

Best options from Toray

• Toray PPS (Polyphenylene Sulfide): Continuous use temperature up to 220°C. Excellent chemical resistance (no known solvent below 200°C). High flow grades available for thin-wall molding. This is the go-to for automotive under-hood components, electrical connectors, and pump parts.
• Toray LCP (Liquid Crystal Polymer): Extremely high flow—can fill walls as thin as 0.3mm. HDT > 260°C. Often used for miniaturized electronic components.
• Toray ABS (Acrylonitrile Butadiene Styrene): For moderate heat (HDT around 90-100°C) and good chemical resistance to dilute acids and alkalis. Excellent for plating or painting. Toray ABS is widely used in automotive interiors and consumer appliances.

The epoxy resin question (thermosetting vs. thermoplastic)

Epoxy resin is a thermosetting polymer—not a thermoplastic. Once cured, it cannot be remelted. This is a critical distinction for processing. We don’t supply epoxy resin as a stand-alone product, but we do supply Toray carbon fiber prepregs that use epoxy matrices. If you’re asking about this, you’re probably looking at composite processing (autoclave, compression molding, or prepreg layup), not injection molding.

How to determine which scenario fits your project

Here’s a quick self-check. Ask yourself these three questions:

1. Does the part need to hold a load or resist bending?
   If yes → Scenario A (look at PC, PA, or carbon fiber reinforced compounds).
   If no → go to question 2.
2. Does the part flex or get hit repeatedly?
   If yes → Scenario B (look at TPU or TPO).
   If no → go to question 3.
3. Does the part face high heat, chemicals, or need thin walls?
   If yes → Scenario C (look at PPS, LCP, or ABS).
   If none of these apply, you likely have a low-cost, low-performance requirement where commodity resins (like general-purpose PP or PE) from Toray’s standard portfolio might suffice.

I see a lot of engineers trying to force one material to do everything—like using a high-grade nylon for a part that needs to be flexible, or using TPU for a part that needs rigidity. That’s a mistake that costs time and tooling money. If you’re unsure, request a sample from our technical sales team. We’ll help you test a small lot (even a few kilograms) to confirm the fit before you commit to a full production run.

(This advice reflects standard material properties as of early 2025. Material grades and specifications may vary by region—always verify with your local Toray representative.)