If your thermoformed part must handle significant loads, pulls, or stress concentrators (tabs, fasteners, lips, etc.), then tensile strength becomes a key material property to evaluate. This guide compares the relative tensile strength of common thermoforming plastics so you can pick a resin suited for your structural loads instead of over-engineering.
What “Tensile Strength” Means Here
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Tensile Strength refers to the stress a material can withstand under tension before failure (ultimate tensile strength) or yield (tensile yield strength).
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It is not the same as modulus (stiffness). Modulus tells how much it deflects under load, tensile strength tells when it breaks.
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For thermoformed parts, tensile strength matters when parts are under pull, clipped, fastened, or have thin sections under load.
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Always check the actual datasheet for the grade of sheet you’re using — data will vary by thickness, filler, and manufacturing process.
Typical Tensile Strength Ranking (Weakest → Strongest)
Here are representative values for tensile strength of typical sheet/resin grades, ordered from lowest to highest based on the best available published data.
| Material | Relative Tensile Strength | Properties (tensile-strength focused) | Typical Applications |
|---|---|---|---|
| HDPE (High Density Polyethylene) | Low — Example: tensile strength yield ~2,180-4,350 psi (≈21.9 MPa) for some HDPE sheet grades. [K-Mac Plastics+1] | Very tough, good chemical and abrasion resistance, high elongation, but low maximum tensile stress before failure. | Liners, tubs, chemical-equipment parts, wear surfaces where impact and abrasion matter more than high tensile loads. |
| PP (Polypropylene) | Medium-low — Typical values vary, but lower than engineering resins like ABS/PC. (General references show polypropylene ultimate tensile strength around ~12-43 MPa.) Wikipedia | Lighter density, decent strength for many applications but weaker in tensile load compared to engineering thermoplastics. | Guards, parts where weight or chemical resistance is important rather than high structural tensile load. |
| PETG (Polyethylene Terephthalate Glycol-modified) | Medium — Yield stress ~52 MPa (for PETG sheet). S-Polytec+1 | Clear transparent sheet, good strength for many functional thermoformed parts, better tensile capacity than basic polyolefins. | Display cases, guards, transparent parts with moderate structural loads. |
| PVC (Rigid Polyvinyl Chloride) | Medium — Data sheet shows tensile strength at yield ~33.4 MPa and at break ~50.0 MPa for a rigid PVC extrusion. SEKISUI KYDEX | Good rigidity and modest tensile strength; affordable; widely available; moderate impact strength. | Enclosures, signage, architectural panels, where moderate loads and stiffness matter more than high tensile loads. |
| HIPS (High Impact Polystyrene) | Medium-high — Example: tensile strength (ultimate) ~4,000 psi (~27.6 MPa) in one datasheet; another shows yield ~22 MPa. david-shapiro-oes0.squarespace.com+1 | Balanced for cost, formability and moderate strength; decent structural performance for lower-load applications. | Trays, packaging, interior panels, point-of-purchase displays, machine housings. |
| ABS (Acrylonitrile Butadiene Styrene) | Medium-high — Typical data shows tensile strength around ~41-45 MPa for many ABS grades. Wikipedia | Balanced strength + toughness + formability. Good structural performance in thermoformed housings and covers. | Equipment covers, enclosures, luggage shells, trims that carry some load. |
| KYDEX T | Medium-high to high — Tensile strength ~42 MPa (6,100 psi) for KYDEX T sheet. Professional Plastics+1 | One of the stronger thermoforming sheets; good tensile load performance plus fire-rated, chemical resistant sheet. | Aircraft interiors, transit panels, medical device housings, equipment cases. |
| PC (Polycarbonate) | High — Data sheets show PC tensile strength at yield in the ~60-70 MPa range (for example a UK datasheet shows “Tensile Strength at Yield” for PC ≈ 65 MPa). Wikipedia | One of the strongest commodity clear plastics for thermoforming. Excellent for parts that must carry tensile loads and also see impact. | Transparent structural covers, machine guards, aerospace/medical housings, parts needing high load + clarity. |
Material Selection Tips: Tensile Strength Focus
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Define your structural demand
If the part has fasteners, tabs, blind-rivets, or areas under tensile/peel load, pick a resin whose tensile strength comfortably exceeds the load plus margin. -
Use geometry before changing resin
If a 0.050″ sheet feels floppy or is under load, adding ribs or increasing thickness may fix the issue rather than moving to a much more expensive resin. -
Match resin strength band to application
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Low tensile load: HDPE or PP may suffice.
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Moderate load: PVC or ABS offers a solid balance.
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High load or demand for clarity: PC is likely the right choice.
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Don’t ignore temperature, environment and forming
Tensile values drop with elevated temperature, chemicals, UV exposure and at thin gauge after draw thinning. Always validate actual part grade under realistic service conditions. -
Check specific sheet data
The resin family gives a ballpark, but tensile strength will vary by filler, gauge, and manufacturer. Use the real datasheet you are quoting.
Bottom Line
If tensile failure is a show-stopper in your part (not just flexure), then:
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Clarify how much load and what mode (tension, peel, fastener) your design will see.
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Pick a resin that gives headroom in tensile strength (not just modulus).
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Favor geometry reinforcement (ribs, flanges, gauge) before moving to higher cost resins.
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Check prototypes or finite element models for failure at tabs/fasteners; a resin only good for bending may crack under pull.
