Top 3 High‑Strength Materials for Plastic Fasteners

Top 3 High‑Strength Plastics

Plastic fasteners are prized for their chemical and acid resistance, non‑conductivity, and ability to withstand water exposure. Although traditionally viewed as less robust than metals, several advanced polymers now deliver strength on par with—or exceeding—metal while preserving the classic advantages of plastic.

Despite this perception, certain polymer blends combine the best of both worlds: superior mechanical strength, flame resistance, and negligible water absorption.

Need a fastener that offers both exceptional strength and corrosion resistance?

1. FR‑4 / G10

FR‑4 is a composite of woven fiberglass cloth and epoxy resin, delivering an outstanding strength‑to‑weight ratio. With a tensile strength of 45,000 psi (310 MPa), FR‑4 fasteners compare favorably to brass and aluminum. Aluminum (Grade 6463‑T6) reaches 35,000 psi (241 MPa), while free‑machining brass (Grade C3600) achieves 50,000 psi (345 MPa).

FR‑4 fasteners are flame‑retardant, achieving a UL 94 V‑0 rating thanks to bromine‑based epoxy resin. They also exhibit near‑zero water absorption, maintaining mechanical and electrical properties in both dry and humid environments. FR‑4 is available as sheets, plates, and rods—not in injection‑molded grades.

Common applications include printed circuit board (PCB) substrates, bushings, washers, screws, bolts, nuts, switches, standoffs, threaded rods, and transformers.

2. Polyarylamide (PARA)

PARA’s semi‑aromatic base resin resists water absorption more effectively than typical polyamides. When reinforced with 50 % glass fiber, PARA fasteners achieve high rigidity, excellent surface finish, minimal creep, and outstanding dimensional stability. This composition also resists automotive chemicals.

With an ultimate tensile strength of 34,000 psi (230 MPa), 50 % glass‑filled PARA fasteners are frequently used to replace metal components. Available in a wide range of colors, PARA is common in cell‑phone covers, automotive parts, aircraft fittings, furniture, power tools, camera housings, bushings, gears, handles, hinges, and knobs. The 50 % glass‑filled grade is marketed under the brand name IXEF®.

3. Thermoplastic Polyurethane (TPU)

TPU is an impact‑modified amorphous polymer that combines the chemical resistance of crystalline resins with a low shrinkage rate, resulting in minimal creep. A 40 % glass‑filled TPU fastener weighs significantly less than its metal counterparts while delivering an ultimate tensile strength of 27,000 psi (186 MPa)—comparable to aluminum.

TPU’s strength, moisture resistance, chemical durability, low creep, and UV resistance make it ideal for internal scaffolding, beam clamps, pipe hangers, post bases, bolts, hex nuts, pipe clamps, clevis hangers, channel nuts, U‑bolts, and more. This grade is sold under the brand name Isoplast®.

Ultimate Tensile Strength

*Creep is the tendency of a solid material to deform permanently under sustained stress.

**Impact‑modified polymer refers to a material whose toughness has been enhanced by incorporating rubbery microdomains.

***Amorphous polymer has a non‑repeating molecular structure.

Looking for more material property information? Check out our full Guide to High‑Strength Engineering Plastics!