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Injection Molding Materials & Resins

The resin sets how a part performs, what it costs, how it molds, and how the tool wears. These guides cover the common injection-molding materials from a buyer's standpoint—what each is good at, where it falls short, and what to know before specifying it.

A practical rule runs through all of them: use the lowest material tier that meets your requirements with margin. Over-specifying resin is a quiet, common source of cost.

The three material tiers
  • Commodity — PP, ABS, PS, PE — lowest cost, high-volume parts
  • Engineering — PC, nylon, acetal, PBT, TPU/TPE — strength, heat, wear, or flexibility
  • High-performance — PEEK, PSU, PPS, PEI — extreme heat, chemical, or regulated use
  • Fillers (e.g. glass fiber) boost strength but change shrinkage and tool wear

Material Guides

Anyone narrowing down a resin before RFQ Plastic Material Selection (Overview) The framework: commodity vs engineering vs high-performance tiers, fillers, the trade-offs that drive cost and moldability, and how to specify material in an RFQ. Read the guide → Cosmetic enclosures and consumer parts ABS Tough, good-finishing, economical all-rounder for cosmetic housings—plus its heat and weathering limits. Read the guide → Impact-, clarity-, or heat-critical parts Polycarbonate (PC) Impact strength, clarity, and heat resistance for demanding parts—with scratch and chemical caveats. Read the guide → Cost-driven, chemical-exposed, or hinged parts Polypropylene (PP) Low-cost, chemically resistant, and uniquely good at living hinges—plan around its warpage. Read the guide → Gears, bearings, structural functional parts Nylon (PA) Strong, wear- and heat-resistant engineering resin, often glass-filled—mind moisture and warpage. Read the guide → Precision gears and moving mechanisms POM / Acetal (Delrin) Precision, low-friction, dimensionally stable resin for gears and mechanisms—watch sink in thick sections. Read the guide → Aerospace, medical, oil & gas, semiconductor PEEK & High-Performance Extreme heat, chemical, and wear resistance for the harshest environments—at the highest cost and processing demands. Read the guide → Flexible, wear-exposed, overmolded parts TPU Flexible, abrasion- and impact-resistant thermoplastic polyurethane—polyester vs polyether matters. Read the guide → Soft-touch overmolds, seals, gaskets TPE Soft-touch, rubber-like elastomers for grips and seals—bonding compatibility is the key decision. Read the guide → Electrical connectors and stable parts PBT Dimensionally stable, electrically strong polyester—the quiet default for connectors and electrical parts. Read the guide → Outdoor cosmetic parts and trim ASA The weatherable alternative to ABS—holds color and gloss outdoors without painting, with similar toughness and finish. Read the guide → Lenses, light guides, clear covers PMMA / Acrylic The optical-clarity benchmark—clearer, harder-surfaced, and more UV-stable than PC, but brittle. Read the guide → Caps, containers, crates, low-cost parts Polyethylene (PE) Cheap, chemically tough, impact-resistant even cold—HDPE vs LDPE sets stiffness; plan for shrink and bonding limits. Read the guide → Under-hood, connectors, chemical service PPS High heat, near-universal chemical resistance, inherent flame retardance, and tight tolerances—below PEEK’s price. Read the guide → Electronics and automotive enclosures PC/ABS The in-between blend—tougher and more heat-resistant than ABS, cheaper and easier-molding than PC. Read the guide → Aircraft interiors, sterilizable medical, hot electrical PEI / Ultem High heat with transparency, inherent flame-smoke-toxicity performance, and autoclave sterilizability—below PEEK’s price. Read the guide → Micro connectors and miniature electronics LCP Extreme thin-wall flow, solder-reflow heat survival, and micron-level precision—the micro-connector resin, with weld lines as its known weakness. Read the guide → Cosmetic or brand-visible parts needing color approval Color Matching — Buyer Guide How to set a color standard, what Delta E and metamerism mean for sign-off, and why texture, regrind, and lighting all move the color you actually get. Read the guide → Cost or sustainability programs using reground or recycled material Regrind & Recycled Content How regrind affects strength, color, and contamination risk, the difference between in-house regrind, PIR, and PCR, and RFQ language that protects quality. Read the guide → Parts near electricity, heat, or a certification path UL 94 Flammability Ratings What V-0, V-1, V-2, HB, and 5VA actually require, why every rating is tied to a tested thickness, what a Yellow Card proves, and how to write the callout in your RFQ. Read the guide →

Related Resources

Plastic Part Design for Manufacturing Material and design interact—wall thickness, shrinkage, and tolerances all depend on the resin. Read the guide → Plastic Injection Mold Cost Material is a large share of piece price, and filled resins affect tooling—see how it flows into cost. Read the guide →
Before you specify

Once you've narrowed the resin, name it (and acceptable equivalents) in your RFQ alongside the drawing. Naming material—rather than specifying only "plastic"—is what makes quotes comparable.

Start with material selection
PlasticsTechnologyAlliance.com is an independent buyer resource. It does not manufacture parts, provide engineering services, guarantee outcomes, or operate a supplier directory. Final material selection should be confirmed with a materials engineer, the resin datasheet, and your supplier.