To choose the right plastic for your product, start from a written requirements table — loads, temperatures, chemical exposure, safety ratings, appearance, and expected lifetime — and only then match materials against it. The material you pick determines strength, look, cost per part, manufacturing method, and even how long the product survives in the field. A wrong choice reveals itself late: an enclosure that cracks after two months in the sun, a part that yellows, or an expensive mold that needs rework because the resin shrinks differently than expected. A systematic approach starts with requirements, not with a supplier's catalog.

Start From Requirements, Not Material Names

Before any acronyms enter the conversation, write down: what forces act on the part, what temperature range it operates in, whether it is exposed to sunlight, water, oils, or cleaning agents, what flammability or safety rating applies (UL 94 for flammability, FDA compliance for food contact, skin-contact requirements for wearables), and how long the product must last. Every line maps to a known engineering metric — flexural modulus, heat deflection temperature, impact resistance, moisture absorption — so you can screen materials objectively. Separate must-have requirements from nice-to-haves: if only one part of the product sees high heat, there is no reason to upgrade every part to an expensive resin, and it is often smarter to split the product across two different materials.

The Common Plastic Families

  • ABS — rigid, easy to mold and paint; a workhorse for enclosures and consumer products, but weak against prolonged sunlight.
  • PP (polypropylene) — cheap, flexible, chemically resistant; excellent for living hinges and containers, but less stiff and hard to glue or paint.
  • PC (polycarbonate) — transparent and exceptionally impact-resistant; ideal for windows, guards, and demanding products, but pricier and sensitive to some solvents.
  • Nylon (PA) — wear-resistant; great for gears and mechanical parts, though it absorbs moisture and shifts dimensionally.
  • POM (acetal) — outstanding dimensional stability and low friction; the go-to for precision mechanisms.
  • TPE and TPU — elastomers for soft grips, seals, and flexible covers.

Many products combine a rigid shell with a soft-touch grip in a single part using two-shot molding — a decision best made early, because it constrains both design and tooling. Note that prototype materials are not production materials: the filament comparison in ABS vs PLA for 3D printing is about prototyping, not what your molded part will be.

Material and Manufacturing Process Go Together

You cannot separate the resin from the process. A material that molds beautifully may not extrude or cast well, and at low volumes a different technology may beat molding entirely — see 3D printing vs injection molding for where that line falls. Shrink rate directly affects mold dimensions, so changing material after the steel is cut is an expensive change. Wall thickness uniformity, draft angles, and rib design all interact with material choice — the discipline covered in our guide to design for manufacturing. Material flow and moisture control also drive molding quality; the failure modes are cataloged in injection molding defects and how to prevent them.

Cost, Availability, and Finish

Price per pound is only part of the story. Part weight, cycle time in the press, scrap rate, and pre-drying requirements matter just as much. Verify the exact grade is available from more than one supplier, or you are betting your production on a single supply chain. On appearance: not every resin takes every finish — texture, gloss, and transparency depend on the material, and they shape how customers perceive quality. Sustainability is an increasingly real constraint too: recyclability, recycled-content grades, and molded-in color instead of paint can all affect which resins qualify for your target market.

Validate Before You Cut Tooling

The final step is physical validation. Produce parts in the final resin or a close analog, run load, drop, UV, and cleaning tests, and only then lock the specification. A mold is a serious investment — see injection molding costs — so know the numbers before committing. Keep in mind that 3D-printed parts do not accurately represent molded-part behavior, so decisive mechanical tests should use parts made in the real material. More guides live in our manufacturing technologies hub.

Get a Material Spec, Not a Guess

Projects House selects materials the systematic way — requirements first, data sheets second, physical validation third — across hundreds of product development projects. Torn between candidate resins and want a decision backed by data instead of a hunch? Tell us about your product through the contact form and we will build a material specification that fits your requirements, quantities, and budget.