How to Choose the Right Plastic for Your Injection Molded Part

Choosing the right plastic material is one of the most important decisions in any injection molding project. The wrong material can lead to warping, brittleness, poor surface finish, or parts that fail under load. Get it right, and you get parts that last.

Here's a practical overview of the most common thermoplastics we work with at Kanak Industries and when to use each.

Polypropylene (PP) — The Workhorse

PP is the most widely used injection molding material globally, and for good reason:

Cost-effective — one of the most affordable engineering thermoplastics
Chemically resistant — resists acids, bases, and most solvents
Lightweight — low density, ideal where weight matters
Flexible — can be formulated in a wide range of stiffness grades
Food-safe grades available — widely used in food and beverage packaging

Best for: Packaging caps and closures, automotive interior parts, household products, containers, living hinges.

Watch out for: Lower impact resistance at low temperatures, UV degradation without stabilisers, poor bonding with adhesives.

ABS — Strength Meets Surface Finish

ABS (Acrylonitrile Butadiene Styrene) is the go-to when you need a good balance of rigidity, impact resistance, and surface quality.

Excellent surface finish — smooth, paintable, and plateable
Good impact resistance — especially at room temperature
Dimensional stability — holds tight tolerances well
Easy to process — wide processing window, low warpage

Best for: Electrical enclosures, consumer electronics housings, automotive interior trims, toys, medical device housings.

Watch out for: Not suitable for outdoor UV exposure without additives, absorbs moisture and needs pre-drying before molding.

Polycarbonate (PC) — When You Need Transparency or Toughness

PC is the material of choice when you need extreme impact resistance or optical clarity.

Very high impact strength — virtually unbreakable under normal conditions
Optically transparent — used in lenses, windows, and light diffusers
High heat resistance — maintains properties up to 130°C
Dimensional accuracy — very low shrinkage

Best for: Safety helmets, riot shields, medical device windows, LED diffusers, automotive headlamp lenses, water bottles.

Watch out for: Sensitive to certain chemicals (acetone, hydrocarbons), needs careful drying before molding, scratch-prone without hard coating.

Nylon (Polyamide — PA6 / PA66) — The Engineering Material

Nylon is the choice when parts must handle mechanical stress, friction, or elevated temperatures.

High strength and stiffness
Excellent wear and abrasion resistance — ideal for gears, bushings, and slides
Good heat resistance — PA66 rated up to 180°C
Self-lubricating — reduces friction in moving parts

Best for: Gears, cams, bushings, automotive under-hood parts, cable ties, power tool components.

Watch out for: High moisture absorption — parts can change dimension in humid environments. Always pre-dry material before molding.

Masterbatches and Filled Grades

Beyond base resins, we regularly process:

Colour masterbatches — custom colour matching for any base resin
Glass-filled grades — significantly improves stiffness and heat resistance (e.g., 30% GF Nylon for structural parts)
Mineral-filled PP — improves stiffness and reduces cost
Flame-retardant grades — required for electrical and electronic applications

How to Decide

Ask these questions:

| Requirement | Recommended Material | |-------------|----------------------| | Low cost, chemical resistance | PP | | Good finish, impact resistance | ABS | | Transparency, high impact | PC | | Mechanical loads, friction | Nylon (PA) | | UV resistance outdoors | PP + UV stabiliser | | High temperatures | PA66, PC | | Food contact | Food-grade PP |

Let Us Help You Decide

Not sure which material is right for your part? Share your application details with us and our team will recommend the best material and grade — including sourcing the right resin for your budget and performance requirements.