There are many types of materials that may be used in the injection moulding process.
Most polymers may be used including all thermoplastics, and many elastomers. When these materials are used in the injection moulding process, their raw form is usually small pellets but can occasionally be a fine powder. Also, colourants may be added in the process either as a compound with the base material or by blending masterbatch to control the moulded colour of the final part.
The selection of a material for creating injection moulded parts is not solely based upon the desired characteristics of the final part. While each material has different properties that will affect the strength and function of the final part, these properties also dictate the parameters used in processing these materials. Each material requires a different set of processing parameters in the injection moulding process, including the injection temperature, injection pressure, injection speed, mould temperature, ejection method and cooling time.
A comparison of some commonly used materials is shown below:
Acetal (POM)
Properties
Strong, rigid, excellent fatigue resistance, excellent creep resistance, chemical resistance, moisture resistance, naturally opaque white, low/medium cost
Applications
Bearings, cams, gears, handles, plumbing components, rollers, rotors, slide guides, valves
Acrylic (PMMA)
Properties
Rigid, brittle, scratch resistant, transparent, optical clarity, low/medium cost
Applications
Display stands, knobs, lenses, light housings, panels, reflectors, signs, shelves, trays
Acrylonitrile Butadiene Styrene (ABS)
Properties
Strong, flexible, low mould shrinkage (tight tolerances) chemical resistance, electroplating capability, naturally opaque, low/medium cost
Applications
Automotive (consoles, panels, trim, vents) boxes, gauges, housings, inhalers, toys
Cellulose Acetate (CA)
Properties
Tough, transparent, high cost
Applications
Handles, eyeglass frames
Polyamide 6 (Nylon) (PA6)
Properties
High strength, fatigue resistant, chemical resistant, low creep, low friction, almost opaque/white, medium/high cost
Applications
Bearings, bushings, gears, rollers, wheels
Polyamide 6/6 (Nylon) (PA6/6)
Properties
High strength, fatigue resistant, chemical resistant, low creep, low friction, almost opaque/white, medium/high cost
Applications
Handles, levers, small housings, zip ties
Polyamide 11+12 (Nylon) (PA11+12)
Properties
High strength, fatigue resistant, chemical resistance, low creep, low friction, almost opaque to clear, very high cost
Applications
Air filters, eyeglass frames, safety masks
Polycarbonate (PC)
Properties
Very tough, temperature resistance, dimensional stability, transparent, high cost
Applications
Automotive (panels, lenses, consoles) bottles, containers, housings, light covers, reflectors, safety helmets and shields
Polyester – Thermoplastic (PBT, PET)
Properties
Rigid, heat resistance, chemical resistance, medium/high cost
Applications
Automotive (filters, handles, pumps) bearings, cams, electrical components (connectors, sensors) gears, housings, rollers, switches, valves
Polyether Sulphone (PES)
Properties
Tough, very high chemical resistance, clear, very high cost
Applications
Valves
Polyetheretherketone (PEEK)
Properties
Strong, thermal stability, chemical resistance, abrasion resistance, low moisture absorption
Applications
Aircraft components, electrical connectors, pump impellers, seals
Polyetherimide (PEI)
Properties
Heat resistance, flame resistance, transparent (amber colour)
Applications
Electrical components (connectors, boards, switches) covers, shields, surgical tools
Polyethylene – Low Density (LDPE)
Properties
Lightweight, tough and flexible, excellent chemical resistance, natural waxy appearance, low cost
Applications
Kitchenware, housings, covers and containers
Polyethylene – High Density (HDPE)
Properties
Tough and stiff, excellent chemical resistance, natural waxy appearance, low cost
Applications
Chair seats, housings, covers and containers
Polyphenylene Oxide (PPO)
Properties
Tough, heat resistance, flame resistance, dimensional stability, low water absorption, electroplating capability, high cost
Applications
Automotive (housings, panels) electrical components, housings, plumbing components
Polyphenylene Sulphide (PPS)
Properties
Very high strength, heat resistance, brown, very high cost
Applications
Bearings, covers, fuel system components, guides, switches and shields
Polypropylene (PP)
Properties
Lightweight, heat resistance, high chemical resistance, scratch resistance, natural waxy appearance, tough and stiff, low cost
Applications
Automotive (bumpers, covers, trim) bottles, caps, crates, handles, housings
Polystyrene – General Purpose (GPPS)
Properties
Brittle, transparent, low cost
Applications
Cosmetics packaging, pens
Polystyrene – High impact (HIPS)
Properties
Impact strength, rigidity, toughness, dimensional stability, naturally translucent, low cost
Applications
Electronic housings, food containers, toys
Polyvinyl Chloride - Plasticised PVC
Properties
Tough, flexible, flame resistance, transparent or opaque, low cost
Applications
Electrical insulation, housewares, medical tubing, shoe soles, toys
Polyvinyl Chloride - Rigid (UPVC)
Properties
Tough, flexible, flame resistance, transparent or opaque, low cost
Applications
Outdoor applications (drains, fittings, gutters)
Styrene Acrylonitrile (SAN)
Properties
Stiff, brittle, chemical resistance, heat resistance, hydrolytically stable, transparent, low cost
Applications
Housewares, knobs, syringes
Thermoplastic Elastomer/Rubber (TPE/R)
Properties
Tough, flexible, high cost
Applications
Bushings, electrical components, seals, washers
