Materials
Moulding materials library
Properties, grades, and design notes for the 25 materials we mold, machine, print, and form most often, starting with the 13 thermoplastics we injection mould. Every entry gives real datasheet values and the reason you would choose it over the alternative.
Choosing a moulding plastic
Thermoplastics for injection moulding compared
Pick the cheapest thermoplastic that meets your one binding constraint. Service temperature rules out most commodity plastics first, then clarity, wear, chemicals or food contact narrow the rest. Plan the mould around the shrinkage of the grade you choose: acetal and HDPE shrink several times as much as PETG or acrylic, so a tool cut for one resin will not hold size in the other.
| Material | Choose it for | Mould shrinkage | Heat deflection, cost |
|---|---|---|---|
| Polypropylene (PP) | A living hinge, chemical resistance, or the lowest part price | 1.3 to 1.8 % | 100 °C (0.45 MPa), very low cost |
| HDPE | Low friction, food contact, or toughness in cold service | 1.5 to 3.0 % | 75 °C (0.45 MPa), very low cost |
| Polystyrene (GPPS, HIPS) | A rigid, low cost part with no real toughness demand | 0.4 to 0.7 % | 75 °C, very low cost |
| ABS | An enclosure that must be tough, easy to mould and easy to finish | 0.4 to 0.7 % | 88 °C, low cost |
| Acrylic (PMMA) | The best optical clarity and scratch resistance | 0.3 to 0.6 % | 95 °C, low cost |
| PETG | A clear, tough part for food contact | 0.2 to 0.5 % | 70 °C (0.45 MPa), low cost |
| Polycarbonate (PC) | A transparent part that has to survive impact | 0.5 to 0.7 % | 130 °C, medium cost |
| PC/ABS | PC toughness and heat with ABS processing and finish | 0.5 to 0.7 % | 100 to 115 °C, medium cost |
| Nylon (PA) | Strength and wear resistance, where water uptake is acceptable | 0.7 to 1.5 % | 70 °C unfilled, 220 °C GF30, medium cost |
| Acetal (POM) | Gears, clips and sliding parts that must hold size | 1.8 to 2.5 % | 100 °C, medium cost |
| PBT | Connectors and electrical housings in humid service | 1.5 to 2.0 % unfilled | 60 °C unfilled, 210 °C GF30, medium cost |
| PEI (Ultem) | Flame retardant parts that must stay stable at high temperature | See page | 200 °C, high cost |
| PEEK | Metal replacement where nothing cheaper survives the service | See page | 250 °C continuous service, very high cost |
Heat deflection is at 1.8 MPa unless a lower load is stated; for PEEK the figure is its continuous service temperature. Typical published values for the grades named, from each material page. For the presses, volumes and tooling behind these materials, see our injection moulding capabilities; to compare two candidates spec by spec, use the head-to-head comparisons below.
14 materials
Thermoplastics
ABS
The default enclosure plastic. Tough, easy to mold, easy to finish.
Polycarbonate
Transparent, and the toughest common engineering thermoplastic.
Polypropylene
Cheap, chemically inert, and the only common plastic with a real living hinge.
HDPE
Low friction, chemically inert, and tough at low temperature.
Nylon (PA)
Strong, tough, wear resistant, and it absorbs water.
Acetal (POM)
The precision plastic. Stiff, slippery, and dimensionally stable.
Acrylic (PMMA)
The clearest common plastic, and the most scratch resistant.
PETG
Clear, tough, easy to form, and safe for food contact.
PBT
The connector plastic. Stable, insulating, and it barely takes up water.
PC/ABS
PC toughness and heat, ABS processing and finish.
PEEK
The high performance polymer. Metal-adjacent properties, metal-adjacent price.
PEI (Ultem)
Amber, transparent, flame retardant, and stable to 170 °C.
Polystyrene (HIPS)
The cheapest molding plastic. Rigid, clear in GPPS, tough in HIPS.
PLA
The default printing polymer. Accurate, easy, and not for service parts.
| Material | Full name | Tensile strength | Processes |
|---|---|---|---|
| ABS | Acrylonitrile butadiene styrene | 40–45 MPa | Molding, CNC, 3D printing |
| Polycarbonate | Polycarbonate (PC) | 60–70 MPa | Molding, CNC, 3D printing |
| Polypropylene | Polypropylene (PP) | 30–35 MPa | Molding, CNC |
| HDPE | High density polyethylene | 22–31 MPa | Molding, CNC |
| Nylon (PA) | Polyamide 6 and 6/6 | 70–85 MPa (dry) | Molding, CNC, 3D printing |
| Acetal (POM) | Polyoxymethylene, Delrin | 62–70 MPa | Molding, CNC |
| Acrylic (PMMA) | Polymethyl methacrylate | 70–75 MPa | Molding, CNC |
| PETG | Glycol-modified polyethylene terephthalate | 50 MPa | Molding, 3D printing |
| PBT | Polybutylene terephthalate | 55 MPa (135 GF30) | Molding |
| PC/ABS | Polycarbonate / ABS alloy | 55 MPa | Molding, 3D printing |
| PEEK | Polyether ether ketone | 95–100 MPa | Molding, CNC, 3D printing |
| PEI (Ultem) | Polyetherimide | 105 MPa | Molding, CNC, 3D printing |
| Polystyrene (HIPS) | General purpose and high impact polystyrene | 45 MPa (GPPS), 25 MPa (HIPS) | Molding |
| PLA | Polylactic acid | 50–60 MPa | 3D printing |
3 materials
Elastomers
TPU
A rubber you can injection mold and print.
TPE (SEBS)
The soft-touch overmold material. Very soft, easy to bond to ABS and PP.
Silicone (LSR)
Wide temperature range, biocompatible, and molded as a thermoset.
| Material | Full name | Hardness | Processes |
|---|---|---|---|
| TPU | Thermoplastic polyurethane | 70 Shore A – 75 Shore D | Molding, 3D printing |
| TPE (SEBS) | Styrenic thermoplastic elastomer | 20–90 Shore A | Molding |
| Silicone (LSR) | Liquid silicone rubber | 10–80 Shore A | Molding |
8 materials
Metals
Aluminum 6061
The default machining alloy. Strong enough, light, and it cuts fast.
Aluminum 7075
Aerospace aluminum. Near steel strength, but it does not weld or corrode well.
Aluminum 5052
The sheet metal aluminum. Forms tightly and resists salt.
Stainless 304
The general purpose stainless. Corrosion resistant, hygienic, and formable.
Stainless 316L
Marine and medical stainless. Molybdenum for chloride resistance.
Mild steel (CRCA)
The cheapest formable sheet. Needs a coating.
Brass C36000
The fastest metal to machine, and it conducts.
Titanium Grade 5
Steel strength at half the weight, fully biocompatible, hard to cut.
| Material | Full name | Tensile strength | Processes |
|---|---|---|---|
| Aluminum 6061 | Aluminum 6061-T6 | 310 MPa (T6) | CNC, Sheet metal |
| Aluminum 7075 | Aluminum 7075-T6 | 572 MPa (T6) | CNC |
| Aluminum 5052 | Aluminum 5052-H32 | 228 MPa (H32) | Sheet metal |
| Stainless 304 | Stainless steel 304 / 1.4301 | 515 MPa | CNC, Sheet metal |
| Stainless 316L | Stainless steel 316L / 1.4404 | 485 MPa | CNC, Sheet metal |
| Mild steel (CRCA) | Cold rolled close annealed steel, IS 513 / DC01 | 270–350 MPa | Sheet metal, CNC |
| Brass C36000 | Free machining brass, C36000 / CuZn39Pb3 | 340–470 MPa | CNC |
| Titanium Grade 5 | Ti-6Al-4V, Grade 5 | 950 MPa | CNC, 3D printing |
12 comparisons
Head-to-head comparisons
Mild Steel vs Stainless 304
Cost and formability against corrosion resistance and coating upkeep, the sheet-metal decision.
ABS vs Polycarbonate
Impact toughness and heat resistance compared, the enclosure-plastic decision.
Polycarbonate vs Acrylic (PMMA)
Impact resistance against optical clarity, for a part you need to see through.
Nylon (PA) vs Acetal (POM)
Toughness against dimensional precision, the classic engineering trade-off.
Aluminum 6061 vs Stainless 304
Weight and cost against corrosion resistance, when either metal could work.
Aluminum 6061 vs 7075
Strength and weldability compared, for a machined part under real load.
Stainless 304 vs 316L
Cost against chloride resistance, the one spec that decides it.
Titanium Grade 5 vs Stainless 304
Weight and biocompatibility against cost, the CNC material decision.
TPE vs TPU
Softness and abrasion resistance compared, for soft-touch and wear parts.
Polycarbonate vs PC/ABS
Heat resistance and clarity against moldability and finish, the alloy decision.
Silicone (LSR) vs TPE
Heat resistance and biocompatibility against cost, the soft-part decision.
HDPE vs Polypropylene
Toughness and low-temperature impact against heat resistance and the living hinge.
How to use this
Material choice is usually decided by one binding constraint: a service temperature, a chemical, a load, a certification, or a cost target. Find the constraint first, then read the alternatives section on the candidate page, it names what to move to when the first choice fails.
Values here are typical published figures for unfilled grades at 23 °C. They are for narrowing the field, not for design calculation. Confirm against the supplier datasheet for the exact grade before release.
Not sure yet?
Send the part and the environment it works in. We will come back with two or three candidate materials, what each would cost, and what each would compromise.