Injection Moulding Materials: Which Plastic Should You Choose?

The resin you specify determines mechanical performance, surface quality, chemical resistance, and per-part cost. For most Nordic and Baltic OEM applications, the choice narrows to seven standard materials: ABS, PP, PC, PMMA, POM, TPE, and TPU. This guide gives the key properties and a clear use-it-when rule for each.

How do the standard resins compare at a glance?

Material	Density (g/cm³)	Tensile strength (MPa)	Heat deflection (°C)	Relative cost	Typical MOQ
ABS	1.02–1.06	40–50	80–95	Low	100 pcs
PP	0.90–0.91	25–40	55–65	Very low	100 pcs
PC	1.20–1.22	55–75	120–135	Medium	100 pcs
PMMA	1.17–1.20	55–75	85–100	Medium	100 pcs
POM	1.41–1.43	60–70	100–115	Medium	100 pcs
TPE	0.88–1.10	5–20	40–70	Low–medium	100 pcs
TPU	1.10–1.25	25–55	60–90	Medium	100 pcs

All figures are indicative for unfilled commercial grades. Glass-filled variants increase tensile strength and heat deflection significantly. Confirm exact datasheet values with your material supplier before finalising tolerances.

When should you choose ABS?

ABS (acrylonitrile butadiene styrene) is the default choice for enclosures, housings, and consumer-facing parts where cosmetics and paintability matter.

Property	Typical value
Tensile strength	40–50 MPa
Impact strength (Izod notched)	150–300 J/m
Heat deflection temperature	80–95 °C
Shrinkage	0.4–0.9%
Surface finish quality	Excellent — accepts paint, plating, textures

Use it when: the part is a visible enclosure or housing, paintability or electroplating is required, impact resistance is moderate (not extreme cold), and cost control matters. ABS is not suitable for prolonged UV exposure without a UV-stabilised grade, and it degrades in contact with strong solvents or fuels.

Nordmould stocks multiple ABS grades including flame-retardant (FR) variants for electronics housings.

When should you choose PP?

PP (polypropylene) is the highest-volume thermoplastic globally, valued for its low density, chemical resistance, and living-hinge capability.

Property	Typical value
Tensile strength	25–40 MPa
Flexural modulus	1,000–1,500 MPa
Heat deflection temperature	55–65 °C
Shrinkage	1.0–2.5%
Chemical resistance	Excellent (acids, bases, alcohols)

Use it when: the part requires a living hinge (a thin integral flex feature), chemical resistance to household or industrial substances, low weight, or low unit cost at volume. PP's higher shrinkage rate requires careful gate placement and wall-thickness control; Nordmould's free DFM review will flag any issues before tooling is cut.

Avoid PP where stiffness above 65 °C is required or where the part must be bonded with standard adhesives — PP's low surface energy makes adhesion difficult without pre-treatment.

When should you choose PC?

PC (polycarbonate) delivers the highest impact strength and temperature performance in Nordmould's standard range, along with optical transparency in natural grade.

Property	Typical value
Tensile strength	55–75 MPa
Impact strength (Izod notched)	600–900 J/m
Heat deflection temperature	120–135 °C
Light transmission (natural grade)	~88%
Shrinkage	0.5–0.7%

Use it when: the part must survive high-energy impact (safety covers, protective housings), resist temperatures above 100 °C (lamp housings, under-bonnet components), or transmit light (light pipes, diffusers, optical lenses). PC is more expensive than ABS and more demanding to process — moisture must be removed before moulding to prevent hydrolytic degradation of molecular weight.

ABS/PC blends are a common middle ground: better impact than pure ABS, easier to process than pure PC, and available in many colours.

When should you choose PMMA?

PMMA (polymethyl methacrylate, acrylic, Plexiglas) is the optical clarity material — lighter than glass and with higher light transmission than PC.

Property	Typical value
Tensile strength	55–75 MPa
Light transmission	~92%
Haze (3 mm plaque)	<1%
Heat deflection temperature	85–100 °C
Shrinkage	0.2–0.8%
Impact strength	Low — brittle under point impact

Use it when: maximum optical clarity is the priority: display covers, instrument lenses, light diffusers, signage. PMMA scratches more easily than PC and is brittle under impact — it is not suitable for structural or impact-loaded applications. It accepts excellent surface finishes and can be polished to optical quality.

When should you choose POM?

POM (polyoxymethylene, acetal, Delrin) is the precision engineering material: stiff, slippery, and dimensionally stable.

Property	Typical value
Tensile strength	60–70 MPa
Flexural modulus	2,500–3,200 MPa
Heat deflection temperature	100–115 °C
Coefficient of friction (dry, vs steel)	0.2–0.35
Shrinkage	1.8–2.5%
Water absorption	Very low

Use it when: the part is a gear, cam, bearing, bushing, fastener, valve seat, or any precision sliding component where tight dimensional tolerance and low friction without external lubrication are required. POM's high shrinkage demands careful tooling design; its high stiffness means sink marks are more visible if wall thickness is inconsistent.

Nordmould supports both POM homopolymer and copolymer grades. Copolymer is preferred for complex geometries due to better hydrolysis resistance.

When should you choose TPE?

TPE (thermoplastic elastomer) covers a family of flexible materials that process like thermoplastics but feel and flex like rubber.

Property	Typical value
Shore hardness	20A–80A (grade-dependent)
Tensile strength	5–20 MPa
Elongation at break	300–700%
Heat resistance	40–70 °C (grade-dependent)
Chemical resistance	Moderate

Use it when: the part needs a soft-touch feel, sealing function, grip surface, or vibration damping — without the processing complexity of thermoset rubber. TPE is frequently over-moulded onto a rigid ABS or PP substrate to create two-component parts (handles, tool grips, device seals). It is recyclable, which is an advantage for EU-market sustainability claims.

When should you choose TPU?

TPU (thermoplastic polyurethane) is the high-performance flexible material, offering superior abrasion resistance and mechanical load capacity compared to standard TPE grades.

Property	Typical value
Shore hardness	60A–75D (wide range)
Tensile strength	25–55 MPa
Abrasion resistance	Excellent (DIN 53516)
Elongation at break	400–600%
Oil and fuel resistance	Good

Use it when: the part is a cable jacket, wheel, drive belt, sealing boot, sports equipment component, or industrial protective cover where abrasion wear, oil resistance, or dynamic mechanical loading would cause a standard TPE to fail prematurely. TPU is more hygroscopic than TPE — it must be dried before moulding to maintain consistent mechanical properties.

Nordmould can quote over-moulding of TPU onto PC or POM substrates for demanding two-component assemblies.

How do you decide between these materials?

Work through three questions in order.

1. What is the primary functional requirement? Structural load → PC or POM. Optical clarity → PMMA or PC. Chemical resistance → PP or POM. Flexibility/seal → TPE or TPU. Cost-driven enclosure → ABS or PP.

2. What is the operating environment? Above 100 °C → PC or POM. UV exposure → UV-stabilised PP or ASA (available on request). Food or pharmaceutical contact → PP with compliant grade. High abrasion → TPU.

3. What does the geometry demand? Living hinge → PP. Precision gear or bearing → POM. Optical surface → PMMA. Multi-component over-mould → ABS or PC substrate with TPE or TPU overmould.

When the requirements conflict — e.g., clarity and impact strength — consider a blend (ABS/PC) or a Nordmould materials consultation. Submit your STEP file with a written description of the operating conditions and Nordmould will include a material recommendation in the DFM note.

Frequently asked questions

What plastics does Nordmould support for injection moulding? Nordmould moulds ABS, PP, PC, PMMA, POM, TPE, and TPU as standard. Engineering grades, glass-filled variants, and flame-retardant compounds are available on request. Send a STEP file and material requirement to get a written recommendation.

What is the strongest plastic for injection moulding? For structural rigidity, PC (polycarbonate) has the highest impact strength and heat deflection of Nordmould's standard resins. For fatigue resistance and self-lubrication, POM outperforms. The right choice depends on load type, temperature, and chemical environment.

Which plastic is best for outdoor products? ASA or UV-stabilised PP are preferred outdoors; ABS yellows and chalks without UV additives. Nordmould can advise on UV-stabilised grades — note this as a requirement in your RFQ.

Can Nordmould mould soft, rubber-like parts? Yes. TPE and TPU are both standard Nordmould materials. TPE suits consumer grips and seals; TPU is used where abrasion resistance or higher mechanical load is required. Both can be over-moulded onto rigid substrates.

Is polycarbonate food-safe? Standard PC grades are not recommended for direct food contact. PP and specific HDPE grades are the common food-contact choices. State FDA or EU 10/2011 food-contact compliance in your RFQ and Nordmould will specify a compliant grade.

What is the cheapest plastic for injection moulding? PP (polypropylene) is typically the lowest-cost resin in the standard range and processes efficiently. For high-volume commodity parts, PP is almost always the first material to evaluate.

How do I choose between ABS and PC? Choose ABS when cosmetics, paintability, and moderate impact are the priority and cost matters. Choose PC when you need higher impact strength, optical clarity (in natural grade), or resistance to temperatures above 80 °C. Nordmould can also quote ABS/PC blend for a balance of both.

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Send your STEP file and material requirements to Nordmould for a free written DFM review and material recommendation.