Plastic Injection Molding Materials
30+ injection molding resins — from commodity plastics to high-performance thermoplastics
Plastics Material Selection
Start with your most critical requirement and use these guides to quickly identify candidate materials.
High Temperature Performance
Parts that operate near heat sources, inside engine bays, or must survive sterilization cycles.
Chemical & Fluid Resistance
Exposure to fuels, oils, lubricants, acids, bases, or sterilization chemicals.
Optical Clarity & Transparency
Light transmission, lenses, display covers, and lighting components.
Structural & Load-Bearing
Parts under sustained mechanical stress, compression, or impact loading.
Outdoor & UV Exposure
Long-term color and impact stability under sunlight and weathering.
Cost-Sensitive High Volume
Millions of parts where raw material cost is a primary driver.
Medical & Food Contact
Biocompatibility, sterilizability, and compliance with FDA/ISO 10993.
Soft-Touch & Overmolding
Grip surfaces, seals, gaskets, and multi-material assemblies.
Precision Mechanical Parts
Gears, bushings, and cams requiring tight tolerances and low friction.
Key mechanical and thermal properties for the most commonly specified injection molding materials at RpMolds.
| Material | Category | Density (g/cm³) |
Tensile (MPa) |
Flex Modulus (GPa) |
HDT (°C @ 1.8MPa) |
Shrinkage (%) |
Impact | Cost |
|---|---|---|---|---|---|---|---|---|
| ABSAcrylonitrile Butadiene Styrene | Commodity | 1.02–1.10 | 38–52 | 2.1–2.8 | 70–106 | 0.4–0.8 | ||
| PPPolypropylene | Commodity | 0.90–0.91 | 25–40 | 1.1–1.7 | 100–115 | 1.5–2.5 | ||
| HDPEHigh-Density Polyethylene | Commodity | 0.94–0.97 | 22–35 | 0.7–1.4 | 60–80 | 1.5–3.0 | ||
| PCPolycarbonate | Engineering | 1.19–1.22 | 55–65 | 2.2–2.4 | 127–138 | 0.5–0.7 | ||
| PC/ABSPolycarbonate Blend | Engineering | 1.10–1.18 | 45–60 | 2.2–2.8 | 100–130 | 0.5–0.8 | ||
| Nylon PA6Polyamide 6 | Engineering | 1.12–1.14 | 70–85 | 2.6–3.5 | 65–85 | 0.6–1.5 | ||
| POM (Delrin®)Polyoxymethylene | Engineering | 1.41–1.43 | 60–70 | 2.6–3.1 | 100–125 | 1.8–2.5 | ||
| PMMA (Acrylic)Polymethyl Methacrylate | Engineering | 1.17–1.20 | 60–80 | 3.0–3.3 | 85–100 | 0.2–0.5 | ||
| PEEKPolyether Ether Ketone | Hi-Perf | 1.30–1.32 | 90–100 | 3.6–4.1 | 160–170 | 1.0–1.5 | ||
| PEI (Ultem®)Polyetherimide | Hi-Perf | 1.27 | 105 | 3.3–3.6 | 200 | 0.5–0.7 | ||
| PPSPolyphenylene Sulfide | Hi-Perf | 1.34–1.38 | 65–80 | 3.8–4.5 | 135–260 | 0.5–1.0 | ||
| TPUThermoplastic Polyurethane | Elastomer | 1.10–1.25 | 20–60 | 0.01–0.2 | – | 0.5–1.5 |
Commodity Plastics
High-volume, cost-effective resins for general-purpose molding. Best for non-critical structural applications where cost and processability are priorities.
ABS
The industry workhorse for consumer products and electronics enclosures. ABS delivers an excellent balance of rigidity, impact resistance, and surface quality at a moderate cost. It machines and finishes well, accepts paint and electroplating readily, and is available in hundreds of colors.
Processing Details
PP
The world’s highest-volume injection molding resin. PP’s outstanding fatigue resistance makes it ideal for integral living hinges (capable of millions of flex cycles). It has excellent chemical resistance to most acids, bases, and polar solvents, and its low density (0.90 g/cm³) keeps part weight minimal.
Processing Details
HDPE
Tough, lightweight, and highly resistant to chemicals and moisture. HDPE is widely used for industrial containers, pipes, and components that require resistance to harsh chemical environments. FDA-compliant grades are available for food-contact applications.
Processing Details
LDPE
Softer and more flexible than HDPE, with excellent toughness at low temperatures. Used where flexibility and compliance are needed rather than rigidity. LDPE is easily recyclable and available in food-safe grades.
ASA
The go-to ABS replacement for outdoor applications. ASA maintains its color and impact resistance after prolonged UV exposure without yellowing or becoming brittle. Processing conditions are similar to ABS, making it a drop-in upgrade for exterior parts.
PVC
Available in rigid (uPVC) and flexible (plasticized) forms. Rigid PVC offers strong, flame-retardant performance for pipes and electrical housings; flexible grades replace rubber in many sealing and insulation applications. Inherently flame retardant due to chlorine content.
Engineering Plastics
Superior mechanical, thermal, and electrical performance over commodity resins. Suitable for functional structural components in demanding industrial and automotive applications.
PC
Outstanding impact resistance combined with optical clarity makes PC unique among engineering plastics. It is 200× more impact-resistant than glass at equivalent thickness and maintains performance from -40°C to 125°C. PC is used wherever transparency plus structural integrity are both required.
Processing Details
PC/ABS
The most widely used engineering blend, combining PC’s heat resistance and impact toughness with ABS’s processability and lower cost. PC/ABS strikes an excellent balance for large, complex parts that need both structural integrity and good surface finish. It processes more easily than pure PC at lower melt temperatures.
Nylon (PA6 / PA66)
Nylon is the standard engineering resin for moving and load-bearing parts. Its inherent lubricity reduces friction against metals and other plastics, making it ideal for gears and bushings without added lubricants. PA66 offers higher heat resistance (HDT ~250°C with glass fill) than PA6, while PA6 has slightly better impact resistance and surface quality.
Processing Details
PMMA (Acrylic)
Acrylic transmits 92% of visible light — more than glass — with excellent UV resistance and outdoor durability. The go-to transparent engineering plastic where weight reduction over glass is needed. Scratch resistance is better than PC but impact resistance is lower. Available in a wide range of colors and optical grades.
POM (Acetal)
POM is the precision engineering plastic. Its combination of high stiffness, low friction, excellent creep resistance, and tight-tolerance moldability make it the preferred material for mechanical components that must maintain dimensions under sustained load. Available as homopolymer (Delrin® — higher strength) or copolymer (Celcon® — better chemical resistance).
Processing Details
High-Performance Thermoplastics
Superior mechanical, thermal, and electrical performance over commodity resins. Suitable for functional structural components in demanding industrial and automotive applications.
PEEK
The gold standard in high-performance injection molding materials. PEEK maintains structural integrity up to 260°C continuous service (316°C short-term), resists virtually all chemicals including concentrated acids, and is biocompatible and sterilizable. Glass- and carbon-fiber-filled grades are used as metal replacement in aerospace and orthopaedic implants.
Processing Details
PPS
PPS provides unmatched chemical resistance across the broadest range of solvents, acids, and bases of any common engineering thermoplastic. No known solvent attacks PPS below 200°C. Its inherent flame retardancy (V-0) and high stiffness make it a go-to material for harsh-environment automotive and industrial applications.
Elastomers & Flexible Materials
Rubber-like thermoplastics and silicones for soft-touch, sealing, vibration damping, and overmolding applications. Processable on standard injection molding equipment.
TPE
TPEs combine the elastic properties of rubber with the processability of thermoplastics — no vulcanization required. They can be overmolded onto rigid substrates (ABS, PP, PC) to create soft-grip surfaces, seals, and gaskets. Shore A hardness ranges from 20A (very soft) to 70A (firm). Fully recyclable.
TPU
TPU offers the highest abrasion resistance of any flexible injection molding material — often outperforming natural rubber. Available in polyester (better oil resistance, higher modulus) and polyether (better hydrolysis and low-temp flexibility) variants. Excellent clarity grades are available for transparent protective applications.