Ultimate guide to engineered plastics
Engineering plastics are designed for high-stress, high-performance applications where commodity polymers fall short. They hold their shape, strength, and performance even when exposed to heat, stress, and harsh chemicals. They're built to operate where ordinary materials would degrade or fail. Engineers rely on engineering plastics when applications demand long-term durability, tight tolerances, wear resistance, or electrical insulation, especially in dynamic or continuous-use environments. Engineering plastic materials frequently take the place of metal, glass, or ceramics when weight savings, corrosion resistance, or manufacturability matter. They offer high performance without the penalties of heavier or more rigid materials.
We’ll take a closer look at engineering plastics in this guide, covering:
What are the different types of engineering plastics?
Understanding engineering plastics
Technical properties
How engineering plastics are made
Selecting the right plastic material for your applications
Sustainability and engineered plastics
What are the different types of engineering plastics?
While some of these materials are widely known, their specialised, high-performance grades are what qualify them as engineering plastics when used in structurally or thermally demanding applications. Below is a breakdown of key engineering plastics, highlighting how they differ from general-purpose variants and why they're trusted in critical industrial, automotive, medical, and electronic applications.
1. Acrylonitrile Butadiene Styrene (ABS)
ABS is available in both commodity and engineering grades.
Commodity ABS is used in low-demand applications where mechanical load and dimensional precision are not critical—such as packaging, toys, or basic consumer housings. Engineering-grade ABS is specified when higher impact strength, thermal resistance, and tighter tolerances are required. It performs reliably in structural components like automotive interior panels, tool housings, and equipment enclosures, where consistent performance and surface integrity matter under loading conditions.
You can learn more about ABS in the guide our experts have put together, PVC vs ABS: which plastic should you choose?
2. Polyamide (PA) – Nylon (PA6, PA66, etc.)
While nylon fibres are used in textiles, engineering-grade nylons are tailored for structural applications, offering high tensile strength, wear resistance, and low friction. Grades such as PA66 (with or without glass reinforcement) are engineered for mechanical components like gears, pulleys, and bushings—delivering performance far beyond that of general-purpose nylons used in packaging or consumer goods.
3. Polycarbonate (PC)
General-use polycarbonate can be found in items like CDs or low-load transparent parts. Engineering-grade PC, however, is reinforced for impact strength, flame retardance, and optical clarity under stress. It’s used in safety visors, bullet-resistant glazing, and industrial lighting, where both strength and transparency must be preserved in high-load or high-heat conditions.
4. Polyethylene (PE) – HDPE, UHMW-PE
Polyethylene in its basic form (like LDPE) is a commodity plastic, widely used in bags and flexible films. But High-Density PE (HDPE) and Ultra-High Molecular Weight PE (UHMW-PE) are engineered for load-bearing, chemical-resistant, and low-friction applications. HDPE is used in chemical tanks, fuel systems, and piping, while UHMW-PE is trusted in sliding components and high-wear surfaces for its self-lubricating properties.
5. Polyethylene Terephthalate (PET)
As opposed to standard PET, its engineering-grade variant is typically semi-crystalline, offers higher stiffness, better wear resistance, and low moisture uptake. It performs well in tight-tolerance applications and maintains dimensional stability under load. Common uses for engineered PET include relay housings, slide rails, and machined components where creep, warp, or water absorption would rule out lower-grade materials.
6. Polyether Ether Ketone (PEEK)
PEEK is exclusively an engineering plastic. There is no commodity-grade equivalent. It's designed for high-load, high-temperature, chemically aggressive environments, retaining mechanical integrity up to 482°F. Industries such as aerospace, oil & gas, and medical implants rely on PEEK for applications where even slight material failure is unacceptable.
If you’re designing for the healthcare industry, we urge you to read our guide, What is medical-grade plastic?
7. Polypropylene (PP)
Standard polypropylene, low load, low precision, and low cost, is widely used in packaging, fibres, and household goods. Engineering-grade PP has higher molecular weight, better fatigue resistance, and holds up under heat and mechanical stress. It’s used in living hinges, pump housings, battery casings, and chemical tanks. Filled grades add stiffness while nucleated types improve processing and shrinkage control.
8. Polytetrafluoroethylene (PTFE)
PTFE is a speciality material, not used in high-volume applications due to its high cost and processing limitations. It operates continuously at temperatures up to 260°C, resists nearly all industrial chemicals, and has a dry coefficient of friction as low as 0.05. It’s chemically inert, non-stick, and dimensionally stable under thermal and mechanical load. Applications include valve seats, gaskets, seals, and insulation in aggressive chemical and high-temperature systems. PTFE is typically processed through extrusion or machining. It's too viscous to injection mould.
Understanding engineering plastics
Choosing the right engineering plastic goes beyond looking at strength or temperature limits. Material structure, fillers, moisture behavior, and compliance requirements all affect how a part will perform. These are the factors that typically drive material selection in real-world applications:
1. Material structure: thermoplastics vs. thermosets
Most engineering plastics are thermoplastics—they soften when heated and can be reshaped without major property loss. This enables reprocessing, easier forming, and in some cases, recyclability. Common examples include ABS, PC, and PA.
Thermosets form permanent cross-linked networks during curing and cannot be reprocessed. Thermosets cross-link during cure and do not reflow with heat. They hold shape under load at elevated temperatures and resist creep better than most thermoplastics. Epoxies and phenolics are typical, used in PCB substrates, structural adhesives, and thermal insulation where re-melt or deformation is not acceptable.
Our experts explain what you need to know in our guide, Thermosets vs. thermoplastics.
2. Reinforcement and fillers: glass-filled and fibre-modified grades
Adding glass, carbon, or mineral fillers to a base resin increases stiffness, strength, and heat resistance. Glass-filled nylon is a typical choice for parts like brackets or housings that see sustained load or elevated temperatures. Reinforced grades don’t mould as easily, can be abrasive to tooling, and may affect surface finish. Those trade-offs are usually worth it when mechanical performance is the priority.
3. Hygroscopic behaviour: moisture absorption
Several engineering plastics, particularly polyamides (nylons), are hygroscopic and absorb moisture from ambient air. This can lead to dimensional changes, shifts in mechanical properties, or altered electrical performance over time.
In tight-tolerance or insulating applications, this has to be accounted for. Material choice, pre-drying, and storage conditions all play a role. When moisture uptake is a problem, more stable options like PBT or PET are often used instead.
4. Loaded retention: creep resistance
Creep is the gradual deformation of a material under constant load. Materials like PEEK, PPS, and reinforced nylons are selected for parts that need to hold shape over time, especially under load and heat. Fasteners, seals, and structural components often call for materials with proven long-term creep performance. Commodity plastics typically deform too quickly to be used in these applications.
5. Cost performance optimisation
Engineering plastics aren’t cheap. Materials like PEEK or PTFE only make sense when the part can’t fail—high heat, aggressive chemicals, or sustained load. You won’t use them across an entire assembly. They show up where they’re needed most, and the cost gets weighed early in design alongside Finite Element Analysis (FEA), test data, and real-world performance.
6. Regulatory and compliance considerations
In regulated sectors, compliance is non-negotiable. Material selection often starts with certification, not performance.
Key standards include:
● UL94 for flammability
● ISO 10993 for biocompatibility
● FDA 21 CFR for food contact
● REACH/RoHS for substance restrictions
The resin must meet these requirements in final form, not just as supplied. Processing, sterilisation, and post-treatment can all affect compliance, and that has to be accounted for in material approval.
Technical properties
Because properties vary slightly depending on grade, additives, and manufacturing method, values are given as typical ranges. For precise engineering plastic material selection, especially in critical applications, consult the specific technical datasheet from the material supplier.
| Engineering plastic material | Tensile Strength (MPa) |
Max Service Temp | Water Absorption (24 h%) | Chemical Resistance | Impact Strength (Izod, kJ/m²) |
| ABS | 5,800–7,300 | ~185–210°F | 0.3–0.4 | Resists acids & alkalis; not solvents | 7–12 |
| Nylon (PA) | 10,000– 13,000 (dry) |
~250–300°F | 1.0–1.5 | Resists oils and fuels; sensitive to strong acids & moisture | 1.5–2.5 |
| Polycarbonate (PC) | 8,000–11,000 | ~240–275°F | 0.15–0.35 | Tolerates weak acids and alcohols; breaks down with solvents | 16–18 |
| Polyethylene (HDPE) | 3,000–5,000 | ~175–250°F | <0.01 | Handles acids, bases, and alcohols well; avoid strong oxidisers | No break |
| PET | 7,300–11,600 | ~240–275°F | 0.15–0.25 | Stable with oils, greases, and weak acids; not suited for bases | 0.7–1.5 |
| PEEK | 13,000– 15,000 |
~480–535°F | 0.05–0.1 | Resistant to almost all chemicals, including acids, bases, and solvents | 1.5–3.5 |
| Polyethylene (PP) | 4,300–5,800 | ~210–265°F | <0.01 | Excellent with most acids, bases, and solvents; poor with oxidisers | 1–2.5 |
| PTFE | 2,900–4,400 | ~500°F | <0.01 | Chemically inert to nearly everything, even strong acids and bases | 0.6–1.0 |
How engineering plastics are made
Plastic engineering starts with monomers—small molecules that react to form long polymer chains. The process varies by material, but usually involves either addition or condensation polymerization under controlled heat and pressure, often with a catalyst. The polymer is then processed into usable forms like pellets, sheet, or near-net parts by moulding, extrusion, or machining.
1. ABS
ABS is created through emulsion or mass polymerization, combining three monomers:
● Acrylonitrile for chemical resistance and strength
● Butadiene for toughness and impact resistance
● Styrene for rigidity and processability
These are usually blended in a two-step process: a rubbery polybutadiene backbone is grafted with acrylonitrile and styrene, forming a tough, mouldable plastic.
2. Nylon
Nylon is produced by condensation polymerization. For example:
● Nylon 6 is made by ring-opening polymerization of caprolactam.
● Nylon 6.6 comes from combining hexamethylenediamine and adipic acid.
Water is removed during polymerization, and the resulting polymer is cooled, pelletised, and ready for further processing like injection moulding or extrusion.
For a closer look at how injection moulding works, see What is plastic injection moulding and how does it work?
3. PC
Traditionally made via interfacial polymerization between:
● Bisphenol A (BPA)
● Phosgene (a toxic gas, handled in controlled environments)
This creates long, tough chains with carbonate linkages. More recent processes use non-phosgene routes, such as melt polymerization, for safer and more sustainable production.
4. PE
PE is produced through addition polymerization of ethylene gas using catalysts:
● LDPE: Made via high-pressure free-radical polymerization.
● HDPE: Made using Ziegler–Natta or metallocene catalysts at low pressure.
The type of catalyst and conditions control the branching of the polymer chains, which affects flexibility and strength.
5. PET
PET is made via condensation polymerization of:
● Terephthalic acid (or dimethyl terephthalate)
● Ethylene glycol
Water (or methanol) is removed during polymerization. PET is then solidified, chipped into pellets, and later reheated for moulding or extrusion.
6. PEEK
PEEK is synthesised via step-growth polymerization, typically using:
● Hydroquinon
● 4,4'-Difluorobenzophenone in the presence of a high-boiling solvent like diphenyl sulfone.
It’s a tightly controlled, high-temperature process that produces a semi-crystalline polymer with exceptional thermal and chemical stability.
7. PP
PP is made through addition polymerization of propylene gas, using either:
● Ziegler–Natta
or
● metallocene catalysts
The process allows control over polymer structure (isotactic, syndiotactic, or atactic), which affects properties like strength and transparency.
8. PTFE
PTFE is made via free-radical polymerization of tetrafluoroethylene (TFE), a highly reactive and hazardous gas.
This is done in aqueous suspension or emulsion systems, under pressure. The resulting powder is paste-extruded or compression-moulded, as PTFE doesn't melt-process like most thermoplastics due to its extremely high melting point.
Summary
| Material | Polymerization type | Key raw materials |
| ABS | Emulsion / mass polymerization | Acrylonitrile, butadiene, styrene |
| Nylon | Condensation polymerization | Caprolactam (PA6), hexamethylenediamine + adipic acid (PA66) |
| PC | Interfacial or melt polymerization | Bisphenol A, phosgene |
| PE | Addition polymerization | Ethylene |
| PET | Condensation polymerization | Terephthalic acid, ethylene glycol |
| PEEK | Step-growth polymerization | Hydroquinone, difluorobenzophenone |
| PP | Addition polymerization | Propylene |
| PTPE | Free-radical polymerization | Tetrafluoroethylene |
Selecting the right plastic material for your applications
Choosing the right plastic for an industrial application depends on more than just strength or cost. It’s about matching the material to the environment and mechanical demands of the job. The table below highlights common engineering plastics, typical industrial uses, and the specific advantages that make each material a strong fit for those applications.
| Material | Industrial application | Why it’s used |
| ABS | Housings for industrial equipment (e.g., tool enclosures, control panels) | Impact-resistant, easy to mould, holds tight tolerances, resists cracking under stress |
| Nylon | Mechanical gears, bushings, and moving parts in machinery | Strong, wear-resistant, low friction, handles repeated stress well |
| PC | Safety shields, machine guards, transparent panels | Tough, impact-resistant, clear, performs well in high-heat or clean environments |
| PE | Chemical storage tanks, transfer pipes, and fittings | Excellent chemical resistance, lightweight, moisture-resistant, easy to fabricate |
| PET | Bottles and containers for industrial fluids and chemicals | Strong, thermally stable, good chemical resistance, maintains shape under stress |
| PEEK | Insulating components in aerospace, oil & gas, or high-voltage systems | High strength at high temperatures, chemical and radiation resistant, reliable under load |
| PP | Valves, pump housings, tubing in chemical/water systems | Excellent chemical resistance, doesn't absorb moisture, fatigue-resistant, weldable |
| PTPE | Seals and gaskets in chemical processing equipment | Outstanding chemical resistance, handles extreme temperatures, very low friction |
Sustainability and engineering plastics
When it comes to sustainability, engineered plastics often get overlooked. But in the right applications, they can actually reduce environmental impact. Because they’re strong, durable, and lightweight, they’re often used in place of heavier materials like metal. That means less energy is needed for production, transport, and operation.
Engineered plastics also last a long time. They resist corrosion, chemicals, and wear, which can cut down on maintenance, replacements, and waste over a product’s life. And since many can be processed at lower temperatures than metals, they often require less energy to manufacture.
Of course, not all engineered plastics are easy to recycle, and end-of-life planning is still a challenge in some cases. But materials like PET and certain grades of nylon are recyclable, and there’s growing interest in bio-based alternatives and closed-loop systems. As technology improves, so does the potential for making these materials part of a more sustainable supply chain.
We recommend that you check out what our experts have to say about sustainability in manufacturing: Sustainable manufacturing: using recycled plastic in components manufacturing and Design for Sustainability: Optimising Plastic Injection Moulding Processes.
You can also see what our experts are up to with sustainability:
Essentra accelerates trials of bioplastic alternatives
Centre of Excellence trials into PCR plastic materials begin to bear fruit
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