ABS vs PC vs PA vs POM: Matching Engineering Plastics to Your Application

Engineering plastic selection is a decision that is expensive to reverse: the polymer sets the service temperature, the impact behaviour, the chemical resistance and the wear life of a part long before the mold is cut, and changing material later usually means a new gate position, a new shrink allowance and a new tool. ABS, polycarbonate, polyamide and POM cover most of the parts buyers ask for, and each one wins on a different property.

This guide compares the four families on heat, impact, chemical and wear performance, sets out a selection path you can work through with a drawing in hand, and shows what each choice does to molding conditions, cost and lead time.

Xiamen Yistar Precision Manufacturing Co., Ltd has molded engineering plastic components in Xiamen, Fujian, China since 1995, with tooling, molding and assembly under one roof, so material, mold and process decisions are reviewed together before the first sample is cut.

Key Takeaways

• ABS is the low-cost, easy-molding choice for housings that work below 85 °C, but it is attacked by ketones, esters and concentrated acids and degrades in direct sunlight without a UV-stabilised grade.
• Polycarbonate holds notched impact strength of 60 to 85 kJ/m² and stays usable to about 120 °C, which makes it the material for transparent covers, safety guards and hot-air housings.
• Unfilled polyamide 6 or 66 absorbs 1.5% to 2.8% moisture by weight at equilibrium, so PA parts grow in humid service and must be toleranced against conditioned dimensions rather than dry ones.
• POM is the wear material: a coefficient of friction of 0.2 to 0.35 against steel and continuous service to about 95 °C make it the default for gears, cams, sliders and latches.
• Glass filling at 15% to 30% multiplies stiffness and cuts shrinkage to 0.2% to 0.5%, but it halves notched impact strength and raises tool wear, so it is specified only where load or tolerance demands it.

What Are Engineering Plastics and When Do You Need One?

Engineering plastics are polymers specified for mechanical load, temperature or wear rather than appearance alone, and ABS, PC, PA and POM sit in that class. You need one when a commodity polypropylene or polystyrene part would creep, crack, wear or distort in service, or when the part has to carry load without a metal insert to help it.

Commodity resins are chosen on cost and moldability: polypropylene, polyethylene and polystyrene. Engineering resins are chosen on measured performance, which is why a datasheet for ABS, PC, PA or POM states tensile strength, heat deflection temperature and impact strength at defined test conditions. Most of the cost difference between the two classes is paid for by skipping inserts, secondary machining and field failures.

How Do ABS, PC, PA and POM Compare?

ABS offers toughness and appearance at the lowest cost; polycarbonate adds impact strength and heat resistance to about 120 °C; polyamide adds strength above 120 °C once glass filled; POM adds wear resistance and the lowest friction. Heat, impact and wear rarely peak in the same material, so the ranking depends on which property your part loads.

The table lists typical ranges for unfilled grades unless a glass content is stated, measured at standard conditioning and test speed. Confirm every figure against the datasheet of the specific grade, because impact strength in particular drops sharply at low temperature and after ageing.

Which Engineering Plastic Fits Your Part?

Work through four questions in order: continuous service temperature, load and impact, chemical exposure, and wear or friction. The first question that eliminates a material removes it for good, because a part that fails on heat cannot be rescued by better wear resistance. Cost decides only between the materials that already pass those four filters, never before them.

1. Service temperature. Above 120 °C sustained, choose glass-filled PA or PBT rather than ABS, PC or unfilled POM.
2. Impact and load. A part that takes a drop or a snap-fit cycle at 20 °C points to PC or ABS; a part under sustained load points to glass-filled PA.
3. Chemical exposure. Oils, fuels and grease favour PA or POM, while bleach, ketones and solvent cleaners rule both ABS and PC out.
4. Wear and friction. Sliding contact without lubrication points to POM, or PA with a PTFE additive when the load is higher.
5. Tolerance and stability. Tight tolerances in humid service favour POM or glass-filled PA over unfilled PA, whose conditioned dimensions move by 0.2% to 0.5%.
6. Cost and volume. Compare the finished part, not the resin: a cheaper ABS part that needs a metal insert can cost more than a POM part molded in one shot.

Why Does Glass Filling Change the Choice?

Adding 15% to 30% glass fibre multiplies tensile strength and stiffness and cuts shrinkage to 0.2% to 0.5%, which is how tight tolerances are held. It also halves notched impact strength, raises melt viscosity, abrades tool steel, and creates anisotropic shrinkage that warps a long, flat part unless the gate and cooling layout are designed for it.

Glass-filled grades also change the economics: they cost 20% to 40% more per kilogram than the unfilled grade, wear a standard tool faster, and often need hardened steel or a surface treatment on the cavity. They are specified where stiffness or dimensional stability decides the design, and skipped where a rib pattern could deliver the same stiffness more cheaply in an unfilled grade.

How Do These Materials Mold, Dry and Cost?

Molding conditions separate the four families as much as properties do: ABS and POM run from undried pellets, while PA and PC must be dried to below 0.02% moisture or they splay and hydrolyse. POM has the widest processing window of the four, PC the narrowest, and the two polyamides sit between them depending on glass content.

POM's shrinkage of 1.8% to 2.2% is the highest here, so the tool has to be cut oversize by that allowance and the cooling layout has to be symmetric, or the part will be oval rather than round. Resin cost per kilogram tells only part of the story: a 40-second cycle in ABS against a 75-second cycle in PC changes the piece price by more than the 1.5 times resin difference does, as our breakdown of what drives the cost of a molded part sets out.

Where Do ABS, PC, PA and POM Commonly Fail in Service?

POM fails against strong acids and in hot chlorine bleach, polycarbonate fails by environmental stress cracking in contact with alkalis, amines and solvent cleaners, polyamide fails through moisture absorption and dimensional growth, and ABS fails by UV degradation and solvent attack. Every one of those failures has a design fix that costs less than the field failure it prevents.

• POM in strong acids or bleach: change to PP or glass-filled PA where the chemistry reaches the part, and check the cleaning agent used by the end user, not only the fluid in the assembly.
• PC stress cracking: move the gate away from the stressed corner, anneal the part at 120 °C for 2 hours where the design allows, and ban solvent-based cleaners from the service instructions.
• PA dimensional growth: tolerance against conditioned dimensions, keep walls uniform, and specify glass filling where 0.2% to 0.5% growth cannot be accommodated.
• ABS outdoor exposure: specify a UV-stabilised grade, or move to ASA or PC-ABS where colour and impact have to survive direct sunlight.

Automotive programs add their own constraints on top of these, and the material and compliance side of that work is covered in our guide to automotive plastic parts and the standards they must meet.

Which Grades Meet Food-Contact, Flame and Compliance Requirements?

Compliance attaches to the grade, not the family: an ABS copolymer can be listed for food contact under FDA 21 CFR 177.1020 in one formulation and not in another, because the additive package differs. UL 94 V-0 is valid only for the grade and wall thickness that were tested, and a RoHS statement must name the grade it covers.

Three documents answer most audit questions: the resin supplier's food-contact declaration naming the regulation and the grade, a UL yellow card for the flame rating, and a RoHS and REACH statement covering additives and colourants. Medical and fluid-path parts are molded under tighter material handling, which our guide to medical device plastic components and cleanroom molding explains.

How Do You Prototype and Scale an Engineering Plastic Part?

Prototype in the production material wherever the part carries load, because ABS and PA substitutes behave differently on creep and moisture. Cut the tool once the DFM review confirms wall thickness, draft and gate position, then validate with first-article inspection, conditioned dimensions for PA, and a functional test at service temperature rather than at room temperature only.

The scaling path for a new part is short if the material is fixed early:

1. Run the selection questions with the drawing and the service conditions, and record the result on the drawing rather than in an email.
2. Confirm the grade with the resin supplier and ask for the datasheet, the food-contact or UL document and the shrinkage range for that grade.
3. Design the tool around the measured shrinkage, with draft of 0.5° to 1° per side and a gate position that keeps weld lines out of the stressed areas.
4. Mold first samples, measure conditioned dimensions for PA, and test the part at service temperature before approving the tool.
5. Keep the process sheet for the approved cycle, including drying conditions and packing profile, so later production lots repeat it.

FAQ

Which engineering plastic is best for gears, POM or PA?

POM is the default for unlubricated gears because its coefficient of friction against steel is 0.2 to 0.35 and it holds shape in humid air. PA is used for gears when the load is higher, the temperature above 100 °C, or the gear runs against another plastic gear. Both are usually combined with a lubricant additive for continuous duty.

Is polycarbonate stronger than ABS?

Polycarbonate is roughly twice as impact resistant as ABS, with notched impact strength of 60 to 85 kJ/m² against 20 to 40 kJ/m², and it keeps that toughness to about 120 °C instead of 85 °C. ABS is stiffer in thin walls, takes a better cosmetic finish and costs about half as much per kilogram, so it wins most visible housings.

What is the maximum service temperature of ABS, PC, PA and POM?

Continuous service temperatures are about 85 °C for ABS, 120 °C for polycarbonate, 95 °C for POM, and 140 °C for PA6 or PA66 with 30% glass fibre. Those figures assume no sustained load; under load the usable limit falls to the heat deflection temperature at 1.82 MPa, which for ABS is 80 to 95 °C.

Do POM and PA need drying before molding?

POM is normally molded without drying because it absorbs very little moisture. PA grades must be dried, typically for four hours at 80 to 100 °C to below 0.1% moisture, and PC to below 0.02%, otherwise the melt hydrolyses and the parts show splay marks and a measurable loss of impact strength.

Are ABS, PC, PA and POM FDA food-contact approved?

Each family contains grades that are food-contact compliant and grades that are not, so the answer depends on the formulation rather than the polymer. Grades listed under FDA 21 CFR 177, or compliant with EU 10/2011, exist in all four families. The resin supplier must issue a declaration naming the grade and the regulation.

Which engineering plastics meet UL 94 V-0?

Flame-retardant grades of ABS, polycarbonate, PA and POM are available at UL 94 V-0, and polycarbonate reaches V-0 more easily than the others without heavy additive loading. The rating applies only to the tested grade at the tested wall thickness, so a part relisted at 1.5 mm cannot claim the rating tested at 3.0 mm.

Conclusion

ABS, PC, PA and POM are not interchangeable grades of one plastic; they are four different answers to four different service conditions, and the selection starts with temperature, load, chemistry and wear, in that order. Fix the material on the drawing with its shrinkage, drying condition and compliance document, and the tool, the cycle and the piece price all follow from a decision you can defend. Send the drawing, the service temperature and the fluid the part meets, and the team at Xiamen Yistar Precision Manufacturing Co., Ltd will recommend the grade, the wall thickness and the tool layout, then mold Custom Engineering Plastic Components and Custom consumer electronics projects to the tolerances and documentation your program requires. For the molding side of the same decision, see our guide to the injection molding process step by step, and for the wider comparison behind it, how to choose the right plastic material for your product.

Contact Us

Xiamen Yistar Precision Manufacturing Co., Ltd
Address: Room 401, No. 37 Huliyuan, Tong'an District, Xiamen, Fujian, China
Phone / WhatsApp: +86-18064076912
Email: info@yistar-plastic.com
Open Hours: 24 Hours