Material selection for a molded part is made once and locked in by tooling. Change your mind after the mold is cut and shrinkage differences alone may make the tool unusable, since cavity dimensions are sized around the specific resin’s shrink rate.
That makes it worth more analysis than it usually receives. Four materials cover a large proportion of molded engineering parts, and each has a domain where it clearly wins.
This guide compares them on the properties that actually decide the choice, then covers the practical points that catch people out.
ABS
Acrylonitrile butadiene styrene, an amorphous thermoplastic and one of the most widely used molding materials.
Strengths. Molds easily with good flow and low shrinkage, produces good surface finish, takes texture and paint well, is readily bonded and machined, has decent impact resistance, and is inexpensive. Dimensionally stable and forgiving of design imperfections.
Weaknesses. Modest temperature resistance, poor UV resistance without stabilisation, and limited chemical resistance, particularly to solvents.
Typical uses: consumer product housings, enclosures, automotive interior trim, toys, appliance components, anything where appearance and cost matter and the environment is benign.
Why it is the default. ABS is forgiving. It fills easily, shrinks predictably, tolerates imperfect wall thickness better than most, and finishes well. Where requirements do not rule it out, it is usually the sensible starting point.
폴리카보네이트
An amorphous engineering thermoplastic known for exceptional impact resistance and optical clarity.
Strengths. Outstanding impact strength across a wide temperature range, natural transparency, good heat resistance, and good dimensional stability.
Weaknesses. Notch sensitive, meaning sharp internal corners substantially reduce its impact performance. Poor resistance to many solvents and some cleaning agents, which can cause stress cracking. Prone to scratching. Requires thorough drying before molding, since moisture causes degradation. Higher cost than ABS.
Typical uses: safety equipment, transparent covers and lenses, electrical housings, medical device components, anything requiring impact resistance or clarity.
The notch sensitivity point matters practically. Polycarbonate’s impact performance depends heavily on avoiding stress concentrations. Generous radii at internal corners are not a refinement, they are necessary to realise the material’s advantage.
PC-ABS
A blend combining properties of both.
Strengths. Better impact and heat resistance than ABS, better processability and lower cost than PC, reduced notch sensitivity compared to PC, and good surface finish.
Weaknesses. Not as strong or heat resistant as PC, not as cheap as ABS. Chemical resistance is moderate.
Typical uses: automotive interior and exterior components, electronics housings, applications where ABS is marginal on impact or temperature but PC is more than required.
Why it exists. PC-ABS occupies genuine middle ground. It is not a compromise in the pejorative sense but a practical answer where ABS falls short and PC is over-specified or difficult to process for the geometry.
나일론
Polyamide, a semi-crystalline engineering thermoplastic. PA6 and PA66 are the common grades.
Strengths. Excellent mechanical strength and stiffness, good wear resistance and low friction, good chemical resistance particularly to oils and fuels, and good heat resistance. Glass-filled grades are substantially stronger again.
Weaknesses. Absorbs moisture, which changes both dimensions and mechanical properties. Higher shrinkage than amorphous materials, and shrinkage is directional in filled grades, making warpage harder to control. Requires thorough drying before molding. Poor UV resistance without stabilisation.
Typical uses: gears, bearings, bushings, mechanical components, under-bonnet automotive parts, electrical connectors, anything requiring strength, wear resistance or chemical resistance.
The moisture point is the main design consideration. Nylon absorbs moisture from the atmosphere and swells as it does. Parts change dimension between molding and equilibrium, and mechanical properties change with them. For precision parts this must be designed around, and it is a frequent source of surprise for engineers new to the material.
Comparison
| 속성 | ABS | PC | PC-ABS | 나일론 |
| 내충격성 | Good | 우수 | Very good | Good |
| Heat resistance | 보통 | Good | Good | Good |
| 내화학성 | 제한적 | 제한적 | 보통 | Good |
| Dimensional stability | Good | Good | Good | Moisture sensitive |
| Transparency | 아니요 | 예 | 아니요 | 아니요 |
| Moldability | 우수 | Requires care | Good | Requires care |
| 수축 | 낮음 | 낮음 | 낮음 | Higher, directional |
| 표면 마감 | 우수 | Good | Very good | 보통 |
| Relative cost | 최저 | Highest | Middle | Middle to high |
Selecting by Requirement
Impact resistance is the driver: PC, or PC-ABS where PC is over-specified.
Transparency is required: PC among these four, though acrylic and some other materials are alternatives depending on the application.
Wear, friction or mechanical loading: nylon, likely glass-filled.
Chemical or fuel exposure: nylon.
Appearance and cost: ABS.
Elevated temperature: PC or nylon, with PC-ABS adequate for moderate cases.
Outdoor exposure: none of these without UV stabilisation. Specify a stabilised grade or design in protection.
Tight dimensional tolerance: ABS or PC, since nylon’s moisture absorption complicates it.
Moldability Differences
Material choice affects tooling and processing, not just part properties.
ABS is forgiving. It fills easily, shrinks predictably at a low rate, and tolerates less-than-ideal wall thickness. Tooling is straightforward.
PC has higher viscosity and needs higher melt temperatures. It requires thorough drying, since moisture causes hydrolytic degradation. Molded-in stress is a concern, and annealing is sometimes required.
PC-ABS processes more easily than PC while retaining most of the property advantage over ABS.
나일론 flows well but shrinks more than amorphous materials, and shrinkage in glass-filled grades is directional, following fibre orientation. This makes warpage prediction harder and increases the value of flow simulation. Drying is essential.
The practical implication is that switching material after tooling is designed is often impossible. Cavity dimensions are sized to the specific resin’s shrink rate, so a change to a material with different shrinkage may require tool modification or a new tool. Settle material before steel is cut.
Filled and Modified Grades
Each of these materials is available in numerous grades, and the differences between grades can exceed the differences between base materials.
Glass fibre substantially increases strength and stiffness and reduces shrinkage, at the cost of surface finish, impact resistance and increased tool wear from abrasion.
Mineral fillers improve dimensional stability and reduce cost, with less impact on surface finish than glass.
Impact modifiers improve toughness at some cost to stiffness.
UV stabilisers are necessary for outdoor use in all four materials.
Flame retardant grades are required for many electrical applications and change processing behaviour, sometimes considerably.
Specify the actual grade, not just the material family. “Nylon” is not a specification. A specific PA66 grade with a defined glass content is.
Note also that glass-filled grades are abrasive and wear tooling faster, which affects mold steel selection. Running glass-filled resin in a soft tool degrades it quickly.
Common Selection Mistakes
Specifying PC where PC-ABS would do. Adds cost and processing difficulty for performance the part does not need.
Ignoring nylon’s moisture absorption in precision applications, then finding parts out of tolerance after conditioning.
Sharp internal corners in polycarbonate, which defeats its main advantage.
Forgetting UV stabilisation on outdoor parts, producing yellowing and embrittlement in service.
Specifying a material family without a grade, leaving the choice to the molder with unpredictable results.
Changing material after tooling design, which shrinkage differences may make impossible without tool modification.
Overlooking chemical exposure, including cleaning agents. Many failures trace to a solvent nobody considered, and stress cracking in polycarbonate from cleaning products is a recurring example.
A Selection Sequence
- Define the mechanical requirements, including loading type and magnitude
- Define the temperature range in service, including transport and storage
- Identify every chemical the part will contact, including cleaning agents
- Determine whether UV exposure applies
- Establish appearance requirements, including colour, finish and transparency
- Establish dimensional tolerance requirements
- Check any regulatory requirements, such as food contact or flammability
- Shortlist materials meeting all of the above
- Compare cost and moldability across the shortlist
- Select a specific grade and confirm availability before finalising tooling
Steps 3 and 4 are the ones most often skipped and most often responsible for field failures.
Getting Material Advice Before Tooling
Material choice interacts with geometry, tooling and process together, and the right answer sometimes differs from the obvious one once wall thickness, flow length and finish requirements are considered.
Elite Mold Tech provides material recommendations as part of DFM review before quoting on 플라스틱 부품 생산, covering moldability and shrinkage implications alongside properties. Sending a part file with your application requirements produces a material assessment before tooling is committed, when the choice is still free to change.
자주 묻는 질문
Q: Is polycarbonate stronger than ABS?
A: In impact resistance, considerably, across a wide temperature range. It is also notch sensitive, so sharp internal corners substantially reduce that advantage, and it costs more and is harder to mold.
Q: When should I use PC-ABS instead of PC or ABS?
A: When ABS is marginal on impact or temperature but PC is more than the application requires. PC-ABS processes more easily than PC and costs less, while outperforming ABS on both counts.
Q: Why does nylon absorb moisture, and does it matter?
A: Polyamide chemistry attracts water, causing parts to swell and mechanical properties to change as they reach equilibrium. For precision parts this must be designed around rather than ignored.
Q: Can I change material after the mold is made?
A: Often not. Cavity dimensions are sized to the specific resin’s shrink rate, so a material with different shrinkage may require tool modification or a new tool entirely.
Q: Do I need to specify a particular grade?
A: Yes. Differences between grades within a material family frequently exceed differences between families, particularly with glass filling, impact modification, UV stabilisation and flame retardancy.
