Selection of Common Plastic Materials: ABS / PC / PP / PA / POM
Material selection directly affects mold design, molding process, product performance and cost in plastic component development. ABS, PC, PP, PA and POM are widely used general and engineering plastics. They differ greatly in strength, heat resistance, toughness, wear resistance and chemical resistance. Matching materials with application scenarios reduces molding defects and product failure in later stages.
1. ABS Material
ABS is copolymerized by acrylonitrile, butadiene and styrene, balancing rigidity, impact toughness and processability. It has good surface gloss and supports secondary treatment such as painting, electroplating and silk printing. Stable melt flow brings moderate requirement on mold machining, so it is suitable for appearance parts. Its long-term service temperature ranges from -20℃ to 70℃. It has weak resistance to acid, alkali and solvent. Contact with acetone and thinner easily causes cracking and whitening, and low-temperature impact drops obviously. Typical applications include home appliance housings, toys and decorative panels. It is not suitable for long-term high-temperature environment, strong chemical corrosion or sliding structural parts requiring continuous wear resistance.
2. PC Material
PC is high-performance amorphous engineering plastic with outstanding impact resistance, high light transmittance and better heat resistance than ABS. Normal grade can sustain continuous use around 110℃, and flame-retardant grades meet electrical fire safety standards. PC melt has high viscosity, requiring higher injection pressure and barrel temperature. Slow cooling easily induces internal stress, and stress cracking occurs when contacting solvent. Mold venting and cooling uniformity must be well designed. Transparent PC is used for lamp covers and sight windows. Toughened PC is used for helmets and protective housings. PC/ABS alloy combines processability and heat resistance for automotive interior and small home appliance structural parts. PC cannot be exposed to strong alkali and halogenated hydrocarbons for a long time.
| Material | Core advantages | Main limitations | Typical application |
|---|---|---|---|
| ABS | Good surface finish, easy plating and painting, balanced toughness | Poor chemical resistance, limited heat resistance | Home appliance shells, decorative parts |
| PC | High impact strength, transparent, good heat resistance | Easy to generate internal stress, high melt viscosity | Lamp covers, safety protective housings |
| PP | Low cost, excellent chemical resistance, good hinge property | Large shrinkage, low rigidity, easy to scratch | Food containers, pipe fittings, hinges |
| PA | Low friction, high strength, good oil resistance | Water absorption leads to dimensional change | Gears, bearings, automotive connectors |
| POM | Self-lubricating, high wear resistance, stable dimension | Hard to be flame retarded, thermal decomposition risk | Precision sliders, buckles, transmission parts |
Note: Modified grades such as glass-filled, flame-retardant and toughened materials have different performance parameters, which need to be verified by trial molding.
3. PP Material
PP is crystalline polyolefin with low density and prominent cost advantage. It has excellent acid, alkali, water and grease resistance, and outstanding fatigue bending performance without easy fracture after repeated folding. PP has low rigidity and poor low-temperature toughness. Unmodified PP is prone to brittle fracture at low temperature. Large molding shrinkage causes dimensional instability and warpage, and low surface hardness leads to easy scratch. Rigidity and low-temperature performance can be improved by glass fiber and toughening modification. PP is used for packaging containers, pipe fittings, bumper, hinges and food-contact products. It is not fit for high-load and high-precision appearance components.
4. PA (Nylon)
Common PA grades are PA6 and PA66, crystalline engineering plastics with low friction coefficient, high mechanical strength, good fatigue and oil resistance. Continuous service temperature is high, and glass fiber reinforced PA greatly improves rigidity and dimensional stability. Nylon absorbs moisture: moisture absorption increases toughness while reducing rigidity and changing dimension. Raw material must be fully dried before molding to avoid bubbles and silver streaks. Pure nylon has good wear resistance, and grades filled with molybdenum disulfide or PTFE are used for transmission structures. PA is widely used for gears, bearing bushes, connectors and engine surrounding auto parts. It is not suitable for products requiring stable low water absorption or working in strong acid environment.
5. POM (Polyoxymethylene)
POM is high-crystallinity engineering plastic with excellent self-lubrication, wear resistance, fatigue resistance and stable dimension. It has high rigidity and good resilience for high-precision moving structural parts. Its maximum continuous service temperature is 80~90℃. Flame retardant modification is difficult, and thermal decomposition releases irritating gas. Good flow performance comes with large molding shrinkage, so shrinkage compensation must be reserved in mold design. It is widely used for precision gears, sliders, buckles, valve fittings and bearings as substitute of small metal transmission parts.
6. Material Comparison and Selection Logic
Select ABS for decorative appearance parts needing electroplating or painting with low load; choose PC or PC/ABS alloy for high-impact transparent parts and heat-resistant housings; adopt PP for low-cost chemical-resistant bending parts and food-grade products; use PA for high-load oil-resistant transmission parts; prioritize POM for parts with continuous sliding friction and high-precision movement. Synchronize mold scheme with material property: DFM review focuses on tolerance control for PP, POM and PA with large shrinkage; optimize vent and cooling for high-viscosity PC; set drying procedure for moisture-absorbing nylon. Modified grades including glass fiber reinforced, flame retardant, toughened and weather-resistant types have different performances. Material suitability can be confirmed by sample test and trial molding before final selection.
