High Temperature Plastics Automotive
Under-hood temperatures are brutal.
We’re talking about environments that can reach 150°C (300°F) continuously, with spikes to 200°C (392°F) or higher. Standard engineering plastics simply can’t survive there,melt, deform, or degrade rapidly. I’ve specified high-temperature plastics for dozens of automotive programs. Here’s what works, what doesn’t, and how to select the right material for your application.
Understanding Automotive Temperature Requirements
Temperature Zones
| Zone |
Temperature Range |
Typical Components |
Materials Needed |
| Passenger compartment |
-40 to +85°C |
Dash, panels, trim |
Standard ABS, PP |
| Exterior body |
-40 to +65°C |
Mirror housings, trim |
Weatherable PP, ABS |
| Engine bay (cool) |
-40 to +120°C |
Fuse boxes, relay trays |
High-temp ABS, PPE |
| Engine bay (hot) |
-40 to +150°C |
Air intake, covers |
PPA, PPS, LCP |
| Near engine |
-40 to +200°C |
Valve covers, oil pans |
PPS, PEEK, high-temp PPA |
Under-Hood Temperature Profile
| Component Location |
Continuous |
Short-Term Peak |
| Top of engine |
120-140°C |
180°C |
| Front of engine bay |
100-120°C |
150°C |
| Near exhaust manifold |
150-180°C |
220°C |
| Transmission housing |
120-150°C |
180°C |
| Fuse/relay box |
85-105°C |
125°C |
High-Temperature Material Options
Material Comparison Matrix
| Material |
HDT @ 264 psi |
Continuous Use Temp |
Melt Temp |
Cost Index |
| Standard ABS |
200°F (93°C) |
160°F (71°C) |
430°F |
1.0 |
| High-temp ABS |
215°F (102°C) |
185°F (85°C) |
450°F |
1.3 |
| PC |
270°F (132°C) |
250°F (121°C) |
500°F |
1.8 |
| PPE/PPO |
265°F (129°C) |
220°F (104°C) |
480°F |
1.6 |
| PPA (Nylon 6T) |
500°F (260°C) |
410°F (210°C) |
580°F |
3.5 |
| PPS |
500°F (260°C) |
430°F (221°C) |
560°F |
3.0 |
| PEEK |
305°F (152°C)* |
480°F (249°C) |
700°F |
25-40 |
| LCP |
500°F (260°C) |
430°F (221°C) |
650°F |
4-6 |
| PSU |
345°F (174°C) |
300°F (149°C) |
650°F |
4-5 |
| PES |
390°F (199°C) |
340°F (171°C) |
680°F |
5-7 |
*PPS HDT depends heavily on grade; engineering grades higher
Engineering-Grade High-Temp Materials
PPA (Polyphthalamide)
- Continuous use to 210°C (410°F)
- Excellent mechanical properties at temperature
- Superior chemical resistance
- 30-45% glass-filled common
- Moderate hydrolysis resistance (dry as-molded)
- Applications: Turbo components, air intake manifolds, engine covers PPS (Polyphenylene Sulfide)
- Continuous use to 221°C (430°F)
- Excellent chemical and solvent resistance
- Inherent flame retardance
- low moisture absorption
- 40% glass-filled typical
- Applications: Pump housings, valve bodies, electrical components LCP (Liquid Crystal Polymer)
- Continuous use to 221°C (430°F)
- Excellent flow for thin walls
- Superior chemical resistance
- Outstanding dimensional stability
- High cost limits to critical applications
- Applications: Connectors, thin-walled sensors, high-frequency components PEEK (Polyetheretherketone)
- Continuous use to 249°C (480°F)
- Excellent mechanical properties
- Outstanding chemical resistance
- Steam sterilizable
- high cost (25-40× ABS)
- Applications: Seals, bearings, fuel system components, medical (automotive adjacent)
Automotive Standards and Testing
Key Automotive Material Standards
| Standard |
Scope |
Key Requirements |
| GMW15572 |
Automotive interiors |
VOC emissions, fogging |
| VDA 275 |
Interior fogging |
Test method for fogging |
| PV 1200 |
Heat aging |
Heat aging requirements |
| PV 1505 |
Temperature cycling |
Thermal shock |
| USCAR |
Wire harness |
Multiple standards |
| ASTM D618 |
Conditioning |
Standard lab conditions |
| ISO 16750 |
Environmental testing |
Road vehicle standards |
Typical Automotive Testing Requirements
| Test |
Purpose |
Typical Duration |
| Heat aging |
Thermal stability |
500-2,000 hours @ temp |
| Thermal cycling |
Thermal shock resistance |
500-1,000 cycles |
| Humidity exposure |
Moisture effects |
1,000 hours @ 85°C/85% RH |
| Salt spray |
Corrosion resistance |
500-1,000 hours |
| UV/weathering |
Outdoor durability |
1,000-2,000 hours |
| Chemical exposure |
Fluid resistance |
24-168 hours immersion |
Flammability Requirements
| Standard |
Application |
Rating Required |
| FMVSS 302 |
Interior materials |
Self-extinguishing |
| UL 94 |
Electrical |
V-0, 5VA typical |
| IEC 60695 |
Burning behavior |
Glow wire testing |
Application-Specific Selection
Engine Bay Components
| Component |
Temp Range |
Recommended Materials |
Notes |
| Air intake manifold |
120-160°C |
PPA, PPS |
Welded or bolted construction |
| Valve cover |
140-180°C |
PPA, PPS, LCP |
Oil exposure, needs seals |
| Oil pan |
120-150°C |
PPA, PPS |
Structural, oil exposure |
| Engine cover |
120-160°C |
PPA, high-temp PP |
Cosmetic surface |
| Turbo inlet |
160-200°C |
PPA, PPS, PEEK |
Highest temp zone |
| Fuse box |
100-130°C |
PPE, high-temp ABS |
Electrical, needs UL rating |
| Relay tray |
100-130°C |
PPE, PPA |
Structural, retention clips |
Underhood thermal stability properties
Factors
| Factor |
Impact on Selection |
| Continuous temperature |
Primary selection criterion |
| Thermal cycling frequency |
Fatigue resistance important |
| Chemical exposure |
Oil, coolant, fuel resistance |
| Mechanical loads |
Strength at temperature |
| Regulatory requirements |
Flammability, emissions |
| Cost targets |
Engineering grade vs. specialty |
| Processing requirements |
Tooling and parameters |
Electrical/Electronic Components
| Component |
Temp Range |
Recommended Materials |
Key Requirements |
| Connectors |
125-150°C |
LCP, PPS, PPA |
Dimensional stability |
| Sensors |
125-180°C |
LCP, PPS |
Precision, reliability |
| LED housings |
100-140°C |
PPA, LCP |
Clarity or heat resistance |
| Battery components |
80-120°C |
PPE, PPA |
Chemical resistance |
| Wire coating |
125-200°C |
PPS, PPA |
Electrical insulation |
Mechanical Properties at Temperature
| Material |
RT Tensile |
@150°C Tensile |
% Retained |
| High-temp ABS |
6,500 psi |
3,000 psi |
46% |
| PC |
9,500 psi |
5,500 psi |
58% |
| PPA (30% GF) |
26,000 psi |
18,000 psi |
69% |
| PPS (40% GF) |
25,000 psi |
19,000 psi |
76% |
| LCP (30% GF) |
23,000 psi |
17,000 psi |
74% |
| PEEK (30% CF) |
32,000 psi |
25,000 psi |
78% |
Long-Term Heat Aging
| Material |
1,000 hr @ 150°C |
1,000 hr @ 180°C |
1,000 hr @ 200°C |
| PPA |
✓ Stable |
⚠ Some degradation |
✗ Significant |
| PPS |
✓ Stable |
✓ Stable |
⚠ Some degradation |
| LCP |
✓ Stable |
✓ Stable |
⚠ Some degradation |
| PEEK |
✓ Stable |
✓ Stable |
✓ Stable |
✓ = Acceptable ⚠ = Monitor ✗ = Not recommended
Processing Considerations
Drying Requirements
| Material |
Dry Temp |
Dry Time |
Max Moisture |
| PPA |
250-280°F |
4-6 hours |
0.10% |
| PPS |
250-280°F |
4 hours |
0.10% |
| LCP |
250-280°F |
4 hours |
0.05% |
| PEEK |
300-350°F |
4-6 hours |
0.02% |
| PSU |
250-300°F |
4 hours |
0.10% |
Melt Temperatures
| Material |
Melt Temp Range |
Mold Temp |
| PPA |
580-620°F |
275-325°F |
| PPS |
540-580°F |
250-300°F |
| LCP |
600-660°F |
200-250°F |
| PEEK |
680-720°F |
350-400°F |
| PSU |
620-680°F |
250-300°F |
Processing Challenges
| Material |
Key Challenges |
Mitigation |
| PPA |
Moisture sensitivity, viscosity |
Rigorous drying, higher temps |
| PPS |
Ablative wear on steel |
Coated or hardened tooling |
| LCP |
Low viscosity, jetting |
Fast fill, controlled parameters |
| PEEK |
High temps, cost |
Dedicated tooling, careful handling |
| PSU |
Stress sensitivity |
Annealing, careful mold design |
Material Cost Index (ABS = 1.0)
| Material |
Unfilled |
30% GF |
40% GF |
Cost Impact |
| ABS |
1.0 |
1.4 |
1.6 |
Baseline |
| PPE/PPO |
1.6 |
2.2 |
2.5 |
+60-150% |
| PPA |
N/A |
3.5 |
4.0 |
+250-300% |
| PPS |
N/A |
3.0 |
3.5 |
+200-250% |
| LCP |
N/A |
4.0 |
5.0 |
+300-400% |
| PEEK |
N/A |
25.0 |
30.0 |
+2500-3000% |
Total Cost Analysis Framework
When selecting high-temperature materials, consider:
| Cost Factor |
Impact |
| Material cost/lb |
Direct procurement |
| Scrap rate |
+5-15% for engineering grades |
| Tool life |
-20-50% vs. standard materials |
| Processing cost |
Similar or +10-20% |
| Productivity |
Similar or -10-20% |
| Secondary operations |
May be reduced |
| Part replacement |
May be eliminated |
Validation and Qualification
Automotive-Specific Testing
| Test Type |
Typical Duration |
Purpose |
| Material datasheet |
N/A |
Baseline properties |
| Color matching |
2-4 weeks |
Visual approval |
| Heat aging |
8-16 weeks |
Long-term stability |
| Fluid exposure |
2-4 weeks |
Chemical resistance |
| Thermal cycling |
4-8 weeks |
Fatigue resistance |
| Environmental cycling |
8-12 weeks |
Combined stressors |
| Full validation |
6-12 months |
Complete approval |
Documentation Requirements
| Document |
Content |
Retention |
| Material data sheet |
Properties, processing |
Permanent |
| FDA/NSF status |
Food contact if needed |
Permanent |
| REACH/Ro HS compliance |
Restricted substances |
Permanent |
| Homologation |
Vehicle approval |
Permanent |
| PPAP data |
Production qualification |
Per OEM |
Selection Decision Framework
Quick Selection Guide
| Temperature |
Non-critical |
Moderate Load |
High Load |
| <120°C |
High-temp ABS |
ABS + glass |
PPA (15% GF) |
| 120-150°C |
PPE/PPO |
PPA (15-30% GF) |
PPA (30% GF) |
| 150-180°C |
PPA (15% GF) |
PPA (30% GF) |
PPS (30-40% GF) |
| 180-200°C |
PPS (30% GF) |
PPS (40% GF) |
LCP or PEEK |
| >200°C |
LCP |
LCP or PEEK |
PEEK |
Questions to Answer First
- What is the continuous operating temperature?
- What are the peak temperatures and duration?
- What mechanical loads are expected at temperature?
- What fluids will the part contact?
- What are the regulatory requirements (flammability, emissions)?
- What are the cost targets?
- What is the required service life?
The Bottom Line
High-temperature automotive applications demand engineering respect for the thermal environment.
The difference between PPA and PPS, between 30% and 40% glass fill, between continuous and peak temperature,these details matter enormously. The data tells you the maximum allowable temperatures. Your application’s actual requirements tell you what you truly need. And the cost analysis tells you what you can afford. Don’t overspecify,you’re paying for performance you don’t need. Don’t underspecify,the consequences of heat-related failure are severe. Match the material to the requirement. Validate thoroughly. Document everything. That’s how you survive under the hood.