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PET Guide
Introduction
Polyethylene Terephthalate (PET) is a semi-crystalline engineering thermoplastic widely used for its excellent strength, dimensional stability, chemical resistance, and barrier properties.
While PET is commonly recognized for packaging applications, engineering-grade PET provides reliable mechanical performance and precision molding capability for demanding industrial applications.
With good wear resistance, low moisture absorption, and stable performance over time, PET is often selected for components requiring accuracy, durability, and consistent production quality.
This guide covers PET material properties, common applications, advantages, limitations, and injection molding considerations to help engineers make informed material selection decisions.
What Is PET Material?
PET (Polyethylene Terephthalate) is a polyester-based thermoplastic with a semi-crystalline structure that provides a combination of mechanical strength, dimensional stability, and chemical resistance.
Compared with general-purpose plastics such as ABS and PP, PET offers:
- Higher stiffness and strength
- Better dimensional stability
- Lower moisture absorption
- Excellent wear resistance
- Good chemical resistance
Engineering PET is commonly modified with reinforcing materials to improve performance for specific applications.
Common PET grades include:
Unfilled PET
Provides good mechanical properties, chemical resistance, and electrical insulation performance.
Glass Fiber Reinforced PET
Improves:
- Tensile strength
- Stiffness
- Dimensional stability
- Heat resistance
Commonly used for structural and precision components.
Mineral Filled PET
Enhances:
- Dimensional accuracy
- Reduced shrinkage
- Surface finish consistency
Flame Retardant PET
Designed for electrical and electronic applications requiring improved fire safety performance.
Key Properties of PET
1. Excellent Dimensional Stability
PET provides reliable dimensional performance due to its low moisture absorption and controlled shrinkage characteristics.
Benefits include:
- Tight tolerance capability
- Reduced dimensional changes during operation
- Stable performance under environmental variations
This makes PET suitable for precision molded components requiring consistent geometry.
2. High Mechanical Strength and Stiffness
Engineering PET offers a strong balance of strength and rigidity.
Key advantages include:
- High tensile strength
- Good impact resistance
- Excellent fatigue resistance
- Good wear performance
These properties make PET suitable for mechanical components exposed to repeated movement or loading.
3. Good Chemical and Wear Resistance
PET provides resistance against many common industrial environments, including:
- Oils and lubricants
- Solvents
- Cleaning agents
- Moisture exposure
Its wear resistance also makes it suitable for moving components requiring long service life.
4. Excellent Electrical Properties
PET is widely used in electrical applications because of its:
- Good dielectric strength
- Stable insulating performance
- Resistance to electrical aging
It is commonly selected for precision electrical and electronic components.
Advantages of PET Injection Molding
PET is suitable for injection molding applications requiring consistent quality and high-volume production.
1. Precision Manufacturing Capability
PET can achieve accurate dimensions for components requiring:
- Tight tolerances
- Complex geometries
- Stable mechanical performance
2. High Production Efficiency
Injection molding PET enables:
- Repeatable production
- Consistent part quality
- Cost-effective manufacturing for large volumes
3. Long-Term Reliability
PET components maintain performance under:
- Mechanical stress
- Temperature variations
- Chemical exposure
making them suitable for demanding industrial applications.
Common Applications of PET
1. Electrical and Electronics
PET is commonly used for electrical components requiring strength and insulation performance.
Examples include:
- Connector housings
- Insulating components
- Coil forms
- Electrical brackets
- Sensor components
2. Automotive Components
Engineering PET is used in automotive applications requiring durability and dimensional stability.
Applications include:
- Engine components
- Electrical connectors
- Structural brackets
- Sensor housings
- Mechanical supports
3. Industrial Equipment
PET is selected for industrial components requiring precision and wear resistance.
Applications include:
- Gears
- Bearings
- Bushings
- Mechanical housings
- Equipment components
4. Consumer and Precision Products
PET is also used in products requiring durability and accurate molding.
Examples:
- Functional housings
- Precision mechanisms
- Appliance components
- Consumer product assemblies
PET Injection Molding Considerations
Although PET provides excellent performance, proper processing control is essential for achieving consistent molded parts.
1. Material Drying Requirements
PET is hygroscopic and absorbs moisture from the environment.
Proper drying is critical to prevent:
- Hydrolysis
- Reduced mechanical strength
- Surface defects
- Poor molding quality
Engineers should ensure proper material storage and drying conditions before processing.
2. Mold Temperature Control
PET is a semi-crystalline material, and mold temperature significantly affects crystallinity and final part performance.
Important considerations include:
- Proper mold temperature setting
- Uniform cooling
- Controlled crystallization
3. Shrinkage and Warpage Control
PET shrinkage behavior depends on:
- Material grade
- Fiber reinforcement
- Part geometry
- Processing parameters
DFM review is important for maintaining dimensional accuracy and preventing deformation.
4. Gate Design and Flow Optimization
Proper gate location and runner design help achieve:
- Uniform filling
- Reduced weld lines
- Improved surface quality
- Better mechanical performance
PET Material Selection Guidelines
PET is recommended when your application requires:
- Good strength and stiffness
- Excellent dimensional stability
- Low moisture absorption
- Wear resistance
- Reliable electrical insulation
Consider alternative materials when:
- Higher temperature performance is required → consider PPS or PEEK
- Extreme chemical resistance is required → consider PPS or PEEK
- Higher impact resistance is required → consider PC or reinforced materials
PET vs Other Engineering Plastics
| Material | Strength | Temperature Resistance | Dimensional Stability | Typical Applications |
| ABS | Medium | Medium | Moderate | Consumer products |
| PC | High | High | Good | Impact-resistant parts |
| Nylon (PA) | High | Medium-High | Moderate | Mechanical components |
| POM | High | Medium | Excellent | Gears and precision parts |
| PET | High | Medium | Excellent | Electrical and precision components |
| PPS | Very High | Very High | Excellent | High-temperature applications |
Need Engineering Support?
Selecting the right PET grade and optimizing injection molding parameters requires careful consideration of material properties, part design, tooling requirements, and production conditions.
AccuMolds provides engineering support from material selection and DFM analysis to precision injection molding production, helping customers develop reliable plastic components for demanding applications.
