PBT (unfilled) vs PET (Polyester): Both semi-crystalline polyesters — PBT faster crystallization, PET better creep
PBT (unfilled) vs PET (Polyester)
Side-by-side chemical composition and mechanical property comparison.
Overview
PBT (unfilled)
Polybutylene Terephthalate — semi-crystalline polyester with fast crystallization (short cycle times), very low moisture absorption (0.15%), excellent dimensional stability, and good electrical properties. Key advantage over PA: properties nearly independent of humidity. Trade names include Ultradur (BASF), Celanex/Crastin (Celanese/DuPont), Valox (SABIC), Arnite T (DSM). Used for electrical connectors, relay housings, automotive sensors, and any precision part in humid environments.
PET (Polyester)
Polyethylene Terephthalate (semi-crystalline stock shape) — combines the stiffness of POM with the wear resistance of PA, without centerline porosity or moisture sensitivity. Excellent dimensional stability, low friction, very low water absorption (~0.1%). Better creep resistance than POM or PA. Widely known from bottles/packaging, but engineering PET-P is semi-crystalline and much stiffer. Trade names include Ertalyte (MCAM), Arnite (DSM), Rynite (DuPont, GF grades). Used for precision bearings in water, gears, slide elements, pump parts, and electrical insulators.
| PBT (unfilled) | PET (Polyester) | |
|---|---|---|
| Material Number | — | — |
| Category | Polymers | Polymers |
| Standard | ISO 10350 | ISO 10350 |
Mechanical properties
| Property | PBT (unfilled) | PET (Polyester) | Unit |
|---|---|---|---|
| tensile_strength | 50–65 | 55–80 | MPa |
| yield_strength | 50–62 | 50–60 | MPa |
| elongation | 50–100 | 30–80 | % |
Compatibility Assessment
PBT crystallizes faster (shorter mold cycle times) and has better chemical resistance. PET has higher Tg (84 vs 30°C), better creep resistance, and no centerline porosity in stock shapes. Both have very low moisture absorption. Choose PBT for injection-molded connectors; PET for machined precision bearings.
Frequently Asked Questions
Is PBT (unfilled) the same as PET (Polyester)?
PBT (unfilled) and PET (Polyester) have a 70% composition overlap. Both semi-crystalline polyesters — PBT faster crystallization, PET better creep
Can I replace PBT (unfilled) with PET (Polyester)?
In many cases, yes. The compositions overlap significantly (70%). However, always verify mechanical property requirements and heat treatment compatibility for your specific application.
What is the difference between PBT (unfilled) and PET (Polyester)?
The main differences are in the following elements: overall alloying content. PBT (unfilled) is a Polymers grade, while PET (Polyester) is a Polymers grade.
Related Comparisons
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Data provided for reference only. Always verify against the applicable specification for critical applications.
All data is for reference only. Equivalents indicate similarity, not identity. Always verify against the applicable specification for safety-critical applications. materialref.com accepts no liability for decisions based on this data.