PBT vs PET.
Two polyesters.
Different uses.
PBT and PET are both polyesters, but optimized differently. PBT for engineering parts. PET for bottles, packaging, fibers. Understanding the differences guides selection.
Key principles.
Fast
Crystallizes in mold rapidly. Short cycles. Engineering use.
Slow
Slower crystallization. Stretched-blow process for bottles.
Stiffer
Higher modulus, dimensional stability, electrical-grade.
Transparent
Amorphous PET clear. Used for bottles, packaging, films.
HDT 60°C
Lower heat resistance unfilled. Glass-filled HDT 200°C.
HDT 70°C
Slightly higher unfilled. Used in oven-safe containers.
FAQ
Which crystallizes faster?
PBT — molds 10× faster than PET. Used for injection-molded parts.
Which is clearer?
PET — amorphous PET water-clear. Used for transparent bottles.
Glass-filled comparable?
Both available glass-filled. PBT 30% glass standard. PBT-GF more common in engineering.
Recycling streams?
PET #1, PBT #7 (other). PET large recycling stream from bottles. PBT minimal recycling.
Cost comparison?
Similar — PBT slightly higher due to engineering applications. ~$3-4/kg both.
When to choose?
PBT for engineering parts (electrical, automotive). PET for transparent containers, films, fibers.
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