Heat deflection temperature
Stiffness loss under load and heat.
Heat deflection temperatureGlossary
What Is Glass Transition Temperature? Injection Molding Explained
Glass transition temperature is where amorphous polymers lose stiffness as heat rises.
Glossary
Glass transition temperature is where amorphous polymers soften markedly with heat
Service temperature discussions for amorphous parts often reference Tg with margin.
Below Tg the polymer behaves more glass like and stiff. Above Tg stiffness drops quickly for amorphous regions.
Semi crystalline resins also have melt behavior beyond Tg style softening.
Datasheets list Tg alongside other limits buyers must read together.
Glossary
How glass transition temperature shows up on real programs
Library photos illustrate molding and tooling context for this term.
- Use the term in RFQs with geometry and material context, not in isolation.
- Link to the design guide when the term affects steel or part design.
- Upload CAD when the term changes tooling scope or piece price.
Datasheet
Read Tg alongside these properties
One number rarely defines a field part.
Heat deflection temperature under load
Continuous use temperature if listed
Chemical exposure in the end environment
Part design thickness and load path
Go deeper
Where this term connects
Each link is a different angle on the same program, not a duplicate definition.
Tensile strength
Mechanical limits on coupons.
Tensile strengthFlexural modulus
Stiffness in bending tests.
Flexural modulusDesign guide hub
Wall design for hot environments.
Design guide hubVisual reference
Photos from molding and tooling programs
Images are selected from the NetProto Forge media library for this topic.
Injection molded production parts on a tray
Injection molded production parts on a tray
Engineer reviewing a molded part drawing
Engineer reviewing a molded part drawing
Plastic housing components from a steel tool
Plastic housing components from a steel tool
FAQ
Glass transition questions
Is Tg the same as melting point?
Semi crystalline grades also have melt regions. Read full datasheet curves.
Can molding process change effective Tg?
Degradation from overheating can hurt properties, not raise Tg safely.
Should buyers spec Tg on PO?
Spec end use temperature and loads. Material choice follows.
Next step
Match resin to environment
Upload CAD and service notes when heat is part of the RFQ.