Single HDT number on PO
- May ignore creep under sustained load
- May ignore chemical exposure at temperature
Glossary
What Is Heat Deflection Temperature? Injection Molding Explained
Heat deflection temperature indicates how stiffness drops under load and heat in standard testing.
Glossary
Heat deflection temperature shows stiffness loss under load and heat in a standard test
Under hood and warm environment comparisons often start with HDT when datasheets align.
HDT is not a field failure prediction by itself. It ranks grades in comparable lab conditions.
Load, time at temperature, and part geometry drive real performance beyond one HDT line.
Pair HDT with Tg, continuous use notes, and design margins from your industry.
Glossary
How heat deflection 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.
Use
HDT only versus full thermal review
Avoid picking resin from one datasheet row.
HDT plus design and FEA margin
- Wall thickness and ribs carry load in the real part
- Test bars do not match weld lines or gates
Go deeper
Where this term connects
Each link is a different angle on the same program, not a duplicate definition.
Glass transition temperature
Amorphous softening reference.
Glass transition temperatureTensile strength
Peak stress on coupons.
Tensile strengthDesign guide hub
Wall and rib design for hot service.
Design guide hubPlastic molding
Production material qualification.
Plastic moldingVisual 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
HDT questions
Can HDT predict field failure alone?
No. Combine with loads, time, and chemical exposure.
Do filled grades change HDT?
Fillers can raise HDT in some families. Compare within same test method.
Should HDT drive gate location?
Indirectly through fill and orientation that affect performance.
Next step
Document service environment
Upload CAD with temperature and load notes on material RFQs.