Plastics engineering and injection molding glossary
A plastics engineering glossary is a lexicon of technical terms used in the injection molding industry. This glossary covers 70+ essential terms with their definitions, reference ISO/IEC standards, and units of measure. The essential vocabulary for plastics professionals, from press setter to materials engineer.
Find these measured properties in our injection molding material datasheets. For production troubleshooting, consult the injection molding defects guide.
Mechanical properties
- Density (ISO 1183)
- Mass-to-volume ratio in g/cm³. Key indicator for part weight and material cost.
- MFI — Melt Flow Index (ISO 1133)
- Measurement of melt fluidity in g/10 min. Determines how easily the material fills the mold.
- Molding Shrinkage (ISO 294-4)
- Contraction of the material upon cooling, expressed as a percentage.
- Tensile Strength (ISO 527)
- Maximum stress before rupture, in MPa.
- Flexural Modulus (ISO 178)
- Stiffness of the material, in MPa.
- Charpy Impact Strength (ISO 179)
- Toughness of the material, in kJ/m².
Thermal properties
- Melting Point Tm (ISO 11357-3)
- Temperature at which the material transitions to the molten state (semi-crystalline polymers).
- Glass Transition Temperature Tg (ISO 11357-2)
- Transition from rigid to flexible state.
- HDT — Heat Deflection Temperature (ISO 75)
- Structural integrity under load at elevated temperature.
- Vicat Softening Point VST (ISO 306)
- Surface softening temperature.
- CTE — Coefficient of Thermal Expansion (ISO 11359-2)
- Dimensional variation as a function of temperature.
Electrical properties
- CTI — Comparative Tracking Index (IEC 60112)
- Resistance to surface tracking and short circuit, in Volts.
- Volume Resistivity (IEC 60093)
- Opposition to current flow, in Ω·cm.
- Dielectric Strength (IEC 60243-1)
- Maximum voltage before breakdown, in kV/mm.
Other terms
- UL 94
- Flammability classification standard (HB, V-2, V-1, V-0, 5VA).
- RoHS
- Restriction of Hazardous Substances directive in electronics.
- REACH
- European chemical regulation governing chemical substances.
- Hot Runner
- System of heated channels running up to the injection gate.
- Holding Pressure
- Post-fill pressure applied to compensate for material shrinkage.