PA6 GF30 Versus GF50, and How Reinforced PC Processing Differs

GF30 to GF50: diminishing returns

PA6 GF30 delivers roughly 165 MPa tensile strength and 8,500 MPa flexural modulus; GF50 rises to about 200 MPa and 15,000 MPa. Notched impact barely improves and can even fall, while melt flow degrades noticeably and thin walls become hard to fill.

Appearance is the bigger difference: high glass content causes severe fibre show-through, making it unacceptable for visible parts. GF50 is normally reserved for internal high-strength structures.

Processing differences with reinforced PC

PC is amorphous with no sharp melting point, so moulding depends on viscosity drop above the glass transition. The processing window is narrower than PA and the material is extremely moisture sensitive — dry below 0.02% first.

Mould temperature must also be higher: typically 90-120 °C for PC versus 70-90 °C for PA6. Insufficient mould temperature leaves high residual stress and cracking risk.

Shared critical factor: fibre length retention

For both PA and PC the real benefit depends on retained glass fibre length. Shear during twin-screw compounding, together with screw and gate design in injection moulding, determines the final length — usually only about one third of the original pellet length survives in the moulded part.

That explains why the same 30% glass grade can vary 10-20% in performance between machines. Test on plaques produced on the target press with target parameters wherever possible.