PA6+GF30 vs PA6+GF50: Glass Fiber Content Determines Performance Curve
The two most common grades of reinforced PA6 are PA6+GF30 (30% glass fiber) and PA6+GF50 (50% glass fiber). Although only 20% apart in glass fiber content, their performance curves, processing characteristics, and cost structures differ significantly. Proper material selection requires a deep understanding of these differences. This article provides a detailed comparison across four dimensions: mechanical properties, thermal properties, processing characteristics, and cost effectiveness.
Mechanical Properties: Stiffness vs Toughness
Increasing glass fiber content from 30% to 50% in reinforced PA6 shows a clear trend of "increased stiffness, decreased toughness." PA6+GF30 typically exhibits tensile strength of 140-170 MPa and flexural modulus of 7500-9000 MPa. PA6+GF50 achieves tensile strength of 190-230 MPa and flexural modulus of 13000-16000 MPa, representing a 50%-70% improvement in stiffness and strength. Notched impact strength of PA6+GF30 is typically 8-14 kJ/m² (23°C), while PA6+GF50 drops to 5-9 kJ/m², meaning higher susceptibility to brittle fracture under high impact loads.
Thermal Properties Comparison
Glass fiber content significantly enhances the thermal properties of reinforced PA6. PA6+GF30 has a heat deflection temperature (HDT, 1.82MPa) of approximately 195-210°C. PA6+GF50 achieves HDT of 215-225°C, approaching the level of reinforced pure PA66. In terms of long-term heat aging resistance, PA6+GF50 exhibits better thermal dimensional stability due to its higher glass fiber skeleton ratio, with dimensional change rates 30%-40% lower than PA6+GF30 after 150°C×1000h aging.
Processing Characteristics Comparison
PA6+GF50 has significantly poorer melt fluidity than PA6+GF30, with spiral flow length 30%-40% shorter. PA6+GF50 requires higher demands on gate design, and large or thin-walled parts may experience incomplete filling. Injection pressure requirements also increase significantly. Regarding mold wear, PA6+GF50 causes approximately 2-3 times more abrasion to mold steel compared to PA6+GF30, and mold life may be reduced by 30%-50%.
Shrinkage and Dimensional Stability
PA6+GF30 exhibits mold shrinkage of approximately 0.2%-0.5% in the flow direction and 0.6%-1.0% in the transverse direction. PA6+GF50 shows lower shrinkage: approximately 0.1%-0.3% in the flow direction and 0.4%-0.7% in the transverse direction. Higher glass fiber content means lower shrinkage and better dimensional stability, but also means anisotropy issues persist or become even more pronounced.
Cost-Effectiveness Analysis and Material Selection
PA6+GF50 typically costs 10%-20% more per unit than PA6+GF30. The real added costs come from reduced yield due to processing difficulties and higher mold maintenance expenses. Selection recommendation: If the product's stiffness and strength requirements fall within the performance range of PA6+GF30, upgrading to PA6+GF50 should not be considered lightly. The proper approach is to first optimize product structure design to meet stiffness requirements, and only consider higher glass fiber content grades when design optimization cannot satisfy requirements or space is constrained.
