Glass fiber reinforcement is the most common way to modify nylon. In grade names, GF15 and GF30 indicate a glass fiber content of about 15% and 30%. Many customers ask: how much is the right amount? And what if the part warps once glass fiber is added?
1. The higher the glass fiber content, the more pronounced the changes
As the glass fiber ratio increases, the material's strength, stiffness, heat resistance and dimensional stability all improve, and the impact of moisture absorption becomes smaller. The trade-offs are lower toughness, possible fiber floating on the surface, greater mold wear and poorer flowability.
2. Which content suits which parts
1. GF10~GF15: a balance between toughness and stiffness, suitable for snap fits that need some elasticity, thin-walled parts and parts with higher appearance requirements.
2. GF25~GF30: the most commonly used range, suitable for most structural parts, brackets, housings and power tool parts.
3. GF35~GF50: for parts that demand high stiffness, high heat resistance or metal replacement; places higher demands on molds and processing.
More glass fiber is not always better; once strength and stiffness requirements are met, just enough content is sufficient.
3. Why warpage occurs
During melt flow, glass fibers align along the flow direction, which causes different shrinkage rates in the flow direction and the transverse direction. Combined with uneven wall thickness and uneven cooling, parts easily warp and deform. The higher the glass fiber content, the more pronounced this anisotropy tends to be.
4. Common ways to control warpage
1. Design: keep wall thickness as uniform as possible, use ribs instead of thicker walls, and avoid large flat-plate structures.
2. Gating: set gate location and number sensibly so that fiber orientation is more uniform.
3. Mold temperature: raise mold temperature appropriately and control it uniformly to reduce cooling differences.
4. Material: reduce the glass fiber content while still meeting performance, or switch to glass fiber plus mineral or dedicated low-warpage grades.
5. Process: adjust holding pressure and time to avoid internal stress caused by over-packing.
5. What about fiber floating on cosmetic surfaces?
Raising mold temperature and injection speed and choosing a grade with better flowability generally improves fiber floating significantly. For cosmetic parts, dedicated low-fiber-floating formulations are also an option.
RJF Plastics supplies PA66 and PA6 reinforced compounds in various glass fiber contents (including black 10%, 30%, etc.) and can recommend the content based on part design and service conditions. The above is general information; specific data are subject to the actual datasheet.