How to Improve the Mechanical Properties of Glass Fiber-Reinforced Injection Molded Parts
Glass fiber-reinforced injection molded parts are widely used in automotive, electronics, and household appliances due to their superior strength, rigidity, and heat resistance. However, meeting higher performance requirements necessitates a focus on enhancing the mechanical properties of these parts.
Optimizing Glass Fiber and Matrix Resin Selection
1. Glass Fiber Length and Content
Fiber Length: Long fibers (≥10 mm) significantly improve the impact strength and fracture toughness of composites compared to short fibers.
Fiber Content: Increasing the fiber content (typically 20%-50%) enhances the mechanical properties. However, excessive content may reduce flowability and increase processing difficulty.
2. Matrix Resin Selection
Thermoplastics: Materials like PA (nylon), PP, and PBT, commonly used with glass fibers, offer high strength and excellent chemical resistance.
Resin Modification: Adding toughening agents or compatibilizers (e.g., maleic anhydride grafted polymers) improves the interfacial bonding between glass fibers and the resin.
3. Interface Modification Techniques
Surface treatment of glass fibers (e.g., coating with silane coupling agents) or chemical modification enhances the bonding between fibers and the resin, reducing fiber pull-out phenomena.
Optimizing Injection Molding Parameters
1. Injection Speed and Pressure
High Injection Speed: Promotes better fiber dispersion and densifies the molded part but may cause weld lines and air bubbles if too high.
High Injection Pressure: Ensures uniform fiber orientation during molding, reduces fiber breakage and improves mechanical properties.
2. Melt and Mold Temperature
Raising the melt temperature allows a more uniform distribution of fibers in the resin but must avoid excessive temperatures that could degrade the fibers.
Higher mold temperatures improve crystallinity and minimize shrinkage, enhancing part strength.
3. Cooling Time
A uniform and adequately extended cooling process reduces the internal stress concentration and warpage, improving overall performance.
Enhancing Fiber Orientation and Uniform Distribution
1. Optimizing Fiber Orientation
Adjust the flow direction and molding parameters to align the fibers with the direction of applied stress, significantly improving strength and rigidity.
2. Improving Uniform Distribution
Utilize compounding processes or static mixers to improve fiber dispersion within the melt, preventing localized performance inconsistencies.
