Views: 0 Author: XINYITE PLASTIC Publish Time: 2025-07-11 Origin: Site
Critical Length (Lo):
For PP, the critical fiber length is 3.1 mm. Fibers shorter than this are easily pulled out under stress, failing to transfer load effectively. SGFPP typically uses fibers < 3.1 mm (often 0.2–0.6 mm after processing), while LGFPP starts with 10–25 mm fibers and retains >3.1 mm in the final part.
Fiber Architecture:
SGFPP forms a discontinuous, random arrangement, whereas LGFPP creates an interconnected 3D network that mimics a "skeleton" structure. When burned, LGFPP retains structural integrity, while SGFPP collapses.
(Key properties compared)
| Property | SGFPP | LGFPP | Improvement |
|---|---|---|---|
| Tensile Strength | 20–50 MPa | 70–150 MPa | Up to 200% higher |
| Impact Strength | Low (brittle-prone) | High (energy-absorbing) | 6× higher |
| Creep Resistance | Poor (deforms under load/heat) | Excellent (stable at 100°C) | — |
| Isotropy | High anisotropy (warpage) | Low anisotropy (uniform shrinkage) | Warpage reduced by 30–50% |
| Fatigue Resistance | Moderate | Superior | 2–3× lifespan |
Mechanism: Longer fibers in LGFPP enable efficient stress distribution and resist crack propagation. SGFPP relies on matrix dominance, limiting reinforcement.
SGFPP:
Smoother surface (Ra < 1 µm) due to shorter fibers that do not protrude. Ideal for visible parts (e.g., consumer electronics).
LGFPP:
Rougher texture (Ra > 2 µm) with frequent fiber exposure ("fiber float"). Requires painting/coating for aesthetics. Trade-off for structural strength.
SGFPP:
Standard injection molding; fibers break minimally but disperse poorly.
LGFPP: Needs modified screws, lower shear rates, or direct processing (LFT-D/LFT-G) to preserve fiber length. Higher viscosity demands robust equipment57.
| SGFPP | LGFPP |
|---|---|
| Non-structural parts (e.g., housings, covers) | Automotive structural components: Front-end modules, battery trays, seat frames |
| Low-cost consumer goods | Integrated modules: Replaces 10+ metal parts, reducing weight by 30% |
| — | High-stress industrial: Ski bindings, safety helmets |
Material Cost: SGFPP is cheaper (standard compounding). LGFPP costs 20–30% more
Sustainability: LGFPP reduces energy use by 35–50% vs. aluminum and 20–40% vs. steel during production.
Opt for SGFPP: Cost-sensitive, high-volume parts with smooth surfaces and moderate loads.
Opt for LGFPP: Structural components requiring impact resistance, dimensional stability, and weight reduction (e.g., automotive safety parts).
