Our Polyether Imide PEI Injection Molding Services

Step 1: Material Preparation (Drying)​

PEI is hygroscopic (absorbs moisture), which causes bubbles and surface defects. We dry PEI pellets in a dehumidifying dryer at 150 °C for 4 hours (target moisture content: <0.02%). For medical-grade PEI (e.g., Ultem HU), we use nitrogen-purged dryers to prevent contamination.​

Step 2: Mold Design & Preparation​

• Hot-Runner Manifold: We use hot runners (instead of cold runners) to keep PEI molten, reducing scrap by 30–35% and ensuring uniform flow into the mold.​

• Mold Temperature Control: Molds are heated to 140–180 °C (via oil heaters) to prevent premature cooling (which causes flow marks in amorphous materials). For thin-wall parts (0.2 mm), we use gradient heating to maintain consistent mold temp across cavities.​

Step 3: Machine Setup​

• High-Heat Barrel Profile: Barrel zones are set to a precise gradient:​

• Feed zone: 340 °C (melts pellets without degradation)​

• Melt zone: 360–370 °C (maintains optimal viscosity)​

• Nozzle: 370–380 °C (prevents material solidification)​

• Low-Shear Screw Design: Our screws have deep flights and slow rotation (50–70 RPM) to minimize shear stress—excessive shear breaks PEI’s polymer chains, reducing strength by 15–20%.​

Step 4: Injection & Packing​

• Injection Speed: Moderate (80–100 mm/s) to fill cavities without creating air pockets. For thin-wall parts, we use fast injection (120–150 mm/s) to avoid short shots.​

• Packing Pressure: 85–90% of injection pressure, held for 15–20 seconds to compensate for amorphous shrinkage (PEI shrinks 0.5–0.8% during cooling).​

• Nitrogen Assist: For complex parts (e.g., with undercuts), we inject nitrogen into the mold to push PEI into hard-to-reach areas—reducing defects by 40%.​

Step 5: Cooling & Demolding​

Cooling time varies by part thickness (10 seconds for 0.2 mm parts, 60 seconds for 5 mm parts). We use controlled cooling to avoid internal stresses—critical for maintaining dimensional stability. Demolding is done with soft ejectors to prevent scratching (especially important for optical-grade molding).​

Step 6: Post-Processing & Quality Control​

• Annealing Stress Relief: Parts are heated to 160–180 °C for 1–2 hours, then cooled slowly (5 °C/min) to relieve internal stresses. This step improves dimensional stability by 25–30%.​

• Automated Degating: Robots remove runners/gates, ensuring consistent part quality and faster production.​

• Inspection: Parts undergo CT scanning (for internal defects), dimensional testing (CMM), and transparency testing (ASTM D1003). For medical parts, we add biocompatibility testing (ISO 10993).

• Extreme Thermal Resistance: PEI maintains 90% of its strength at 217 °C (continuous use) and can withstand short-term exposure to 300 °C. This outperforms PA66 (continuous use limit: 150 °C) and matches PEEK—at a lower cost.​

• Inherent Flame Retardancy: UL 94 V-0 inherent (no additives needed) means PEI won’t catch fire or release toxic smoke—critical for aircraft, electronics, and medical facilities. It also meets NASA’s low-smoke requirements (ASTM E662).​

• Transparent High-Heat: Transparent amber grade PEI transmits 90–94% of light (for thin parts) while withstanding 217 °C—something no other transparent plastic (e.g., PC, acrylic) can do. Ideal for high-heat optical components.​

• Sterilization Compatibility: PEI withstands 1,000+ autoclave cycles (134 °C, 3 bar), gamma radiation (25 kGy), and ethylene oxide (ETO) sterilization—perfect for reusable medical tools.​

• Low Smoke Toxicity: When exposed to fire, PEI releases minimal toxic gases (e.g., cyanide, chlorine) compared to halogenated plastics. This makes it the top choice for enclosed spaces (aircraft cabins, hospitals).​

• High Dielectric Strength: PEI has a dielectric strength of 21 kV/mm—excellent for electrical insulation (e.g., EV battery insulators, 5G antenna filters). It also maintains insulation properties at high temperatures.​

• Dimensional Stability: As an amorphous polymer, PEI has low shrinkage (0.5–0.8%) and a low coefficient of thermal expansion (CTE: 5.5 × 10⁻⁵/°C). This ensures parts retain their shape in temperature fluctuations.​

• Chemical Resistance: Resistant to hydrocarbons (oils, fuels), weak acids, and alcohols. It’s also resistant to most cleaning agents—ideal for medical and food-service parts.​

• Metal Replacement Weight-Out: PEI is 50–60% lighter than aluminum and 70–80% lighter than steel. For aircraft parts, this cuts fuel consumption by 5–10%; for EVs, it extends range by 3–5%. For example, replacing aluminum aircraft seat clips with PEI cuts each clip’s weight by 30%, reducing total aircraft weight by 150 lbs and saving airlines $20,000+ in fuel annually per plane.

Case Study 1: Aerospace Seat Clip (30% Weight Reduction, Fire Safety Compliance)​

• Challenge: A major airline needed to replace aluminum seat back clips to reduce aircraft weight (for fuel savings) while meeting strict FAA fire safety standards (UL 94 V-0, low smoke toxicity). Aluminum clips were heavy (20g each) and failed the smoke test; standard plastics (PA66) melted at 180 °C (too low for cabin heat).​

• Solution: We recommended Aerospace Ultem 9085—a grade engineered for aircraft interiors. Our tight-tolerance ±0.01 mm molding ensured the clips fit existing seat hardware, and automated degating kept production costs low for high volume (100,000 clips/year). We also performed fire testing to validate UL 94 V-0 compliance.​

• Result: The PEI clips weighed just 14g (30% lighter than aluminum), reducing total aircraft weight by 150 lbs. They passed FAA fire tests with flying colors (low smoke, no flame spread) and lasted 2x longer than aluminum (resisting corrosion from cabin humidity). The airline saved $22,000 in fuel per plane annually, with a ROI of 18 months.​

• Customer Testimonial: “The PEI clips solved two problems at once—weight and fire safety. We’re now rolling them out across our entire fleet.” — Aerospace Interior Engineering Manager​

Case Study 2: Reusable Medical Autoclave Tray (3,000 Sterilization Cycles)​

• Challenge: A medical device company needed a reusable tray for surgical instruments that could withstand autoclave cycles (134 °C, 3 bar) without warping or yellowing. Their current polycarbonate trays failed after 200 cycles, forcing hospitals to replace them monthly—creating waste and high costs.​

• Solution: We used Medical Ultem HU (biocompatible, USP Class VI) for the tray material. Our clean-room ISO 8 production prevented contamination, and annealing stress relief ensured dimensional stability (trays retained their shape even after repeated heating). We added laser marking amber for permanent lot numbers (critical for traceability).​

• Result: The PEI trays survived 3,000 autoclave cycles (15x longer than polycarbonate) and showed no yellowing or warping. Hospitals reduced tray replacement costs by 93% (from ​500/monthto35/month) and cut plastic waste by 2,800 trays per year. The device company won a $2M contract with a large hospital network due to the tray’s durability.​

• ROI Analysis: For a hospital using 50 trays, the switch to PEI saved $27,900 annually. For the device company, the product’s unique selling point (3,000 cycles) increased market share by 12%.​