Complete Injection Molding Specification for Medical-grade PC Plastic

Medical-grade PC acts as core raw material for medical device manufacturing, widely applied to infusion fittings, surgical parts and optical protective components that contact human bodies directly or indirectly. Unlike ordinary industrial PC, it must satisfy ISO 10993, USP Class VI and FDA certification standards. Its injection molding demands strict control over raw materials, clean workshops, molding parameters and post-treatment to stop material hydrolysis, particulate contamination and sterilization-induced cracking, which are critical to biocompatibility and clinical safety.

1. Raw Material Preprocessing Rules

Only original certified medical-grade PC is permitted; recycled plastic and general industrial pellets are banned to cut cross-contamination risks. Raw materials are stored in temperature-humidity controlled dust-free warehouses, separated from sulfur, chlorine and fluorine-containing substances. Due to strong moisture absorption, PC pellets need dehumidifying drying at 120℃ for 3 to 4 hours with drying air dew point below -40℃, limiting moisture content under 0.02%. Dried materials should be consumed within 2 hours, and repeated drying shall not exceed three times to prevent thermal degradation and reduced toughness. Damp raw materials must be re-dried separately before use.

2. Mold & Equipment Cleanliness Standards

Dedicated molds and production lines are required without sharing equipment for non-medical plastic products. Mold cavities and runners adopt S136 stainless steel with mirror polishing, leaving no residue dead corners. Standard exhaust grooves are machined to avoid trapped gas carbonization. Silicone-based release agents are completely forbidden; only trace silicon-free water-based release agents can be used for auxiliary demolding. Molds are wiped with medical anhydrous ethanol before startup and mold change, and disassembled for deep cleaning weekly. Injection machines adopt low-shear stainless steel barrels and screws, paired with medical-grade lubricants to avoid oil dripping contamination. Full barrel purging is mandatory during production switching to clear residual foreign plastic.

3. Core Injection Molding Process Parameters

Gradient barrel heating is adopted: feeding zone 270–280℃, middle zone 285–300℃, metering zone 290–310℃, nozzle 290–300℃. Melt temperature shall never exceed 320℃ to avoid yellowing and harmful precipitation. Mold temperature ranges from 80℃ to 110℃, and stays above 100℃ for transparent, sterilization-resistant products to lower internal stress. Multi-stage low-speed filling at gates prevents jetting and silver streaks. Two-stage holding pressure and low screw rotation reduce shear heat. Cooling time is adjusted based on wall thickness to ensure full solidification and cut ejection stress.

4. Clean Production On-site Control

All molding operations are conducted in Class 10,000 clean workshops. Staff wear full dust-free garments, gloves and masks, and bare-hand contact with product liquid-contact surfaces is prohibited. Special sealed containers store sprues and defective parts, and crushed recycled scraps cannot be reused for medical products. Operators conduct half-hourly appearance inspections and two-hourly dimensional sampling; production halts immediately once bubbles, black spots or silver marks occur.

5. Post-processing, Sterilization Matching & Traceability

All molded medical PC components must undergo annealing at 110–120℃ for 1 to 2 hours with natural cooling to eliminate internal stress, verified via glacial acetic acid soaking test. Molding parameters are adjusted to fit EO moist heat or gamma irradiation sterilization, reducing yellowing and residual adsorption. A complete batch traceability archive covers raw material batches, drying data, molding parameters, mold cleaning logs, inspection records and sterilization reports. Finished goods are sealed in sterile PE bags with batch labels to meet medical audit requirements.

Conclusion

Medical-grade PC injection molding centers on clean production, temperature control against degradation and internal stress elimination. Standardized raw material drying, mold disinfection, precise parameter tuning and standardized annealing help eliminate contamination, cracking and precipitation defects. Full implementation of these specifications guarantees medical PC products pass biocompatibility and sterilization resistance tests, delivering stable, safe parts for clinical medical use.