Equipment Requirements for High-temperature Resistant PEEK Plastic Injection Molding
PEEK has a melting point of 343℃, with forming temperature ranging from 360℃ to 400℃. It features high melt viscosity and is prone to hydrolysis degradation under high temperature, requiring high mold temperature during forming. Ordinary general injection molding machines cannot support stable mass production. Equipment must meet high-temperature working standards from plasticizing system, temperature control, hydraulic pressure, auxiliary machines, mold matching and safety protection.
1. Mandatory Standards for Host Plasticizing System
1.1 Material Barrel, Screw and Nozzle Material & Structure
All melt-contact parts cannot use ordinary nitrided steel; double alloy, Hastelloy or tungsten carbide coating materials are required, with temperature resistance up to 450℃ to resist abrasion of glass fiber modified PEEK. The screw adopts length-diameter ratio of 20:1~24:1 and compression ratio of 2.5:1~3:1, with low-shear gradual thread to avoid local overheating decomposition of melt. The screw head is equipped with dead-angle-free anti-reverse ring to prevent carbonization caused by melt retention. The nozzle is high-temperature tip type with temperature resistance above 420℃ without dead material space; copper fittings are totally forbidden, as copper ions will accelerate molecular chain fracture of PEEK.
1.2 Heating and Feeding Cooling Configuration
The barrel is equipped with ceramic heating rings with maximum heating capacity over 450℃, divided into 5~8 independent PID temperature control sections with fluctuation controlled within ±1℃. Standard temperature sections: feeding zone 350~360℃, compression zone 370~380℃, metering zone 380~395℃, nozzle 385~400℃; the whole temperature shall rise by 10~15℃ for glass/carbon fiber modified PEEK. The feeding port installs independent water circulation cooling equipment, stably controlled at 70~100℃ to block reverse high temperature conduction and avoid bridging blockage of pellets.
2. Hydraulic Clamping and Injection Pressure System Requirements
The clamping force needs to increase by 20%~25% compared with ordinary plastics. The injection resistance of PEEK melt is large, and flash easily occurs under high pressure. The clamping force shall reach 8~10 tons per square centimeter of mold projection area with high-rigidity templates free of elastic deformation under high temperature and pressure. The rated maximum injection pressure of equipment is above 220MPa, with actual production range of 120~180MPa and stepless speed regulation to adapt thin-wall and thick-wall parts. Back pressure is stably adjustable within 0~20MPa, maintained at 10~15MPa during production to guarantee uniform plasticization. Independent oil cooling device for hydraulic oil prevents pressure drift caused by long-time high-temperature operation.
3. Core Auxiliary Machines: Dehumidifier, Feeder and Mold Temperature Controller
Closed-loop dehumidifying dryer is essential, instead of ordinary hot air oven. The dew point of drying air shall be ≤-40℃, with standard drying process of 150~160℃ for 4~6 hours, and moisture content of discharged pellets controlled below 0.02%. High-temperature oil-type mold temperature machine is required rather than water temperature machine, with maximum oil temperature over 300℃ and independent loop control for moving mold, fixed mold and mold core. Standard mold temperature: pure PEEK 170~180℃, fiber-reinforced PEEK 180~200℃ to stabilize crystallinity and reduce warpage. Sealed vacuum feeder isolates moisture and dust; special high-temperature cleaning material is used during material replacement to avoid cross contamination.
4. Mold Matching Hardware and Equipment Safety Configuration
H13 hot working steel is adopted for molds instead of ordinary P20 steel to prevent softening under long-time high temperature. The cooling water channel adopts conformal surrounding layout with independent temperature control loops, and ejection parts use high-temperature resistant steel to avoid jamming. For high-standard products, nitrogen protection device can be installed at the barrel and nozzle to isolate air and inhibit oxidation carbonization. All high-temperature pipes are wrapped with thermal insulation layers, equipped with local exhaust and over-temperature automatic shutdown protection. Ordinary injection machines can only be used for short-time sample testing; stable mass production needs dedicated high-temperature PEEK injection molding machines.
