Polyethylene Terephthalate (PET)

(1) Barrel Temperature

Feed Zone:  50-70°C (70°C)

Zone 1:        240-260°C (250°C)

Zone 2:        240-260°C (250°C)

Zone 3:        250-290°C (270°C)

Zone 4:        250-290°C (270°C)

Zone 5:        250-290°C (270°C)

Nozzle:        250-290°C (270°C)

Note: Temperatures in parentheses are recommended starting points. Data applies at 35% and 65% stroke utilization, with flow length to wall thickness ratio of 50:1 to 100:1.

(2) Melt Temperature 270-280°C

(3) Barrel Residence Temperature 220°C

(4) Mold Temperature 120-140°C

(5) Injection Pressure Up to 160 MPa (1600 bar) for thin-walled sections.

(6) Holding Pressure Typically 50-70% of injection pressure to prevent sink marks. Optimize holding time - excessive duration can induce internal stresses (particularly in amorphous resins) and reduce impact strength.

(7) Back Pressure 5-10 MPa (50-100 bar). Avoid higher values to prevent shear heating.

(8) Injection Speed High speed required due to rapid solidification and crystallization rates. Prevents premature cooling/setting. Adequate mold venting is crucial to avoid trapped air and potential burn marks at flow path ends.

(9) Screw Speed Maximum peripheral speed: 0.5 m/s.

(10) Metering Stroke (0.5-3.5)D. Since melt is sensitive to overheating and prolonged residence, total residence time in barrel should not exceed 5 minutes.

(11) Cushion 2-5 mm, depending on metering stroke and screw diameter.

(12) Pre-Drying 4 hours at 120°C.

(13) Regrind Up to 20% regrind can be used, provided it's properly pre-dried and shows no thermal degradation. No significant reduction in tensile, flexural, or impact strength compared to virgin material should occur.

(14) Shrinkage Varies significantly with wall thickness, mold temperature, and holding pressure. Typically 1.2-2.0%. For 30% glass-filled grades: 0.4-0.6%.

(15) Gating System Most standard types can be used. For hot runner systems, precise closed-loop temperature control is essential.

(16) Machine Shutdown Switch off heater bands. Purge continuously until no more plastic emerges (extruder mode). When switching from other thermoplastics, purge with PE or PP.

(17) Barrel Equipment Standard screw, non-return valve, open nozzle.