Common Engineering Plastics: Injection Molding Temperature Ranges

Engineering plastics are widely applied in automotive, electronic and mechanical industries due to outstanding mechanical performance, heat resistance and chemical stability. Molding temperature stands as a core parameter determining finished product quality. The setting of temperature must comply with material crystallinity, thermal sensitivity and modification characteristics. This article elaborates on the applicable temperature ranges and key operational points of mainstream engineering plastics for injection molding.

1. Polyamide (PA, Nylon)

PA6 and PA66 are typical crystalline engineering plastics with high water absorption, so temperature control must coordinate with melting and drying processes. For PA6, the barrel temperature is set between 220°C and 270°C, nozzle temperature from 230°C to 260°C, and mold temperature within 40°C to 80°C. PA66 features a higher melting point, with barrel temperature ranging 250°C–290°C, nozzle temperature 270°C–290°C and mold temperature 60°C–100°C. A relatively high mold temperature improves crystallinity, mechanical strength and dimensional stability of molded parts. Raw materials should be dried at 80°C to 90°C for 4 to 6 hours to prevent silver marks and bubbles.

2. Polycarbonate (PC)

PC is an amorphous transparent engineering plastic with good heat resistance yet high sensitivity to temperature. Excessively high temperature will cause molecular degradation and yellowing. Its barrel temperature is controlled at 270°C–320°C, nozzle temperature 280°C–310°C and mold temperature 70°C–120°C. The melt temperature shall not exceed 340°C to avoid reduced mechanical strength. A higher mold temperature relieves internal stress and lowers cracking risks. Raw PC needs drying at 120°C for 2 to 4 hours, with moisture content controlled below 0.02%.

3. Polyoxymethylene (POM)

POM is a highly crystalline and heat-sensitive plastic. Overheating will trigger decomposition and release formaldehyde gas. Homopolymer POM requires barrel temperature of 170°C–200°C, while copolymer POM ranges from 180°C to 220°C. The nozzle temperature is 190°C–220°C and mold temperature 80°C–120°C. The overall molding temperature must never exceed 240°C. Low back pressure is adopted to reduce shear heat. Proper mold temperature optimizes surface finish and relieves internal stress. Drying is conducted at 80°C–100°C for 3 to 4 hours before production.

4. Polybutylene Terephthalate (PBT)

As a crystalline thermoplastic polyester, PBT delivers good fluidity and heat resistance, and glass fiber reinforced grades are commonly used in production. The standard barrel temperature is 220°C–260°C, nozzle temperature 230°C–250°C and mold temperature 50°C–80°C. For glass fiber reinforced PBT, the barrel temperature is adjusted to 240°C–270°C and mold temperature to 60°C–100°C to enhance bonding between fiber and plastic matrix. Raw materials are dried at 120°C–130°C for 3 to 5 hours to prevent hydrolysis.

5. Polyethylene Terephthalate (PET)

PET has a slow crystallization rate, so a high-temperature mold is required to accelerate crystallization. Its barrel temperature is 250°C–290°C, nozzle temperature 270°C–285°C and mold temperature 80°C–120°C. Melt temperature above 290°C will lead to degradation and discoloration. A mold temperature below 80°C results in unstable dimensions. Deep drying at 130°C–140°C for 4 to 6 hours is required to keep moisture content under 0.01%.

6. Acrylonitrile-Butadiene-Styrene (ABS)

ABS is a universal amorphous engineering plastic with balanced toughness and rigidity, featuring a wide applicable temperature range. The barrel temperature is 200°C–260°C, nozzle temperature 220°C–250°C and mold temperature 40°C–80°C. Flame-retardant ABS needs a temperature reduction of 10°C to 20°C to avoid decomposition of flame retardants. High-impact ABS can be processed at a slightly higher temperature to improve material dispersion. Drying parameters are 80°C–90°C for 2 to 3 hours.

7. PC/ABS Alloy

PC/ABS combines the heat resistance of PC and excellent fluidity of ABS, with temperature settings between the two base materials. The barrel temperature is 230°C–300°C, nozzle temperature 240°C–280°C and mold temperature 50°C–100°C. Melt temperature should not exceed 280°C to protect PC components. Excessively high mold temperature causes warpage, while low mold temperature increases internal stress. Raw materials are dried at 100°C–110°C for 2 to 4 hours.

8. Polymethyl Methacrylate (PMMA)

PMMA is a transparent amorphous plastic prone to yellowing under high temperature. The barrel temperature is 200°C–260°C, nozzle temperature 220°C–250°C and mold temperature 40°C–80°C. The optimal melt temperature is 220°C–240°C. Higher mold temperature reduces internal stress and surface defects. Raw materials are dried at 80°C–90°C for 2 to 3 hours before molding.

9. High-Performance Special Engineering Plastics

PEEK requires extremely high processing temperature: barrel temperature 350°C–390°C, nozzle temperature 360°C–380°C and mold temperature 150°C–200°C. For PSU, the barrel temperature is 300°C–360°C, nozzle temperature 320°C–380°C and mold temperature 100°C–150°C. PES has barrel temperature of 340°C–370°C, nozzle temperature 350°C–370°C and mold temperature 120°C–160°C. All three materials need strict temperature control and drying at 120°C–150°C for 4 to 6 hours.

10. General Principles of Temperature Control

Crystalline plastics need a relatively high mold temperature to promote crystallization. Amorphous plastics adopt medium or low mold temperature to control internal stress. Heat-sensitive materials must be processed within a narrow temperature range. High-performance plastics require high temperature to guarantee fluidity. For modified materials, glass fiber reinforced products need a temperature rise, while flame-retardant products use a lower temperature. Molding parameters should be adjusted according to material properties, product structure and equipment conditions to achieve stable production.