Case Analysis: How Mold Temperature Affects the Quality of PEEK Injection-Molded Parts

Common Issues in Mold Temperature Control

For ZYPEEK injection molding, the recommended mold surface temperature is typically between 175°C and 205°C. However, many customers report that even when the oil temperature controller shows a qualified temperature, the actual mold temperature fails to reach the set value.

Case 1: A customer in the energy and chemical industry found that during the production of ZYPEEK parts, insufficient mold temperature caused sticking, uneven color, and deformation during ejection, seriously affecting product quality and production efficiency.

The upper image shows the defective part; the lower image shows the standard part.

Case 2: During injection molding, the oil temperature controller was set at 200°C, but the measured mold temperature was only 150°C. When the oil temperature was increased to 220°C, the mold temperature reached 170°C. This indicates a significant difference between the displayed oil temperature and the actual mold temperature, especially for large molds where uniform local temperature is difficult to achieve.

Actual temperature: 150°C

How to Accurately Measure Mold Temperature

Many customers rely on the mold temperature controller display or infrared thermometer readings instead of the actual mold temperature, but both methods are inaccurate. The correct method is to use a professional mold temperature meter with a contact K-type thermometer. The steps are as follows:

1. Heat the mold temperature controller to the ZYPEEK molding temperature (e.g., 180°C);

2. Manually operate the injection molding machine to open the mold and leave a detection gap between the moving mold and fixed mold;

3. Insert the thermocouple probe into the cavity and press it tightly against the inner wall surface;

4. Wait for the temperature reading to stabilize; the displayed value is the true mold temperature.

Relationship Between Mold Temperature and Mold Sticking

Practical tests show that mold temperature directly affects the demolding performance of parts, and improper temperature will cause sticking.

Generally, mold temperature directly affects the crystallinity and appearance of molded parts. At too low a temperature, parts have poor crystallinity, dull and yellowish-brown color. As mold temperature increases, crystallinity improves and color gradually approaches the standard shade. Therefore, precise mold temperature control is critical to improving product qualification rate.

How Mold Temperature Affects Crystallinity and DSC Testing Method

Mold temperature also directly affects the crystallinity of ZYPEEK parts. We conducted DSC tests (a thermal analysis method) on ZYPEEK parts molded at different mold temperatures and found that:

Generally, when the mold temperature is below 160°C, a "cold crystallization peak" appears on the DSC curve. This is because at too low mold temperature, the ZYPEEK melt cools too quickly in the cavity, leaving insufficient time for molecular chains to arrange orderly, resulting in incomplete crystallization.

DSC testing records the endothermic or exothermic behavior of a material during heating. A cold crystallization peak between the glass transition temperature (Tg, ~143°C) and melting temperature (Tm, ~343°C) indicates insufficient crystallization of ZYPEEK during cooling.

Case 3: A customer reported poor wear resistance of ZYPEEK parts. DSC analysis revealed a cold crystallization peak, indicating insufficient crystallinity. We recommended raising the mold temperature to 180°C. After implementation, part crystallinity improved significantly, wear resistance was greatly enhanced, and the cold crystallization peak disappeared from the DSC spectrum.

Case 4: A customer encountered ejection deformation and warping during ZYPEEK injection molding. DSC testing confirmed a cold crystallization peak, further verifying that **insufficient crystallization due to low mold temperature** was the root cause. Raising the mold temperature significantly reduced deformation and warping.

With our technical guidance, many customers have successfully resolved mold temperature control issues in ZYPEEK injection molding, achieving significantly higher product qualification rates and optimized production efficiency. Customers express high recognition and satisfaction with the final results.

Want to learn more about Joinature’s ZYPEEK products and solutions, or request free samples? Contact our expert team today!

Email：sales@zypeek.cn