How to improve the processing safety of PC/PBT

Polycarbonate (PC) exhibits excellent mechanical properties, heat resistance, dimensional stability, and electrical insulation. It is non-toxic, has low water absorption, and can be used across a wide temperature range. However, PC has high melt viscosity, poor flowability, limited chemical resistance, and wear resistance, which restrict its application to some extent. On the other hand, polybutylene terephthalate (PBT) is a semi-crystalline material with fast crystallization, good melt fluidity, and strong solvent resistance. Yet, it suffers from poor heat resistance, insufficient rigidity at high temperatures, and sensitivity to notches, leading to brittleness.

The PC/PBT alloy, developed through blending modification and by leveraging the strengths of both materials, has found widespread use in various industries. Common applications include automotive components such as luggage support bases, bumpers, traction covers, and safety equipment like helmets, body guards, safety toe caps, and medical connectors.

In recent years, with technological advancements and the demand for specialized product functions, the use of PC/PBT alloys has expanded in terms of molding methods. Beyond traditional injection molding, gas-assisted molding has gained attention due to its ability to improve dimensional stability and reduce material costs. A typical example is the car door handle, where this technique is increasingly favored in the industry.

Gas-assisted molding processes place high demands on materials, requiring good viscosity, processability, thermal stability, mechanical strength, and chemical resistance. These stringent requirements have made it challenging for standard PC/PBT materials to perform well in gas-assisted applications. Issues such as pitting, yellowing, shrinkage, and failure in strength tests often arise during the process.

Jia Yi Rong TMSAG-005 is an epoxy polymer anti-hydrolysis agent specifically designed to address the excessive transesterification and hydrolysis that occur during gas-assisted molding of PC/PBT. It enhances the thermal stability of the material and ensures safe processing during the manufacturing cycle.

The gas-assisted molding cycle is significantly longer than that of conventional injection molding. To evaluate the thermal stability of the material, we simulated the actual processing temperature and conducted enhanced thermal aging tests. The PC/PBT material was left in the injection molding machine for different durations to observe changes over time.

As shown in the figure, the PC/PBT alloy without SAG-005 developed significant silvering on the surface after just 10 minutes of residence time. In contrast, the material containing SAG-005 demonstrated excellent thermal stability, maintaining its integrity under prolonged exposure.

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