How to improve the processing safety of PC/PBT

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

The PC/PBT alloy, created through blending modification and by leveraging the strengths of both materials, has gained widespread use in the market. Common applications include automotive luggage support bases, bumpers, traction cover plates, safety helmets, body guards, safety toe caps, and medical instrument connectors.

In recent years, as technology advances and special product functions become more demanded, the application of PC/PBT alloys has expanded in terms of molding methods. Beyond traditional injection molding, gas-assisted molding has gained attention due to its advantages in dimensional stability and cost efficiency. A typical example is the car door handle.

Gas-assisted molded products, such as exterior door handles, require high-performance materials that meet strict standards, including material viscosity, processability, thermal stability, mechanical strength, and chemical corrosion resistance. These demanding requirements make it challenging for standard PC/PBT materials to perform well in gas-assisted molding. Issues like 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 designed to protect against excessive transesterification and hydrolysis during gas-assisted molding of PC/PBT. It enhances the thermal stability of the material and ensures safe processing during production.

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.

As shown in the image, the PC/PBT alloy without SAG-005 developed a significant amount of silvering on the surface after 10 minutes of residence time. In contrast, the material containing SAG-005 demonstrated excellent thermal stability.

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