Polycarbonate is a popular polymer, which consists of unique characteristics. It provides benefits of transparency, along with immense resistance to impact and heat. It has the capability to transmit light, and can be flame retardant depending on the grade.
When it comes plastic injection molding, companies are always trying to find ways to improve their molding processes, especially when using polycarbonate. This post provides tips to meet this need.
Initial Four Tips
The following points showcase tips on how to process polycarbonate and produce different products.
- Account for the High Thermal Diffusivity: Thermal diffusivity is related to erratic heat conduction. Polycarbonate does not respond to heat as well as other plastics. It tends to lose heat as it passes through the mold to the barrel and molding gun nozzle. This can result in delamination. One solution to reduce this problem is to tune the molding equipment to proper temperature control constants. This will help stabilize the process quickly, and ensure faster polymer melting and processing.
- Use New Endcap Designs: Traditionally, endcap designs have many transitions in the flow path. This leads to polycarbonate shearing and degradation. Also, the old designs do not provide proper sealing at high pressures. New endcap designs comprise consolidated components. This allows for a constant taper flow path, which ensures a streamlined delivery.
- Pay Attention to the Screw Design: Do not create polycarbonate products using molding machines with olefinic screws. Such machines tend to degrade the material during rapid compression phases. Use machines with moderate feed lengths and long compression sections. This will optimize the molding process. Also, you can ensure that the screw design includes a Non Return Valve (NRV). This can accommodate differences in materials.
- Try Heat Soak for Splay. If the screw is not designed for polycarbonate, then there can be a tendency for the polymer to splay. However, this can be eliminated by adding heat soak. The heat soak can soften the pellets in the feed section. Due to this, the polycarbonate will be able to handle the compression transition of the screw.
These are the initial four tips you can use when working with polycarbonate.
Tips Regarding the Molding Machine and Polycarbonate Components
While the previous post focused more on design elements, this post concentrates on the components and machines.
- Utilize Chromed, Smooth Parts: Polycarbonate products have a tendency to adhere to alloys with high amounts of iron. This can be prevented by plating the screw to create a smooth surface. This will reduce contact with the screw base metal. You can also use chrome-plated endcaps to reduce the possibility of polycarbonate products will stick to the machine parts.
- Dry the Poly Carbonate Quickly: When moisture is in the atmosphere, pellets on the polycarbonate can absorb moisture rapidly. Molding moist polycarbonate can cause splaying, while reducing the polymer’s impact and tensile strength. A desiccant drier should be used to dry the polycarbonate products to less than 0.02% moisture.
- Ensure Machine Purging: In injection molding, purging refers to cleaning the molding machine of one material or color. This is performed by using another color or material to force the existing one out of the machine. Purging is a task that should be done regularly. If not, it is possible that two different pieces of polycarbonate may adhere together. This can result in loss of material, and unnecessary expenditure of time, effort, and money.
Other errors can also take place. The valve can adhere to the endcap. This can result in the valve breaking off when the screw is turned. If the screw hasn’t been given enough time to warm up, the melted polymer can turn into a glue-like substance. It can also stick to and pull off the screw plating.
These points can ensure that the process of molding polycarbonate can be completed without too many problems. Using them can also maintain the strength and durability of the final product.
