This is a term that is used to describe thermoplastic injection molding components under low pressure. Rather than being a material, it is a process that forms thermoplastic resins to form a rigid material with a relatively hard surface. The injected plastic melt is foamed with nitrogen gas or any other chemical blowing agent that makes it harden.
This process is achieved by injecting the molten plastic material mixed with the chemical blowing agent into a mold. This agent produces bubbles in the plastic causing it to foam. This process causes the material to retain its plastic properties but reduces its density causing it to weigh much less. This density reduction gives the material the ability to be stronger in relation the weight while it is not much affected by heat and sound waves.
The key element in this process is low pressure. This allows the melt to flow for a longer distance thus making larger moldings achievable. As the melt enters the mold a thin layer solidifies along the wall while the inside section consists of a cellular foamed structure. The cellular structure allows expansion and contraction to a certain degree while also making it a stronger and longer lasting material.
This can be achieved through two processes. The low pressure process uses special purpose injection molding machines that achieve quality moldings. The machine injects the melted plastic that consists of the gas into the mold to form the material. The other process utilizes blowing agents incorporated into the material. The melt is then charged causing the blowing agent to react to form a gas which consequently foams the plastic.
Thermoplastic injection molding method is preferred since it can use cheaper and lighter molds, has a lower setup and can produce large parts. The use of low pressure means that the materials used in the process should be more economical. As a result, it is highly viable to mass produce the parts.
Contrary to popular belief, high density polyethylene is not the only thermoplastic that can be used though it is the most common due its quality and its chemical resistance property. Other materials include ABS and PPO where stiffness and dimensional repeatability is required. Structural foam does also not have to be black in color. Other colors can be integrated into the material though it requires an extra bit of material to achieve this. GenerallyBusiness Management Articles, this is an excellent method to cater for your packaging and material handling needs.