Gas assist injection molding involves a multi-step molding process, it is a way to make thick plastic parts without issues created from excess shrinkage of the part. It is a type of injection molding that uses an inert gas to create a very dense and strong plastic part that uses nitrogen to pack out the part and compensate for shrinkage. First the polymer is injected into a mold though not all filled. Nitrogen under high pressure is injected into the polymer, pushing it into areas of the mold that are not yet filled. The nitrogen pressure is maintained during the cooling phase of the molding process, and gas pressure is released and the part is ejected.
Plastic extrusion is the process of melting raw plastic material and pressing through a die to create a long, continuous shape which may be used for piping, tubing, weather stripping, and more. Oxygen in the extrusion process can result in residue that is harmful to the extruders. Nitrogen is used to displace the oxygen and prevent damage to the equipment and final product.
Film extrusion is achieved by extruding a molten thermoplastic using a screw through a die. Afterward, it is inflated to many times its initial diameter forming a thin tubular film. Screw carbonization and frequent die cleaning, caused by oxygen in the feed throat hopper, are issues with blown film extrusion that can be improved or eliminated by using a nitrogen purge.
Molten plastic is often housed in a tank prior to it being sent to the molding process. Nitrogen is used to blanket the tank which purges the oxygen away from the polymer. Nitrogen is also used in the hopper in the same capacity. When removing oxygen from coming into contact with the polymer, you eliminate oxidation and discoloration while improving performance.
Curing is used to give a tyre its final shape and tread pattern. It involves the chemical cross-linking of rubber and vulcanising agents, resulting in an elastomer. In the past, steam was typically used to create the heat and pressure needed for curing. Steam has a number of disadvantages, however, including the high price of steam energy, handling difficulties, high maintenance effort, lack of flexibility in setting individual parameters, the need for additional protective antioxidants in some cases, and the risk of quality impairment as a result of local overheating following condensation.
In order to overcome these disadvantages, steam can be replaced with nitrogen as the pressure agent. This flexible and inert gas keeps the system pressure at the desired level. In addition, operators of nitrogen-based tyre presses can select the system pressure independently of the curing temperature. The elimination of steam reduces the risk of local overheating, and less steam can condense in subsequent stages of the curing process.
To ensure the optimum supply system, process parameters and safety precautions for your individual needs, our application engineers would be delighted to assist with in-house trials and efficiency optimisation advice.
