Gas assisted injection molding technique

Lightened plastic, methods of production

With the aim of producing sustainable and competitive products, the weight of the components plays an important role. Weight saving is one of the main characteristics for many applications, mostly in the packaging and automotive fields, where the cost of materials and the reduction of the weight allow the decreasing of the price of the final product and a lower fuel consumption in the vehicles, other than an improvement of the vehicle performances.

Sometimes, in order to satisfy the always different necessities of the customers or for some specific applications, it is necessary to use different injection molding techniques. These allow to obtain a lighter plastic product which can have more stable dimensions and contained deformations. To do so there are 3 available methods:

  • MuCell technology;
  • Use of expanders;
  • The gas assisted (nitrogen) injection molding

The MuCell technology

The MuCell technology allows to produce expanded plastic components and consists in injecting and blending in the melted polymer inert gasses (nitrogen or carbon dioxide) directly in the reciprocating screw cylinder. This makes it possible to obtain an easier filling and a physical expansion of the resin at a low pressure during the injection molding process, diminishing the density of the items (making them lighter) and reducing their deformations thanks to more even and controlled plastic shrinkages. During this process, the cycle time and the power usage are reduced too.

Use of expanders  

Using specific additives allows to improve and therefore make more performant some plastic materials. More specifically, the expanders grant a reduction in the weight of injection molded items by decreasing their density and improving their aesthetic. These agents decompose under the heat influence and develop some gasses that produce the cellulation and therefore allow the melted material to compress homogeneously inside the mold. Usually, they are used in application that require lightened objects as, for example, floaters.

Gas assisted (nitrogen) injection molding

Gas assisted injection molding consists in the deployment of an inert gas that forms a bubble inside the melted plastic mass previously injected in the mold. The pressure to which the gas is injected has to push the plastic material making it fully cover the socket of the mold. This gas can be injected through dot matrix nozzles inserted in the mold that allow to create in the same item even more than one gas bubble. This technique makes it therefore possible to significantly reduce the object’s weight, it lowers the production timings, it eliminates the plastic shrinkages where there are important width variations, without compromising the mechanical characteristics of the final item.