Foam injection molding for reducing the cost of injection molding raw materials and improve the mechanical strength of the product has a considerable significance, through the use of foam technology injection molded plastic products mechanical strength can be increased to 2-4 times of the non-foaming state, is a cheap and efficient method. The gas produced in the chemical foaming process is mainly nitrogen, followed by carbon dioxide and water, as well as a small amount of other gases, almost non-toxic and tasteless, which does not cause secondary pollution to the product and air, and is an environmentally friendly injection molding process.

Because the foam injection molding process has many advantages, it is of great significance for the utilization and redevelopment of foam technology, Haozhi new materials on the principle of chemical foam injection molding for a simple description:

PA12 nylon injection molding foam

popularisation method foam injection molding process includes four stages:

mix foaming agent and raw materials;

A large number of bubble monomers are rapidly generated;

bubbles diffusion and mutual fusion through;

foaming agent decomposition is complete, the product into a stable period.

The first stage: blowing agent and polymer are fully mixed, in this process must choose the activation temperature higher than the melting temperature of the foaming agent, to ensure that foaming agent and melt fully uniform mixing before the foaming reaction does not occur, in order to improve the dispersion effect;

The second stage: the temperature increases, the activation blowing agent decomposing gas, by first adding nucleating agent in the raw material, promote the effect of bubble formation, nucleating agent is generally the use of very small inert particles, such as calcium carbonate, kaolin carbon black and so on, high-quality nucleating agent helps to produce high-quality bubbles;

The third stage: the continuous production of bubbles, and began to fuse through, the expanding gas foam in the fusion of the fusion through. In this process due to the proportion of blowing agent is different, there will be two situations, one is in the molten material produced disconnected bubble holes, called closed cell foam; The other is the formation of connected bubble holes, called open-cell foaming; If the foam is allowed to go on without limit, the foam will collapse;

The fourth stage: when the foam decomposition is complete, the foaming reaction stops, the polymer viscosity rises, the porosity no longer increases, and the molding curing begins. By cooling, crosslinking or other solidification methods, the polymer viscosity rises and solidifies.

The whole foaming to molding process is actually very short, from a fraction of a second to a few seconds, to the product and foaming effect is different, by controlling the quality and quantity of foam to control the quality of the product is the focus of the whole foam injection process. Control of the gel process and foaming process has a very big impact on the quality of the product, if the gel lags behind the foam, the formed bubble wall viscosity is too low, resulting in soft products, serious collapse may occur; If the gel is foamed in advance, the pore wall is too hard, so that the pressure in the pore is too high, it is easy to tear the pore wall, and finally make the product crack in a large area.

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