Soft foam in Injection molding.


I need informations concerning TPE foaming in injection molding operation. (the goal is to obtain a soft thermoplastic foam by injection molding) Density achieved. Blowing agent. Thickness (Max/Mini) TPE formulation (PP/EPDM; PP/SEBS, PP....)


Reply to
Loading thread data ...


Foams can be produced in this way by using a physical blowing agent such as expancel

formatting link
Expancel is composed of hollow microcellular spheres containing a low melting point liquid. When heat is applied to the compound containing the spheres the shells soften and the liquid expands, causing controlled, homogenous foaming of the compound. A shut off nozzle is required on the injection moulding machine to prevent pre-expansion in the barrel. With this technique very low densities can be achieved, but with higher loadings of Expancel the compound can become stiffer/harder due to the hardness of the shells. This is a very reliable and controllable method of foaming, but you have to be careful not to produce too much shear otherwise the spheres can be broken. Additionally, a low melt strength material is preferable since this will encourage better expansion of the spheres.

Alternatively there is the mucell process

formatting link
This involves injecting super-critical fluids into the melt which expand once the pressure is released, within the tool. This method requires machine modifications and a license from trexel, and I don`t believe it is easy to get good results with TPE's.

Chemical blowing agents such as azodicarbonamides could be used, but I don`t think these would be very easy to control in an injection moulding process. These are well established for extrusion processes, though.

Hope this has been some help.


Reply to
Charles Page

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.