Self formation of "mucell" from PS/polyaniline-halloysite clay (PHC) injection molding

In injection molding, cycle time and dimensional stability are critical factors for process economics and product quality. In general, decreasing the cycle time has an adverse effect on dimensional stability. Microcellular injection molding,"MuCell" [1] is an special injection molding process, that decreases the cycle time without an adverse effect on dimensional stability or mechanical properties. However, this technology requires equipment modifications, which will significantly increase the manufacturing costs. In this work, we introduce an alternative approach to microcellular injection molding, which does not require any equipment modifications. We have developed an additive which is compounded with the thermoplastic pellets which are then run in standard injection molding equipment. The additive was produced by an in-situ polymerization of polyaniline (PANI) into Halloysite-Clay (HC) [2], where the HC is naturally exfoliated because of its tubular shape and uniform surface charge. The PANI has the function of adsorbing both water and CO ₂ gas. Previous to injection molding, the plastic pellets pre mixed with additive microparticles are pressurized with water/CO₂ in a batch process under controlled pressure and temperature. Preliminary results show that cycle time can be decreased without an adverse effect on part dimensional stability and mechanical properties.