Development of Innovative Gas-Assisted Foam Injection Molding Technology

Links

Abstract

Injection molding technology is utilized for a wide range of applications from mobile phone covers to bumper fascia of automotive vehicles. Foam injection molding (FIM) is a branched manufacturing process of conventional injection molding, but it was designed to take advantage of existing foaming technology, including material cost saving and weight reduction, and to provide additional benefits such as improvement in dimensional stability, faster cycle time, and so on. Gas-assisted injection molding (GAIM) is another supplemental technology of injection molding and offers several advantages as well. This thesis study takes the next step and develops innovative gas-assisted foam injection molding (GAFIM) technology, which is the result of a synergistic combination of two existing manufacturing technologies, FIM and GAIM, in order to produce a unique thermoplastic foam structure with proficient acoustic properties. The foam structure manufactured by GAFIM consists of a solid skin layer, a foam layer, and a hollow core; and its 6.4-mm thick sample outperformed the conventional 22-mm thick polyurethane foam in terms of the acoustic absorption coefficient. With respect to foaming technology, GAFIM was able to achieve a highly uniform foam morphology by completely decoupling the filling and foaming phases. Moreover, the additional shear and extensional energies from GAFIM promoted a more cell nucleation-dominant foaming behavior, which resulted in higher cell density and smaller cell sizes with both CO2 and N2 as physical blowing agents. Lastly, it provided more direct control of the degree of foaming because the pressure drop and pressure drop rate was controlled by a single parameter, that being the gas injection pressure. In summary, innovative, gas-assisted foam injection molding technology offers not only a new strategy to produce acoustically functioning thermoplastic foam products, but also technological advantages over the conventional foam injection molding process. Gas-assisted foam injection molding can become the bedrock for more innovative future applications.

Cited Works (10)

Year	Entry
1995	Park CB, Baldwin DF, Suh NP. Effect of the pressure drop rate on cell nucleation in continuous processing of microcellular polymers. Polym Eng Sci. March 1995;35(5):432-440.
2012	Wong AT. In Situ Observation of Plastic Foaming Under Static Condition, Extensional Flow and Shear Flow [PhD thesis]. University of Toronto; 2012.
1996	Park CB, Suh NP. Filamentary extrusion of microcellular polymers using a rapid decompressive element. Polym Eng Sci. January 1996;36(1):34-48.
1999	Sato Y, Fujiwara K, Takikawa T; Sumarno, Takishima S, Masuoka H. Solubilities and diffusion coefficients of carbon dioxide and nitrogen in polypropylene, high-density polyethylene, and polystyrene under high pressures and temperatures. Fluid Phase Equilib. August 1999;162(1-2):261-276.
1998	Park CB, Behravesh AH, Venter RD. Low density microcellular foam processing in extrusion using CO₂. Polym Eng Sci. November 1998;38(11):1812-1823.
2002	Naguib HE, Park CB, Panzer U, Reichelt N. Strategies for achieving ultra low-density polypropylene foams. Polym Eng Sci. July 2002;42(7):1481-1492.
2009	Leung SNS. Mechanisms of Cell Nucleation, Growth, and Coarsening in Plastic Foaming: Theory, Simulation, and Experiment [PhD thesis]. University of Toronto; 2009.
2009	Lee JWS. Investigation of Foaming Behaviors in Injection Molding Using Mold Pressure Profile [PhD thesis]. University of Toronto; 2009.
2003	Xu X, Park CB, Xu D, Pop-Iliev R. Effects of die geometry on cell nucleation of PS foams blown with CO₂. Polym Eng Sci. July 2003;43(7):1378-1390.
2007	Chu RKM. Synthesis and Characterization of Rotational Molded Polymeric Foams for Optimal Acoustic Absorption [Master's thesis]. University of Toronto; 2007.