Injection foam molding of poly lactic acid (PLA) blended with poly hydroxy alkanoate (PHA) to improve impact properties

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Macro Engineering and Technology Inc. has been making remarkable efforts to develop innovative plastic processing equipment for foaming the commercialized polymers for diversified applications. Macro would like to develop an affordable material recipe and foam injection molding process which can produce high-density PLA foam products with excellent mechanical properties and a cellular structure. PLA is a bio-based, biodegradable and environmentally friendly thermoplastic polymer which has a huge potential for a variety of applications such as automotive parts, medical devices, construction, packaging, and so on. However, PLA has a couple of intrinsic drawbacks of low melt strength and high brittleness. In order to achieve high melt strength enough to obtain finer and more closed cells, we will try to add polytetrafluoroethylene fibers which are expected to increase the number of molecular chain entanglement of PLA. As an attempt to increase the ductility of PLA foam, PHA will be blended with PLA. Poly hydroxy alkanoate (PHA) is more desirable to be blended with PLA to enhance the toughness and ductility. Regarding the content of added impact modifiers, it needs to be minimized to the level of marginally satisfying the requirement of the mechanical properties in each application, because these polymers are much more expensive than PLA. In a bid to achieve excellent foam products using a foam injection molding process, the foam processing conditions and parameters should be optimized as well. Since PLA is a semi-crystalline polymer, basically the processing window for foaming is very narrow, which makes foaming of PLA more challenging. Therefore, an economically viable material recipe and injection foaming parameters will be developed through systematically planned foam experiments using a foam injection molding machine.