Injection Molding of Bio-based Plastic with Petroleum-based Plastic to Yield Articles with Low Carbon Footprint and Acceptable Mechanical Properties
Publication Date: 2011-Apr-22
The IP.com Prior Art Database
AbstractDisclosed is a method to increase the ‘green’ content of an injection molded part while simultaneously maintaining flex/fatigue performance.
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There is currently a push in the electronics industry for companies to green their product portfolio. For instance, both Fujitsu* and Apple** have recently introduced products that have replaced petroleum-based thermoplastics with bio-based materials. Wider acceptance of bio-based resins is hampered by their shortcomings with respect to specific performance requirements. For example, many of the bezels used in IBM*** server products are designed with snap fit latches that must survive multiple actuation cycles. PC/ABS resin has traditionally been used in these applications due to its excellent flexural strength and fatigue resistance. Bio-based resins, such as compounded PLA, are presently incapable of replacing PC/ABS in these applications due to inferior flex/fatigue performance. Consequently, there exists a need to replace petroleum-based thermoplastics without sacrificing performance.
Since the majority of a typical bezel serves no other function other than aesthetics, this concept uses injection molding techniques to form a hybrid plastic part that incorporates a large fraction of bio-based resin. That is, the majority of the part is molded from the bio-based material, but the latches or snap fits are molded from a traditional PC/ABS resin. In this fashion, the 'green' content of the part is greatly increased while simultaneously maintaining flex/fatigue performance.
Two non-limiting embodiments are discussed. Co-injection molding works on the following principle. The co-injection process requires two injection/processing units. The units generally inject material through a manifold located at the end of the injection barrels. The manifold ports the two melt streams into a centrally located nozzle. The machine controls the injection units to achieve a skin-core-skin flow sequence through the manifold into the mold. The last skin flow is needed to clear the short nozzle section of core material and to seal the gate area with skin. This arrangement can be used on any single or multiple cavity, conventional cold runner mold. This same process can be achieved on a hot runner mold by utilizing a hot runner system from Incoe Corporation in Troy, Michigan. This syste...