Micro Molded Bio-Resorbable Polymers
04/27/2016 MICRO MOLDING: Although there is no standard definition of micro molded components in the industry, most micro manufactured components have one or more of the following attributes:
• Fractions of a plastic pellet or weighing fractions of a gram
• Having wall thickness of less than .005”(0.127mm)
• Having tolerances of .0001” to .0002”(0.0025 to .0050mm)
• Having geometry seen only by use of a microscope
BIO- RESORBABLE MATERIAL: Bi-resorbable polymers have been on the market for over 20 years. These polymers are typically PLA based (Poly Lactic Acid) or milk based. They are commonly compounded with PGA called PLA/PGA compounds (Lactide/glycolide). These materials are used in implantable applications when the device is only needed in vitro short term.
INTRINSIC VISCOSITY: Most polymer processing uses melt flow index as an indicator for processability. With BIO-resorbable polymers, an IV (Intrinsic Viscosity) test is used to determine the characterization of the polymer as it relates to Molecular Weight, processability, and in vitro stability. IV is a measure of a polymer’s capability to enhance the viscosity of the solution it lives in. It is important to find the viscosity at different concentrations and extrapolate to zero concentration.
The above chart shows common applications for Bio-Resorbable micro molded components. In this life cycle curve, most of the work being done is in the new product area, R&D developments, drug-eluding products, and implants being used as pharmaceutical “carriers”. Growth products in the hundreds of thousands of parts annually are bone screws, anchors, and swallowable pills. Bone screws typically made of Titanium can be replaced with bio-resorbable materials so that patients are not “stuck” with that bone screw for the rest of their lives. The resorbable bone screw, unlike the titanium one, after an approved amount of time, the bone fuses together and no longer required the screw, and the resorbable material then gets absorbed by the body and turns into carbon dioxide and water and is flushed from the human system naturally.
Mature products is also a very busy segment due to what is called “a work around method” whereby conventional molders may be putting micro components into large mold frames and conventionally-sized molding machines. These programs are almost always an immediate return on investment to re-tool due to the runners and sprues being so very costly in material scrap they generate.
High volume (Growth) bio-resorbable products are facial implants from reconstructive surgery for aesthetic reasons or accident/disfiguring reasons. Additional high volume products (100k+) are seen in bone screws and sutureless devices such as resorbable sutures, anchors, and staples.
Bio-Resorbable Polymer Applications (provided by MES)
Check out our micro molding projects page for more information here.
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