Material Science: The Transition from Glass to PET Plastic
Historically, vacuum blood collection tubes were manufactured from borosilicate glass. While glass offers excellent chemical resistance and maintains a vacuum for extended periods, it presents significant safety risks due to breakage during centrifugation or transportation. In recent decades, the industry has transitioned toward Polyethylene Terephthalate (PET) plastic.
PET is a clear, lightweight, and shatter-resistant polymer that can withstand high G-forces during centrifugation. However, plastic surfaces are naturally hydrophobic and can cause blood cells to adhere to the walls or delay natural clotting. To mitigate this, manufacturers spray-coat the interior walls with microscopic silica particles (clot activators) or surfactants to ensure smooth blood flow. Additionally, plastic is slightly more permeable to air than glass over long durations; therefore, PET tubes often have a strictly defined shelf life to ensure the internal vacuum remains within the calibrated tolerance for accurate draw volumes.