PVC and Medical Application
Western Europe consumes over six million lifesaving blood bottles each year. PVC is the material for blood bottles and IV-tubes. It is as transparent as glass but lightweight and unbreakable. The blood which is conserved in PVC blood-bottles is longer maintainable as in other boxes. PVC is the dominant material for blood-bottles: The application demands high standards on the used material: Resistant to heat during sterilisation, having low-temper-flexibility during freezing of the blood-bottles, flexible during filling and during infusion.
The blood-bottle should to be safely fused and to care for a long storage of the blood. During intensive care PVC is the preferred synthetic for gloves, elements for artificial hearts, for IV-tubes and dialysis machines.
PVC shows its special advantage within the combination of specific attributes: During the use of pumps for example to roll up tubes the used PVC hoses are expected to be very flexible and to have a grit as low as possible at the same time. PVC conforms to both requirements and permits a simple optical control of the transported liquid by its transparency.Irrespective of its concrete use the material has to be easily sterilised. Neither during sterilisation by vapour nor Ethylenoxid or irradiation – It is possible to sterilise PVC without any change of its material properties. The used material does not emit wearing substances to the blood or to the liquid of infusion.PVC for medical applications is produced by the use of only selected and strictly controlled additives which are safe to use. With a market-share of 30 percent PVC is the most used synthetic within this area of medical application.
PVC is by far the most widely-used plastic material in medical intensive care. Approximately 10,000 tonnes of PVC are used each year in Germany as blood bags and tubes for various applications, which constitutes about 30% of the overall plastic consumption in this sector. This primarily involves soft PVC with a plasticiser amount of 5% to 25%. Gloves, wound dressings, tube clamps and other accessories are also manufactured from PVC.
One of the main prerequisites in medical care is sterilisation. Whether by means of steam, ethylene oxide, or radiation – PVC can easily be sterilised germ-free by any of these methods.
For blood bags, extreme elasticity when cold is important since blood supplies are frozen for a long period of time. Simultaneously, blood bags must be soft and flexible when defrosted so that they collapse when emptied. Otherwise, sterilised air would have to be used for the pressure balance and would make their use considerably more difficult. PVC has other favourable properties in health care. Its transparency facilitates examination of the level and type of its content. Its material resilience and abrasion properties allow for the use of roller pumps. Another advantage of PVC is the possibility of so-called high-frequency welding. This process provides very reliable, pore-free welded seams. The great strength of the seams is important when the blood is centrifuged and separated into parts.
Furthermore, long-term studies have shown that the plasticiser DEHP (Di-(2-ethylhexyl)-Phthalate) protects red blood cells from breakdown while being stored in blood bags and thereby guarantees a long life for blood.
Calcium and zinc compounds are used primarily as stabilising systems; DEHP of medical quality is used mostly as a plasticiser. Blood can dissolve small amounts of the PVC plasticiser due to its fat content. The effects of plasticisers on humans have therefore been extensively examined. The research results show that there is no indication of health risks.
