POLY VINYLCHLORIDE(PVC) as a BiomaterialJeff Jose

2nd M.sc biopolymer scienceCBPST KOCHI

jeffjose09@gmail.com

Introduction

• The most widely used thermoplastic material in the medical device industry is PVC.

• PVC was originally developed to replace the rubber and glass that was historically used to make flexible tubing and containers.

• PVC is the dominant material used for the storage of IV fluids, dialysis solutions, as well as blood and blood products

• Studies suggest that 25% of all plastics used in hospital environments are PVC-based

PREPARATION OF VINYL CHLORIDE

1) Laboratory preparation

2) Commercial preparation

POLYMERISATION

• Bulk polymerization• Suspension polymerizations• Emulsion polymerization

Properties and advantages

• It can be sterilized with steam withstanding temperatures as low as -40°C and as high as 121°C.

• PVC can also be sterilized using an ETO (Ethylene Oxide) and with a Gamma Irradiation Electron Beam.

• PVC can also be joined together with high frequency welding thus allowing for a wide variety of container shapes and numerous types of attachments.

• Commercially available PVC is highly branched and has low crystallinity. However, high molecular weight PVC has a more ordered structure, is less linear and has a higher degree of crystallinity

• Medical products made from PVC are usable inside the body, easy to sterilize and simple to assemble into products that do not crack or leak.

Reasons To Use PVC in Medical Applications

• 1) Safety

• Before PVC can be used in medical devices, it must be thoroughly tested from a toxicological point of view.

• PVC material sterilized in Ethylene Oxide and consequently Re-sterilized in EO show NO TOXICITY

• 2) Chemical Stability • chemically stable, inert• Alkali resistant ,non pyrogenic odorless and tasteless

• 3) Clarity and Transparency

• Products made from PVC can be formulated with excellent transparency to allow for continual monitoring of fluid flow. It can even be colour coded to virtually any colour needed.

• 4) Biocompatibility • When plastics are used in direct contact with a patient’s tissue or

blood, a high degree of compatibility is required between the tissue/blood and the material. The significance of this property increases with the time over which plastic is in contact with the tissue or blood.

• 5) Flexibility, Durability and Dependability • Not only does PVC offer the flexibility necessary for

applications such as blood bags and IV containers, but it can also be relied upon for its strength and durability, even under changing temperatures and conditions. PVC can also be easily extruded to make IV tubing, thermoformed to make 'blister' packaging or blow moulding to make hollow rigid containers. This versatility is a major reason why PVC is the material of choice for medical product and packaging designers.

• 6) Low Cost

• PVC accounts for almost one third of the cost of medical plastic today, hence its low cost has a profound effect on maintaining the lower costs of medical plastics generally. A switch to another plastic could cost the healthcare industry hundreds of millions of dollars per year.

• 7) Resistance to Chemical Stress Cracking • Stress cracking is one of the most common symptoms of

polymer damage. Stress causes the secondary linkages between polymers resulting in little fractures, like you may have seen in a plastic cup that didn’t survive the dishwasher. PVC's resilience helps assure that medical products function consistently for extended use and in demanding applications.

Plasticizers in medical applications

• Most medical devices made from PVC use plasticizers to give the flexibility that makes the material so appropriate for use. The main plasticizer types are known as phthalates. These are a group of colorless, odorless and, in the presence of oxygen, readily biodegradable liquids.

• One of the most important phthalates by tonnage is DEHP[Di(2-ethylhexyl) phthalate], which is currently the only listed plasticizer recommended by the European Pharmacopoeia as the substance of choice for softening disposable medical items, blood bags and tubing.

• major beneficial consequences of plasticizers migration in that some plasticizers (DEHP and BTHC) actually contribute to enhanced red cell survival and therefore increased shelf-life for whole blood. This is explained by the fact that the plasticizer interacts and stabilizes the red cell membrane.

• DEHP can leach out into solutions that come into contact with the plastic. The amount of DEHP leaching out depends on the temperature

Alternatives for medical device

• Plasticizers

• Trioctyl trimellitate (TOTM)• Butryl trihexyl citrate (BHTC)• Di isonoyl cyclohexane-1,2-dicarboxylate(DINCH)• Bis(2-ethylhexyl) adipate

• Stabilizers• Ca- Zn stabilizers

APPLICATIONS

Solution packagingdialysis tube

Urine bag Gas mask

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