Materials

Present trends and future prospects of Plastics in Medical Applications 

- Dr. B Ramaraj, Senior Technical Officer, CIPET, Mysore

Introduction

Plastics need no introduction in today’s world, in every sphere of life its indispensability is felt by each and all of the society. Enormous breakthroughs in medical science over the last forty years made plastics are important to our health care. Plastics are now inextricably linked to the well being of millions of people across the globe. Plastic being hygienic, strong , light, inert, protective disposable, versatile and flexible, plastics have proved vital in producing medical equipment’s and instruments. The medical equipment and components made out of plastics will be smaller in size. The Plastic is with incredible versatility and able to maintain the critical properties of high performance and safety. The use plastics in the medical field is constantly increasing . New materials with improved properties are developed in order to satisfy the requirements of infection control standards.

Polyvinyl Chloride(PVC)

PVC is the world’s most versatile thermoplastic with a wide range of applications than any other plastics. Chlorine based plastics are most widely used in medical devices and equipments, The most common one is the Polyvinyl chloride. PVC is the most useful biomaterial for single use pre-sterilized medical devices, it has versatility, sterilisability , safety appearance and favourable cost/performance ratio. PVC compounds should be extraction, X-ray, gamma irradiation resistant, opaque and biocompatible. An important factor to be tested in PVC is the free vinyl chloride monomer, because it is suspected to have harmful reactions. The PVC compounds are formulated in such a way that the final product meet the requirements of pharmacopoeia and other standards. The factors that currently make PVC as the most widely used thermoplastic for medical devices are 

• Clarity and transparency. Because of its physical properties, products made from vinyl can be formulated with excellent transparency to allow for continual monitoring of fluid flow.

• Flexibility, durability and dependability. Not only does vinyl offer the flexibility necessary for applications such as blood bags and I.V. containers, but it can also be relied upon for its strength and durability, even under changing temperatures and conditions. 

• Sterilizability. Vinyl products can be easily sterilized using such methods as steam, radiation or ethylene oxide. 

• Compatibility. Vinyl is compatible with virtually all pharmaceutical products used in healthcare facilities today. It also has excellent water and chemical resistance, helping to keep solutions sterile. 

• Resistance to chemical stress cracking. Vinyl’s resilience helps assure that medical products consistently function for extended use in demanding applications. 

• Ease of processing. Vinyl can easily be extruded to make IV tubing, thermoformed to make “blister” packaging or blow molded to make rigid hollow containers. This versatility is a major reason why vinyl is the material of choice for medical product and packaging designers. 

• Low cost. The use of vinyl plays a big role in containing rising healthcare costs
  

The PVC compound which have to been used are 

• Polyvinyl chloride- high purity, high K-value, suspension grade 

• Plasticizers such as di-2-ethylehexyl phthalate and adipates, which has been used in the blood bag manufacture in the last thirty years. And tri(2-ethylhexyl)trimelitate, polymeric adipate have also been used.

• Epoxidised oils such as epoxidised soya bean oil and epoxidised linseed oil 

• Stabilizers, it is not desirable to use powerful stabilizers based on tin, cadmium and barium for PVC meant for medical applications- particularly for blood bag applications because of their toxicity. The most suitable system is based on Calcium and Zinc salts. 

• Lubricants and other additives

Major application areas 

The versatile properties of PVC and the ability to tailor the properties to specific end use permit a wide range of flexibilities for Blood bags, blood tubing, surgical gloves, suction pipe, infusion drip chamber, blister packaging, transparent tubing’s, rigid compositions for check valves and needle cubs and barium sulfate grades for X –ray tractability, etc. 

Urine bag 

A urine bag is simple device for the collection of urine. Basically a urine bag has to be a PVC bag with an inlet and an outlet. The other features that are required for urine bag are 1. a soft and flexible tubing for easy irrigation, 2). Top angles drainage to avoid spillage, 3). Volumetric graduations to measure even small out put, and 4). Universal adapter etc., 

Tur Bag

This product is meant for the collection of urine during and after trans uretheral resection of prostate. The features are similar to a urine bag, but for the large diameter tubing for the unobstructed flow of effluents, a bottom outlet with a push pull opening for the easy disposal of the collected fluid, a self sealing sampling port. 

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