Materials

Calcium And Zinc Based Heat Stabilizers For Medical Applications

applications as it not only provides required compatibility and chemical resistance but also the toughness of material in terms of mechanical properties allows it to be used with little care. Similarly, PVC also gives advantage over metal as it doesn’t corrode and has great chemical resistance. Hence lipids, alcohol, acids and bases can be stored safely in PVC container.

Single use medical applications of PVC like gloves, masks, sterile syringes, blood bags, IV bags, tablet packaging, is a game changer. Sanitization is a constant challenge in front of medical workers and historically multi-use medical devices were the main reason behind infections due to cross contaminations. Moreover, traditional sterilization facilities such as use of ethylene dioxide, steam and autoclave were time consuming. Whereas, new age sterilization techniques like use of gamma rays is very well suited for polymer based medical equipment and these devices can be sealed or made ‘ready for use’ in very short time. PVC and its additives that are used in the medical applications fulfill all the requirements of safety during working period and also retain the properties of the compound even after modern sterilization techniques.

Since, PVC is not stable when it is exposed to heat, the performance of PVC is largely dependent on the additives especially heat stabilizers. In the case of manufacturing medical devices, non-toxic and eco-friendly heat stabilizers are the natural choice of processors. These stabilizers are also expected to provide final products high degree of clarity, good mechanical properties and excellent chemical resistance.

Generally, for transparent applications Calcium and Zinc based stabilizers are recommended to use. Calcium Stearate and Zinc Stearate are the core stabilizing agents which are manufactured using plant based stearic acid, calcium hydroxide and zinc oxide. Both of these ingredients can be used for food contact applications safely. But since these grades are to be used for medical applications, all raw materials used to manufacture stabilizers must be USP compliant. Apart from metallic stearates other organic and inorganic co-stabilizers are also used in the formulations. The inorganic stabilizers are mainly acid scavengers that restrict the release of toxic gases such as hydrochloric acid and organic co-stabilizers are used to improve color hold and UV stability of the final product. Along with these stabilizers many processors also use Epoxidized Soya-Bean Oil (ESBO) in flexible compound to improve heat stability and UV resistance of the final article. ESBO is also bio based product and can be used safely in all food contact or insertable parts of devices such as tubes.

Moreover, PVC is being used in hospitals in the form of floorings and wall claddings in hygienic rooms. Hygienic surfaces need to be cleaned with various cleaning agents and due to chemical resistance PVC claddings are preferred. The added advantages such as durability, low maintenance cost and acoustic properties in the material, PVC is preferred by modern health care architects for interior design of the hospitals. For such rigid applications internal and external lubricants are also used in combination with the stabilizers to make processing easy.

Use of PVC and Ca-Zn based stabilizers is a sustainable solution. All single use and multi-use articles can be recycled. Mostly material is transparent and made with premium grades of additives. Hence, once sterilized it can be sold at a very good price to the recyclers. Secondly, in many other transparent applications, methyl tin stabilizers are used which are not compatible with Lead based stabilizers. But since, Ca/Zn stabilizers are primarily used in medical applications the material to be recycled can be used in any system as Ca/Zn based stabilizers are compatible with all ingredients.