Vinay Pandey, Rubber Technologist, Ami Polymer, gives an outlook about silicone rubber used for healthcare products in pharma and biotech applications
Polymer industries have been serving the pharmaceutical industry through various polymeric product compositions to meet critical requirements of food, pharma and biotech industries. Silicone resin formulations very easily meets with FDA and USP requirements with ultra low extractable and leachable properties.
Silicone rubber is the most widely used polymer in pharma and biotech industries due to its inherent properties like biocompatibility and inertness to cells/human tissues. Every product puts a demand on the material used, but none so more than the medical industry. In terms of meeting both the regulatory requirement and performance, the answer is thermosetting Liquid Silicone Rubber (LSR).
Overview of silicone rubber chemistry
Silicone rubber is chemically known as PDMS (Polydimethylsiloxane). It contains Si-O Backbone Structure in polymeric chain, which is responsible for its superior performance as mentioned below:
- Flexibility at lower temperature up to – 80°C
- High heat resistance up to 250°C.
- Greater weather and oxidative resistance
Key properties of product made of silicone resin
Silicone resin is translucent polymer widely preferred for pharma industry because of below reasons:
- Non-reactive and inert to biological tissues/ cells
- Excellent biocompatibility
- Smooth surfaces tend to prevent contamination of fluid on its surface
- Easy to clean and sterilise by any standard sterilisation process.
- Free from toxic ingredients
- Free of phthalate and bisphenol content
- Low level of extractable compare to any other polymers
- Excellent flexibility to facilitate dynamic applications (Peristaltic Pump)
- Translucent compare to other rubbers to visualise flow of material
Types of available silicone rubber:
Based on chemistry of Cure Mechanism, there are two types of silicone rubber available as stated below:
- Peroxide Cured Silicone Rubber
- Platinum Cured Silicone Rubber
Understanding peroxide cured silicone rubber:
While processing of Silicone Resin, catalyst is added to strengthen its physical properties. When peroxide catalyst is used for processing, it is called as peroxide cured silicone rubber. Most common catalyst is DCP (Dicumyl Peroxide).
The peroxide curing process leaves behind by-products in the form of volatile organic acids. To remove by-products, Peroxide Grade Silicone products are treated in Tray Drier (hot air circulating oven) at 200°C for three to four hours.
This treatment is called post curing process, which eliminates the by-products by converting it into gaseous form. But still, ineffective post curing process may lead to leaching of by-products in food contact and medical applications.
Understanding platinum cured silicone rubber:
Platinum complex-based catalyst is added in Silicone Resin while it’s processing. Chemically it is known as addition reaction. There is no generation of any kind of by-products in platinum curing system of silicones.
Prevention of by-product generation makes it safe to use in critical application of food, pharma and biotech industries.
Advantages of platinum cured silicone products over peroxide cured silicone products:
- Superior transparency to see visibility of fluid flow transfer
- Free of by-products and odour
- Smooth surface resists stickiness of transfer fluid. It prevents contamination and bacterial growth.
- Better physical properties like tensile strength, tear resistance.
- By-product free silicone resin contains low level of extractable and leachable enhances its usage of critical product transfer in pharma and biotech industry.
- Maintains physical characteristics in storage condition of long period enhance its shelf life. Doesn’t turn yellowish during prolonged storage period.
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