Originally Published MPMN January/February 2007

HOTLINE

Nanotreatment Used for Purification of Silicone Rubber

Susan Shepard

A tempering and cleaning technique for silicone rubber has been developed by Nanon A/S (Copenhagen, Denmark; www.nanon.dk). The environmentally friendly process consists of a 45-min wash in liquid CO₂, which helps remove the volatile residues in silicone rubber and replaces the traditional method of four hours of postcuring in a 200°C oven.

The company’s Cold Curing process has a sterilizing effect on the treated parts. The pressurized CO₂ kills pathogenic bacteria, which helps produce biologically clean products. It reduces the content of free silicone oils and other residues in medical products that may be toxic or even carcinogenic.

The treatment significantly reduces the risk of the silicone harming users or creating allergies, according to the company. Other advantages the firm cites include time savings of about 75% in postcuring, and cost savings of between 15 and 35%.

In the Cold Curing process, liquid CO₂ penetrates and dissolves the volatile residues in the silicone rubber, and, by normal diffusion, the content of the substances, such as free silicone oils, is reduced to less than 0.3%. This is lower than the EN 14350-2 requirement of 0.5%, and helps avoid contamination during highly sensitive medical operations.

The technique takes place at low temperatures and permits precision molding, so repolymerization does not take place. This eliminates common problems with slit healing occurring from traditional oven tempering at 200°C. Applications include producing nipples for baby bottles and duckbill valves. The technology allows for keeping the holes made in silicon open during and after the treatment.

Nanon A/S provides in-house treatments and can also install Cold Curing machines in its customers’ facilities.

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