Medical Device Link.

MATERIALS

Often called organic glass, the allyl diglycol carbonate monomer has a high transmission value, low haze, and chemical resistance. In addition to ophthalmic products, the material is used to manufacture instrument displays and data capture systems.

Thermoset monomer allyl diglycol carbonate (ADC) was initially developed as a replacement for glass in prescription ophthalmic lenses because the two materials had similar properties. ADC’s 92% transmission value, low haze, and chemical and gamma radiation resistance closely resemble the attributes of mineral glass. In fact, ADC is often called organic glass. It has captured more than 50% of the prescription lens market, and is extensively used in the manufacture of instrument displays and data capture systems. Cast ADC optical sheet increasingly is also becoming a replacement for glass in a number of medical devices, according to Fosta-Tek Optics Inc. (Leominster, MA, USA).

The company’s custom formulation of ADC provides the aforementioned properties in a low-cost material that is easy to process, says Danielle Provencher, the firm’s ADC coordinator. “Excellent chemical and solvent resistance makes ADC especially suitable for medical and lab environments,” she says. “The optical and mechanical properties of ADC sheet are unaffected by long-term exposure to virtually any organic chemical, including ketones, alcohols, aliphatic and aromatic hydrocarbons, and cleaning solvents and alkalis.”

The thermosetting process—unlike extrusion or injection moulding—generates very little birefringence in ADC, notes the firm. Furthermore, the material’s Abbe value of 59 is close to that of glass and higher than that of any other optical plastic. (The Abbe value is an indicator of light dispersion or chromatic aberration.)

ADC can be laser cut to specific shapes and sizes at a lower cost than glass, according to the firm. It can be cast in thicknesses from 0.030 to 0.250 in. and cut to sizes up to 25 in. square.

With a specific gravity of 1.3, the material weighs half as much as glass. Antiglare finishes can be cast directly into a display window, and a secondary thin film can be applied when an antireflective coating is required. Dyes are available in a range of colours, providing peak transmission values at specific nanometre ranges to optimize display readability.

Medical applications of the material thus far have included blood analyzers and defibrillators.