POLYCARBONATE

It is a thermoplastic resin and the lens is manufactured by pouring the material into metal moulds at high pressures and temperatures.

It has excellent anti-impact properties which make it ideal for sports and industrial uses. The specific weight is slightly lower compared to CR 39's. When used in rigid frames or in contact with non compatible materials, phenomena of"stress cracking"might occur (i.e. cracks on the anti-scratch coating).

SINTER® APX (patent pending)

SAME IMPACT RESISTANT AS POLYCARBONATE BUT FREE FROM STRESS CRACKING AND PLASTICIZER MIGRATION

The Sinter® APX lens has been developed to overcome the well known problems polycarbonate lenses encounter in mounting (stress cracking in metal frames, migration crazing from acetate frames and electrostatic stickers) limiting their use in high quality sophisticated frame designs.

The Sinter® APX lens is manufactured by injection moulding using a new patented material which gives the product an exceptional resistance to stress cracking as well as absence of haze and micro cracking lens phenomenons caused by plasticizer migration. Sinter®APX lenses are hard coated, same as polycarbonate. The Sinter®APX lens is totally compatible with all types of materials used in frames whereas the polycarbonate is not. The main advantages of Sinter®APX over polycarbonate lenses are:

Plasticizer migration does not occur when inserted in acetate frames or when applying electrostatic stickers to the Sinter®APX. The stress cracking phenomenon does not occur when Sinter®APX are mounted in rigid, sharp shaped metal frames, even when lenses are screwed to the frame. Sinter® APX impact resistance is equivalent to polycarbonate lenses. Particularly, Sinter® APX lens passes all high and low energy tests required by the ANSI Z87.1-1989 STANDARD for occupational eye and face protection. The most severe tests are:

High speed impact: the lens resists the impact of a shot gun by a stainless steel ball weighing 6,35 mm at a speed of 45.7 m/sec. High mass impact: Sinter®APX passes the impact test of a stainless steel sharp dart weighing 500 gr. dropped from a height of 1,3 metres. With Sinter®APX you can forget all problems known to polycarbonate. Contact us for samples and further information.

Lenses are manufactured by injection molding and, like polycarbonate, are covered by an anti-scratch coating to improve their resistance to abrasion. While they maintain a high mechanical resistance, APX lenses are totally compatible with all the materials used for frames. The impact resistance is the same of Polycarbonate lenses. In particular, the lens with 2 mm thickness passes all the high and low energy tests established by the ANSI Z87.1-1989 standard for sunglasses and shields for industrial protection.

These tests include:
a) High speed impact: the lens resists the impact of a steel ball with diameter of 6.35 mm shot at a speed of 45.7 meter/second.
b) Impact with high mass dart: Intercast SINTER®APX lens passes the test with a steel dart with sharp conic point weighing 500g dropped by gravity from a height of 1.3 meters.

Poly Dietilenglycole bis Allilcarbonate CR39®

CR 39®is undoubtedly the most common optical polymer in the ophthalmic field. It is a heat hardening resin and as such it is not attacked by any chemical agent. The lens comes from pouring the liquid polymer into a mould of optically treated glass. This enables to obtain a lens with the same characteristics of the originating glass.

It has a higher scratch resistance than the other plastic materials and does not require any anti-scratch treatment.

The specific weight is 1.3 versus 2.53 of glass and this means that, with the same thickness, the weight of a CR 39 lens is approximately 48% lighter than a similar one made of glass. As for impact resistance, afocal lenses with a thickness of 1.8 mm, easily pass the test of the steel ball falling from 16mm height (Drop Ball Test) imposed by the FDA to sell lenses in the USA. They are four times as resistant as Crown Glass and always more resistant than tempered glass.

CR39 lenses are easy to process and surface tintable with uniform and gradient colors, enabling to obtain a wide range of colors. However, mass colors are also possible.