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Dear Friends,
I would like to know which is better in terms of impact resistance. For rimless frame, what should I suggest, poly or 1.6 material. I heard that 1.6 materials are impact resistant material suitable for rimless. Kindly advice
Regards
Maju
I have been using trivex or 1.67 over poly lately...I find alot of the poly materials split and crack at drill points and on semi rimless where the nylon line starts and a metal frame begins the poly wil chip or split internally. I like the thinness of the 1.67 material and thats its aspheric
I have heard of a new 1.60 material that has many of the same properties that trivex has. You may want to check that out. Otherwise if the RX is -3.00 or less I would use trivex.
TRIVEX, TRIVEX, TRIVEX, TRIVEX :dance:
I have used a 1.60 in the past,are you referring to something new and is it thinner and lighter than trivex?
From another thread authored by DragonLensmanWV -> http://www.ppgtribrid.com/Quote:
Originally Posted by mshimp
There are different plastics with 1.6 refractive index (acrylic, MR6, MR8).
The most common (and best at the moment) is the MR8.
It is our preferred rimless material, it is strong (higher tensile strength than Trivex) and rigid (central thickness: 1mm).
It is very hard to brake, BUT if it does it shatters into pieces.
On the other hand, Trivex is more like rubber (or chewing gum). It does not brake as much as flexes etc. Here is a nice example:
https://www.youtube.com/watch?v=Eogq4HDtcnY
(also Trivex tolerates well poorly done drilling and assembly)
We use Trivex instead of MR8 when the client is of a "careless" disposition and the RX is small positive one (thin edges). Trivex bends and does not shater when the thin edges of the mount are abused.
On polycarbonate: We left this clunker in the previous century.
We can get the same poor optics with 1,74 and 1,67 if we are so inclined.
I actually can't comprehend why it is still in use at some places?!
You'd be amazed how many people on OB think Poly is the only matherial to use. The other day I was in the waiting room of an OMD which ajoined his in office dispensary overhearing that Poly was "Our most durable material."
Chip
The assumed safety properties is the reason. Kids, sports glasses, etc. Industrial safety accounts require it be used.Quote:
Originally Posted by Nikolay Angelov
Trivex
Phoenix
And cost. Trivex is still usually more expensive.
Quote:
Originally Posted by eyes4u
There are ways to get around it. No Poly crazing or cracking when doing a proper job................................
I didn't know prices were like that.
Here polycarbonate, MR8 and Trivex are about the same price.
We have some quality brand name MR8 lenses that are actually cheaper then the other two.
The Chinese polycarbonate AR lenses are indeed the cheapest here but their quality is unacceptable.
They self-destruct like a "Mission Impossible" prop.
Cool Video!!!
Mechanical Properties of Multilayer Coatings on Polycarbonates
Prepared by PECVD
V. Buršíková1, L. Zajíčková1, J. Buršík2 and J. Janča1
1Department of Physical Electronics, Faculty of Science, Masaryk University,
Kotlářská 2, 611 37 Brno, Czech Republic, e-mail: vilmab@physics.muni.cz
2Institute of Physics of Materials, Academy of Sciences of the CR, Žižkova 22, 616 62 Brno, Czech Republic
Abstract
In the present work, several different types of intermediate layers between the polycarbonate (PC) substrate
and the plasma deposited hard SiO
x-like protective coatings have been studied and their influence on the
mechanical properties of the whole coating/substrate system has been compared. By the help of an optimized
fracture resistant intermediate multilayer system and the hard SiO
x-like protective coating the original PC
surface hardness (~0.2 GPa) was increased by almost two orders of magnitude (5-9 GPa).
Read whole report: http://134.147.148.178/ispcdocs/ispc...Papers/845.pdf
Atleast here in the Indian market place. The most widely used lenses for rimless are poly. Essilor does Airwear in 1.59 index. Check them out.Quote:
Originally Posted by majucalicut
Benny
All polycarbonate is 1.59 index, Essilor does not make theirs any different, just more expensive. For drill mount lenses, at my place they ONLY get Trivex, nothing else. Have never had a single breakage or crack.
Most rimless frame manufactuers recommend the MR-8 1.60 because it has very good tensile strenght, but the patient appreciates the thinner lenses.
I also think 1.60 finishes cleaner than Trivex. With an ABBE of 42, the advantage of Trivex is very very small.
Am I the only one who's tried 1.60 in drill mounts and had them break?
We do OK with 1.60 in drill mounts...but we also do fine with poly. We just hardly ever see cracks with OUR work. We do see it frequently with work patients bring in from other sources. I attribute it to our drill-edger (NO 7e).
Would you really do a -4.50 drill mount in Trivex? Too thick.
I did a -15 in 1.70. (they were mine) Tricky part was drilling into the lens just enough to seat the frame. The back of the lens was undrilled. Then I had to invent a compression plier to mount them with.
My optician complains that Trivex seems to drill unevenly. More bushings come loose even though they seem to fit well originally.
As I said earlier, this is the most commonly used Poly in the Indian market. And its not that expensive here in India.Quote:
Originally Posted by DragonLensmanWV
Cheers.
Nope. I've seen everything crack or break or chip, except Trivex.Quote:
Originally Posted by DragonLensmanWV
How about HI-VEX: hi-velocity impact resistant, COLTS Laboratories certified for all rimless and safety, refractive index 1.556, ABBE 46, specific gravity 1.25 g/cm^3. Try it you will like it :smile:
I prefer 1.60 for drills, it finishes with a very clean edge, I have never chipped one, and the drill holes are clean and straight. We get more irregular drill holes on Trivex, the edges don't look as crisp, and patients are dissappointed that its just not that much thinner. It has the perfect amount of shine on the edge, not too much.
Most premium rimless lines, like Lindberg, recommend 1.60 over Trivex and Poly.
Poly has been cracking more and more the last few years. I order it extra thick to compensate, so it ends up thicker than 1.60.