question for lab managers....

[Chris Ryser]

BTW, I use denatured alcohol from the paint stripper section. Is that wrong? Stressful on AR?

Not if used occasionally..........however continous use of lens cleaners containing alcohols will do it.

[jb@kso]

We are using All-Off ink remover for that.

[chip anderson]

You should see the number of PMMA conformers my prosthetic eye patients come in with that are crazed because at the time of surgery the doctor "sterilized" them by putting them in alcohol.

Chip

[thep]

I'm convinced that the basic poly monomer has changed in the last 1 to 1 and 1/2 years. We have had more stress fractures in this material from ALL manufacturers recently. Someone please tell me if I'm nuts!
Janet:hammer:

[Jacqui]

I don't think you're nuts, I've been seeing them too.

[Leo Hadley Jr]

I'm convinced that the basic poly monomer has changed in the last 1 to 1 and 1/2 years. We have had more stress fractures in this material from ALL manufacturers recently. Someone please tell me if I'm nuts!
Janet:hammer:

Funny you should say that.........
I was teaching a new technician about optics when I mentioned that poly lenses were bullet proof. I took a name brand poly lens out of the envelope and blasted it with a hammer.
To my suprise it shattered all over the room.

I suspect some polys are being blended for better optics.

[GAgal]

I'm convinced that the basic poly monomer has changed in the last 1 to 1 and 1/2 years. We have had more stress fractures in this material from ALL manufacturers recently. Someone please tell me if I'm nuts!

I don't think you're nuts, I've been seeing them too.

Ditto...

[JMoondog]

I suspect some polys are being blended for better optics.

I know in the 20 years I have been cutting Poly it is definitly a different breed.

We use to hammer nails to it to show how tough it was :D

I use to tell people to get poly cause will never chip or break, haven't said that in a while

Ric

[HarryChiling]

I know in the 20 years I have been cutting Poly it is definitly a different breed.

We use to hammer nails to it to show how tough it was :D

I use to tell people to get poly cause will never chip or break, haven't said that in a while

Ric

It's been cracking, chipping, and crazing. It hasn't been the same beast for a while.

[hipoptical]

Not only poly, but most other materials have changed. Sometimes the biggest changes come when a factory is "relocated" to another country to make processing cheaper. We continue to demand cheaper prices, and failed to realise this comes at a cost. Cheaper usually means cheaper. Rarely does cheaper mean "lower cost".
Pure alcohol (99.999%) is what many labs are using to clean with due to A/R requirements. When you clean mounted lenses with it, you will find that destroying plastic frames is incredibly easy, as well as the lenses. Poly in particular will fracture on the edges when the alcohol sits in points of stress between the lens and frame. As the quality of the lenses continues to decline, the occurrence of stress fractures will continue to rise. It is a nationwide problem because most lenses are made in the same factories overseas.

[chip anderson]

1: Alcohol cannot be made that pure by any means, if it could no one could afford it.
2: Who would waste good Everclear to clean lenses. If it gets to 180 proof, it's for drinking not wasting on a silly clean up job.

Chip

[hipoptical]

1: Alcohol cannot be made that pure by any means, if it could no one could afford it.
2: Who would waste good Everclear to clean lenses. If it gets to 180 proof, it's for drinking not wasting on a silly clean up job.

Chip

1. Uh-huh, we use it every day. It is expensive, but some people think it's worth it.
2. "We don't have beer. Just tequila."
"What's tequila?"
"Uhh.. it's like beer."

[Paul van Wyk]

We only use alcohol (ethanol) to clean all the lenses we make , CR39 ,hi-index , poly and trivex.
I never saw any problems with the lenses cracking after edging and we did not get any lenses back from clients.

Paul

[HarryChiling]

1: Alcohol cannot be made that pure by any means, if it could no one could afford it.
2: Who would waste good Everclear to clean lenses. If it gets to 180 proof, it's for drinking not wasting on a silly clean up job.

Chip

Chip,
I use Everclear in the lab instead of denatured, less toxic VOCs and when a patient gets outta hand you can take a swig if you wanted and the day get's a little better.:D

(I'm just kidding about the swig, I don't advocate drinking at work.)

[Chris Ryser]

I did a bit of checking into Poly materials. There are 3 main brands in Poly Resins that produce the resins which is divided for industrial and transparent use as the following:

AGENCY APPROVALS OR LISTING : FDA, USP
BASE RESINS TRADE NAMES : Lexan® , Makrolon®

MECHANICAL PROPERTIES:
Specific gravity (ASTM D 792) : 1.20
Tensile strength, Ultimate (ASTM D 638) : 9,000 p.s.i.
Elongation at break (ASTM D 638) : 130%
Tensile modulus (ASTM D 638) : 3.1x10~5 p.s.i.
Rockwell hardness (ASTM D 785) : R118
Impact strength (73° F) (ASTM D 256) (notched) : 17.0 ft-lb/inch
Flexural strength (ASTM D 790) : 14,200 p.s.i.
Flexural modulus (ASTM D 790) : 3.4x 10~5 p.s.i.
Wear factor against steel 40 psi 50fpm : 2500x10~10
Coefficient of friction 40psi 50fpm : 0.38 Dynamic

THERMAL PROPERTIES:
Melting point : 310° F
Heat deflection at 66 psi (ASTM D 648) : 285° F
Heat deflection at 264 psi (ASTM D 648) : 270° F
Maximum serving temperature for short term : 275° F
Maximum serving temperature for long term : 240° F
Thermal conductivity (ASTM C 177) : 1.35 Btu-inch/hr-ft~2- ° F
Specific heat : 0.30 Btu/lb- ° F
Coefficient of linear thermal expansion (ASTM D 696) : 3.7x10~5
Applicable temperature range for thermal expansion : 0-200° F

ELECTRICAL PROPERTIES:
Dielectric constant at 60Hz (ASTM D 150) (73° F, 50% RH) : 3.2
Dissipation factor at 60Hz (ASTM D 150) (73° F) : 0.001
Volume resistivity (ASTM D 257) : 10~17 ohm-cm
Dielectric strength (ASTM D 149) : 380 v/MIL

MISCELLANEOUS:
Water absorption - 24 hours (ASTM D 570) : 0.15%
Water absorption - saturation (ASTM D 570) : 0.35%
Density (ASTM D 792) : 0.0434 lb/inch~3
Flammability (UL 94) : V-2
Weathering Resistance : Limited resistance (UV Sensitive)

Annealing to reduce stress

Annealing
Polycarbonate slab (Zelux) has been stressed relieved using Liquo-Temp annealing process. In some instances where extensive machining is required, a secondary annealing of semi-finished parts is highly recommended. Secondary annealing can be accomplished by heating parts at 250"F in a desiccated air circulating oven for one hour per one inch of thickness. After heating, the oven should be turned off and allowed to cool to room temperature spontaneously.




See the BAYER procedure of Polycarbonate Annealing at:

http://www.bayermaterialsciencenafta.com/faq_pcs/pdf/annealing.pdf

[chip anderson]

I still, despite what has been said on this post, remember from high school science and anatomy classes:
"About 98% is as pure as a alcohol can be distilled or filtered." 99.9% is not possible. One can distill and re-distill from now until Doomsday and it will retain at least 2% water.

Chip

[hipoptical]

I still, despite what has been said on this post, remember from high school science and anatomy classes:
"About 98% is as pure as a alcohol can be distilled or filtered." 99.9% is not possible. One can distill and re-distill from now until Doomsday and it will retain at least 2% water.

Chip

Thanks for clearing that up...
I'll notify the company that produces the alcohol and puts the label on the drum and provides the MSDS sheet that they are wrong. It's a conspiracy!!

[Chris Ryser]

"About 98% is as pure as a alcohol can be distilled or filtered." 99.9% is not possible. One can distill and re-distill from now until Doomsday and it will retain at least 2% water.

Chip

Material Safety Data Sheet

Ethanol, Absolute Section 1 - Chemical Product and Company
Identification MSDS Name: Ethanol, Absolute

Catalog Numbers: NC9602322
Synonyms: Ethyl Alcohol; Ethyl Alcohol Anhydrous; Ethyl Hydrate; Ethyl Hydroxide; Fermentation Alcohol; Grain Alcohol; Methylcarbinol; Molasses Alcohol; Spirits of Wine.

Percent ca.100

https://fscimage.fishersci.com/msds/89308.htm

[HarryChiling]

I still, despite what has been said on this post, remember from high school science and anatomy classes:
"About 98% is as pure as a alcohol can be distilled or filtered." 99.9% is not possible. One can distill and re-distill from now until Doomsday and it will retain at least 2% water.

Chip

It's usually very easy to reduce the water content now the other alcohols are a bit more difficult to distill outta the process but it can be done. I would love to drink some of that 99.99% stuff that everyone here is talking about.

Chip here's a recipe to pay the rent:

10 btl - Everclear
20 gal - Fruit punch
2 dzn - Apples halved
2 dzn - Oranges halved
1 x 50 gallon trash bag
1 x 50 gallon trash can

Cut up your fruit in half or quarters doesn't really matter too much how you cut them, stick them in a clean trash bag inside of a clean trash can (by clean I mean brand new) fill with eveclear and punch use a boat oar to mix.

Put this trash can out in the middle of a field with a bonfire going, get a few cars and trucks in a circe with the radio's blaring and charge $10.00 a head to get in, worked for me a few times. :cheers:

[obxeyeguy]

[QUOTE]10 btl - Everclear
20 gal - Fruit punch
2 dzn - Apples halved
2 dzn - Oranges halved
1 x 50 gallon trash bag
1 x 50 gallon trash can
[/QUOTE]I bet I know what the extra trash bag is for...;)

[DragonLensmanWV]

[QUOTE=obxeyeguy;297743]

10 btl - Everclear
20 gal - Fruit punch
2 dzn - Apples halved
2 dzn - Oranges halved
1 x 50 gallon trash bag
1 x 50 gallon trash can
[/QUOTE]I bet I know what the extra trash bag is for...;)

For hurling the fruit into?;)

[nate509]

We used to use a ton of poly for any grooved or drilled lens mounts.....We have stopped. Started noticing a spike in the cracks about 6-12 mos. ago. I have always known that cleaning agents (alchohol, all-off, etc.) crach poly if they come in contact with areas that are not hard coated, and so we have been very careful about that not happening. I even experimented with different spray cleaners to see if that made a difference, but it did not.

It's a bummer about this because we also liked the poly due to the flatter base curves that the stock lenses come in. I know that there are flatter bc CR lenses from the manufacturers but nobody brings them in due to the lack of demand :(

[Chris Ryser]

We used to use a ton of poly for any grooved or drilled lens mounts.....We have stopped. Started noticing a spike in the cracks about 6-12 mos. ago. I have always known that cleaning agents (alchohol, all-off, etc.) crach poly if they come in contact with areas that are not hard coated, and so we have been very careful about that not happening. I even experimented with different spray cleaners to see if that made a difference, but it did not.

It's a bummer about this because we also liked the poly due to the flatter base curves that the stock lenses come in. I know that there are flatter bc CR lenses from the manufacturers but nobody brings them in due to the lack of demand :(

You just said what I have been saying for a long time on Optiboard.

However the optical world is saving money and still purchases lens cleaners that contain alcohols because they can get them for 10 or for 5 cents cheaper than a good surfactant based cleaner that contains no solvents. The same goes for markings removers, there are some on the market that wont affect poly. You just have to look around to find them.

[rdcoach5]

You just said what I have been saying for a long time on Optiboard.

However the optical world is saving money and still purchases lens cleaners that contain alcohols because they can get them for 10 or for 5 cents cheaper than a good surfactant based cleaner that contains no solvents. The same goes for markings removers, there are some on the market that wont affect poly. You just have to look around to find them.

Chris, which ink removers won't affect poly that's been grooved or drilled?

[fjpod]

I dunno guys and gals...we edge a ton of poly at my place...into zyl, metal, semi-rimless and 3 piece mounts. I don't want to say never, but we almost never see a cracked lens...not around the holes, not at the edges, not in the grooves...nowhere... Not 6 minutes later, not 6 weeks later, not 6 months later, not 6 years later. Maybe I shouldn't say this so loud.

This includes virtually any stock poly lens as well as surfaced, with or without AR. We edge with an Optronics 7E and we change the blade out every 300 or so cuts. We also change the drill bit at recommended intervals, which I forget what it is. No fancy cleaners. No edge treatments. Nothin. I just don't see the problem.

I can also tell you that poly work that we get in from Davis, will occasionally show stress cracks after awhile.