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what is diff in cr 39 lenses and polycarb

Discussion in 'Shooting Related Threads' started by Unknown1, Jan 14, 2010.

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  1. Unknown1

    Unknown1 Active Member

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    CR-39 is optical plastic; poly carb is shatterproof plastic being made into lenses. The optical clarity of CR-39 is far better than that of poly carb expecially when prescriptions are involved. You'll have to ask Randolph what they're selling you.

    MK
  2. mixer

    mixer Active Member

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    Everything you ever wanted to know about Polycarbonate-vs-CR39.

    CR-39 refers to the material that is used to make the majority prescription lenses. It is an optical grade plastic polymer recognised for its light weight, chemical resistance properties and 'tint-ability'. In comparable prescriptions it is approximately half the weight of glass lenses, while being slightly thicker. Its impact resistance is greater than glass but does not rise to the level of polycarbonate and it should not be considered for applications where impacts are prevalent. On this basis, it is not recommended for active sports and motorcycling. It is more scratch resistant than polycarbonate, but will scratch if not properly taken care of.

    Polycarbonate is an impact resistant material. It is becoming used more widely in recent times - especially for motorcycling and action sports. It is also used frequently for the glazing of rimless frames because of these properties. Although polycarbonate is impact resistant, it should not be considered indestructible. Polycarbonate is the strongest material available and will have the tendency to break into larger pieces, instead of the CR39's smaller pieces, and is, consequently, less hazardous. Polycarbonate is thinner than standard CR39.

    Polycarbonate lenses are ten times more impact resistant than other plastics making them highly suitable for action sports or folk that are a little (shall we say) heavy-handed! They offer UV protection and stop 99.9% of rays from the sun, fluorescent lights and computer screens. Our polycarbonate lenses are supplied with a scratch resistant coating and are thinner than standard lens and therefore more comfortable to wear.

    Comparison of Lens Materials & Material Characteristics

    Polycarbonate

    - Strongest material for impact resistance
    - Lightweight
    - Can be coated for scratch resistance
    - Most have built-in UV radiation protection

    Plastic (CR39)

    - About one-half the weight of glass
    - Resistant to solvents and pitting
    - More choices for coatings and tinting



    Eric
  3. idoc

    idoc Member

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    Good job Eric,

    Ranger put out a directive to all their vendors about three years ago that if any vendor used CR-39 in their frames they would pull their franchise. I have to really commend them for their action. It took a lot of guts because there were a number of people putting CR-39 in their frames.

    Last year they changed their military sunglasses over to trivex, which is a new material that has the safety of poly and the clarity and tintability of CR-39. I think the only reason they did not switch their shooting glasses over is cost. But I don't know that for sure.

    There are lenses available presently in Trivex based materials, you can find them in Hidefspex and also Rudy Project.

    I feel Trivex is the shooting lens of the future and recommend it above all others. It is expensive.

    If you received a lens from Ranger you can be sure it's a good safety lens and not CR-39. Hope this helps
  4. zzt

    zzt Active Member

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    Well, all that being said, I have ranger frames and I INSIST on CR-39 lenses. Looking through the best polycarbonate lenses I could find still leaves me cold. It's like looking through a pale white veil.

    I will look up this Trivex stuff. Sounds like the cat's meow.
  5. mixer

    mixer Active Member

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    Here's Trivex-vs-Polycarbonate:

    "Trivex vs Polycarbonate: A Material Comparison

    Polycarbonate
    Born from the space race in the 1960's and introduced to the ophthalmic lens market in the late 1970's, polycarbonate has been around the block a few times and enjoys a sizeable market share, particularly in children's and safety eyewear due to its superior impact resistance. With a higher index of refraction and lower specific gravity, polycarbonate lenses are thinner and lighter than their plastic and glass counterparts. Inherent UV protection and wide product availability also contribute to its popularity.

    Polycarbonate, however, is not without its drawbacks. One of the chief complaints about polycarbonate is its optical quality, or lack thereof. With an Abbe value of 29, polycarbonate's chromatic aberration is the highest of any lens material in use today. Furthermore, with the increase in popularity of drill mount frames, some dispensers are hesitant to use polycarbonate because of its lack of tensile strength and likelihood of cracking around drill holes.

    Enter Trivex
    Introduced in 2001 by PPG, as the only lens material other than polycarbonate to pass FDA Impact Resistance Test (@ 1mm CT), the High Velocity Impact Test, and meet ANSI Z87.1 '89 standards, Trivex has been slowly increasing in both popularity and availability. While Trivex has a slightly lower refractive index (1.53 compared to 1.58), it�s specific gravity, 1.11g/cm3, makes it the lightest of any lens material available today. Like polycarbonate, Trivex also has inherent UV protection. However, unlike polycarbonate, Trivex has an Abbe value of 45, making it optically superior. Further distinguishig itself, Trivex is ideal for drill mounting. The tensile strength of Trivex makes it highly resistant to cracking around drill holes, so much in fact, Younger Optics guarantees its Trivex products (Trilogy) for life, against stress fractures and drill mount cracking.

    Summary
    In summary, Trivex has the impact resistance and inherent UV protection of polycarbonate. With a lower index of refraction, Trivex may be slightly thicker than polycarbonate, but is lighter, and can be surfaced to the same 1mm center thickness. Trivex rises above polycarbonate with both its optical quality and suitability for drill mounting, however since Trivex is still a relatively new product, availability may be limited.

    Finally, when comparing the price of Trivex to polycarbonate, make sure you are comparing apples to apples. If you are looking at an aspheric Trivex product, compare it to an aspheric polycarbonate product; likewise if you are looking at a spherical polycarbonate product, compare it to a spherical Trivex product. You'll likely find the difference to be less than you might think."


    Eric
  6. Barry C. Roach

    Barry C. Roach Well-Known Member

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    What does Decot use?
  7. mixer

    mixer Active Member

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    According to the Decot website they offer both CR39 & Polycarbonate.

    Eric
  8. idoc

    idoc Member

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    Almost all of Decot's stuff is CR-39. Ranger's is poly. Hidef is a an advanced type of Trivex called NXT.
  9. hmb

    hmb Active Member

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    What would be the approximate cost of a set of trivex, single perscription, tinted lenses be for a pair of decot frames. HMB
  10. Unknown1

    Unknown1 Active Member

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    "Almost all of Decot's stuff is CR-39. Ranger's is poly. Hidef is a an advanced type of Trivex called NXT."

    When I bought a pair of full frame prescription Ranger Sporters from Morgan Optical in NY, they specifically steered me to Tryvex over poly because of the optical superiority and weight saving of the thinner lenses. The full frames and the single prescription 62mm lenses cost me under $300 last year.

    MK
  11. idoc

    idoc Member

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    MK,

    That price seems right on. I'm glad to see that the optical guy's are going that way. It's the only way to go in my opinion unless cost is a significant factor.......Rich
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