Cr – 39 lenses

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1. CR –39 LENSES
MADE BY: SWATI PANARA
FROM : BHARTIMAIYA COLLEGE OF
OPTOMETRY
2
nd
YEAR 4
th
SEMESTER
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2. CR -39
•It is also called as Columbia resin or
allyl diglycol carbonate.
•CR –39 or allyl diglycol carbonate is
a plastic polymer commonly used in
manufacture of eyeglass lenses.
•It was developed by Pittsburgh
Plate Glass industries.
•It is the thermosetting material.
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3. •CR stands for Columbia Resin & it
is 39
th
formula of a thermosetting
plastic developed by the Columbia
resin project of PPG industries back
in 1940.
•“CR” stands for Columbia Resin, and
the number 39 denotes the type of
Columbia Resin used.
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4. •COLUMBIA RESIN batch no. 39
•Petroleum derivative from polyester
group
•Chemically diallyglycol carbonate
•Refractive index = 1.498
•Specific Gravity = 1.32
•Abbe value = 58
•Transparency = 92.2 %
•UV cutoff = 355 nm
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5. •For years CR-39 was used without
anti scratch coating.
•Now, however, most CR-39 lenses
come with an anti scratch coating,
making the material much more
scratch resistant.
•For smaller, high velocity, sharply
pointed objects, CR-39 lenses
perform better than chemically
tempered glass.
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6. •CR-39 plastic lenses do not fog up
as easily as glass lenses.
•Whereas welding or grinding spatter
will pit or permanently stick to glass
lenses, it does not adhere to plastic
lens material.
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7. 7

8. •The material is highly impact
resistant and carries high
transparency.
•Multiple tinting and coating is
possible.
•only drawback is weak resistant to
abrasion.
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9. ADVANTAGES
•High impact resistance
•Light in weight
•Resistance to chemicals and solvents
•Resistance to heat & temperature
fluctuations
•Available in photo chromic glasses
•U.V. protection
•Can be tinted & coated
•Inexpensive
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10. characteristics
•Lightness
•Impact resistance
•Chemical inertness
•Resistance to pitting
•Resistance to fogging
•Tint ability
•Versatility in optical design
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11. DISADVANTAGES
•Low scratch resistance i.e.
scratches are easily formed
•Increase thickness
•Index variability with temperature
•Inferior photo chromic properties
•Surface abrasion
•Warp age upon glazing
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12. •Can yellow with age
•Softer material surface –scratches
more easily
•Lower refractive index and
variability with temp.
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13. •THANK
YOU
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