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1. CR – 39 LENSES
MADE BY: SWATI PANARA
FROM : BHARTIMAIYA COLLEGE OF
OPTOMETRY
2nd YEAR 4th 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 39th 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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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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