optical property of plastics used for transparent applications

optical property of plastic

1. INTRODUCTION
The unique property of plastic are
seen such as transparency , clarity
and low cost, so these property
basically related with light comes in
the category of optical property .

2. OPTICAL PROPERTIES
•Refractive Index
•Light Transmission
•Haze & Clarity
•Gloss
•Colour Measurement
•Microscope Studies
•Photo elastic Effect

3. Refractive Index-ASTM D (542):-Refractive Index-ASTM D (542):-

Refractive index is a fundamental property of
transparent material .It is very important to
design engineer involved in designing lenses for
camera, microscope ,etc . The refractive index is
define as the ratio of the velocity of light in
vacuum to its velocity in a transparent medium.
Index of refraction= sin of angle of incidence
sin of angle of refraction

4. Classification of Plastics
•Highly Transparent
•Semi Transparent
•Opaque

5. Refractive Index
Measured by
Abbé Refractometer
& Microscope
In microscopic method measure
apparent thickness and ratio of
Apparent thickness to Original
thickness of the specimen will
give refractive index
Sample size -
6.3 mm x 12.7 mm x 1-2 mm
with contacting surface
satisfactory







Sin
Sin


7. Refractive index of any materials is basically Refractive index of any materials is basically
depend on following factor-depend on following factor-

1 . Medium used for light passes
2 . Wave length of light
3 . Temperature

8. Fig 6.3 (A) Schematic diagram of Abbe Refractometer Fig 6.3 (B) Double
prism of an Abbe Refractometer

9. Refractive index value for PlasticsRefractive index value for Plastics:-:-

PTFEPTFE 1.351.35
Cellulose acetateCellulose acetate 1.491.49
PPPP 1.491.49
LDPELDPE 1.511.51
PVCPVC 1.521.52
NylonNylon 1.531.53
HDPEHDPE 1.541.54
PCPC 1.581.58
PSPS 1.601.60
GlassGlass 1.601.60

10. Refractrometic method:-Refractrometic method:-
• The abbe refracto metric is used.
• A source of white light contacting liquid is
require.
• A test specimen conveniently fits on the face
of the fixed half of the refractometer prism .
• The surface of the specimen in contact with
prism
• Using a drop of contacting liquid .
• The polished surface of the specimen should
kept towards the light source .
• Now the refractive index is determine by
moving the index arm of the light refractometer.

11. Luminous transmittance and haze Luminous transmittance and haze
(ASTMD-1003):-(ASTMD-1003):-
Light transmittance is defined as the
ratio of transmitted light to the incident
light .
Example PMMA transmitted 92% of the
normal incident light.

12. Luminous transmittance and haze Luminous transmittance and haze
(ASTMD-1003):-(ASTMD-1003):-
Haze is defined as the cloudy appearance
comes on the surface of specimen.
The amount of transmitted light is
deviated more than 2.5°c from the
incident beam .
Haze is caused by surface
imperfections ,density change .

13. Method of testingMethod of testing:-
Test specimen-Test specimen-
*Test specimen for this test shall be large
enough to cover a 2.5 by 2.5 cm.
*A disk 3.5 cm. diameter can be used.
*The specimen should have plane parallel
surfaces , free of dust, grease ,scratches and
internal voids.
ConditioningConditioning- Condition the test specimen at
the 23 ± 2ºc
and 50 ± 5% relative humidity.

14. * * The two procedure have been The two procedure have been
developed to measure light developed to measure light
transmittance and light scattering transmittance and light scattering
properties. properties.

* * Procedure (Procedure (a)a) require the use of a require the use of a
hazemeter.hazemeter.
* * Procedure (Procedure (b)b) require the use of a require the use of a
recording spectrophometer.recording spectrophometer.
PROCEDURE:-

16. Procedure A- HazemeterProcedure A- Hazemeter:-:-
*A disc of 1.375 inch in diameter to must commonly usedA disc of 1.375 inch in diameter to must commonly used
**The test is conducted by taking four different The test is conducted by taking four different
consecutive reading and measuring the photocell output consecutive reading and measuring the photocell output
as follows-as follows-
TT
11= specimen and light trap out of position = specimen and light trap out of position
TT
22=specimen and reflectance standard in position=specimen and reflectance standard in position
TT
33=light trap in position specimen and reflectance=light trap in position specimen and reflectance
TT
44=specimen and light trap in position=specimen and light trap in position
Total transmittance TTotal transmittance T
tt=T=T
22/ T/ T
1 1
Diffuse transmitted TDiffuse transmitted T
dd=T=T
44-T-T
33(T(T
22)/T)/T
11
Haze percent=THaze percent=T
dd/T/T
tt ×100 ×100

18. Photo-elastic Properties
Photo-elastic properties of the
transparent material have been used
by design engineers for stress
analysis and by process engineers
for determine residual stress as well
as the degree of orientation in
molded part.

19. ColorColor :- :-
•There are following terminology to understand
the color theory.
1. Value:-It is color range from dark to light in
which black being darkest and white being
lightest .
2. Hue:- Color has basic difference appearance
such as red differ form blue green or yellow
these distinction as called Hue.
3. Chroma:- Chroma is defined as the attribute
of color perception that express the degree of
departure from gray of the same lightness.

21. There are two type of measurement are
used for color detection property of
plastic.
Calorimeter.
Spectrophotometric.

24. A spectorphotometer is normally
required for color
•The instrument is first calibrated using a calibration
standard.
•The specimen relatively flat and colored.
•A specimen holder and illuminating a light source are
can obtain % spectral reflectance value at 16 mm
intervals over the visible specimen.
•The color match in is carried out simply by exposing.
•The comparing the two overlapping spectred
reflectance curves.

25. Specular Gloss(ASTMD -523)
•Specular Gloss is defined as the relative luminous
reflectance factor of a specimen at the specular
direction.
•The light beam is direct towards the specimen at a
specified angle.
•The light reflected by the specimen is collected and
measured
•A highly polished black gloss with an assigned
specular gloss value of 100.
•Three basic angle of incidence 60,20,85 are used for
specular gloss measurement.
•The angle of incidence increase the value of gloss of
any surface also increase.

26. Gloss meter
•The gloss meter basically consist of a source
optical assembly which houses an
incandescent light source, a condenser lens
and a projection or source lens. An incident
beam created by this assembly is directs
towards the specimen, a sensitive photo
detector collects the reflected light and
generates an electrical signal that is amplified
to energize an analog or digital panel meter to
display the value in gloss unit.

27. GLOSS METER