NATIONAL BUREAU OF STANDARDS REPORT

3^76

Color Characteristics of a Green Plastic

Developed by the Rohm and Haas Company for

Beacon Covers

by

F. C. Breckenridge

<nb|>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
U. S. DEPARTMENT OF COMMERCE

Sinclair Weeks, Secretary NATIONAL BUREAU OF STANDARDS

A. V. Astin, Director

THE NATIONAL BUREAU OF STANDARDS

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^Office of Basic Instrumentation ^Office of Weights and Measures.
NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

0201-20-22 28 August 12, 1954 3476

Color Characteristics of a green Plastic

Developed by the Rohm and Haas Company for

Beacon Covers

by

F. C. Breckenridge

Photometry and Colorimetry Section

Optics and Metrology Division

Test No. 21A-7/53

Sponsored by

Office of Federal Airways

Civil Aeronautics Administration

Department of Commerce

Washington 25, D. C.

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

Tn-: publication, reprint Approved for public release by the

uniees permisoion in obte Director of the National Institute of

Standards and Technology (NIST)

25, D, C. Such permissl

cal ly prepared If that a on October 9, 2015

irt, is prohibited

irds, Washington

has been specifi- er its own use,
'

I
Color Characteristics of a Green Plastic

Developed by the Rohm and Haas Company for

Beacon Covers

1. SCOPE

Early in 1952 the Office of Federal Airways informed this Bureau that it was experiencing difficulty

in obtaining green cover glasses for beacons and requested that we cooperate with the Rohm and Haas

Company in the development of a green plastic suitable for this use. This report summarizes the work

done in response to that request, especially the testing of the initial order of green plastic cover plates.

2. PLASTICS TESTED

The initial request for this work was dated

March 28, 1952 but by that date three samples had

already been tested and informal reports made indicating that they were unsatisfactory. Subsequently, two

written reports were submitted, covering these and

other samples. Table I li ts the designations of the

filters which have been tested and the report numbers.

TABLE I

Samples Tested

Makers

Sample No.

Sample

Received

N.B.S.

Report No. Findings

LPC-624A1-1

No. C-lblO-A

Prior to

3-24-52

21A-6/52 Too low transmittance

Blue 6o6 3-26-52 21A-6/52 Too blue

Green 582 3-26-52 21A-6-52 Too yellow

LPC6^AL-1

No. C-I679

4-30-52 21A-6/52 Promising but higher

transmittance desired

LPC-633B1-1

No. C-1914

2-13-53 21A-3/53 Satisfactory for color,

transmittance acceptable

Sample cover

plate

5-22-53 21A-7/53 Acceptable, s^e conclusions
It
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3. SOLAR HEAT TEST

Since many plastics soften at relatively moderate

temperatures, it was thought possible that the sun's

radiation, concentrated by a beacon reflector, might

soften the plastic which could result in some distortion

of the plate. To determine if there was any evident

danger of this occurring in service, the green plastic

plate which had been sent to this bureau was mounted in

the bezel ring of a 24u drum-type rotating beacon and

placed on a beacon on the roof of the East Building -St

the National Bureau of Standards. The beacon was faced

in a direction to cause the image of the sun to fall on

the plastic cover at the location which would apparently

produce the greatest heating. To do this it was necessary

to elevate the beacon at angles considerably above those

to which it would be directed in service. W^n tests v^re

being made in the afternoon angles of 35 to 45’ were

necessary. For a sunrise test an angle of 6- was used.

The tests were continued throughout one afternoon and

from sunrise until after 9:30 the following morning. The

weather was clear and there was no wind blowing directly

on the cover plate on either occasion. As the test was

made early in June, the ambient temperature did not rise

very high, but was about 75° Fahrenheit at the time the

test was started.

At no time was any softening of the plastic detected.

The temperature of the plastic, when touched, was not hot

enough to cause any serious discomfort, and when the test

had been completed, visual examination of the plate revealed no deterioration in any respect.

4. INITIAL CHROMATIC ITY

As it was impracticable to make spectrophotometric

measurements on the entire disc, a 2-inch circle was cut

from the center of it for such measurements. The hole

left by this circle was filled with a piece of clear

plastic cemented into the cover plate and the cover plate

was then returned to the Office of Federal Airways so that

it could be included in the field tests.

Measurements of spectral transmittance were made on

a General Electric recording spectrophotometer equipped

with slits equivalent to approximately 10 millimicrons of

spectrum for the visible region, 400 to 750 millimicrons.

A second measurement of spectral transmittance was made in

each case with the sample oriented 90° from the first position. The spectrophotometric curves were read at each

10 millimicron interval making corrections for 100$, zero,

and wavelength errors.
I

I

\

i
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-

The chromaticity of the light transmitted by the

cover plate has been computed for sources of color

temperature 1500C K, 1900°K, 2350°K, 2850°K, and 3000°K.

These computations were made for the C.I.E. coordinates

and the results have been transformed into R-U-C-S co»

^^dinates. The values in both systems of coordinates are

given in Table II along with the transmittance as computed from the spectrophotometric measurements. These

values have also been plotted in Figures 1 and 2 which

show the relationship of the chromaticities to the

boundaries of both Specification ANC-56 and Federal

Standard No. 3 in the C.I.E. and R-U-C-S coordinate

systems. The chromaticities of the earlier samples are

shown in Figure 2, Test 21A-6/52 and Figure 2, Test

21A-3/53 j which have been incorporated into this report.

5. ACCELERATED WEATHERING TEST

Accelerated weathering tests were made on the green

plastic disk described above. The tests were conducted

in accordance with Federal Specification L-P-4o6a for

4 periods of 120 hours each, totaling 430 hours. After

each interval of weathering, the sample was spectrophotometered and its chromaticity and transmittance were

computed. These values are given in Table II. They are

not shown in the diagrams as the differences are not significant.

TABLE II

Specimen Weath- Color Transmit c. I. Eh R-U-C -S

ering Temp. tance X y x

n yn Samples

LPC6’2TfAl-l

(Hrs.

)

None 3100 0.056 0.084 0.625 +0.035 +0.209

Blue 6o6 it it 0.109 0.116 0.328 -0.044 +0.179

Green 5^2 tt it 0.128 0.183 O .671 +0.056 +0.160

LPC633A1‘ 1

tt tt 0.196 0.177 0.562 +0.03^ +0.157

LPC633B1-1 t* 1900 0.145 0.207 0.557 +0.039 +0.140

it It 2350 0.180 0.185 0.512 +0 . 026 +0.148

Et It 2850 0.208 0.172 0.428 +0.014 +0.152

It It 3100 0.219 0.167 0.456 +0.009 +0.154

2

tt Disk* It 1500 0.103 0.235 0.604 +0.052 +0.130

it tt 1900 0.142 0.204 0.564 +0.040 +0.142

tt It 2350 0.176 0.184 0.520 +0.027 +0.150

ti It 2350 0.203 0.170 0.482 +0.016 +0.154

it tt 3000 0.210 0.168 0.472 +0.013 +0.155

u 120 tt 0.209 O .167 0.470

u 240

tt 0.208 0.167 0.480

It 360 tt 0.204 0.164 0.467

It 480 tt 0.207 O.I67 0.472

* Cut from beacon cover
IVi
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)

6. CONCLUSIONS

All the tests made on the specimen representing the

cover plate have given satisfactory results indicating,

so far as it is possible to learn from these tests, that

the plastic cover plates should be satisfactory in service

with respect to initial color, variation of color with

light source temperature, resistance to changes of color

with weathering, and softening due to the reflection of

sunlight from the beacon reflector.

Table II shows a small change in chromaticity after

the 360 hours of accelerated weathering. While this color

change might be detectable on visual comparison of two

samples of plastic, it is not sufficient to be detected

in the color of the beacon flash. While no explanation

is known for this variation in the numerical results, it

is not considered significant.

Although not tested in the present case, the abrasion

resistance of plastics is a characteristic which needs to

be considered in determining whether or not this type of

material can be used for a specific application. The

service tests now going on should yield some information

with reference to the limitations of this type of plastic

from the standpoint of abrasion deterioration. If no

difficulty is experienced from abrasion, an analysis should

be made to learn if it would be economically practicable

to use plastics for some other types of aviation lighting

equipment. Plastics can be molded more accurately than

glass which may make it possible to design plastic units

which are physically smaller than the corresponding glass

units and still maintain the candlepower of the units.

This may be important in keeping the overall cost of an

installation of plastic units comparable to that of other

types now in use.

Other considerations favoring the use of plastic

units for runway and taxiway lighting are the lightness

of the material and the fracturing characteristics both

of which could make plastic units less hazardous than glass

units to aircraft when a unit is struck by the wheel of a

fast moving airplane.
i

t: " .
Green Plastic Beacon Cover Plate

Famished by Rohm & Baas Co.

Chroaaticlty of Signal for Lamps of

Indicated Color Temperatures

6 0 .7 0 0.80

* Figure 1

AH-C-456

Fed.Std.No. 3

4

Green Plastic - Rohm & Haas

Chromaticity vs Color Temperature of Source

-3 -.2 -I 0 +.1

AN-C-56

Fed* Std. No.3

21A-7/53 Figure 2
i
-4 -.3 -.2 -.1 0 +.1

NBS. TEST NO. 2IA-G/S2 FI GUf*e Z
Iii
-.4 -3 -.2 0 +.1

N 55 TEST NO HA ~ J/SJ FIGURE 2
#ii
THE NATIONAL BUREAU OF STANDARDS

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The functions of the National Bureau of Standards are set forth in the Act of Congress, March

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NBS