ASTM DI725 70 黄变指数美国版

黄变指数美国版~
ASTM  DI725  70  0759530  0023633 7
[[Tb  Designation: D 1925 -  70 (Reapproved 1988)"  An American National Standard
AMERICAN SOCIETY FOR TESTING AND MATERIALS
1916 Race SI.. Philadelphia, Pa.  19103
Reprinted from  the Annual Book of  ASTM  Standards. Copyright ASTM
If  not  listed  in  lhe current combined index. will  appear  in  the next  edition.
Standard Test Method for
Yellowness Index of Plastics'
This standard is issued under the fixed designation D 1925;  the number  immediately  following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript  epsilon (e)  indicates an editorial change since the last revision or reapproval.
'I  NOTE-Section  1.3  was added editorially October 1988.
1.  Scope
1.1  This  test  method  is  intended  primarily for deter-
mining the  degree  of  yellowness  (or  change  of  degree  of
yellowness) under  day-light  illumination  of  homogeneous,
nonfluorescent, nearly colorless  transparent or nearly white
translucent or opaque plastics. It  is  applicable to  transmit-
tance of  transparent  and  translucent plastics and  to  reflec-
tance of opaque plastics (Note 1).  It is based upon tristimulus
values calculated from data obtained on the Hardy-G.E.-type
spectrophotometer,* but  other apparatus  is  satisfactory  if
equivalent results are obtained.
1.2  The values stated in SI units are to be regarded as the
standard.
NOTE I-This  test  method  has  not  been demonstrated  for  the
determination  of  transmitted  yellowness of  plastics having a  luminous
transmittance  below  25 %,  and  it has not been demonstrated  for  the
determination  of reflected yellowness of translucent plastics.
1.3  This standard may involve hazardous materials, oper-
ations,  and eqicipment.  This  standard  does  not  purport  to
address all of the safety problems assaciated with  its iae. It is
the  responsibility of  the  user  of this  standard to establish
appropriate safety  and health practices  and determine the
applicability of regitlatory  limitations prior to use.
2.  Referenced Documents
2.!  .-lSï'hí Standards:
D 6 18 Methods  of  Conditioning  Plastics  and  Electrical
E 259  Recommended Practice  for Preparation  of  Refer-
E 308  Method for Computing the Colors of  Objects by
Insulating Materials for Testing3
ence White Reflectance Standards4
Using the CIE System'
3. Terminology
3.1  Definitions:
I  This test method is under the jurisdiction of the ASTM Committee D-20  on
Plastics  and  is  the direct  responsibility  of  Subcommittee D20.40 on  Optical
Propenies.
Current edition approved Jan.  22.  1970.  Published March  1970.  Originally
published as D 1925  -  62T.  Last previous edition 63T.
This spectrophotometer is described  in  Recommended Practice E 308.  It  is
available as the Diano/Hardy Recording Spectrophotometer manufactured by  the
Diano Corp.. P.O. Box 346.75  Forbes Blvd.. Mansfield. MA  02048.
.-!titiirn/  ßook oJ.4ST.V  Sinridnrds, Vol 08.01.
..lntiim/ Book qf  ..lST.\f  Siatidards. Vol 06.0  I.
.-!ritiira/  ßook qf.4S'ï.ìf Siatidards. Vol  14.02.
3.1.1  yellowness-deviation  in chroma from whiteness or
water-whiteness in the dominant wavelength range from 570
to 580 nm.
NOTE 2-A  definition  of  a  method  of  obtaining  dominant  wave-
length may be found  in the literature:
3.1.2  yellowness index (YI)-the  magnitude of yellowness
relative to magnesium oxide for CIE  Source C. Yellowness
index is expressed as follows:
where:
XCIEi  YCIE, and  ZcIE  = tristimulus values  (Note  3)  of  the
specimen relative  to Source C.
NOTE 3-By  this  test method, positive (+)  yellowness index describes
the presence and magnitude of yellowness; a specimen with a negative
(-)  yellowness index will appear bluish.
3.1.3  change  in  yellowness  index  (AYZ)-the  difference
between  an  initial  value,  YIo,  and  YI  determined after a
prescribed treatment of the plastic.
AYI = YI - YIo
YI = [loo(  1.28&-,,  - 1.06&~~)]/Yc~~
NOTE  4-By  this calculation,  positive  (+) AYZ  indicates  increased
yellowness  and  negative  (-)  AYZ  indicates  decreased yellowness  or
increased blueness.
4.  Significance and Use
4.1  Yellowness index obtained by this test method corre-
lates reasonably  well  with  the magnitude  of  yellowness
perceived under day-light illumination.
4.2  Yellowness  index of transparent and translucent plas-
tics is a function of  thickness. Comparison should be made
only between specimens of comparable  thickness.
4.3  For control work,  tristimulus colorimeters are useful
so  long as  their  inaccuracies  and  differences  from this
primary test method are known.
4.4  This test method  achieves its greatest accuracy in the
determination of  differences in yellowness index of  sample
versus a control of similar material  and colorant composi-
tion.  Change  of  yellowness  index  determined  by  this  test
method  has proved useful  in evaluation of  degradation  of
plastics under exposure to heat, light, or other environment.
5.  Apparatus
5.1  Spectrophotometer, Recording,= conforming  to  the
requirements of Practice E  308. Other apparatus is satisfac-
Hardy. A.  C.. Handbook of Colorinierry. Technology Press, Cambridge, MA.
COPYRIGHT ASTM International
Licensed by Information Handling Services
COPYRIGHT ASTM International
Licensed by Information Handling ServicesASTM  DI725 70  I  0757530  0023b32  9 M
(#  D  1925
tory  if equivalent results are ~btained.~
6. Reference Standards
6.1  Primary Standard-The primary  standard for reflec-
tance measurement  is a layer of freshly prepared magnesium
oxide prepared  in  accordance with Recommended  Practice
E 259. The primary standard  for transmittance measurement
is air.
6.2  Instrument  Standard-Because  of  the  difficulty of
preparing a  primary  reflectance  standard, magnesium  car-
bonate, barium  sulfate, or calibrated pieces  of white  struc-
tural  glass  known  as Vitrolite may be  used  as  instrument
standards.2869