SRM 1476, a branched PE certified for melt flow rate, was
discontinued because insufficient material remained for recertification
as a melt flow rate standard. During its availability SRM 1476
was also used in studies aimed at characterizing branching in
PE, a desirable molecular characteristic for certain types of
products. Although chemists now have methods to produce a variety
of branch structures, measurement methods to quantify critical
aspects of branching are lacking. Owing to available molecular
data on SRM 1476 manufacturers of chromatographs include small
quantities of the original SRM 1476 with purchases of their
instruments for comparative measurements. NIST has received
inquires from manufacturers, researchers and resin producers
about making this SRM available, not as a melt flow rate standard,
but as an aid in branching characterization.
Experimental Approach
The remaining 500g of resin from which the original SRM 1476
was certified was deemed sufficient for production of SRM 1476a,
designed for use in chromatographic and other molecular characterization
methods. The melt flow rate was the certified quantity, however,
to assure continuity with the original material. A new extrusion
plastometer was used to certify melt flow rate by both procedures
A and B of ASTM D1238-01.
Results
The melt flow rate of SRM 1476a was determined to be 1.23
g/cm3 g/cm3 using procedure A of ASTM D1238-01. This results
compares favorably to the certified value of 1.19 g/cm3 for
SRM 1476.
Contributors
Polymers Division:
Charles Guttman, Kathleen Flynn, William Blair and John Maurey
Characterization and Measurement Group
Polymers Division
Materials Science and Engineering Laboratory
