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The National Bureau of Standards (NBS), now the National Institute of Standards & Technology,
established the first formalized, large-scale interlaboratory testing program for rubber in 1969 and
issued its first report in 1970. The program initially focused on tensile properties of vulcanized
rubber. CTS expanded the program in 1971 to include tests for other characteristics of raw and
vulcanized rubber. Responsibility for the program's operation was transferred to the private
sector in the mid 1970s.
CTS consults with the ACS Rubber Division's Advisory Committee on Testing Procedures and
with instrument manufacturers to ensure that the program remains relevant to the industry. After
more than 30 years several of the original NBS round-robin participants still subscribe to the CTS
Rubber Interlaboratory Testing Program -- quite a testimony to the program's usefulness as a
quality assurance tool.
Each rubber test consists of two sample sets, data reporting sheets,
and instructions. Labs measure appropriate properties in accordance with
the test instructions and return results to CTS by a specified Data Due Date. CTS analyzes the data and issue individual Performance Analysis
Reports to all enrolled labs. For a copy of the Guide to Interpreting
Individual Rubber Reports click on "Report Guide" which is located in the left margin of this Web page. A Summary
Report that includes data from all participants appears on this Web site.
If a lab wishes to locate its data in the Summary Report, the lab will
need its WebCodes, which can be found in the individual report and on
each data sheet.
The analysis of laboratory data is based on consensus statistics,
comparing each laboratory's measurements to the Grand Mean for that property. In addition, the
property measurements for both sample sets are analyzed together (bi-variate analysis) to evaluate
the lab's ability to make consistent measurements. Finally, the results are shown on a two-sample
plot with a control ellipse; this graphical representation is a powerful analysis tool describing the nature and
magnitude of the difference between a lab's results and the consensus results.
Rubber testing is conducted quarterly. Reports are issued within three weeks of a Data Due Date,
giving each participant sufficient time to review its performance and take corrective action,
if necessary, before the next testing round.
Types of rubber tests offered include tensile properties and hardness
of pre-cured rubber, tensile properties of rubber cured by the participating
labs, mooney viscosity of raw polymers, and vulcanization characteristics
(ODR and MDR) of compounds. Please refer to the CTS Catalogue for test
methods and test specifications.
If you would like more information about the
CTS Rubber Interlaboratory Testing Program,
please contact program staff directly through this link.
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