Background

Since the first plastics tests were offered by CTS in 1992, there has been continuous growth in participation as laboratories around the world have learned how proficiency testing can improve the quality of their measurements. Participants in the CTS plastics program include resin producers, automotive suppliers, molders, and independent testing laboratories. In destructive testing there are few reference materials available to verify instrument performance. The use of in-house control materials is a valuable quality assurance tool to maintain day-to-day consistency of measurements, but this practice does not evaluate a lab's ability to make measurements that agree with other laboratories. Some companies attempt to determine the accuracy of their measurements through a round-robin program among three or four other facilities. This is often unsuccessful because the small number of participants makes it difficult to determine a consensus value with a high degree of confidence. Participation in the CTS Plastics Program assesses laboratory performance by comparing each participant's results to a consensus value based on the results from as many as 100 laboratories testing the same material. An additional benefit of the CTS program is the use of "blind" samples. As the participant does not know what the result should be, the CTS program is a true assessment of the testing process including sample labeling and preparation, instrument operation, and calculation of the test result.

Analysis Techniques

The CTS Plastics Program is conducted quarterly. Two samples with slightly different properties are distributed for each test. No molding is required for rigid plastic samples. The participants are asked to test the samples with a single instrument on the same day and return the data to CTS. CTS utilizes a two-sample statistical analysis to assess accuracy in comparison to the consensus as well as consistency in testing for each lab. CTS issues individual Performance Analysis Reports to all enrolled labs. For a copy of the Guide to Interpreting Individual Plastics Reports, click on "Report Guide", found in the left margin of this page. A Summary Report that includes data for all participants is available on this Web site.

Test Areas

For most properties, CTS offers tests using either ASTM or ISO test methods. Each test is offered separately so that participants can individualize their testing programs by subscribing to the tests that best meet their needs. Tests include, but are not limited to:

Tensile Properties
Deflection Temperature
Vicat Softening Temperature
Specific Gravity
Flexural Properties
Melt Flow Rate
Notched Izod Impact
Notched Charpy Impact
Ash Content
Moisture Content

CTS also offers tests for Films and Laminates including Tensile Properties, Coefficient of Friction,Tear Resistance, Optical Properties, and Secant Modulus.