Standard Test Method for Tear Strength of Conventional Vulcanized Rubber and Thermoplastic Elastomers

Theory:

ASTM D624 is used to evaluate the tearing strength of elastomers, rubbers, and silicones. These materials are generally included under the umbrella term of Thermoplastic Elastomers (TPEs). The bulk of elastomer output (over 50%) is used for automotive tires with the second biggest end-user market being footwear. TPEs are used to get around, they have innate spring-like qualities due to the weak intermolecular forces within the polymer. 

 

TPE consumption is driven by China, however as this market matures, the outlook will shift twoards Africa and the Middle East. Monitoring the global TPE industry is a great leading indicator for the overall economy because elastomers are necessary for the movement of both people and products. Similar to Dow Theory, Increased activity in the TPE market bodes well for everything else. 

 

Geometry:

There are several sample geometries that can be used for this test. The sample types are easily found on the google machine or in the associated ASTM specification. Type C is the most common, however Type B is also used to some degree.

 

Solution:

Scissor Grips are a great solution for this elastomer tear strength test. The samples have a tendency to thin out during the test which causes vise grips to slip and fail. Scissor Grips as well as roller grips are self-tightening and thus are able to avoid maintain a constant lateral gripping force throughout the test. 

 

The Universal Grip Company also offers sample cutting dies for those who need to prepare their own samples for testing. Different dies and presses are available based on desired sample Type.

 

Results:

The results and calculations for this test are extremely straight forward. The tearing strength is the maximum force or load experienced by the TPE. The units are represented in load divided by the width of the sample. Other deriviative calculations that characterize variabillity between similar testing samples can also be made.