Revision of C1289-25 Standard Specification for Faced Rigid Cellular Polyisocyanurate Thermal Insulation Board
Rationale
ASTM C1289 has two flexural strength requirements. One requirement is modulus of rupture/yield strength as a ratio of the load versus area. The second requirement is a minimum break load, or minimum load at yield requirement in terms of pounds force. Compliance to the standard for Types I and II are based on test results conducted on 1 inch thick boards.
As seen in Table 1, the yield strength requirement for both types is 40 psi. However, the breaking/yield load requirement is different between Types I and II. The Type I requirement is 8 lbf, the Type II requirement is 17 lbf. Doing the math, the 17 lbf requirement for Type II is equivalent to approximately 75 psi, which is nearly double the yield strength requirement. This ballot is to correct the minimum break load requirement of the Type II to match the Type I requirements that also corresponds with the yield strength requirements.
Work Item Status
Date Initiated: 09-09-2025
Technical Contact: Michael Joyce
Item: 000
Ballot:
Status: