1. C.M. Roland Naval Research Laboratory Gary S. Buckley Cameron University

2. Outline A little terminology Work with hydrogels Can this shift to rubber materials? Materials used in rubber work Results Conclusions

3. A Little Terminology Crosslink – a covalent bond between two separate polymer molecules

4. Work with Hydrogel Materials Jing Ping Gong and Yoshinori Katsuyama, Advanced Materials, 15(14), 2003. Single Network Double Network (0.4 MPa) (17.2 MPa)

5. Key factors: 1. The two networks were homogeneous. 2. The difference in crosslink densities was maximized.

6. Can this idea translate to rubber materials? Two selected rubber materials: EPDM – contains double bonds and can be crosslinked with sulfur EPM – contains no double bonds and cannot be crosslinked with sulfur The idea: Blend EPDM and EPM followed by crosslinking with sulfur to see if mechanical properties are improved

7. Tensile Strengths Is the EPM chemically a part of the network?

8. Did EPM become a bonded part of the network? All EPM should be soluble if not a chemical part of network Soxhlet extraction to determine gel fraction

9. Gel fractions Indicates that EPM was not a chemical part of the network

10. Network Density

11. Tensile Strength and Network Density Is there a homogeneity issue?

12. Are EPDM and EPM homogeneous initially? C-C bond length: ~ 0.15 nm

13. Potential Applications – Ballistics Bad response Good response

14. Conclusions Blended EPDM and EPM crosslinked with sulfur provides better tensile strength than crosslinked EPDM Blended EPDM/EPM tensile strengths continue to increase even as the network density levels off The increase in tensile strength of the blended material is modest – not on the order of the hydrogel work The EPDM/EPM system is not particularly homogeneous - work remains to be done to see if its homogeneity increases as the cure package increases

15. Street lights Fireworks