Submitted to: Latex International Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 3/14/2005
Publication Date: 7/25/2005
Citation: McMahan, C.M., Pawlowski, H.A., Williams, J. 2005. Crosslinking of latex films: a dynamic mechanical approach. Latex International Conference Proceedings. p.7-22.
Interpretive Summary: The vulcanization (crosslinking) characteristics for natural rubber latex from Parthenium argentatum (guayule) are known to be different than those of Hevea brasiliensis or synthetic polyisoprene, and kinetics of the vulcanization reaction can significantly impact production. The dynamic mechanical properties before, during, and after cure of films cast from latex were measured using an Advanced Polymer Analyzer (APA 2000). Comparison of uncompounded lattices show significant differences in the rheological behavior of the purified latex films. Curing characteristics as measured by the APA allows comparison of various approaches to cure package compounding.
Technical Abstract: A methodology has been introduced to obtain rheological information from thin films of coagulated latex polymers. Vulcanization characteristics at typical latex processing times and temperatures can be measured accurately. Evidence of an advanced state of precure in Hevea formulations with 90 minutes of 60C heat treatment and 15 days of aging were observed in coagulation testing. Dynamic mechanical testing proved a more sensitive indicator of precure sooner; the minimum torque value in a cure test for coagulated latex films is one such measure. A study of the rheological fingerprint of a latex film can yield new insight as to the nature of crosslinking with and without precure treatments. Finally, in this study, up to 10 phr filler did not significantly impact vulcanization per se; dynamic moduli of the fully cured films do indicate a strengthening effect.