The 153rd Rubber Division ACS Technical Meeting (Indianapolis, Indiana, May 5-8, 1998) featured a 12-topic symposium, which focused on numerous key issues facing the rubber industry. One of the most popular topics was the use of alternate vulcanization systems versus sulfur cure. This topic selection reflected the recent growth and interest in peroxide-cure vulcanization, whichis due to the high-temperature demands of today’s compounds. Ten other technical papers were presented throughout the day to a packed, standing-roomonly audience. Based on this success, a follow-up to this peroxide-cure-focused symposium
ACS Technical Meeting
has been tentatively slated for the 158th Rubber Division ACS Technical Meeting andMini-Expo (scheduled to be held in Cincinnati, Ohio at the Cincinnati Convention Center from October 17-20, 2000). If you would like more information about the meeting and exhibition or if you are interested in submitting a contribution, please contact: ACS Rubber Division Phone (330) 972-7814 Fax (330) 972-5269 Web Site www.rubber.org
• Peroxide-Coagent vs. Sulfur-Accelerator Cure •Methacrylate Coagents for Improved Hot Tear Strength • Fiber/Fabric to Rubber Adhesion • New Reactive Dispersions for Rubber Applications • Basic Principles of PeroxideCoagent Curing of Elastomers • New Technical Resources
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Peroxide-Coagent vs. Sulfur-Accelerator Cure
IntroductionAdding reactive coagents (such as methacrylate and acrylate monomers) to peroxide-cure systems delivers notable improvements. Enhancements in compression set and heat resistance (relative to sulfurcure products) have expanded the use of peroxide-coagent systems in stringent end-use applications, such as automotive under-the-hood applications. them due to perceptions of higher cost. However, morerecent focus on the total cost of manufacturing reveals a different picture. Peroxide-coagent systems are simple, usually requiring a single peroxide and a single coagent to achieve the desired properties. Sulfur-cure applications, in contrast, may require three, four, or even five expensive accelerators to overcome deficiencies in the cure systems. Once the costs associated with comparable orimproved performance are examined, the peroxide-coagent systems are favored. with peroxide-only curing. The coagents homopolymerize and graft onto the polymer backbones, which yields lower compression set and higher tensile strength, tear strength, elongation, and modulus. Converting from peroxideonly cure to a peroxidecoagent system also yields a reduced peroxide level.
Comparison of Cure Systems–Typical EPDM Compound
SulfurAccelerators Cure Variability Reversion Resistance Tensile Strength Ultimate Elongation Tear Strength Heat-Aging Resistance Compression Set, Ambient Compression Set, >100º C Very good Moderate Good Good Good Good Good Peroxide Only Moderate Very good ~15% less ~30% less ~30% less ~30% less Good
PeroxideCoagent Very good Very good Good Good Good Good GoodModerate
Comparing Cure-System Features
Table 1 lists specific performance benefits of peroxidecoagent crosslinking over sulfur vulcanization.
Cure Property Comparison Table 3A
55 555 555 555 55 – 555 55 5 555 0 555 5 55 55 55 5 55 555 555 555 0 55 55 555 555 555 55 555 55 5 555 0
The Role of the Coagent
Is acoagent really needed? The answer to Peroxide-Coagent Crosslinking Sulfur Vulcanization this question is, "yes." • Good tear strength • Excellent compression set Sulfur-accelerator • Superior heat stability • Often bad smell, staining, systems yield superior • Exceptional aging stability and blooming • Unsaturated rubbers only • Excellent scorch safety performance over • Simple compounding •...