Evaluating Peroxide Blends in HNBR How This Impacts Cure Speed and Compound Aging Properties

摘要

There are several different classes of organic peroxides used in crosslinking HNBR.However,this selection compared to the number of options available for sulfur cure is relatively small.Understanding these peroxides and how co-agents interact with them is important for developing optimized compounds for the manufacturing and curing methods that are utilized in the industry.The most used are Dialkyl type organic peroxides.These peroxides offer high crosslink efficiency and good scorch safety.Cure temperature can be somewhat of a limitation because these peroxides require cure temperatures in excess of 160°C,or long cure times if below the optimum decomposition temperatures.This paper shows how selection of available types in combination with co-agent can provide HNBR compounds with optimized processing and physical properties.While the Dialkyl peroxides are the most common they are not the only option.Peroxyketal peroxides have been around for a long time but are not widely used.The Peroxyketal peroxides offer advantages in applications where the cure temperature is below 160°C.The negative to these peroxides is that Peroxyketals are lower in activity and can be somewhat scorchy compared to the Dialkyl peroxides.Studies have been done looking at blends of Dialkyl and Peroxyketal peroxides to optimize HNBR formulations for low temperature cures.However,these blends can also be advantageous for high temperature cures where fast cycle times are needed.In addition to the curing characteristics,how these blends impact long term aging performance will also be discussed.To obtain the best long-term property retention in hydrogenated nitrile rubber(HNBR)the use of peroxides has Song been the cure system of choice.The peroxides form radicals that can result in crosslinks by interacting with residual double bonds and through hydrogen extraction.This mechanism can be augmented with the use of co-agents to increase the efficiency and speed of the reaction.Dialkyl peroxides are the most commonly used peroxides in HNBR,these peroxides include Dicumyl(DCP)peroxide and 1,3 l,4-Bis(tert-butylperoxyisopropyl)benzene(BPIB).These peroxides are known for their high efficiency and scorch safety.However,they do have one draw back in that they have a relatively slow cure rate,resulting in higher temperatures and longer cure times compared to sulfur cures.