Terpolymers, vulcanization systems

Basic Components of the Fast, Safe Vulcanization System for Terpolymers... 

The terpolymer has excellent low temperature and very good fuel, ozone, and weathering resistance, and in addition, has better reversion resistance. The terpolymer contains a small amount of AGE in the form of an aUyl side group, which allows for the utilization of a broader range of vulcanization systems. In addition, polyepichlorohydrin... 

We will now report the results of autohesion for homogeneous, symmetric joints of polyisoprene rubber (IR) and styrene-butadiene copolymer (SBR) both vulcanized by a sulfur-based system (Section 24.2.1), and of ethylene-propylene diene terpolymer (EPDM) crossHnked by an electron beam (Section 24.2.2). 

The EP thermoplastic elastomers are distinguished from the crossUnked analogues, which are not thermoplastics since reforming is impossible. A very important thermoplastic elastomer is comprised of a blend of an EP copolymer with an ethylene-propylene-diene (EPDM) terpolymer. This latter material is, of course, a crosslinkable thermoset however, these materials can be processed as thermoplastics if the crosslinkable component is present at low enough concentration to be present as an isolated phase. Melt-processing causes the formation of chemical bonds within the isolated rubber phase, a process called dynamic vulcanization. A commercial example of this type of material is Santoprene [4] manufactured by Advanced Elastomer Systems. Other blends of noncrosslinkable TPEs with crosslinkable materials are used commercially. These materials are classified as elastomer blends and are the subject of Chapter 12. 

CO and ECO are vulcanized without sulfur. Rather, they are generally cured by the action of thioureas or triazines in the presence of acid acceptors such as MgO or dibasic lead phosphite. The terpolymers can be cured by accelerated sulfur or peroxide curing systems as well as by the action of thioureas, and so on. 

Uncured ethylene-propylene copolymers are soluble in hydrocarbons and have rather poor physical properties useful technological properties are developed only on vulcanization. As mentioned above, the saturated copolymers are vulcanized by heating with peroxides whilst the terpolymers are vulcanized by conventional sulphur systems. The peroxide-cured rubbers have somewhat better heat aging characteristics and resistance to compression set but sulphur-cured rubbers are more convenient to process and allow greater compounding freedom. 

Epichlorhydrin-Propylene oxide-allyl glycidyl ether terpolymers These materials were prepared (Hsieh and Wright, 1972) in attempts to combine the very good low temperature properties of PO rubber with the oil resistance of the polyepichlorhydrins. A terpolymer of these monomers in proportion 70 24 6 was claimed to exhibit a good combination of properties and could be vulcanized with conventional sulphur systems. 

Introduction of the unsaturated double bond into the polymer chains makes these copolymers easier,to be grafted with polar vinyl monomers, such as methyl methacrylate(MMA) and maleic anhydride. The results of grafting on the EB and PB copolymers with low butadiene content are shown in Table 6. The EPB terpolymers with adequate butadiene units can be efficiently vulcanized with the conventional sulfur-based systems to improve the mechanical properties, it is probably useful for preparing some kind of gaseous separate membranes. 

The curves in Figure 5 are a bit of a digression and are included only to show that the vulcanization time dependency of peel strength values is not necessarily diagnostic of adhesion mechanism. Both EPDM s were bonded with the fast adhesive system referred to previously. But the dicyclopentadiene terpolymer recipe was so very slow to vulcanize itself that it imposed a profile of sluggishness in the curve for peel value development. 

VULCANIZATION TERPOLYMERS—FAST DIAMINE/PEROXIDE CURE SYSTEMS... 

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