Peroxide Cure Applications

SR-633 iB a aatallic dlacrylate aonomer, developed to aaalBt rubber-to-aetal adhesion in peroxide cure applications. Reconmended use levels are 4-10%. 

SR-634 is a methacrylate version of SR-633. SR-634 features excellent hardness and tear strength. Usage levels of 4-10% are recommended. 

---

SR-709 is a metallic monoaiethacrylate monomer that assists adhesion to metals and plastics in peroxide cure applications. SR-709 features good tear strength. Recomsiended usage levels are 4-10%. 

Elastomeric composition for dynamic application of cross-linked E-plastomers has been made with filer-reinforced systems which contain a metal salt (typically zinc) of an alpha, beta unsaturated acid. These additives improve the tensile and tear strength of the elastomer and are cured with a peroxide cure system. These cross-linked articles are suitable for dynamic loading applications such as belting, including power transmission and flat belting. 

Peroxidic cure systems are applicable only to fluorocarbon elastomers with cure sites that can generate new stable bonds. Although peroxide-cured fluorocarbon elastomers have superior heat resistance, their difficult processing has been an obstacle to their wider use for years. Only recent improvements in chemistry and polymerization are offering more opportunities for this class of elastomers.32... 

The comonomer diene confers sulfur vul-canizability on the elastomer. Otherwise, a peroxide cure is required for cross-linking. The polymers are readily oil-extended with 20-50 percent oil for many applications. Some uses result from the ability of these products to resist oxidation by ozone. 

Ethylene-propylene elastomers are one of the main choices of automotive chemists and material engineers for sealing applications, as well as isolation systems, weather stripping, electrical components, etc. Heat aging resistance up to 130°C can be expected with certain sulfur cures and up to 160°C with peroxide-cured compounds [3], They also respond well to high tiller and plasticizer loads. Typical properties are shown in Table 8.7 [4],... 

The silicone elastomers most commonly used for medical applications are the high consistency (HC) and liquid injection molding (LIM) types. The former is most often peroxide cured and the latter platinum cured although there are variations. Both materials are similar in properties. LIM offers greater advantages to the medical device molder and is gaining in popularity. This form of silicone may become the molder s material of choice within the next few years. 

Commercial vinylsilanes usually have the vinyl group directly attached to the silicon atom. Common hydrolyzable groups are methoxy, ethoxy, or 2-methox-yethoxy. The vinyl functionality is used in polymers that are cross-linked by a free-radical process (peroxide cure), but it is, however, not sufficiently reactive for all systems, and methacryloxy functionality is sometimes preferred as shown in Table 4.2 [35]. Vinylsilanes because of their overall cost/performance advantages have become the industry standard for EPR and EPDM and wire and cable applications. 

These additives are mainly used in elastomer applications, where they are suitable for both sulfur and peroxide cures. The effects of both acid content and MW have been reported in Ref. [46]. Property improvements were found to plateau at an average MW of about 10 000 and with about 20% w/w of grafted maleic anhydride. 

Nitrile polymers are vulcanized in essentially the same manner as styrene butadiene rubber (SBR) and natural rubber. The same ingredients are used, although not necessarily in the same amounts. Sulfur is less soluble in nitrile rubber than in SBR or natural rubber, and smaller amounts are used. A corresponding increase in accelerator is required. Sulfur/accelerator, sulfur donor, and peroxide cures are chosen depending on the ultimate processing methods and applications. 

The most widely used plasticizers are paraffinic oils. For applications that specify high use temperatures, or for peroxide cures, paraffinic oils of low volatility are definitely recommended. Because paraffinic oils may tend to exudation at low temperatures from EPDM vulcanizates, or from high ethylene EPDMs, they are sometimes blended with naphthenic oils. On the other hand, naphthenic oils interfere with peroxide cures. Aromatic oils reduce the mechanical properties of vulcanizates, and they also interfere with peroxide cures. Therefore, they are generally not recommended for EPM/EPDM. 

---