EPDM™. rubber-like

Blends of carboxylated nitrile rubber (XNBR) with EPDM are likely to provide an attractive combination of properties including oil resistance, heat and ozone resistance, high tensile strength, modulus, and hardness. However, the polar curing ingredients often diffuse from the nonpolar to polar component, thereby producing cure rate mismatch and inferior properties. Three different measures have been used to overcome the cure rate mismatch [29] ... 

Another product EPDM is a rubber-like material. It comes in 60-mil thickness in 100 ft by 61-1/2 in. rolls. EPDM also comes in 45-mil thickness in 25 ft by 60 ft rolls. This product has gained popularity as a ground cover in crawlspaces because of its durability qualities. 

Rubbers like butyl, EPDM and neoprenes are unreactive to air and corrosive gases and are impermeable to them. 

Cyanoacrylates can be used to bond many materials, including most thermoplastics and even the more difficult ones like polyethylene, polypropylene, and ethylene-propylene-diene ( EPDM ) rubber. The best results are obtained with close contact and narrow bonds (some formulations have limited ability to bridge large or irregular gaps between the surfaces). 

Unconjugated dienes can produce an even more complicated range of macro-molecular structures. Homopolymers of such monomers are not of current commercial importance but small proportions of monomers like 1,5-cyclooctadicne are copolymerized with ethylene and propylene to produce so-called EPDM rubbers. Only one of the diene double bonds is enchained when this terpolymeriza-tion is carried out with Ziegler-Natta catalysts (Section 9.5). The resulting small amount of unsaturation permits the use of sulfur vulcanization, as described in Section 1.3.3. 

General curing system for EPDM rubbers will be a thiazole (mercaptobenzothiazole or dibenzothiazole disulfide) accelerator with a thiuram and/or a dithiocarbamate. For high heat exposure condition in a process industry, sulfur donor types like tetra methyl thiuram disulfide may replace a larger part or all of the sulfur. 

Figure 8.15 TEM images of TPV samples after drawn to a strain of 5.5. The drawing was performed at 23°C and the elongation speed was 200 mm min The EPDM rubber phases were stained with RUO4. The arrow denotes the stretching direction, (a) Before extension, (b) the equatorial PP region between neighboring elongated rubber domains, the microcraze-like fracture is perpendicular to the extension direction, (c) the polar PP region between adjacent rubber domains in the extension direction. (Reproduced from Reference (28) with permission from Elsevier Science.)...

Cure-rate mismatch is extreme when the blends constitute high unsaturated diene mbbers like NR, and low unsaturation rubbers like EPDM. It involves the migration of polar curatives from the low unsaturation phase to a more polar high unsaturation phase, further undercuring the low unsaturation phase (11-13,34) and it has been shown that unvulcanized EPDM exists in the vulcanized blend with NR (35). Several approaches have been made to obtain a cocured blend vulcanizate of NR-EPDM without sacrificing the physical properties by (1) increasing the unsaturation of EPDM elastomer so that the cure rate becomes at par with NR or other diene rubbers... 

Ground rubber tire was used as a partial substitute for EPDM rubber in modified EPDM—high-density polyethylene (HDPE) blends. The blends with higher rubber content showed poor processability, whereas the compositions with higher plastic content behaved like toughened plastics. It was observed that for the 60/40 rubber/ plastic blend, 50% of EPDM could be replaced by the ground rubber without deterioration in properties [58],... 

R.A. Zoppi, at the Chemistry Institute of Campinas State University, performed a series of experiments on the S5mthesis of polypjrrrole in an EPDM rubber matrix, under the supervision of Professors M.A. de PaoH and M.I. Felisberti. The objective of the study was to obtain a product with electrical properties similar to those of polypyrrole and mechanical properties like those of EPDM rubber. Pol rpyrrole, a conducting polymer, is very brittle, which prevents its use in apphcations of practical interest. 

Most of the earlier efforts have been paid in changing the surface character of clay minerals. Albeit the modified clay minerals are fairly compatible with the polar rubber like acrylonitrile butadiene rubber (NBR), carboxylated nitrile rubber (XNBR), chloroprene rubber (CR), etc., its dispersion in nonpolar rubbers like NR, styrene butadiene rubber (SBR), ethylene propylene diene rubber (EPDM), butadiene rubber (BR), etc. is rather unsatisfactory. Figure 8.3(a) and (b) display the state of dispersion of organomodified... 

EPM/EPPM (Ethylene Propylene Rubbers) A group of elastomers (rubber-like material) obtained by copiolymerization of ethylene and propylene for EPM and a third monomer (diene) for EPDM. Their properties are similar to those of rubber. 

Use of nanoparticles as fillers in mbbers is highly relevant because end use applications of rubber compounds require filler reinforcement. Most of the literature on rubber nanocomposites is based on the use of nanoclay as the filler. It has been shown that incorporation of nanoclay in synthetic rubbers, like styrene butadiene rubber (SBR), chloroprene rubber (CR), nitrile rubber (NBR), ethylene propylene diene monomer (EPDM) mbber etc. enhances the mechanical, anti-ageing and barrier properties. 

Cyanoacrylate adhesives will bond most substrates to themselves and to each other. The few adherends which do not bond well with standard adhesives are polyethylene, polypropylene, EPDM rubber, plasticized PVC, teflon, and acidic surfaces. A few manufacturers sell modified adhesives which will bond some of these materials, such as EPDM and flexible PVC. Adhesion to low surface energy plastics like polyolefins and Teflon can be improved by an etching or oxidizing treatment. 

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