Rubber EPDM

Ethene/propene/diene monomer rubbers (EPDM) are elastomeric terpoly-mers used in the production of sealants, tubing and gaskets and, in the USA, is used in roofing applications. As the name suggests they are prepared by the polymerization of mixtures of ethene, propene and diene monomers, to form cross-links. By far the most common diene used is 5-ethylidene-2-norbomene (ENB). 

Several different companies have greened various steps of the process. In VNB production by-products come from competing Diels-Alder reactions and polymerization, largely of cyclopentadiene. The reaction is usually carried out in a continuous tube reactor, but this results in fouling, due to polymerization, at the front end, where the dicyclopentadiene is cracked to cyclopentadiene at temperatures over 175 °C. Whilst fouling does not have a very significant effect on yield, over time it builds up. 

By-products from competing Diels-Alder reactions Reactor fouling - heat-transfer and product-loss issues Distillation required - energy intensive Poor reactor volume utilization Hazardous catalyst 

Distillation required - energy intensive Low reactor utilization Energy-intensive diluent recovery 

The photo-oxidative degradation of two types of EPDM rubbers (terpolymer) has been investigated in detail  

The site of hydrogen abstraction under UV irradiation from the poly(ethylene-co-propylene-co-5-ethyhdene-2-norbomene) is controlled by the liability of the various carbon-hydrogen bonds. The mechanism of the photo-oxidative degradation of this polymer can be presented by the following reactions [1911, 1316]  

The addition of free radicals (R ) to the ethylidene double bonds (reaction 3.452) and photo (and/or thermal) decomposition of hydroperoxide groups results in the formation of hydroxyl (OH) and ketone (CO) groups, which are accompanied by the -chain scission process [1911]  

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EPDM elastomers EPDM lonomers EPDM rubber... 

Both sides of the neoprene or EPDM rubber or metallic expansion bellows. 

The price of these rubbers has become such that for many applications they have been replaced by less expensive alternatives. These include the use of EPDM rubbers for automotive parts not requiring oil resistance and plasticised PVC for applications where flexibility rather than high elasticity is required. 

In consequence ethylene-propylene rubbers were introduced with a small amount (3-8%) of a third, diene, monomer which provided a cross-link site for accelerated sulphur vulcanisation. Such ethylene-propylene-diene monomer ternary copolymers are designated as EPDM rubbers. 

The EPDM rubbers, whilst hydrocarbon, differ significantly from the diene hydrocarbon rubbers considered in Section 11.7 in two principal ways ... 

At one time it was widely expected that EPDM rubbers would become of significance in the tyre sector. For a variety of reasons but primarily because of the high cost of the diene monomers this expectation has not been realised. On the other hand these rubbers have become widely accepted as moderately heat-resisting materials with good weathering, oxygen and ozone resistance and they find extensive use in cars, domestic and industrial equipment. 

Substituted and unsubstituted bi- or multi-cyclic mono-, di- or multi-olefins, i.e. containing condensed rings at least one of which contains a double bond. Norbomene is homopolymerised commercially whilst, as previously mentioned, ethylidenenorbomene and dicyclopentadiene are used as the cure site monomer in EPDM rubbers. 

Initial materials of this super-tough type were blends of nylon 66 with an ionomer resin (see Chapter 11). More recent materials are understood to be blends of nylon 66 with a modified ethylene-propylene-diene terpolymer rubber (EPDM rubber—also see Chapter 11). One such modification involves treatment of the rubber with maleic anhydride, this reacting by a Diels—Alder or other... 

Ionic Thermoplastic Elastomer Based on Maleated EPDM Rubber... 

Zinc salt of maleated EPDM rubber in the presence of stearic acid and zinc stearate behaves as a thermoplastic elastomer, which can be reinforced by the incorporation of precipitated silica filler. It is believed that besides the dispersive type of forces operative in the interaction between the backbone chains and the filler particles, the ionic domains in the polymer interact strongly with the polar sites on the filler surface through formation of hydrogen bonded structures. 

The particle size of the dispersed phase depends upon the viscosity of the elastomer-monomer solution. Preferably the molecular weight of the polybutadiene elastomer should be around 2 x 10 and should have reasonable branching to reduce cold flow. Furthermore, the microstructure of the elastomer provides an important contribution toward the low-temperature impact behavior of the final product. It should also be emphasized that the use of EPDM rubber [136] or acrylate rubber [137] may provide improved weatherability. It has been observed that with an increase in agitator speed the mean diameter of the dispersed phase (D) decreases, which subsequently levels out at high shear [138-141]. However, reagglomeration may occur in the case of bulk... 

This is a nonpolar rubber with very little unsamration. Nanoclays as well as nanotubes have been used to prepare nanocomposites of ethylene-propylene-diene monomer (EPDM) rubber. The work mostly covers the preparation and characterization of these nanocomposites. Different processing conditions, morphology, and mechanical properties have been smdied [61-64]. Acharya et al. [61] have prepared and characterized the EPDM-based organo-nanoclay composites by X-ray diffracto-gram (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy... 

Antony P., Bandyopadhyay S., and De S.K., Thermoplastic elastomers based on ionomeric polyblends of zinc salts of maleated polypropylene and maleated EPDM rubber, Polym. Eng. Sci., 39, 963, 1999. Weiss R.A., Sen A., Pottick L.A., and Willis C.L. Block copolymer ionomers. Thermoplastic elastomers possessing two distinct physical networks, Polym. Commun., 31, 220, 1990. 

In one of the first reports on fiber reinforcement of rubber, natural rubber (NR) was used by Collier [9] as the rubber matrix, which was reinforced using short cotton fibers. Some of the most commonly used rubber matrices for fiber reinforcement are NR, ethylene-propylene-diene monomer (EPDM) rubber, styrene-butadiene rubber (SBR), polychloroprene rubber, and nitrile rubber [10-13]. These rubbers were reinforced using short and long fibers including jute, silk, and rayon [14—16]. 

Mechanical Properties and Cure Rate Index of the Mixes—Role of Dry Bonding System on the Reinforcement of Ethylene-Propylene-Diene Monomer (EPDM) Rubber with Melamine Fiber ... 

The polarity of the matrix helps to improve the adhesion between melamine fiber and rubber because of the polar-polar interaction between the fiber and the matrix [118]. The presence of fiber in the absence of bonding system showed only marginal improvement in tensile strength (from 1.5 to 1.6 MPa) in the case of EPDM rubber-melamine hber composites. However, maleated EPDM rubber-melamine hber composites showed more than 50% improvement in tensile strength in the absence of the bonding system [118]. This is because of the presence of maleic anhydride groups, which imparts polarity to the mbber. 

FIGURE 12.7 Monsanto rheometric curves of ethylene-propylene-diene monomer (EPDM) rubber-melamine fiber composites [64]. A, gum compound B, compound containing 30 phr melamine fiber but no dry bonding system and C, compound containing both dry bonding system and 30 phr melamine fiber. (From Rajeev, R.S., Bhowmick, A.K., De, S.K., Kao, G.J.P., and Bandyopadhyay, S., Polym. Compos., 23, 574, 2002. With permission.)... 

FIGURE 12.10 Tapping mode atomic force microscopy (AFM) images of the section analyzes of ethylene-propylene-diene monomer (EPDM) rubber-melamine fiber composites. A, composite containing no dry bonding system B, composite containing resorcinol, hexamine, and silica in the concentrations 5, 3, and 15 phr, respectively. 

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