Polymer EPDM

EPDM vulcanizates exhibit some unique properties such as ozone, heat, light, weathering, and chemical resistance [25]. Because of this attractive combination of properties, EPDM has taken over a wide variety of applications. EPDM has relatively low unsaturation and therefore requires complex cure systems to achieve the desired properties. Nearly every conceivable combination of curing ingredients has been evaluated in various EPDM polymers over the years [26], the following systems are described as summarized in Table 14.11. 

Ogawa et al. [100,101] reported the use of various EPDM polymers in blends with NR in black sidewall formulations. Laboratory testing showed improved resistance to crack growth and thermal aging. 

Copolymers and terpolymers of ethylene and propene, commonly known as EPM and EPDM polymers, respectively, are useful elastomers [Ver Strate, 1986], EPM and EPDM are acronyms for ethylene-propene monomers and ethylene-propene-diene monomers, respectively. The terpolymers contain up to about 4 mol% of a diene such as 5-ethylidene-2-norbomene, dicyclopentadiene, or 1,4-hexadiene. A wide range of products are available, containing 40-90 mol% ethylene. The diene, reacting through one of its double bonds, imparts a pendant double bond to the terpolymer for purposes of subsequent crosslinking (Sec. 9-2b). 

More than 800 million pounds of EPM and EPDM polymers were produced in the United States in 2001. Their volume ranks these materials fourth behind styrene-1,3-butadiene copolymers, poly( 1,4-butadiene), and butyl rubber as synthetic rubbers. EPM and EPDM polymers have good chemical resistance, especially toward ozone. They are very cost-effective products since physical properties are retained when blended with large amounts of fillers and oil. Applications include automobile radiator hose, weather stripping, and roofing membrane. 

As it was recognized that the number of variations included in many test method standards was not helpful in respect of obtaining input for databases, there was an initiative in the plastics industry that produced international standards for acquisition and presentation of single and multipoint data. These specify the particular test methods and test conditions to produce strictly comparable data. Very recently, this approach has been taken up in ISO TC 45 and drafts circulated based on British standards4, 5. These standards are not explicit about including thermoplastic elastomers and, as discussed in Chapter 2, Section 9, an acquisition standard for these materials has been proposed in ISO TC 61, Plastics. An example of the problems resulting from lack of consensus on test methods was evident for EPDM polymers and the results of collaboration to rectify this have been published6. 

NMR results are quantitative. Analysis of a 13C or H spectrum would reveal the different types of functionalities, as well as their contents in the sample. For example, Figure 9 shows the H NMR spectrum of the diene (ENB) in an EPDM polymer (ethylene-propylene diene monomer). 

DCP and uncured films were deposited on a multi-reflectance prism. Next, the ATR cell was heated to 140 °C and spectra were recorded as a function of curing time, while the angle of incidence was fixed at 45°, which minimised loss of radiation. The decrease of the absorption relating to the third monomer pendent unsaturation was monitored at 1685, 3045, 966 and 870 cm"1 for EPDM polymers containing ENB, DCPD, HD and MNB, respectively. The absorption was normalised with the methyl absorption at 1380 cm 1 which was not affected during curing. 

The influence of steric factors on the organoborane also explains the unexpected insertion into 9-BBN observed in the hydroboration - amination of the dicyclopen-tadiene entity contained in the EPDM polymer [42] (Scheme 17). 

Chlorinated rubbers, synthetic Chlorophene type rubbers Chlorosulfonated polyethylenes Cyclo rubbers, synthetic EPDM polymers... 

EPDMs are utilized in the automobile industry for their heat resistance, ozone resistance, and overall stability. Several key characteristics that are useful to the automotive chemist can be derived from the structure. Figure 8.8 shows the straight chain backbone of the EPDM polymer. EPDM is a terpolymer, or three-monomer polymer, consisting of propylene, ethylene, and another constituent—in this case, ENB (ethylidene norbornene). 

Polysar H DM. iiles/Pdysar Rubber] EPDM polymers for iig. mdding, hose and ptc e extrusion, sponge and cast coring, roofing membranes, black sidewalls. 

Royaltuf. [Uniroyai Uniroyai Chem. Ltd. Modified EPDM polymer blends impact modifier for therm lastics. 

The EPDM polymers (L and M) produced different condensable materials. Sample L evolved a small quantity of naphthenic oil, whereas sample M yielded a high amount of oxidized hydrocarbons. 

EPDM Polymers. The condensable materials from the EPDM polymers, though different in composition, still formed resinous, varnish-like products through a thermal oxidative degradation process. The liquid condensates did not adversely affect light transmittance. The solid products produced a significant reduction similar to the solid product obtained from the butyl polymers and the processing oils. 

PVC Polymers. The condensable products from the PVC also formed a solid, varnish-like material. The percent light transmittance reduction was essentially equivalent to that obtained from the butyl polymers, the processing oils, and the EPDM polymers. 

The efficiency of this process is usually less than one cross-link per peroxide molecule decomposed. To increase the cross-linking efficiency, small amounts of unsaturation are introduced into the polymer structure. We have already discussed EPDM polymers, which are essentially diene monomers copolymerized with ethylene-propylene (EPR) polymers. For polysiloxanes, copolymerization of small amounts of vinyl-methylsilanol greatly enhances cross-linkability (Equation 5.7). The unsaturation introduced into an otherwise saturated structure provides additional sites for cross-linking through chain reaction. 

Figure 36 Mooney siress relaxation results on different production lots of EPDM polymers with the same Mooney viscosity.

The compositions of EPDM elastomers are controlled by using the appropriate monomer feed ratio (see Eq. (2.38)) to obtain the desired composition in a continuous polymerization process. In general the excess propylene required is recycled. The molecular weights of EPDM polymers are controlled primarily by chain transfer reactions with added molecular hydrogen (Eqs. (2.86) and (2.87)), as is common with other Ziegler-Natta polymerizations (Boor, 1979). 

The analysis of an EPDM sample by TGIC-GPC is shown in Fig. 41 [134]. The amorphous EPDM polymer would not crystallize in TREF but it is adsorbed... 

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