Oil-extended EPDM

Determination of the oil content of oil-extended EPDM is another important analytical problem. 

After Noordermeer [56], Reproduced by permission of Rubber World Magazine (Lippincott). 

Methods commonly in use are extraction and precipitation methods. The first category makes use of a solvent which dissolves the extender oil but not EPDM. Depending on the experimental configuration, extraction is achieved either by step-by-step extractions in flasks with regular renewal of the extraction medium or by means of Soxhlet apparatus. The second category uses a suitable solvent/non-solvent combination, where the oil-extended polymer is first completely dissolved EPDM is then precipitated and separated from the liquid phase containing the extender oil. For both procedures either the EPDM moiety or the oil moiety after evaporation of the extraction medium can be used for the calculation of the oil content. Table 6.34 shows some typical results. 

For QC purposes the duration of the test is an important criterion. In this respect, Soxhlet extraction performs better than the conical flask method. A systematic - unexplained - difference was noticed between Soxhlet MEK extraction and the conical flask method using a 2 1 mix of acetone and cyclohexane. The Soxhlet extraction method using MEK as the solvent has been recommended for the determination of the oil content of oil-extended EPDM [57]. 

Migration Rates of Phthaiate Esters from Soft PVC Products 

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Catalyst residues, particularly vanadium and aluminum, have to be removed as soluble salts in a water-washing and decanting operation. Vanadium residues in the finished product are kept to a few ppm. If oil-extended EPDM is the product, a metered flow of oil is added at this point. In addition, antioxidant, typically of the hindered phenol type, is added at this point. 

Standardisation of EPDM characterisation tests (molecular composition, stabiliser and oil content) for QC and specification purposes was reported [64,65]. Infrared spectroscopy (rather than HPLC or photometry) is recommended for the determination of the stabiliser content (hindered phenol type) of EP(D)M [65]. Determination of the oil content of oil-extended EPDM is best carried out by Soxhlet extraction using MEK as a solvent [66], A round robin test was reported that evaluated the various techniques currently used in the investigation of unknown rubber compounds (passenger tyre tread stock formulations) [67]. 

T2 relaxation of oil-extended EPDM revealed two distinct relaxation components whose characteristic decay times are comparable with those of initial rubber and paraffinic oil (Figure 10.7) [74]. This suggests that the components with a short and long decay time mainly originate from the relaxation of rubbery chains and oil molecules, respectively. 

Figure 10.7 The T2 relaxation decay of oil-extended EPDM rubber containing 12.2 (o), 33.7 ( ) and 50.0 mass% (A) paraffinic oil [74]. The line corresponds to the best fit of experimental data points with a linear combination of two exponential functions...

Evaluation procedures, ISO 4097 Jihher, ethylene—propylene—diene (EPDM), Non-oil extended raw general-purpose types, 1992. 

Fig. 2 (a) 2D image of oil-extended PP/EPDM TPVs. Crosslinked EPDM particles are separated by circle, (b) 3D model of blend showing EPDM dispersed particles... 

EPDM ethylene propylene diene rubber with 50 wt% paraffinic oil extended, PP polypropylene, DTBT 2,4-diallyloxy-6-fer/-butylpcroxy-1,3,5-triazinc (95% pure), DCP dicumyl peroxide (40% pure), TAC triallyl cyanurate (50% pure), 1076-Irganox 1076, 168-Irgafos 168 Values in the parentheses correspond to the milliequivalent concentration of corresponding peroxide and coagent per 100 parts of pure EPDM rubber... 

Up to 400 K (127 °C), the fraction of the component with a long decay time was smaller than the concentration of oil hydrogen in the oil-extended rubber. Apparently, a small fraction of oil molecules shows a molecular mobility comparable with that of EPDM chains. The fraction of these physically trapped oil molecules decreased with an increasing temperature, and... 

NS nonstaining OE-EPDM oil extended-ethylene-propylene diene... 

EPDM XG 006 Ethylene-propylene oil extended rubber Polysar-Miles... 

Tire treads are made from oil extended BIMS, butyls, EPDMs, polybutylenes, SBR, and their blends. Butyls contribute skid resistance, brominated butyls BUR + SBR can increase wet traction, and chlorinated butyl (CIIR) increases skid resistance and rebound. BIMS also provides good flex crack resistance. ... 

There is no standard EPDM classification system that has gained wide acceptance. Generally an informal system of Mooney viscosity (ASTM D1646), percent ethylene, type of third monomer, and percent third monomer is used. Also, the oil content in oil-extended grades is noted in these grades. 

A thermoplastic EPDM/iPP vulcanizate consists of a continuous and thermoplastic iPP phase, which forms the minority of this blend (ca. 20 wt%), and a cross-linked, oil-extended, dispersed EPDM phase (ca. 80 wt%). The discrete EPDM phase consists of submicron or several microns size particles. Within the discontinuous EPDM/ iPP vulcanizate morphology, the cross-linked EPDM phases act as excluded volumes into which carbon nanotubes can hardly penetrate during melt-blending, or after performing the four steps of the latex concept, described in depth in earlier chapters of this book. 

Raw EPDM (in the form of bales for instance) can be subject to surface crosslinking when exposed to daylight for a period of even a few days. The time is further reduced if the terpolymer is oil extended or has a high third monomer content. From this point of view, EPMs are stable in fact in many laboratories EPMs are kept for years as reference samples for checking Mooney viscometers. 

All EPDMs and EPMs contain small quantities of antioxidants for protection during storage. We have already mentioned the necessity of avoiding exposure of all EPDMs to light, particularly oil extended types, so as to prevent any surface crosslinking. 

The carcinogenicity of polycyclic aromatic compound-rich tyre extender oils has lead to the proposal of a legislative ban on their use in Europe. The suitability of naphthenic oils as non-toxic plasticisers in tyre treads is discussed and results are presented of experimental studies of the use of these plasticisers in SBR, EPDM, sulphur-cured EPDM and peroxide-cured EPDM. Despite their low aromatic content, the naphthenic plasticisers are shown to give good results in SBR, probably as a result of the contribution to solvent characteristics of the naphthenic molecular structure. The use of naphthenic oils is expected to increase worldwide as they are said to be one of the best alternatives to aromatic extracts with regard to solvent properties, compatibility, performance and availability. 

Extender oils were foxmd to cause a considerable increase in the dose required to attain the optimum cure. This can be explained by reaction of transienf infermediafes formed on the irradiated polymer chain with the oil and with the energy transfer, which is particularly effective when the oil contains aromatic groups. Thus, the ranking of oils as to their cure inhibition is aromatic > naphtenic > aliphatic. This aspect is very important because many carbon-black-reinforced EPDM compounds contain frequently 100 phr or more oil. 

The materials are melt-process able and a critical stress for flow is observed, similar to conventional PP/EPDM-based TPVs. Application of static crosslinking leads to (partial) connectivity of the rubber particles via chemical bridging of grafted PE chains. Dynamic preparation conditions caused the connected structure to break-up, which led to a significant enhancement of the mechanical properties and the melt processability. The addition of 25-80 wt% extender oil resulted in a reduced complex viscosity and yield stress in the melt, without deteriorating the mechanical properties. The relatively good elastic recovery and excellent final properties of these high hardness TPVs can be explained in terms of the submicrometer rubber dispersions. 

The typical commercialized TPV is composed of PP, EPDM, and a high concentration of extender oil, which are used to reduce the modulus and improve the processability. The performance of TPV is also determined by the morphology of the PP/EPDM blend, /W , and MWD of each components and the degree of vulcanization in the hnal products. 

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