Extending oils

Plasticizers and Processing Aids. Petroleum-based oils are commonly used as plasticizers. Compound viscosity is reduced, and mixing, processing, and low temperature properties are improved. Air permeabihty is increased by adding extender oils. Plasticizers are selected for their compatibihty and low temperature properties. Butyl mbber has a solubihty parameter of ca 15.3 (f /cm ) [7.5 (cal/cm ) ], similar to paraffinic and naphthenic oils. Polybutenes, paraffin waxes, and low mol wt polyethylene can also be used as plasticizers (qv). Alkyl adipates and sebacates reduce the glass-transition temperature and improve low temperature properties. Process aids, eg, mineral mbber and Stmktol 40 ms, improve filler dispersion and cured adhesion to high unsaturated mbber substrates. 

EP(D)M is not classified as ha2ardous. It is not considered carcinogenic according to OSHA Ha2ard Communications Standard and lARC Monographs. Commonly used paraffinic extender oils contain less than 0.1 wt % polynuclear aromatics PNAs. 

All these elastomers, especially poly(ethylene- (9-butylene) and poly(ethylene- (9-propylene), are nonpolar. The corresponding block copolymers can thus be compounded with hydrocarbon-based extending oils, but do not have much oil resistance. Conversely, block copolymers with polar polyester or polyether elastomer segments have Htde affinity for such hydrocarbon oils and so have better oil resistance. 

Mineral oils also known as extender oils comprise of a wide range of minimum 1000 different chemical components (Figure 32.6) and are used extensively for reduction of compound costs and improved processing behaviors.They are also used as plastisizers for improved low temperature properties and improved rubber elasticity. Basically they are a mixture of aromatic, naphthanic, paraffinic, and polycyclic aromatic (PCA) materials. Mostly, 75% of extender oils are used in the tread, subtread, and shoulder 10%-15% in the sidewall approximately 5% in the inner Uner and less than 10% in the remaining parts for a typical PCR tire. In total, one passanger tire can contain up to 700 g of oil. 

Process and extender oils function as physical lubricants in elastomer compounds. The oils used in elastomer compounding serve three main purposes [26] ... 

Mostly, 75% of the extender oils are used in the tread, sub tread, and shoulder regions of a tire. About 10%-15% are used in the sidewall, 5% are used in the inner finer, and less than 10% are used in the remaining parts. A typical tire can contain up to 700 g of oil. All types of mineral oils should be handled and used with care, but special care is required in the handling of aromatic oils. High aromatic oils also referred to as distillate aromatic extracts (DAEs) or simply extracts have been traditionally used as extender oils for elastomeric applications [27]. Their popularity is explained by their good... 

Figure 37.5 depicts the general refining techniques for obtaining DAE, MES, and TDAE. AU tires imported to the EU will have to fulfill the above requirements excepting racing and aircraft tires, which can still be extended with PAH-rich extender oil. 

FIGURE 37.5 General refining techniques for production of distillate aromatic extract (DAE), mild extraction solvate (MES), and treated distillate aromatic extract (TDAE). (From Joona, M., High-aromatic tire extender oils implications and future, ITEC, OH, 2004.)... 

None arc inogenic mineral oil-based plasticizers and extender oils are being utilized more and more in elastomer and tire formulations and this interest is prompted by the health and environmental concerns as well as by the coming EU legislation. 

M. Joona, High-aromatic tire extender oils-implications and future, ITEC, OH, 2004. 

M. Joona, Non-carcinogenic tire extender oils providing good dynamic performance. Rubber World, 235(4), 15, 2007. 

Process oils - Extender oils - Mineral oils Reclaiming agents Reducing agents Reinforcements... 

Extending oils for compounds crosslinked with peroxides have to be carefully selected. Synthetic ester plasticisers such as phthalates, sebacates and oleates may be used in combination with crosslinking peroxides without affecting the crosslinking reaction. Some derivatives of alkylated benzenes are also known for their very low consumption of free radicals, which is clearly desirable. Mineral oil with double bonds, tertiary carbon atoms or containing heterocyclic aromatic structure may react with radicals paraffinic mineral oils are more effective than naphthenic types, which usually require extra treatment in order to guarantee optimum results when used in peroxide crosslinked blends. 

An ASTM Extender Oil Classification is published in ASTM D 2226. This table quotes constituents of extender and processing oils under three headings ... 

Oil Modifier MP-8 of the same inventor reduces oil losses by a factor of 1.6, extends oil service life 2- to 3-fold and cuts pollutant discharges by at least 30 %, while enhancing engine power by up to 10 %. Also, this non-toxic additive reduces wear and varnish formation on engine parts and improves detergency and sealing. Its cost is about 40 % that of domestic motor oil. 

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. 

Determination of hydrocarbon groups in rubber extender oils by clay-gel adsorption (ASTM D2007)... 

Solvents, extender oils, and insoluble monomers are used throughout the rubber industry. In addition, miscellaneous oils are used to lubricate machinery. Laboratory analysis indicates the presence of oil and grease in the raw wastewater of these plants. Oil and grease entering the wastewater streams are removed by chemical coagulation, dissolved air flotation, and, to some extent, biological oxidation. 

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. 

An industrial oil-extended synthetic cis-polyisoprene was investigated by von Meerwall and Ferguson30). Following Boss, et al. 29), they substracted the unattenu-atable spin echo arising from the rubber, obtaining the diffusivity of the extender oil from the remainder. They demonstrated that no departures from Fickian diffusion occur, and measured the diffusion of the oil, both in the rubber and in the pure liquid, between —10 °C and 130 °C. Since the plot of log D vs. 1/T was not a straight line it was necessary to invoke the Williams-Landel-Ferry temperature dependence,... 

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