Saturated Rubber Research Articles

EVALUATING ETHYLENE PROPYLENE DIENE RUBBER FOR DYNAMIC APPLICATIONS INSTEAD OF NATURAL

Natural Rubber (NR) has been used in dynamic applications for many years. NR has satisfactory resilience, vibration, and fatigue properties. Besides all these good properties, NR has quite poor aging resistance; also its service temperature is limited to about 90 °C. Improving aging characteristics of NR is a common problem for both rubber industry and academy. Nowadays, especially automotive industry has been focused on thermally resistant static and dynamic rubber based materials in new generation automobiles because of current strict emission regulations. There are a lot of attempts to improve service conditions of NR however; they are not comparable yet, with alternative saturated rubbers such as EPDM. In this study, a new grade EPDM, which had a high molecular weight, narrow molecular weight distribution, and tailor-made chain structure, has been studied in terms of rheological, mechanical, dynamic mechanical, aging, and low temperature properties for target dynamic applications. Especially possible service temperature and dynamic performance of EPDM were compared to that of NR based reference. It was concluded that, EPDM may be an assertive competitor to NR, if its chain structure is modified correctly.

Comparative behavior of in situ silica generation in saturated rubbers: EPDM and hydrogenated natural rubber

ABSTRACTRole of carbon‐carbon double (CC) bonds content and their position in ethylene‐propylene diene ter‐polymer (EPDM), hydrogenated natural rubber (HNR) and natural rubber (NR) on in situ silica formation using tetraethoxysilane (TEOS) as a silica precursor is comparatively investigated. Glass transition temperature (Tg) reflecting rubber chain flexibility is found as an important factor for in situ silica generation via swelling method. Despite of similar solubility parameters, NR has higher TEOS‐swelling degree resulting in the higher in situ silica content (30.8 phr) than EPDM (3.50 phr) and HNR (10.4–17.6 phr) due to the higher Tg of EPDM and HNR providing the less chain flexibility to be swollen in TEOS solution. The morphological analysis implies that CC bonds in saturated rubbers may be agglomeration sites for in situ silica particles. For practical applications, saturated rubbers containing in situ silica/NR vulcanizates showed the improvement of mechanical properties and resistance of thermal and ozone degradation. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44748.

Unvulcanized elastomeric waterproofing materials for construction application

In the construction was widespread elastomer profiles, which have the ability to swell in water. Such products should have a high capacity for swelling, elasticity, resistance to weathering. At the present time for these purposes are used materials, mostly of foreign origin. With the increasing pace of construction in Russia the problem of replacement of imported materials is particularly relevant. The work was dedicated to the creation of water-swellable elastomer materials using bentonite powders and study of their properties. Сomparative testing of imported and domestic hydrophilic sealants were held. Rationale and choice of components for the cords of bentonite was conducted. Polymer base is saturated ethylene-propylene rubber. Bentonite from different manufacturers used to increase the swelling of the samples. Filler added in an amount of 50–100 phr. The elastomeric compositions were prepared using laboratory roller at a temperature of 60 ± 5° C. Profiling was performed on a syringe-machine at a temperature of 120° C. Extrusion indicator of the mixtures were evaluated on a 10-point scale (German-Russian system). It is found that high swelling products provided using field Azerbaijan bentonite. It is noted that the dosage of bentonite than 150 w.p. deteriorates technological properties of bentonite cords. It has been shown that activation of the bentonite and sodium carbonate chloride can significantly improve product swelling, wherein the bentonite content of the composition was 150–200 w.p.

Mechanistic Studies into the New Concept of Co-Agents for Scorch Delay and Property Improvement in Peroxide Vulcanization

Abstract In previous studies a new concept of a peroxide cure system for rubber has been reported where scorch safety and mechanical properties are improved at the same time. This new system consists of the use of a combination of a peroxide, a bismaleimide type co-agent and a sulfur spender for the cure of saturated or low-unsaturated rubber. Several mechanical properties have been studied and were found to be improved by using this curing system, such as tensile strength, moduli, compression set and aging. The present paper deals with the understanding of the reported phenomena. Mechanistic studies have been performed with the aim of comprehending the chemistry that takes place during peroxide vulcanization in the presence of a maleimide co-agent and a sulfur spender. From Nuclear Magnetic Resonance and Infrared analysis the loss of the maleimide unsaturation from the co-agent was observed, due to reaction with the sulfur spender. This reaction already takes place at room temperature, thus previous to peroxide decomposition. Further, Model Compound Vulcanization studies were performed using 3-methylpentane as representative model for the saturated rubber backbone. The reaction products of the peroxide vulcanization of 3-methylpentane in the presence of a maleimide type co-agent and a sulfur donor have been analyzed by means of Liquid Chromatography-Mass Spectrometry. Several reaction products have been identified and a reaction mechanism that explains the scorch delay and the property improvement by the new cure system is proposed.

The role of rubber characteristics in preparing rubber/clay nanocomposites by melt compounding

AbstractRubber/organic clay (OC) nanocomposites were produced by melt blending. Polar or unsaturated matrices (e.g., NBR and SBR) could easily enter into OC layers, whereas using nonpolar unsaturated rubber (EPDM), without other additives' help, intercalation structure could not be directly obtained. For the EPDM system, an intercalated structure was observed in presence of stearic acid (SA) for composites composed of SA and OC. Transmission electron microscopy observation showed that the dispersion of clay in nonpolar saturated rubber matrix was much poorer than that in polar or unsaturated matrix. The same effect of polar matrix was confirmed by comparison between IIR/OC and BIIR/OC systems. Moreover, using OC pretreated by SA (S‐OC), the dispersion of clay was obviously improved in the investigated nanocomposites, due to the intercalation of SA into OC interlayers. Especially in the nonpolar saturated EPDM system, the intercalation structure could be easily observed. Relative to the corresponding nanocomposites using OC, tensile strengths and the stresses at low strain of NBR and SBR based nanocomposites with S‐OC were significantly improved; while with EPDM nanocomposite, using S‐OC, only tensile strengths were improved but the stresses at low strain were almost the same, which should be related to the different interfacial force between OC and different rubber matrices. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Effect of network heterogeneities on the physical properties of nitrile rubbers cured with dicumyl peroxide

AbstractThe scope of this study is to continue our earlier studies on the peroxide curing of diene elastomers. The effect of peroxide content and temperature on the curing and mechanical properties of NBR and H‐NBR rubbers with different acrilonitrile content was evaluated. Experimental evidence indicates that saturated rubbers behave as expected whereas in unsaturated nitrile rubbers abstraction of allylic hydrogen and addition to the double bonds can act as mechanism of crosslinking, the weight of each mechanism is dependent of DCP content and curing temperature. The addition mechanism produces densely crosslinked zones or clusters, generating a heterogeneous network with effect on the vulcanizate properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3377–3382, 2007

有機系配合剤 有機過酸化物架橋剤

Organic peroxides (PO) are used as crosslinking (vulcanizing) agents. Free radicals generated from PO can abstract hydrogens from saturated rubbers such as polyethylene, ethylene-propylene-diene terpolymer and highly hydrogenated acrylonitrile-butadiene rubber to form intermolecular C-C bonds. The crosslinking using PO is effective for the improvement of heat resistance of rubber, and therefore, the technique becomes much important especially in automotive applications. The thermal decomposition rates, mechanisms and products for several kinds of PO are reviewed. Dicumyl peroxide (DCP) is a most typical and widely used crosslinking agent. However, acetophenone derived from DCP as a decomposition product sometimes causes a smell problem of rubber. α, α'-Bis (t-butylperoxy)-1, 3-diisopropylbenene is used as the substitute for DCP, because it has almost same activity as DCP and generates less smell products. The radical generation efficiency of 2, 5-dimethyl-2, 5-di (t-butylperoxy) hexane (HXA) is lower than that of 2, 5-dimethyl-2, 5-di (t-butylperoxy) hexyne-3 because of less hydrogen abstracting ability of the alkyl radical generated from β-scission of the intermediate t-alkoxy radical of HXA. t-Butylperoxy-2-ethylhexyl monocarbonate is low temperature active and has high hydrogen abstracting ability, and then it is used as the substitute for 1, 1-di (t-butylperoxy) cyclohexane.

Radiation degradation of spent butyl rubbers

Radiation methods of materials modification applied in technological chains can have significant economical and ecological advantages as compared to the established chemical, thermal and mechanical methods. Each year the problems of nature resources economy through the use of production and consumption wastes acquire a more significant value, as it allows to solve also ecological issues along with economical ones. This is mostly acute in relation to polymeric systems based on saturated rubbers, for example butyl rubber (BR) used in the tyre industry, as due to their high resistance to the action of oxygen, ozone, solar radiation and bacteria, they contaminate the environment for rather a long period. At VNIIEF and KSPU experiments were carried out on application of electron beams with energy from 6 to 10 MeV for radiation destruction of spent rubber based on BR. The radiation-degraded material was tested for re-use in the formulation of initial diaphragm mixture, rubber mixture for producing rubberized fabric and roofing.

高飽和型ニトリルゴムに対する各種加硫促進剤の基礎性能(1)

高飽和型ニトリルゴムに対する各種加硫促進剤の基礎性能(1)

Applications of an azide sulfonyl silane as elastomer crosslinking and coupling agent

A new coupling agent, a silane sulfonyl azide has been synthesized. This agent was capable of reacting with either saturated or unsaturated rubbers. In unsaturated rubbers reinforcement with mineral filler was inproved when compared with a commercial silane coupling agent. For a saturated rubber, the response when this agent was added to the formulation was superior to the response reached using only a conventional peroxide to crosslink the polymer. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1353–1359, 1997

A New Process for the Preparation of Highly Saturated Nitrile Rubber in Latex Form

Abstract A novel process for the preparation of highly saturated nitrile rubber latex has been developed. This process directly converts NBR latex into HNBR latex in one reaction step. The key to the process is the efficient in-situ generation of diimide within the latex by the oxidation of hydrazine hydrate in the presence of a catalyst. At 40–70°C, diimide smoothly and selectively reduces the olefinic bonds while leaving other functionalities unaffected. The process operates at ambient pressures and produces nitrogen and water as by-products. HNBR latex produced by this process has been applied to the manufacture of superior heat-resistant gasketing via the “Beater-Addition” method. This unique new form of HNBR maintains the well known benefits of HNBR (e.g., solvent, heat, and ozone resistance, etc.) while expanding its potential applications into latex-related products.

Formulation, curing, morphology and impact behaviour of epoxy matrices modified with saturated rubbers

New formulations of rubber toughening agents for difunctional and tetrafunctional commercial epoxies are attempted, on the basis of their increased thermal stability compared with classical unsaturated elastomers. Quite satisfactory results are obtained where a block copolymer of polydimethylsiloxane and polyoxyethylene elastomer or a functionalized poly (1 -butene) in difunctional epoxy are used. On the other hand, poor results are obtained when the same elastomers are employed in tetrafunctional epoxies. A tentative explanation is given on the basis of the different networks obtained in the two matrix systems.

Fundamental Aspects of the Photooxidation of Hydrocarbon Polymers

Abstract Hydrocarbon polymers (polyolefins, polystyrene and many saturated and unsaturated rubbers) make up the largest group of synthetic polymers. They all degrade more or less rapidly on exposure to sunlight, though they should not absorb in the solar uv range (290–400 nm) if they are perfectly pure. This makes a clear understanding of their mechanism of degradation important not only from a practical but also from a fundamental point of view. We try to answer some fundamental questions such as the following. How is the photooxidation initiated? What is the exact mechanism of the reaction? How do chain scission and cross-linking proceed?

Formulation, curing, morphology and impact behaviour of epoxy matrices modified with saturated rubbers

Formulation, curing, morphology and impact behaviour of epoxy matrices modified with saturated rubbers

Filler-Elastomer Interactions. Part I: Silica Surface Energies and Interactions with Model Compounds

Abstract Inverse gas-solid chromatography, operated at infinite dilution, has been used to assess the surface energies of silicas, both fumed and precipitated. The dispersive components of the surface free energies of the silicas were calculated from the free energies of adsorption, corresponding to the —CH2— group, obtained from n-alkane adsorption. The specific components of the surface energies were evaluated separately by comparison of the free energies of adsorption of polar probes with those of n-alkanes, based on the surface areas covered by the probe molecules. The results indicate that while the dispersive components of silica surface energies is somewhat higher for the fumed silicas, the specific components are much higher for precipitated silicas, probably resulting from the higher silanol concentration on their surfaces. Moreover, the interaction able to take place between rubber matrix and the silicas are also estimated chromatographically from the adsorptions of low-molecular-weight analogs of elastomers. The free energies and enthalpies indicate that the interactions of functional groups with the fillers decrease in the order of nitrile, phenyl ring, double bond. The saturated rubber analogs show lower interactions with silicas. The lowest interactions of iso-alkanes imply poor interactions between butyl rubber and the fillers. As expected, the experimental data reflect an attenuation of polymer-silica interactions with decreasing content of functional groups and degree of unsaturation in NR, BR, SBR, and NBR.

Functionalization of ethylene-propylene saturated rubbers: a study on the grafting of monoethylmaleate and its cyclization reaction

A study on the solution grafting of monoethylmaleate onto a saturated ethylene-propylene rubber was conducted. The grafting degree was followed by titration methods as function of the time of reaction and amount of initiator. The insertion of unsaturated molecules always led to some degradation of the polymeric backbone. The subsequent cyclization reaction of grafted monoethylmaleate to maleic anhydride was also studied by Fourier Transform Infrared Spectroscopy either in bulk or in solution. A different behaviour was found in the two cases; furthermore, a different mechanism of reaction led to different amounts of inter- and intra-chain anhydride formation.

Characterization of multi-component polymer blends by multi-step staining techniques

Morphology is one of the important parameters that affects polymer properties and performance. A standard procedure used when characterizing the morphology of many polymer blends by TEM is to stain one of the components with a heavy element rendering it opaque to the electron beam. Among the more common stains used are phosphotungstic acid (PTA) for nylon and OSO4 for unsaturated rubbers. Although these stains work well for simple two component systems, innovative techniques are often essential when the material contains three or more phases, as necessitated by ever expanding industrial demands. This paper describes two such techniques used in characterizing three multi-phase polymer systems.One multi-component system consisted of a polybutadiene-polymer blend, nylon, and a saturated rubber. OSO4 reacts with the double bonds of the butadiene rendering it opaque while slightly darkening its matrix. PTA reacts with the amine groups of nylon rendering it opaque.

Transmission electron microscopy of saturated rubber modified polymer systems

Transmission electron microscopy of saturated rubber modified polymer systems

Grafting of methyl methacrylate on EPR and EPDR: Impact properties of polyvinyl chloride grafted polymer blends

AbstractEPDM rubber can be brought into water suspension after swelling in n‐heptane containing proper emulsifiers and in shear stress; particles reach dimensions as low as 150 Å. Methyl methacrylate in emulsion can be grafted easily with Bz2O2 on the rubber. Grafting yields depend particularly on the monomer/rubber ratio. The grafted polymer can be recovered by precipitating the emulsion with acetone, which eliminates the homopolymer. The grafting mechanism is discussed in terms of different initiators (AIBN and Bz2O2) and unsaturated (EPDM) and saturated rubber (EPR); AIBN and PMMA radicals were inactive in abstracting hydrogen atoms from rubber chains. Mechanical properties of the blends with PVC of the raw graft product are discussed on the basis of the grafted polymer composition and synthesis conditions. Very high impact strength can be reached at 15% rubber content in the blend for a grafted polymer obtained from a monomer/rubber ratio equal to 0.75.

Studies on heterogeneous polymeric systems. II. Polyblends containing saturated rubbers

AbstractSaturated rubbers composed of ethylene–propylene or ethylene–vinyl acetate copolymers and terpolymers were used in the mass polymerization of high‐impact styrene or styrene–acrylonitrile polyblends. Conventional polymerization procedures lead to blends of inferior mechanical properties. The cause for the poor performance was traced to the inability of the rubber‐phase particles to preserve the desired size and particularity during processing.Polymeric blends of saturated rubbers having mechanical properties comparable to those obtainable with polybutadiene rubbers are prepared by (1) controlling the rubber‐particle size during prepolymerization and (2) preserving such size by crosslinking and grafting of the rubber following phase inversion. Extensive crosslinking of the rubber in the final blend must take place prior to processing to resist rubber particle deformation and disintegration during mechanical working. Rubber vulcanization is realized by the presence of peroxides in the final stages of polymerization; pendant unsaturation in the rubber is also needed or helpful. The reactivity and number of unsaturated groups in the rubber must be controlled to avoid excessive grafting prior to phase inversion and to permit efficient crosslinking following phase inversion.