Saturated Elastomer Research Articles

In-situ synthesis of acylated sodium alginate-g-(tetrahydrofuran5-b-polyisobutylene) terpolymer/Ag-NPs nanocomposites

Sodium alginate (SA) is a marine-derived biocompatible polysaccharide with huge reserves and polyisobutylene (PIB) is a saturated elastomer with gas barrier property, bio-inertness, and biocompatibility. Herein, we developed the biomass-based ASA-g-(THF5-b-PIB) graft copolymer/Ag (3–11 nm, 0.7–3.8%) nanocomposites formed in-situ via combination of transition of terminal groups in PIB chains with grafting-onto method. The above graft copolymers exhibit microphase separation by self-assembly for the difference in chemical structure from backbone and branches and annealing process as well. The crystallization morphology from backbone depends on the Mn,PIB and GN, changing from thin strip to rod-like crystal. The pH sensitivity happens in drug release behavior of ASA-g-(THF5-b-PIB) micelles, which reach 100% of drug-release within 40 h at pH = 7.4. The ASA-g-(THF5-b-PIB)/Ag composites behave good antibacterial properties to both E. coli and S. aureus and anti-protein adsorption performance. This novel graft copolymer with comprehensive properties and would have a prospect in biomedical field.

Mechanics of an elastic membrane infused with a liquid

The mechanics of swelling and diffusion in fluid saturated elastomers has long interested workers in nonlinear elasticity theory. Here we broaden this subject by presenting a model for thin membranes, derived as the leading-order-in-thickness approximation to the three-dimensional theory.

Use of Benzene-1,3-Bis(Sulfonyl)Azide as Crosslinking Agent of TPVs Based on EPDM Rubber—Polyolefin Blends

Abstract The use of innovative crosslinking agents for the preparation of thermoplastic vulcanizates (TPVs) is investigated. In this preliminary study, the most common TPV systems, based on polypropylene (iPP) and ethylene—propylene—diene terpolymer rubber (EPDM) blends, are studied. Among typical vulcanization agents, only the peroxides are able to crosslink saturated elastomers, however, they present the disadvantage that give rise to chain scission of the thermoplastic matrix. For this reason, the main goal of the present study is to investigate a new vulcanization agent for elastomeric matrices, which also permit the dynamic vulcanization process in their blends with polyolefins. This agent is based on a diazide derivative, benzene-1,3-bis(sulfonyl)azide that, for the specific behavior of the sulfonyl azide group, allows its interaction with the carbon—hydrogen bonds of the elastomeric phase and of the polyolefin. The study includes the dynamic vulcanization of PP—EPDM blends and their rheological, mechanical and thermal characterization. A comparison with traditional TPVs prepared with sulfur as vulcanization agent is also presented.

Solvent-assisted osmium staining of butyl acrylate and ethylene-propylene-diene in a styrene acrylonitrile matrix

In order to optimize the toughening effect of elastomers in engineering polymers, it is necessary to characterize the size, morphology and dispersion of the specific elastomer within the polymer matrix. For unsaturated elastomers such as butadiene or isoprene, staining with osmium tetroxide is a well established procedure. The residual carbon-carbon double bond in these materials is the reactive site and forms a 1,2-dilato complex with the OsO4. Incorporation of osmium tetroxide into the elastomer not only produces sufficient contrast for TEM, but also crosslinks the elastomer sufficiently so that ultramicrotomy can be accomplished at room temperature with minimal distortion.Blends containing saturated elastomers such as butyl acrylate (BA) and ethylene propylene diene monomer (EPDM) cannot be stained directly with OsO4 because effective reaction sites such as C=C or -NH2 are not available in sufficient number. If additional reaction sites can be introduced selectively into the elastomer by a chemical reaction or the absorption of a solvent, a modified, two-step osmium staining procedure is possible.

Mechanical properties and morphology of polypropylene composites. Talc‐filled, elastomer‐modified polypropylene

AbstractThe balance of impact strength and rigidity of polypropylene can be significantly improved by physical blending of the polypropylene with a talc filler and a variety of elastomer types. Unsaturated elastomers were found to be effective impact strength improvers in 70/15/15 percent PP/elastomer/talc composites, whereas saturated elastomers gave rise to a high stiffness of such compounds. This is attributed primarily to different tendencies of the elastomers to coat the filler surface. Studies on a wider range of compositions, using a butadienestyrene‐butadiene (SBS) block copolymer and a ethylene‐propylene‐diene (EPDM) terpolymer as representatives of the two elastomer classes, indicated that at high stiffness levels (flexural modulus > 1.6 GN/m2), the composites with SBS show the best balance of properties, whereas at higher impact levels EPDM leads to a higher rigidity and impact strength. On the basis of morphological studies such differences can be explained qualitatively, in spite of the complex structure of these composites.

Improvement of Impact Strength of Polystyrene by Compounding with Styrene-Grafted Ethylene Propylene Elastomeric Copolymers

Abstract Ethylene propylene copolymers having good elastomeric properties lend themselves very well to improving impact strength of fragile polymeric materials, such as polystyrene. In order to obtain good results, the percentage of copolymer to be added should be chosen in such a way that the strength of the resulting mixture is as high as possible, but compatible, however, with the practically useful values of the hardness and of the modulus of elasticity, which decrease regularly with an increase in the percentage of elastomer. The best results, for an equal percentage of elastomer, are obtained when the polystyrene is mixed with polystyrene grafted on the ethylene propylene copolymer, rather than with the ethylene propylene copolymer alone. This we attribute to the improved dispersion of the elastomer in the polystyrene matrix that is found in case of the use of the graft polymer. Thus, formation of vitreous and elastomeric microphases, rather than of macrophases, occurs, and there is a better adhesion between these. The use of a graft polymer prevents, in practice, the phenomena of migration and sorting of the phases, and guarantees the maintenance over a period of time of a microphasic structure. The use of a saturated elastomer, such as that used by us, permits, additionally, an improvement in the resistance to aging, in comparison with the traditional materials consisting of mixtures of polystyrene and unsaturated elastomers.

Use of C14 Tagged Cumyl Peroxide to Study Peroxide Vulcanization of Ethylene Propylene Copolymers

Abstract Peroxides are used today as crosslinking agents for elastomers in general, and for saturated elastomers in particular. Among peroxides, cumyl peroxide merits special attention because of the small danger in handling since it decomposes appreciably only above 120–130° C. The mechanism of the vulcanization reaction has been considered very simple, leading to the formation of carbon-to-carbon bonds between polymer molecules. The path of the reaction can be followed if one can determine at every instant the amount of crosslinking and of peroxide decomposition products, or the quantity of residual peroxide. From the existing literature, it appears evident that the degree of crosslinking in natural rubber and the recovery of peroxide fragments justify the reactions proposed in the chemical scheme. However, in the case of ethylene propylene rubber these lead to the conclusion that the peroxide is only partly used. This different fate of cumyl peroxide, depending on whether the decomposition occurs in natural rubber or in an ethylene propylene copolymer, demonstrates that other reactions occur, which involve primary peroxide radicals or the secondary polymeric radicals, or both, in a manner different from the proposed scheme.

Evaluation of Crosslinking Coagents in Ethylene-Propylene Rubber

Abstract Ethylene-propylene rubber (EPR), a saturated elastomer, is usually vulcanized by a peroxide-sulfur curing system. However, several disadvantages associated with this system—undesirable odor for some applications, narrow curing range, and poor strength obtained with mineral fillers—emphasize the need for other reactive chemicals as crosslinking coagents for EPR. Certain polyfunctional monomers such as ethylene dimethacrylate, and polyfunctional polymers such as 1,2-polybutadiene were promising crosslinking coagents for EPR. When used in place of sulfur, they decrease peroxide requirements of moderately filled EPR compounds. They also impart higher states of cure, improve the cure cycle, and decrease odor. The coagents are much superior to sulfur in mineral-filled EPR compounds where, in addition to increasing the crosslinking efficiency, they also improve the wetting of the filler particles by the rubber. However, in highly loaded (carbon black and oil) EPR formulations, the superiority of the peroxide-coagent system is mainly due to the ability to replace sulfur and, consequently, to improve odor.

Crosslinking Chlorosulfonated Polyethylenes

Abstract The broadening practical use of chlorosulfonated polyethylene elastomers for applications where good resistance to heat, oil, light, oxygen, and ozone is needed has been accelerated by the development of several chemically distinct curing systems. Optimum use of these saturated elastomers requires a knowledge of the chemistry of these curing reactions and the effect of the resulting crosslink structures on vulcanizate properties. The high reactivity of the sulfonyl chloride crosslinking sites allows wide latitude in choice of curing chemistry, and crosslink type can be controlled to give a preponderance of ionic salt bonds or to give a mixture of covalent and ionic bonds. The role of water, alcohols, sulfur accelerators and free radical stabilizers in the various practical curing systems is discussed. The development of wholly organic curing systems for chlorosulfonated polyethylenes is reviewed. The properties of vulcanizates of chlorosulfonated polyethylenes are also significantly controlled by the base polyethylene, by chlorine content, and by chlorine distribution. The effects of these variables on vulcanizate properties is briefly reviewed.

The development of radiation process applications

The patent literature provides a measure of applications for radiation processes. At present, there are well over 200 U.K. and U.S. Patents, which can be classified into a. polymerisation, b. crosslinking of polymers, c. degradation of polymers, d. multicomponent polymers (graft and block copolymers), e. general chemical reactions and petroleum products, f. sterilisation, g. specific articles and shapes, h. uses for irradiated polymers, i. inorganic compounds, j. machines for generating radiation (including isotopes). Processes involving polymers account more than 75% of these patents, so it can be fairly claimed that the major application of radiation will lie in the polymer field. The first polymerisation patent was granted in 1927 and the first crosslinking patent in 1933 but the first patent on multicomponent polymers was only granted in 1958 and this is the topic selected for detailed consideration in this paper. The development of multicomponent polymers can be classified into a. direct grafting, b. indirect grafting, c. peroxidation grafting, d. block copolymers and e. attenuated network polymers. These methods are outlined and exemplified, by reference to continuous process techniques. More recently, the application of radiation processes to polyvinyl chloride has attracted interest. This can be converted into infusible and insoluble rigid sheet with potential use as a solvent-resistant and corrosion-resistant structural material, by incorporating a plasticiser containing two or more olefinic double bonds and subjecting to radiation. The plasticiser is caused to polymerise and form a network which is attentuated by the polyvinyl chloride molecular chains. The drawback to this material is its brittleness but recent work has shown this can be overcome by incorporating a small amount of a saturated elastomer. By inference, well-crosslinked materials are not necessarily brittle and this widens the scope for attenuated network copolymers in industrial applications.