Ethylene-propylene monomer mechanism

The diene ethylidiene norbornene in Vistalon EPDM allows sulfur vulcanization (see Table 3.12). 1,4-Hexadiene and dicyclopentadiene (DCPD) are also used as curing agents.The completely saturated polymer backbone precludes the need for antioxidants that can bleed to the surface (bloom) of the finished product and cause staining. Saturation provides inherent ozone and weather resistance, good thermal properties, and a low compression set. Saturation also allows a relatively high-volume addition of low-cost fillers and oils in compounds while retaining a high level of mechanical properties. The ethylene/propylene monomer ratio also affects the properties. 

The polymerization filling was effected by the ion-coordination mechanism [17-19]. The monomers were ethylene, propylene, allene, os-butylene, butadiene. The fillers were mineral materials such as ash, graphite, silica gel, glass fibers. The ultimate aim of filler conditioning prior to polymerization is to secure, on its surface, metal complex or organometallic catalysts by either physical or chemical methods [17-19],... 

This is a nonpolar rubber with very little unsamration. Nanoclays as well as nanotubes have been used to prepare nanocomposites of ethylene-propylene-diene monomer (EPDM) rubber. The work mostly covers the preparation and characterization of these nanocomposites. Different processing conditions, morphology, and mechanical properties have been smdied [61-64]. Acharya et al. [61] have prepared and characterized the EPDM-based organo-nanoclay composites by X-ray diffracto-gram (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy... 

FIGURE 11.3 Dynamic mechanical analysis plots of acrylonitrile-butadiene mbber/ethylene-propylene-diene monomer (NBR/EPDM) vulcanizate of mix B containing chlorinated polyethylene (CM). (From Pandey, K.N., Setua, D.K., and Mathur, G.N., Polym. Eng. Set, 45, 1265, 2005.)... 

Mechanical Properties and Cure Rate Index of the Mixes—Role of Dry Bonding System on the Reinforcement of Ethylene-Propylene-Diene Monomer (EPDM) Rubber with Melamine Fiber ... 

The ductility of GRT-polyethylene blends drastically decreases at ground rubber concentration in excess of 5%. The inclusion of hnely ground nitrile rubber from waste printing rollers into polyvinyl chloride (PVC) caused an increase in the impact properties of the thermoplastic matrix [76]. Addition of rubber powder that is physically modihed by ultrasonic treatment leads to PP-waste ethylene-propylene-diene monomer (EPDM) powder blends with improved morphology and mechanical properties [77]. 

PVC, another widely used polymer for wire and cable insulation, crosslinks under irradiation in an inert atmosphere. When irradiated in air, scission predominates.To make cross-linking dominant, multifunctional monomers, such as trifunctional acrylates and methacrylates, must be added. Fluoropolymers, such as copol5miers of ethylene and tetrafluoroethylene (ETFE), or polyvinylidene fluoride (PVDF) and polyvinyl fluoride (PVF), are widely used in wire and cable insulations. They are relatively easy to process and have excellent chemical and thermal resistance, but tend to creep, crack, and possess low mechanical stress at temperatures near their melting points. Radiation has been found to improve their mechanical properties and crack resistance. Ethylene propylene rubber (EPR) has also been used for wire and cable insulation. When blended with thermoplastic polyefins, such as low density polyethylene (LDPE), its processibility improves significantly. The typical addition of LDPE is 10%. Ethylene propylene copolymers and terpolymers with high PE content can be cross-linked by irradiation. ... 

Bhowmick and co-workers [168] investigated the bulk and surface modification of ethylene propylene diene monomer (EPDM) rubber and fluoro-elastomer by electron beam irradiation. The structure of the modified elastomers was analysed with the help of IR spectroscopy and XPS. The gel content, surface energy, friction coefficient and dynamic mechanical properties of bulk modified fluoro-elastomers and the surface-modified EPDMs were also measured. The resultant properties of the modified EPDM were correlated with the structural alterations. 

Natta et al. (167,188,287,298,312) have built a strong case in favor of a coordinated anionic mechanism in which an electropositive metal complexes and polarizes the monomer and a polymer anion adds to the positively polarized carbon of the monomer. One of the points which was used to support the anionic mechanism was that the order of reactivity for ethylene, propylene and butene is opposite to that of cationic catalysts. The lower reactivity of propylene and butene versus ethylene was attributed to the electron releasing alkyl groups (287), but steric hindrance is believed to be a better explanation. Support for the steric effect is indicated by the influence of bulk placed at some distance from the double bond (116). For example, reactivity decreases sharply in the order pentene-1 > 4-methylpentene-l > 4,4-dimethylpentene-l, although basicity of the double bonds must change only very slightly. 

After the examination of the PS photooxidation mechanism, a comparison of the photochemical behavior of PS with that of some of its copolymers and blends is reported in this chapter. The copolymers studied include styrene-stat-acrylo-nitrile (SAN) and acrylonitrile-butadiene-styrene (ABS). The blends studied are AES (acrylonitrile-EPDM-styrene) (EPDM = ethylene-propylene-diene-monomer) and a blend of poly(vinyl methyl ether) (PVME) and PS (PVME-PS). The components of the copolymers are chemically bonded. In the case of the blends, PS and one or more polymers are mixed. The copolymers or the blends can be homogeneous (miscible components) or phase separated. The potential interactions occurring during the photodegradation of the various components may be different if they are chemically bonded or not, homogeneously dispersed or spatially separated. Another important aspect is the nature, the proportions and the behavior towards the photooxidation of the components added to PS. How will a component which is less or more photodegradable than PS influence the degradation of the copolymer or the blend We show in this chapter how the... 

This chapter reports the results of the literature that concerns the photooxidation of polymer nanocomposites. The published studies concern various polymers (PP, epoxy, ethylene-propylene-diene monomer (EPDM), PS, and so on) and different nanofillers such as organomontmorillonite or layered double hydroxides (LDH) were investigated. It is worthy to note that a specific attention was given to the interactions with various kinds of stabilizers and their efficiency to protect the polymer. One of the main objectives was to understand the influence of the nanofiller on the oxidation mechanism of the polymer and on the ageing of the nanocomposite material. Depending on the types of nanocomposite that were studied, the influence of several parameters such as morphology, processing conditions, and nature of the nanofiller was examined. 

Blends of PET/HDPE have been treated previously in the literature [157, 158]. These are immiscible, but the addition of compatibilizers improves the mechanical properties of the blend, such as styrene-ethylene/butylene-styrene (SEBS) and ethylene propylene diene monomer (EPDM) [157], MAH [158], Poly(ethylene-stat-glycidyl metha-crylate)-graft-poly(acrilonitrile-stat-styrene) (EGMA), poly (ethylene acrylic acid), and maleated copolymers of SEBS, HDPE, ethylene-propylene copolymer (EP). The addition of compatibilizers modifies the rheological properties of blends of PET with HDPE, in such a way that increases in viscosity are observed as the component interactions augment. Changes in crystallization of PET were evaluated in blends with Polyphenylene sulfide (PPS), PMMA, HDPE aromatic polyamides, and copolyesters [159]. 

Because saturated ethylene-propylene copolymers are not crosslinked in this process, it is concluded that the crosslinking reaction is definitely related to the double bonds in the diene monomer imits. However, the double bonds of the EPDM copolymers are not consumed in the crosslinking process, only decreased to some extent. The IR transmission spectra of the thin sections (20 xm) of EPDM containing ENB units has absorption peaks at 1688 and 808 cm l (assigned to C C double bonds) both before and after crosslinking (Fig. 7). Solid state MAS NMR spectra do not give spectra sufficiently resolved to interpret the reaction mechanism. 

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