Polymer processing ethylene—propylene copolymers

Processes for the manufacture of ethylene-propylene copolymer can produce several distinct types of polymer which, although they may contain similar proportions of the two monomer units, differ appreciably in their physical properties. The differences in these properties lie not only in the ratio of the two monomers present but also, and very importantly, in the detailed microstructure of the two monomer units in the polymer molecule. Ethylene-propylene copolymers may consist of mixtures of the following types of polymer ... 

Absorption due to main intermediates such as polymer cation radicals and excited states, electrons, and alkyl radicals of saturated hydrocarbon polymers had not been observed for a long time by pulse radiolysis [39]. In 1989, absorption due to the main intermediates was observed clearly in pulse radiolysis of saturated hydrocarbon polymer model compounds except for electrons [39,48]. In 1989, the broad absorption bands due to polymer excited states in the visible region and the tail parts of radical cation and electrons were observed in pulse radiolysis of ethylene-propylene copolymers and the decay of the polymer radical cations were clearly observed [49]. Recently, absorption band due to electrons in saturated hydrocarbon polymer model compounds was observed clearly by pulse radiolysis [49] as shown in Fig. 2. In addition, very broad absorption bands in the infrared region were observed clearly in the pulse radiolysis of ethylene-propylene copolymers [50] as shown in Fig. 3. Radiation protection effects [51] and detailed geminate ion recombination processes [52] of model compounds were studied by nano-, pico-, and subpicosecond pulse radiolyses. 

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. ... 

Natural Rubber and Synthetic Polyisoprene Polybutadiene and Its Copolymers Polyisobutylene and Its Copolymers Ethylene-Propylene Copolymers and Terpolymers Polychloroprene Silicone Elastomers Fluorocarbon Elastomers Fluorosilicone Elastomers Electron Beam Processing of Liquid Systems Grafting and Other Polymer Modifications... 

The graft polymerization process also applies to other backbone polymers, such as rubbery ethylene-propylene copolymers and amorphous epichlorohydrin polymers. Further work is necessary to bring the resulting products to industrial maturity and to develop their applications. 

Impact-modified polypropylenes are produced by combining the homopolymer with an ethylene-propylene copolymer rubber. Ziegler-Natta processes yield such products in cascaded reactors. The first reactor in the sequence produces a rigid polymer with a high propylene content and feeds the second reactor, where the ethylene-propylene elastomer is polymerized in intimate mixture with the first material. 

HIPP presents a complexmorphology consisting of an ethylene-propylene soft copolymer finely dispersed within a semi-crystalline i-PP. In the Spheripol process [22], this material is produced in two steps. In the first one, i-PP is produced in a slurry of propylene in a loop reactor. In the second one, the ethylene-propylene copolymer is produced in a gas phase reactor. The broad residence time distribution of both the loop reactor and the gas phase reactor leads to an uneven distribution of the ethylene-propylene copolymer among the polymer particles, when single reactors are used in each step. A more even distribution is obtained using two loop reactors in the first step [36,37]. 

The third class of olefin methathesis in Scheme 21.1 is addition metathesis polymerization (ADMET). This reaction is an alternative method to stitch together olefins into polymers, in this case by a combination of dienes with extrusion of ethylene. Control of molecular weight by the ADMET process is less precise than that by ROMP, but this reaction has been used to make polymers with precise architectures, such as polymers that would be perfectly alternating ethylene-propylene copolymers. ... 

Quantitative and qualitative methods were developed to measure the surface mechanical properties of polymers by atomic force microscopies. They were used to study the effects of molding processes and of viscosity on the surface morphology of polypropylene / (ethylene-propylene) copolymer blends (PP/EP). On compression-molded "physical blends", EP nodules are present at the outermost surface while, on injection-molded "reactor blends", they are covered by a PP layer. Resins with high viscosity ratio between EP and PP present heterogeneous surface elastic properties corresponding to the dispersion of spherical EP nodules below the surface. The low viscosity ratio resins have homogeneous surface elastic properties comparable to those measured above EP nodules on high viscosity ratio resins. This is compatible with a fine dispersion of plate-like shaped EP nodules below the surface... 

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