Ethylene-propylene copolymers strength

More recently, modified fluoroplastics such as fluorinated ethylene/propylene copolymer, polychlorotrifluoroethylene, and polyvinylidene fluoride have been offered by DuPont, Allied Chemical, 3M, and Pennwalt respectively, to provide improved processability and mechanical strength at some sacrifice in heat-resistance, electrical properties, and chemical resistance and at prices of 3.70-7.15 these have also been finding appropriate if smaller markets. 

Figure 13.9. Elastomer content vs. impact strength of polypropylene containing 15% talc and maleic anhydride modified ethylene-propylene copolymer. [Data from Yu Long, Shanks R A, J. Appl. Polym. Sci., 61, No. 11, 1996,1877-85.]...

FIGURE 12.2 Variation in tensile strength of unvulcanized, compounded blends of ethylene-propylene copolymer due to differences in molecular weight distribution. 

Fluoriuated Ethylene Propylene Copolymer Thermoplastic copolymer of tetrafluoroethylene and hexafiuoro-propylene. Has deereased tensile strength and wear and creep resistanee, but good weatherability, dielectric properties, fire and ehemical resistance, and friction. Decomposes above 204°C (400°F), releasing toxic products. Processed by molding, extrusion, and powder coating. Used in chemieal apparatus liners, pipes, containers, bearings, films, eoatings, and cables. Also called FEP. 

Common examples of miscible blends are ethylene-propylene copolymers of different composition that result in an elastomer comprising a semicrystalline, higher ethylene content and an amorphous, lower ethylene content components. These blends combine the higher tensile strength of the semicrystaUine polymers and the favorable low temperature properties of amorphous polymers. Chemical differences in miscible blends of ethylene-propylene and styrene-butadiene copolymers can also arise from differences in the distribution and the type of vulcanization site on the elastomer. The uneven distribution of diene, which is the site for vulcanization in blends of ethylene-propylene-diene elastomers, can lead to the formation of two distinct, intermingled vulcanization networks. 

Polypropylene, 100 parts PP, blended with 8-25 parts of amorphous ethylene-propylene copolymer, EPR, and 2-10 parts crystalline EPR showed improved impact strength. In the Idemitsu patent, PP was blended with maleated LDPE, EVAc, and inorganic filler, to give blends with good melt strength and rigidity... 

Semicrystalline ethylene-propylene copolymer, EP, was blended with amorphous EP and inorganic filler. The blends had good processability, mechanical properties, and impact strength. In the Mitsubishi patent, crystalline EP was blended with styrene-isoprene block copolymer, 5-30 wt% SIS, and polystyrene, 3-5 wt% PS, to give good paintability... 

Semicrystalline polyolefin blends and method of their preparation were described. The blends were reported to show enhanced inter-spherulitic and interlamellar strength. The first polymer should have higher crystallinity and crystallization temperature than the second. Thus, 50-99.9 wt% PP was blended with ethylene-a-olefin copolymers, either a stereo block polypropylene or an ethylene-propylene copolymer, EPR... 

These are the first patents on PP/PE/EPR blends. Polypropylene/polyethylene, PP/PE, blends were compatibilized by addition of ethylene-propylene copolymer, EPR. The resulting blends showed improved low-temperature brittle point and Izod impact strength. In UCC patent, 50-96 wt% was blended with 2-25 wt% PE and 2-25 EPR and/or PIB... 

Polypropylene, PP, or polyethylene, PE, was blended with ethylene-propylene copolymer, EPR, and ethylene-acetoxybicycloheptene copolymer, to increase impact and tensile strength, as well as brittle resistance. In the later patent, PP and EPR were separately dissolved then blended, precipitated, and processed. The blends showed fine, uniform dispersion of the rubber phase, resulting in superior mechanical properties... 

Polypropylene, PP, or poly (pentene-co-propylene) was reactor blended with ethylene-butene or ethylene-pentene copolymer. The product was melt blended with PP to give material with improved performance. In the second patent, ethylene-propylene copolymer, EPR, was blended with PP. The alloys showed good mechanical properties. In the Sumitomo patent, to improve impact strength, PP was blended with 5-30 wt% of either polyhexene or polyoctene... 

Polyamides and saturated polyesters can be toughened with ABS, ethylene-propylene copolymers/terpolymers or EPDM rubbers grafted with maleic anhydride to increase the dispersion and adhesion of the modifier. Styrene-butadiene copolymers are also effective. The notched Izod impact strength of polyamide 6-6 can be increased more than 20-fold by impact modifiers, whereas short glass fibres often reduce the impact strength, even though they increase the modulus. 

It can be seen in Table 4.3 that electrical properties cover a wide range and thus the volume resistivity of various polymers is between 2 ohm.cm for epoxy resins to 10 ohm.cm for fluorinated ethylene-propylene copolymer. Similarly, dielectric strength is in the range from 12 mV/m for urea-formaldehyde resins to 55 mV/m for fluorinated ethylene-propylene copolymer and 60 mV/m for PA 12. 

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