Polypropylene types

There are three types of commercial polypropylene resins iso tactic polypropylene, random copolymer and impact copolymer. Both copolymer types use ethylene as comonomer, but otherwise differ significantly. 

Ziegler-Natta catalysts used for propylene polymerization make mostly isotactic polypropylene with a very small fraction of atactic polypropylene, especially later generation catalysts. Aspecific sites are responsible for the formation of atactic chains in Ziegler-Natta 

Random propylene-ethylene copolymers are produced for applications requiring polymers with lower crystallinity and melting points. Random polypropylene copolymers have, 

This broad homopolymer/copolymer distribution is, sometimes, even visible with the naked eye when examining impact copolymer pellets. Pellets where the homopolymer phase is dominant appear opaque due to their higher crystallinity, while those where the amorphous copolymer is the major component are translucent. 

Even though tubular reactors are not used industrially for the production of impact copolymers, some reactor technologies (such as gas phase horizontal reactors) were developed to narrow the reactor residence time distribution and, consequently, produce impact copolymer with narrower homopolymer/copolymer distributions. 

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Immobilization of lipases on membranes have also been described and several bioreactors were developed (see review, Balcao, Paiva Malcata, 1996). The immobilization can be done by simple physical adsorption of the lipase on hydrophobic hollow fibers or flat sheets where polypropylene types are the preferred e.g. Accnrel or Celgard) (Bouwer, Cupenus Derksen, 1997). 

Application Cleaner type Properties Polypropylene type... 

Show that there are 10 and only 10 stereochemical pentads for a polypropylene-type polymer and list them all. 

Epcos offers epoxy resin sealed metallised polyester (polyethylene terephthlate) film types with the addition of a UL 94 VO plastic case. MetalUsed polypropylene types offered by Epcos are claimed to have very good self-healing properties and a very high pulse strength. 

Filtration. Baths should be continuously filtered to remove impurities. Most manufacturers utilize spiral-wound cylindrical polypropylene-type filters with nominal pore-size ratings. Some manufacturers have decreased or actually eUminated the need to dump selected process baths, such as the brown oxide bath, by using a more expensive absolute-type... 

Santrach [1] observed that HDT values were dependent on the amount and types of film former and lubricant. Fiber glass that has been sized for polyamide gives HDT values of about 240-252°C for nylon 6,6 levels above 50% in the polymer phase of compatibilized blends with polypropylene. However, in polypropylene type fiber glass, the HDT is only about 150-155°C. These observations are consistent with Santrach s comments about the addition of glass fibers to crystalline resins giving... 

When propene is polymerized under free radical conditions the polypropylene that results IS atactic Catalysts of the Ziegler-Natta type however permit the preparation of either isotactic or syndiotactic polypropylene We see here an example of how proper choice of experimental conditions can affect the stereochemical course of a chemical reaction to the extent that entirely new materials with unique properties result... 

Figure 1.2 shows sections of polymer chains of these three types the substituent R equals phenyl for polystyrene and methyl for polypropylene. The general term for this stereoregularity is tacticity, a term derived from the Greek word meaning to put in order. ... 

This type of adhesive is generally useful in the temperature range where the material is either leathery or mbbery, ie, between the glass-transition temperature and the melt temperature. Hot-melt adhesives are based on thermoplastic polymers that may be compounded or uncompounded ethylene—vinyl acetate copolymers, paraffin waxes, polypropylene, phenoxy resins, styrene—butadiene copolymers, ethylene—ethyl acrylate copolymers, and low, and low density polypropylene are used in the compounded state polyesters, polyamides, and polyurethanes are used in the mosdy uncompounded state. 

A common surface cartridge is the pleated paper constmction type, which allows larger filtration areas to be packed iato a small space. Oil filters ia the automobile iadustry are of this type. The paper is impregnated, for strength, with epoxy or polyurethane resia. Any other medium ia sheet form, similar to cellulose paper, such as wool, polypropylene, or glass may be used. 

Olefin Polymers. The flame resistance of polyethylene can be increased by the addition of either a halogen synergist system or hydrated fillers. Similar flame-retarder packages are used for polypropylene (see Olefin polymers). Typical formulations of the halogen synergist type are shown in Table 15 the fiUer-type formulations are in Table 16. 

Lamination Inks. This class of ink is a specialized group. In addition to conforming to the constraints described for flexo and gravure inks, these inks must not interfere with the bond formed when two or more films, eg, polypropylene and polyethylene, are joined with the use of an adhesive in order to obtain a stmcture that provides resistance properties not found in a single film. Laminations are commonly used for food applications such as candy and food wrappers. Resins used to make this type of ink caimot, therefore, exhibit any tendency to retain solvent vapor after the print has dried. Residual solvent would contaminate the packaged product making the product unsalable. 

Fig. 7. Polypropylene stmctures (a) Type I Open Cell stmcture formed at low cooling rates (2400x). (b) Type II "Lacy" stmcture formed at high cooling...

Another use of 4-/ f2 octylphenol is ia the productioa of uv stabilizers. 4-/ f2 -Octylpheaol reacts with sulfur dichloride to yield the thio-hisphenol derivative, which thea reacts with nickel acetate to form 2,2 -thiobis(4-/ f2 octylphenolate)-A/-butylamiQe nickel [14516-71 -3]. This type of stabilizer is widely used in the production of outdoor carpeting based on polypropylene fibers. Nickel compounds give a green discoloration which limits their apphcatioas. A second class of uv stabilizers based on the benzotriazole stmcture. 2-(2 -hydroxy-5 -/ f2 octylphenyl)benzotriazole [3147-75-9] is produced from 4-/ i -octylphenol (55). 

Polymerization Reactions. Polymerization addition reactions are commercially the most important class of reactions for the propylene molecule and are covered in detail elsewhere (see Olefin polymers, polypropylene). Many types of gas- or liquid-phase catalysts are used for this purpose. Most recently, metallocene catalysts have been commercially employed. These latter catalysts requite higher levels of propylene purity. 

Styrene—butadiene elastomers, emulsion and solution types combined, are reported to be the largest-volume synthetic mbber, with 28.7% of the world consumption of all synthetic mbber in 1994 (38). This percentage has decreased steadily since 1973 when SBR s market share was 57% (39). The decline has been attributed to the switch to radial tires (longer milage) and the growth of other synthetic polymers, such as polyethylene, polypropylene, polyester, and polystyrene. Since 1985, production of SBR has been flat (Table 3). 

The incorporation of metal salts of amphoteric surface active agents (Mostat Series) as internal antistatic agents in polypropylene fibers has been reported (95). Metal salts of alanine, amidoamine, and imida2oiine-type amphoteric surface-active agents show excellent performance as internal antistatic agents and also improve the dyeing abiUty of the fibers with acid dyes. 

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