Polypropylene block

Block sheiir strength of ECA on polypropylene blocks with different amines as primers. 

Metallocene catalysts produce high-comonomer content products, such as polypropylene block... 

Polypropylene block and graft copolymers are efficient blend compatibilizers. These materials allow the formation of alloys, for example, isotactic polypropylene with styrene-acrylonitrile polymer or polyamides, by enhancing the dispersion of incompatible polymers and improving their interfacial adhesion. Polyolefinic materials of such types afford property synergisms such as improved stiffness combined with greater toughness. 

Various types of well-defined block copolymers containing polypropylene segments have been synthesized by Doi et al. on the basis of three methods (i) sequential coordination polymerization of propylene and ethylene 83-m>, (ii) transformation of living polypropylene ends to radical or cationic ones which initiate the polymerization of polar monomers 104, u2i, and (iii) coupling reaction between iodine-terminated monodisperse polypropylene and living polystyrene anion 84). In particular, the well-defined block copolymers consisting of polypropylene blocks and polar monomer unit blocks are expected to exhibit new characteristic properties owing to the effect of microphase separation. 

Well-defined diblock (P—R) and triblock (P R — P) copolymers consisting of the polypropylene block (P) and the ethylene-propylene random copolymer block (R) were prepared by adding ethylene monomer during the living coordination polymerization of propylene with the soluble V(acac)3/Al(C2H5)2Cl/anisole catalyst U1). 

A typical electrode for tear-seal work would be hinged on a top plate, the hinges insulated (for example, by polypropylene blocks) a lay-up then is placed on the bottom plate, the unit closed and fitted under the head for welding. Hinged systems such as this have many applications—as in making pre-cut covers for books, where card or board inserts must be placed as close to the electrode as possible, to ensure a close fit after welding. 

Effect of Substrate. Several comparisons were made to establish the effect of substrate on conversion of methylvinylpyridine and acrylonitrile. Relative effectiveness in the ethylene-propylene series were ethylene-propylene copolymer > polyethylene > polypropylene on a relativity scale of 4 3 2. The fact that chains terminated with polyethylene blocks are better substrates than polypropylene blocks suggests that random grafting on the backbone is not a major part of the reaction at low polymerization temperatures. The higher conversion on polyethylene... 

The polymer composition for both EPM and EPDM is usually in the 40/60 to 60/40 ethylene/propylene ratio. Outside these ranges, the polymer will start to crystallize because of either polyethylene or polypropylene blocks. 

The parallel plate cell is constructed in two halves each with two electrodes Anode-Cathode (100 cm2 surface each) inlaid in polypropylene blocks. On one of the halves inlet and outlets were provided for circulation of the electrol3d . The interelectrode gap was 4 mm (thickness of the viton gasket). 

Similar results were found when a polypropylene-block-poly(propylene glycol), PP-b-PPG, diblock copolymer was utilized as compatibilizer its ability to increase the interlayer distance of PP/dimethyl dioctadecyl ammonium-modified montmorilonite hybrids was studied and compared with the corresponding behavior of PP-g-MA [55]. The ratio of compatibilizer to organoclay used was low but nevertheless 2 wt% of PP-b-PPG resulted in a 4A increase of interlayer distance, which was better than what was observed utilizing maleated PP under the same conditions. 

POM Polyoxymethylene PPBC Polypropylene block copolymer PPHP Polypropylene homopolymer PPS Polyphenylene sulphide PPO Polyphenylene oxide PS Poly styrene... 

Thermoplastic polyolefin (TPO) is a generic name that refers to polyolefin blends usually consisting of some fraction of polypropylene (PP), polyethylene (PE) or polypropylene block copolymer (PP-b-EP or BCPP ), and a thermoplastic olefinic rubber, with or without a mineral reinforcing filler such as talc or wollastonite. Common rubbers include ethylene propylene rubber (EPR), EPDM rubber, ethylene-octene (EO) copolymer mbber, ethylene-butadiene (EB), and styrene-ethylene-butadiene-styrene (SEBS) block copolymer rubbers. Currently, there are a great variety of commercial polypropylene homopolymers, PP block copolymers, and olefinic rubbers available to make a wide range of TPO blends with densities ranging from 0.92 to 1.1. 

Table 6.8 The effect of bismaleimide structure on the mechanical properties of a 60% w/w magnesium hydroxide-filled polypropylene block copolymer [31].

J. Elastomers Plast. 9(7), 281 (1977). Thermoplastic IPNs. Block Copolymers blended with polypropylene. Block copolymers blended with polyethylene. 

FIGURE 7.21 Superposition of ion pair (solid line) and bare cation (dashed line) insertion transition state models for isotactic polypropylene block formation with 6r/6r MA09. 

FIGURE 8.13 Sawhorse representation of two isotactic polypropylene blocks with same (a) or opposite (b) relative configurations separated by a short stereoirregular sequence. 

In block copolymers the polypropylene block(s) constitute the hydrophobic part and the polyethylene block(s) the hydrophilic part. Random copolymers do not have identifiable hydrophobic or hydrophilic parts. 

Melt blending of polymers is a widely used technique for tailor-making polymeric materials to generate the desired properties. Blending polypropylene block copolymer (PPBC) with elastomeric ethylene-propylene-diene terpolymer (EPDM) produces a range of useful materials commercialized in early 1970 s that found significant uses in the automotive industry. Polyolefin-based bumpers dominate the automobile market in Europe and Japan and have made in-roads in the North American market. In India, the polyolefin blend for car bumpers was commercialized in 1992. 

Polypropylene block copolymer (produced by Indian Petrochemicals Corporation Ltd.) and EPDM (produced by Herdillia Unimers Ltd.) are the base polymers used in preparing the polyolefin blend. 

Fig. 2.19 TEM micrographs of (a) a sphemlite centre in a thin film of high density polyethylene stained with RUO4, (b) section of polyethylene-atactic polypropylene block copolymer stained with RUO4. Reproduced with permission (a) from Figure 15 in Trent, Scheinbeim and Couchman, Macromolecules, 1983, 16 589-598 (Copyright 1983) American Chemical Society, (b) fi om Figure 3 in Hong, Copyright (2001) with permission from Elsevier...

There has been some initial success in forming block copolymers using singlesite catalysts. These catalysts have to show no or only a slow chain transfer reaction, like living systems [132]. In a first step, only propylene is polymerized, forming a hard polypropylene block, then by addition of ethene a soft ethene/propene copolymer or a polyethylene block follows because ethene is inserted much faster. 

Hot-melt adhesives are 100% solids that, in the broadest sense, include all thermoplastic polymers. Polymers that are primarily used as hot-melt adhesives include ethylene-vinyl acetate copolymers (EVA), polyvinyl acetates (PVA), polyethylene (PE), amorphous polypropylene, block copolymers (thermoplastic elastomers), polyamides, and polyesters. The oldest hot-melt adhesive, which has been in use since early times, is sealing wax. In principle, glutins and glue jellies also may be regarded as hot-melt adhesives. However, modern hot-melt adhesives are primarily synthetic products. The simplest hot-melt adhesives are rosin-wax mixtures. But these products have limited strength and thermal stability. 

Recent progress has also been made in the area of homo- and copolymerization of polar monomers. For instance, metallocene catalysts copolymerize ethene with 11-undecene-l-ol to yield hydroxy-functional LLDPE exhibiting improved adhesion [29]. Metallocenes based upon lanthanoids, as developed by Yasuda et al, copolymerize non-polar and polar monomers to produce new families of block copolymers, e.g., polypropylene-block-polymethylmethacrylate [30]. 

Ruan W H, Zhang M Q, Rong M Z and Friedrich K (2004) Mechanical properties of nanocomposites from ball milling grafted nano-silica/polypropylene block copolymer, Polym Polym Compos 12 257-267. 

Kai ger-Kocsis J and Kiss L (1987) Dynamic mechanical properties and morphology of polypropylene block copolymers and polypropylene/elastomer blends, Polym Eng Sci 27 254-262. 

Busico, V., Cipullo, R., Friederichs, N. etal. (2003) The first molecularly characterized isotactic polypropylene-block-polyethylene obtained via quasi-hving insertion polymerization. Macromolecules, 36,3806-3808. 

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