Polypropylene molecular weight

Baramboim and coworkers (93-95, 95 bis) obtained graft copolymers based on polyamides. The extrusion of a polypropylene polycaprolactam mixture at 200-210° C changed the polypropylene molecular weight and formed a block and graft copolymer of linear and three dimensional structure. Investigations showed the radical nature of the process and that the amount of the resulting copolymer was proportional to the intensity of mechanical shear. 

Similar conclusions have been reached on the basis of studies with TiClj and amines (69). These catalysts polymerize propylene at a slow rate to highly isotactic polymers. The active site was long lived because polypropylene molecular weight increased with polymerization time over a long period. Mechanism studies (70) with the TiClj-Et N and Ziegler catalysts indicate a close resemblance and support the view that both catalyst types operate by propagation at a transition metal-carbon bond. 

REQUIREMENTS ON FIBER-FORMING POLYPROPYLENE Molecular weight... 

FIGURE 3.9 Pressure-weight fraction plot of polypropylene(l)-diisopropyl ketone(2) at T = 318 K. Polypropylene molecular weight = 20,000. Comparison of experimental data with the predictions of original (solid line) and the simplified version (dotted line) of PC-SAFT. In both curves, the interaction parameter kij = 0. (From Fluid Phase Equilib., 215, Kouskoumvekaki, I. A., von Solms, N., Michelsen, M.L., and Kontogeorgis, G.M., Application of a simplified perturbed chain SAFT equation of state to complex polymer systems, 71-78, Copyright 2004, with permission from Elsevier.)... 

Bridge Substituents and Syndiotactic Polypropylene Molecular Weight... 

Baramboim and Rakityanskii [136-139] produced graft copolymers based on polyamides. The extrusion of a polypropylene-polycaprolactam mixture at 200-210°C produced radicals with a resultant change in polypropylene molecular weight and formation of block and graft copolymers. The intensity of degradation and, consequently, the extent of polypropylene reaction decreased with an increase in the amount of polyamide in the mixture as noted by a reduction of the mixture melt viscosity. Radical acceptors interfere with copolymerization by interacting with the macroradicals [139]. 

TABLE 8.9. Polypropylene Molecular Weight Control with Hydrogen. 

The thermal degradation of mixtures of the common automotive plastics polypropylene, ABS, PVC, and polyurethane can produce low molecular weight chemicals (57). Composition of the blend affected reaction rates. Sequential thermolysis and gasification of commingled plastics found in other waste streams to produce a syngas containing primarily carbon monoxide and hydrogen has been reported (58). 

Fig. 7. Shear viscosity at 180°C of polypropylene of different molecular weight and distribution vs shear rate (30) see Table 4 for key. Pa-s = 0.1 P...

Table 4. Molecular Weight Characterization Data for Polypropylene Samples ...

After the discovery of isotactic polymerisation of propylene using shconocene catalysts, stmcturaHy analogous hafnium catalysts produced from hafnium tetrachloride [13499-05-3] were found to produce high yields of high molecular weight polypropylene (55), but not enough to lead to commercial development. 

Petroleum resins are low molecular weight thermoplastic hydrocarbon resins synthesized from steam cracked petroleum distillates. These resins are differentiated from higher molecular weight polymers such as polyethylene and polypropylene, which are produced from essentially pure monomers. Petroleum resin feedstocks are composed of various reactive and nonreactive aliphatic and aromatic components. The resins are usually classified as C-5... 

Molecular Weight. The molecular weight of polypropylene is typically determined by viscosity measurements. The intrinsic viscosity [Tj] of the polymer in solution is related to the molecular weight, Af, by the Matk-Houwink equation ... 

The value of the glass-transition temperature, T, is dependent on the stereoregularity of the polymer, its molecular weight, and the measurement techniques used. Transition temperatures from —13 to 0°C ate reported for isotactic polypropylene, and —18 to 5°C for atactic (39,40). 

Carbon Cha.in Backbone Polymers. These polymers may be represented by (4) and considered derivatives of polyethylene, where n is the degree of polymeriza tion and R is (an alkyl group or) a functional group hydrogen (polyethylene), methyl (polypropylene), carboxyl (poly(acryhc acid)), chlorine (poly(vinyl chloride)), phenyl (polystyrene) hydroxyl (poly(vinyl alcohol)), ester (poly(vinyl acetate)), nitrile (polyacrylonitrile), vinyl (polybutadiene), etc. The functional groups and the molecular weight of the polymers, control thek properties which vary in hydrophobicity, solubiUty characteristics, glass-transition temperature, and crystallinity. 

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