Polyolefins product distribution

Table 1.3b Product distribution in the polyolefins cracking dislribution of C15 and Ratio <15/...

Figure 3.15 Product distributions obtained in the catalytic cracking of a polyolefin mixture over HMCM-41 at different temperatures P/C = 100 f = 30 min) (a) selectivity by groups (b) selectivity by carbon atom number [28]. (Reproduced by permission of the American Chemical Society)...

Recently the pyrolysis of polymer mixtures has become a focus of interest due to the increasing role of plastics recycling. Many researchers have investigated the thermal decomposition of various polymers in the presence of PVC. Kniimann and Bockhom [25] have studied the decomposition of common polymers and concluded that a separation of plastic mixtures by temperature-controlled pyrolysis in recycling processes is possible. Czegfny et al. [31] observed that the dehydrochlorination of PVC is promoted by the presence of polyamides and polyacrylonitrile however, other vinyl polymers or polyolefins have no effect on the dehydrochlorination. PVC generally affects the decomposition of other polymers due to the catalytic effect of HCI released. Even a few per cent PVC has an effect on the decomposition of polyethylene (PE) [32], HCI appears to promote the initial chain scission of PE. Day et al. [33] reported that PVC can influence the extent of degradation and the pyrolysis product distribution of plastics used in the... 

FIG. 47 (a) Amount of citations, (b) Patent production on metallocene catalysts for polyolefins, (c) Distribution of filings. 

The theoretical lower limit of the molecular weight distribution for the diblock OBC is 1.58. The observed MJMn of 1.67 indicates that the sample contains a very large fraction of polymer chains with the anticipated diblock architecture. The estimated number of chains per zinc and hafnium are also indicative of a high level of CCTP. The Mn of the diblock product corresponds to just over two chains per zinc but 380 chains per hafnium. This copolymer also provides a highly unusual example of a polyolefin produced in a continuous process with a molecular weight distribution less than that expected for a polymer prepared with a single-site catalyst (in absence of chain shuttling). 

They are able to polymerize a large variety of vinyl monomers. The polymer microstructure can be controlled by the symmetry of the catalyst precursor. Prochiral alkenes such as propylene can be polymerized to give stereospecific polymers,554 572-574 allowing production of polyolefin elastomers. They can give polyolefins with regularly distributed short- and long-chain branches which are new materials for new applications. 

In addition, in recent years the products themselves have become much more complex and therefore more difficult to process. One example is the bimodal polyolefins, which have excellent mechanical properties and processability at the same time. These properties are achieved by the manufacture of extremely broad to multimodal molecular weight distributions in appropriately equipped reactors [1]. 

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