Polyolefin average molecular weight

Hartwig and Hillmyer have recently reported the Rh-catalyzed borylation of polyolefins to yield boronate-functionalized polymers (58) (Fig. 37) in a single step.83 The number-average molecular weight of the borylated polymer that was obtained at a B2pin2 polyethylethylene ratio of 0.3 was found to be the highest (Mn = 52,000 and PDI = 1.09) among the developed boronate-functionalized polyolefins. 

The BP process [7] is based on a sand fluidized-bed pyrolysis reactor. The cracking temperature is kept at 400-600°C. Low-molecular hydrocarbons can be obtained. The process mainly involves converting waste plastics into normal linear hydrocarbons, the average molecular weight of which is 300-500. Most plastics can be treated by this process. Polyolefins are decomposed into small molecules with the same linear structure. PS is converted into styrene monomers and PET into mixture of hydrocarbons, carbon monoxide and carbon dioxide. A maximum of 2% PVC is allowed in this process, and the content of chlorine in the products is lower than 5 ppm. The distribution of alkene products in this process is like that in petroleum pyrolysis. The BP process was industrialized in 1997. 

Low molecular weight polyolefine. Low molecular weight polyolefins are primarily used in CPET for rapid crystallization of otherwise amorphous material. These products are typically sold by the CPET suppliers in a package along with the base resin. Use levels are higher than with the sorbitols and average 1 to 3% of the resin. The major application is in... 

In mechanochemical processes, an alteration of MWD is generally superimposed on the change in average molecular weight. The changes in MWD are both fundamentally and practically important. The former involves an understanding of the mechanism of mechanochemistry (see Section A of this chapter). The latter influences processability, physical and mechanical properties and, in general, the use performance of polymers. The claim has been made that mechanochemistry controls the MWD of already-prepared polystyrene and polyolefins much better than thermal oxidation, which impairs the mechanical properties [1]. 

Here A,- is the number of molecules of molecular weight Mj. Methods are well established for measurement of these two average molecular weights and for examining the entire molecular weight distribution (MWD) of macromolecules. These characterization techniques employ dilute polymer solutions, and thus special difficulties are encountered with the many polyolefins that are semicrystalline in the vicinity of room temperature and soluble only at temperatures where thermal degradation can occur. 

Number-average molecular weights, for polyolefins are most conveniently measured via colligative... 

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