Polyolefin molecular stmcture

Nonpolar - In molecular stmcture, a molecule in which positive and negative electrical charges coincide. Most hydrocarbons, such as polyolefins, are nonpolar. 

For typical random polyolefins, the molecular stmcture can be determined by measuring a few key properties, such as composition, molecular weight, and molecular weight distribution. These same features can be measured for OBCs, but isolated measurements are not sufficient to characterize a block structure. A combination of techniques must be used to confirm that a material is an OBC. The following section describes several characterization techniques that provide evidence of the block stmcture of OBCs and provides illustrative examples. 

Analytical and test methods for the characterization of polyethylene and PP are also used for PB, PMP, and polymers of other higher a-olefins. The C-nmr method as well as k and Raman spectroscopic methods are all used to study the chemical stmcture and stereoregularity of polyolefin resins. In industry, polyolefin stereoregularity is usually estimated by the solvent—extraction method similar to that used for isotactic PP. Intrinsic viscosity measurements of dilute solutions in decahn and tetraHn at elevated temperatures can provide the basis for the molecular weight estimation of PB and PMP with the Mark-Houwiok equation, [rj] = KM. The constants K and d for several polyolefins are given in Table 8. 

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