Short-chain branch distribution SCBD

A scheme of the extended chain molecular population and branching in an LLDPE resin is shown in Fig. la, where it is seen that the larger the molecule the lower chances of comonomer incorporation (lower branch content). Most interesting in LLDPE is the bimodality of the CCD, sometimes referred to as the short-chain branching distribution (SCBD), as shown in Fig. lb, due to the population discontinuity observed between (1) the fraction of linear molecules, practically excluding the comonomer incorporation in certain catalyst sites, and (2) the remaining fractions with increasing amounts of comonomer incorporated. Catalyst sites, where the bulkier and less reactive comonomer can be incorporated. 

Chu K-J, Soares IBP, Penlidis A (2000) Variation of molecular weight distribution (MWD) and short chain branching distribution (SCBD) of ethylene/1-hexene copolymers produced with different in-situ supported metallocene catalysts. Macromol Chem Phys 201 340-348... 

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