Crystallization properties of LDPE and LLDPE Crystalline properties Polyethylene is a crystalline po

Crystallization properties of LDPE and LLDPE

Crystalline properties Polyethylene is a crystalline polymer

Polyethylene with different densities also has different degrees of crystallinity. Crystallinity has a linear relationship with density, and they have a significant impact on many properties of polyethylene.

Since the presence of short-chain branches in polyethylene interferes with the crystallization of the main chain, increasing short-chain branches will destroy crystallization and reduce density. Homopolymerized high-density polyethylene contains very few short-chain branches, so it has high crystallinity and high density.

Although LLDPE sheets and LDPE are both linear polyethylene, LLDPE is completely copolymerized of ethylene and α-olefin. Since LLDPE contains more comonomers than high-density copolymers, there are many short branches on the linear main chain of LLDPE, resulting in low crystallinity and low density. Furthermore, the type and number of short chain branches vary with different comonomers. If the comonomer has more carbon atoms and is more abundant in the copolymer, the density of the copolymer will also decrease significantly.