Study on molecular chain heterogeneity of linear low‐density polyethylene by cross‐fractionation of temperature rising elution fractionation and successive self‐nucleation/annealing thermal fractionation

Abstract

ABSTRACT:The molecular chain heterogeneity of commercial linear low-density polyethylene (LLDPE) was investigated by cross-fractionation of temperature rising elution fractionation (TREF) and successive self-nucleation/annealing (SSA) thermal fractionation by use of DSC. The results indicate that the linear relationships between crystallinity or melting temperature and the elution temperature are confirmed by TREF fractions. Intermolecular heterogeneity exists in the original LLDPE, whereas there is less intermolecular heterogeneity in the TREF fractions. After SSA thermal fractionation, the multiple endothermic peaks for both LL-DPE and their TREF fractions are mainly attributed to the heterogeneities of ethylene sequence length (ESL) and lamellar thickness. The statistical terms, including weighted mean L w , arithmetic mean L n , and broad index L w /L n , were introduced to evaluate the heterogeneities of ESL and lamellar thickness of polyethylene. The difference of broadness index indicates that TREF fractions of LLDPE have less inter-and intramolecular heterogeneities of both ESL and lamellar thickness than those of the original LLDPE.

Effect of small amount of ultra high molecular weight component on the crystallization behaviors of bimodal high density polyethylene

“…This technique is based on the sequential application of self-nucleation and annealing steps to a polymer sample originally devised by Fillon et al [32,44,45] and has been widely used to analyze the chain structures of semi-crystallized polymers such as PE and PP [46][47][48][49][50][51]. For a SSA fractionated polymer sample, the final DSC heating run will reveal a distribution of melting points induced by thermal treatment indicating the heterogeneous nature of the chain structures of the polymer.…”

High Speed SSA Thermal Fractionation and Limitations to the Determination of Lamellar Sizes and Their Distributions

“…The above equation assumes that s and Dh are constant as the material is being melted, and the results are highly dependent on the value of T m 0 . A value in the range 141-145.5 8C has been used in the literature for both linear and branched polyethylene, [4,8,9,20] although such a value corresponds to infinitely thick linear polyethylene, and it is well known that the equilibrium melting point is depressed by the introduction of branches in the polyethylene chains. [18] The determination of the equilibrium melting point of HPB and 11U4 by the Hoffman-Weeks method was attempted by employing isothermal crystallization data, and the results are shown in Figure 8.…”

Thermal, dielectric, and mechanical properties of SiC particles filled linear low‐density polyethylene composites

“…where X c is degree of crystallinity, X is mass fraction of filler, DH f specific melting enthalpy of LLDPE andDH 0 f specific melting enthalpy for 100% crystalline polyethylene, which is set as 290 J/g [25][26][27][28] for this calculation.…”