Influence of Ethylene-1-Alkene Copolymers Microstructure on Thermo-Rheological Behavior of Model Blends for Enhanced Recycling

Abstract

Polyethylenes (PE) are the most commonly occurring ingredients for post-consumer recyclates (PCR). The structure–property relationships of different types of model PE-based blends are established using multiple thermo-rheological analyses. Although considered “simple”, the complex behavior of model PE-based blends is experimentally demonstrated for the first time for metallocene-catalyzed, linear, low-density polyethylenes (mLLDPE) with different microstructures that are commonly encountered in PCR. During non-isothermal crystallization, the microstructure of mLLDPE predominantly influences the interaction between mLLDPE and LDPE. Based on the mLLDPE microstructure, the molten LDPE phase acts either as a nucleating agent or as a crystallization rate promoting agent. Both rheological and thermal analyses show that higher activation energy is required for the reptation or movement of polymer chains in a highly branched microstructure with long chain branching (LCB) compared to a linear microstructure with short chain branching (SCB). The quasi-melt response, as measured by thermal analysis under non-isothermal conditions, is distinctly different and sensitive to both the SCB and LCB present in the LLDPE/LDPE blends.

Critical insights into ethylene‐1‐alkene copolymers and long‐chain branched polyethylene microstructure on thermo‐rheological and sealing behavior of multicomponent systems

“…It is known that LDPE shows a higher shear thinning behavior, mainly due to LCB in its microstructure as compared to linear mLLDPE. [ 11 ] The density and MI 2 of mLLDPE‐3 are closely matching with mLLDPE‐1 and mLLDPE‐2 matrices and yet mLLDPE‐3 has relatively more pronounced shear thinning behavior compared to mLLDPE‐1 and mLLDPE‐2. This indicates the possible presence of LCB in mLLDPE‐3.…”

“…It has been previously reported that the microstructure of mLLDPE‐3 possibly contains LCB‐type architecture. [ 11,12 ] Based on these observations, it can be inferred that mLLDPE‐3 possibly contains LDPE‐T‐like LCB architecture in its polymer chain microstructure.…”

“…Comonomer type, total comonomer content, and SCB/1000 C from nuclear magnetic resonance spectroscopic (NMR) analysis of all mLLDPE are provided in Table 2. [11] 2.2 | Experimental methods…”

“…Based on the mLLDPE microstructure, the molten LDPE‐T phase acts either as a nucleating agent or as a crystallization rate‐promoting agent. [ 11 ]…”

“…[8][9][10] During non-isothermal crystallization, the microstructure of mLLDPE predominantly influences the interaction between mLLDPE and LDPE-T. Based on the mLLDPE microstructure, the molten LDPE-T phase acts either as a nucleating agent or as a crystallization rate-promoting agent. [11] It has been shown that the rheological behavior of the mLLDPE + LT systems was sensitive to LDPE concentration and the presence of LCB in the LLDPE microstructure. [12] The thicker lamellae of LDPE co-crystallize with a high density polyethylene-like fraction of LLDPE.…”