Effect of chain blockiness on the phase behavior of ethylene‐octene copolymer blends

Abstract

New challenges and opportunities for polyolefin blends arise from the recent introduction of olefin block copolymers (OBCs). In this study, the effect of chain blockiness on the miscibility and phase behavior of ethylene-octene (EO) copolymer blends was studied. Binary blends of two statistical copolymers (EO/EO blends) that differed in comonomer content were compared with blends of an EO with a blocky EO copolymer (EO/OBC blends). The blends were rapidly quenched to retain the phase morphology in the melt and the phase volumes were obtained by atomic force microscopy (AFM). Two EOs of molecular weight about 100 kg/mol were miscible if the difference in octene content was less than about 10 mol % and immiscible if the octene content difference was greater than about 13 mol %. The blocky nature of the OBCs reduced the miscibility and broadened the partial miscibility window of the EO/OBC blends compared with the EO/EO blends. The EO/OBC blends were miscible if the octene content difference was less than 7 mol % and immiscible above 13 mol % octene content difference. It was also found that the phase behavior of EO/OBC blends strongly depended on blend composition even for constituent polymers of about the same molecular weight. Significantly more demixing was observed in an OBC-rich blend (EO/OBC 30/70 v/v) than in an OBC-poor blend (EO/OBC 70/30 v/v). An interpretation based on extractable fractions of the OBC described the major features of the EO/OBC (30/70 v/v) blends. V V C 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys

Regulation of crystalline morphologies and mechanical properties of olefin multiblock copolymers by blending polymer with similar architecture of constituent blocks

“…It is synthesized by the Dow Chemical Company via chain shuttling technology, in which two catalysts with different octene-selectivity and chain shuttling agent allowing for changing between the two catalysts are indispensable. [25][26][27][28][29][30] Although the hard and soft blocks of OBC are distinct in comonomer content, they are comparatively short and can be partially miscible in the melt. On the other hand, the hard blocks are long enough to form chain-folded lamellar crystals with a relatively high melting temperature.…”

Correlation of miscibility and mechanical properties of polypropylene/olefin block copolymers: Effect of chain composition

“…This may explain the decreased T g of iPP component in the blends. Noting that the fraction of soft segment rich polymers is about 8 ∼ 10 wt %,17 the iPP T g decrease is slight. Furthermore, one would expect that the small amount of extractable soft segments would have a trivial influence on the crystallization and melting behaviors of iPP.…”

“…In addition to the molecular weight distribution, block length and the number of blocks distribution from multiblocks to diblocks, OBCs can contain hard segment rich and soft segment rich polymers 39, 40. In a recent study, it was suggested that the extraction of hard or soft segment rich polymers reduced the miscibility and broadened the partial miscible window of OBC/EO blends compared with the EO/EO blends 17. Turning to this study, soft segment rich polymers could also play an important role in the miscibility of iPP/OBC blends.…”

“…In the present research, it is hypothesized that the soft segment composition of OBC can be tuned to control compatibility with iPP, while the hard segments, having similar chain architecture to linear low density polyethylene (LLDPE), are expected to be incompatible with iPP 13–16. A recent study showed that chain blockiness had an influence on the phase behavior of EO copolymer blends 17. In a previous study,18 we reported that OBC had better compatibility with iPP than random EO with similar density and crystallinity.…”

Droplet‐in‐Droplet Polymer Blend Microstructures: a Potential Route Toward the Recycling of Co‐mingled Plastics

“…The OBC consists of crystallizable hard blocks with very low octene content alternating with amorphous blocks with high octene content configured through short side chains branches to a high density ethylene backbone. The hard block composition has been estimated at 40 mol% with a weight‐average molecular weight of 21 kg mol −1 whereas the soft blocks have a weight‐average molecular weight of 16 kg mol −1 42. Considering an entanglement molecular weight of 1.2 and 7 kg mol −1 for the high density polyethylene and polypropylene respectively, a good interpenetration of the OBC at the HDPE/PP interface is expected 43…”