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The influences of branch content (BC) and composition distribution (CD) of hexene linear low-density polyethylene (LLDPE) on its miscibility with low-density polyethylene (LDPE) were investigated. Ziegler -Natta (ZN) and metallocene-LLDPE (m-LLDPE) were used to study the melt miscibility using rheological tools. Dynamic, steady shear and transient measurements were carried out in an ARES rheometer at 190 8C. The miscibility was revealed by the dependence of their h o ; h 0 ðvÞ; G 0 ; and N 1 ð _ gÞ on blend composition. The CD of LLDPE has influenced its miscibility with LDPE. The ZN-LLDPE blend with LDPE was found to be more miscible than an m-LLDPE of the same M w and similar BC. On the other hand, a high-BC m-LLDPE (32.2 CH 3 /1000 C) was found to be more miscible with LDPE than a low-BC m-LLDPE (14.4 CH 3 /1000 C) of the same M w and MWD. The high-BC m-LLDPE blends with LDPE were partially miscible and immiscibility is likely to develop in LDPE-rich blends. Agreement was observed between the measured rheology and theoretical predictions of Einstein, Scholz et al., Palierne, and Bousmina emulsion models. q

Summary: The influences of short chain branching (SBC) on the melt miscibility of low‐density polyethylene (LDPE) with linear high‐density polyethylene (HDPE) were investigated by rheological methods. Two LDPE resins with different branch contents were blended with the same linear HDPE. Dynamic and steady shear measurements were carried out using a Rheometrics ARES rheometer at 190 °C. The rheology of the low‐SCB LDPE (9 CH3/1 000 C) blends with HDPE can be predicted by the linear additivity rule. Hence, blends were suggested to be completely miscible at all compositions. However, blends of the high branch content LDPE (SCB = 19 CH3/1 000 C) were completely immiscible. Also, the different viscous and elastic properties of all the immiscible blends were much higher than the corresponding values for the more viscous and elastic blend component. The ratio of interfacial tension to droplet radius was estimated from Scholz et al. model as ≈1 500 N · m−2. The level of SCB in LDPE was found to have a strong influence on its miscibility with linear HDPE.Cole‐Cole plot for blends of LDPE1 with HDPE.magnified imageCole‐Cole plot for blends of LDPE1 with HDPE.

ABSTRACT:The effect of the branch content (BC) and composition distribution (CD) of linear low-density polyethylene (LLDPE) on the thermal and mechanical properties of its blends with LDPE were studied. All blends and pure resins were conditioned in a Haake PolyDrive blender at 190°C and in the presence of adequate amounts of antioxidant. Two metallocene LLDPEs (m-LLDPE) and one Ziegler-Natta (ZN) hexene LLDPE were melt blended with the same LDPE. The effect of the BC was investigated by blending two hexene m-LLDPEs of similar weight-average molecular weights and molecular weight distributions but different BCs with the same LDPE. The effect of the CD was studied by using a ZN and an m-LLDPE with similar weight-average molecular weights, BCs, and comonomer type. Low-BC m-LLDPE blends showed separate crystallization whereas cocrystallization was observed in the high-BC m-LLDPE-rich blends. However, ZN-LLDPE/LDPE blends showed separate crystallization together with a third population of cocrystals. The influence of the crystallization behavior was reflected in the mechanical properties. The BC influenced the modulus, ultimate tensile strength, and toughness. The addition of a small amount of LDPE to a low-BC m-LLDPE resulted in a major improvement in the toughness, whereas the results for the high-BC pair followed the additivity rule. ZN-LLDPE blends with LDPE blends were found to be more compatible and exhibited superior mechanical properties compared to m-LLDPE counterparts with the same weight-average molecular weight and BC. All mechanical properties of ZN-LLDPE blends follow the linear rule of mixtures. However, the CD had a stronger influence on the mechanical properties in comparison to the BC.

Reaction between low molecular weight highly functionalized maleic anhydride grafted polyethylene and several diamines were carried out using xylene as a reaction media. The influence of varying the amine to maleic anhydride (NH 2 /MAH) molar ratio and chain length of diamine on reaction was investigated. It was shown that the reactions of these materials cannot be followed by FTIR measurements alone. In these examples, colorimetric titrations were used to assess residual acid/ anhydride content that was not detected by FTIR. The reaction between anhydride and amine was observed to be fast. The degree of reaction and crosslinking in the reactor was observed to depend on the concentration of the reaction mixture and the NH 2 /MAH molar ratio. In some cases, a gelatinous insoluble mass was produced in the reactor and this material was not easily processed for further characterization. All soluble reaction products obtained were observed to be thermoplastic and could be melt processed at elevated temperatures. However, further reaction and crosslinking of these materials occurred during processing to produce thermosets, as demonstrated by rheological measurements and sintering experiments.