Linear and Short Branched Polyethylene Blends

A similar branching effect on the miscibility was observed in the HDPE/ LLDPE-O blends, which were prepared from HDPE (49,400 and 3.60 PDI) and LLDPE-O polymers (69,200-104,000 M and 1.8-3.40 PDI) with 2-87 hexyl branches per 1000 backbone carbons (42). It was observed that the critical branch number in the LLDPE-O component capable of causing immiscibility in the HDPE/ LLDPE-O blend was 50 branches per 1000 backbone carbons, as determined using inverse gas chromatography, rather than the SANS technique. 

The miscibility of HDPE/LLDPE blends was also studied using differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), rheological analysis, excimer fluorescence analysis, and transmission electron microscopy (TEM). Lee et al. (43) studi blends of HDPE (121,000 an 6.8 PDI) 

As reviewed above, the miscibility of the HDPE/LLDPE blends seems to depend on the molecular weight, polydispersity, composition, and temperature, as well as on the branch content and length of the components. However, the HOPE and LLDPE samples used in the blend studies were limited to certain ranges of molecular weight, polydispersity, and branch content. Further, there was a distinct lack of information regarding the phase diagram. Therefore, more quantitative analysis is still needed in order to completely understand the miscibilities and phase diagrams of HOPE/ LLDPE blends. 

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