(21b) USING Nanclays AS BOTH Compatibilizer and Reinforcing Filler for Immiscible POLYMER Blends: Toword MAKING the PLASTIC Waste RECYCLING Industry MORE COST EFFECTIVE

Plastic waste products accumulate annually in the environment in huge quantities worldwide and need proper waste management and cost-effective recycling approaches.  One innovative polymer recycling approach is to fill a polymer blend (composed of more than homopolymer waste) with low loading of inorganic filler of high aspect ratio such as nanoclays, aiming to conceptually enhancing both the miscibility and the bulk properties of the recycled polymer blend at the same time. This recycling approach has two advantages.  First, it eliminates the need of for adding a costly conventional copolymer compatibilizer to the system.  Second, combining nanoclays with recycled polymer blends could produce advanced materials with broad range of properties by combination of the advantages of polymer blends (such as low cost and easy processability) with the superior merits of nanoclays (such as high stiffness and thermal stability, flame retardancy, and gas-barrier properties). This study evaluated the possibility of improving the compatibility and properties of immiscible polymer blends made of polypropylene (PP) and poly (ethylene oxide) (PEO) by the incorporation of nanoclays as additives.  The selected nanoclay type was Cloisite^® 10A, with its surface organically modified with 2MBHT (dimethyl benzyl hydrogenated tallow quaternary ammonium).  The blends were prepared by melt-blending method, with fixing the PP/PEO mass ratio at 70/30 but with varying the loading of nanoclays from 0 to 10 wt%.  Tensile mechanical testing, rheological testing, Scanning Electron Microscopy (SEM) and Differential Scanning Calorimetry (DSC) were used to characterize the resulting nanocomposites.  SEM confirmed that the presence of Cloisite^® 10A in the PP/PEO blend reduced the domain size of the minor phase (PEO) significantly, suggesting that Cloisite^® 10A is acting here as a true compatibilizer for the PP/PEO system.  Tensile mechanical testing showed the considerable increase in the stiffness as the loading of Cloisite^® 10A increased, suggesting that Cloisite^® 10A is also acting here as a reinforcing filler for the PP/PEO system.  Rheological testing showed the considerable increase of storage modulus of the blends as the loading of Cloisite^® 10A increased, with clear plateau observed at low frequency range for 5 wt% and above nanoclay-filled samples, indicating a pseudo solid-like behavior and the network formation of nanaoclays for the filled samples inside the host matrix. An interesting observation was also noticed as revealed by DCS: while fractionated crystallization was observed for unfilled PP/PEO samples, it was totally absent for the case of nanoclays-filled PP/PEO system filled at 5 wt% loading and above. These results suggested that Cloisite^® 10A, in addition to play a conventional role of reinforcing filler by increasing the stiffness of the material, could also play simultaneously the role of a compatibilizer by fine-tuning the morphology of the PP/PEO blend.  The results could have direct benefits for the polymer recycling industry, since using nanoclays as a compatibilizer is a much cheaper option compared to block copolymer compatibilizer, in addition to the additional extraordinary properties nanoclays have and could translate to the recycled polymer products making them more profitable.