Microhardness of ternary blends of polyolefins with recycled polymer components

Microhardness tests, Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC) measurements were performed on melt‐pressed films of multicomponent blends based on low‐density polyethylene (LDPE), linear LDPE (LLDPE), high‐density polyethylene (HDPE), and polypropylene (PP), and their recycled homologues. Some of the PE blends also contained ethylene‐propylene‐diene monomer (EPDM) as compatibilizer. In all cases, the variation of microhardness as a function of content of the recycled component follows the additivity law of components. Thus, the range of hardness values of polyolefin blends can be controlled by choice of both components and their relative content in the blend. The hardness of the components increases from LDPE, to LLDPE, to HDPE, to PP and increases from 20 to 84 MPa. For recycled components, the hardness values are reduced by ～15%. According to DSC results, all the blends are immiscible. Results are discussed in terms of the levels of crystallinity reached for the different blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2046–2050, 2003