Investigation of morphology and miscibility of isotactic polypropylene, ethylene-butene copolymer and chlorinated polyolefin blends via LSCFM, SEM, WAXD, and DMA

Thermoplastic olefins (TPOs) are an important class of material used in the automotive industry. They are blends of isotactic polypropylene (iPP) and a polyolefin impact modifier. Chlorinated polyolefin (CPO) is a polymer used as an adhesion promoter to promote the paintability of TPO. The synthesis of a coumarin dye-labeled chlorinated (21.8 wt% Cl) maleated polypropylene (CPO), HY dye-labeled MEBR (maleated ethylene-butene copolymer with 28 wt% butene), and CPO (21.8 wt% Cl) was described. They were introduced as tracers into iPP/EBR9 (ethylene-butene copolymer with 9 wt% butene), iPP/CPO, EBR9/CPO binary, and iPP/EBR9/CPO ternary blends. The annealing effect on morphologies of the blends was examined by laser scanning confocal fluorescent microscopy (LSCFM). LSCFM revealed that the annealing caused phase coarsening in iPP/CPO and iPP/EBR blends, but had no obvious effect on the morphology of EBR/CPO blends, while In iPP/EBR/CPO ternary blends, iPP and EBR formed a completely separate domain, iPP and CPO formed their own domains EBR was distributed in the CPO domains. The morphology of iPP, EBR, and CPO binary blends was further Investigated by SEM. SEM images showed that EBR and CPO interpenetrated each other on the nanometer scale in EBR/CPO blends, while obvious phase separation was observed in iPP/CPO and iPP/EBR blends. Differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD) results showed that iPP and EBR, iPP and CPO crystallized respectively In binary blends, while there was a new population of crystals formed in EBR/CPO blend. Further exploration by dynamic mechanical analysis (DMA) revealed that there were two beta relaxation transitions in iPP/CPO and iPP/EBR blends, and only one beta relaxation transition with a small shoulder in EBR/CPO blends. Thus, we concluded that iPP/EBR and iPP/CPO blends are immiscible; the EBR/CPO blend is miscible in the melt and partially miscible in solid state, which is in agreement with the predictions based on calculations of the results by binary interaction energy density (B-ij-B-c). Copyright (C) 2009 John Wiley & Sons, Ltd.