In this work, the effect of adding organoclay (Cloisite 20A) to a poly(methyl metacrylate) (PMMA)/polystyrene (PS) blend was evaluated in order to understand the compatibilization mechanism taking place. The blend morphology was quantified using micrographs obtained by scanning electron microscopy and observed by transmission electron microscopy. The state of dispersion of the clay was studied using small angle X-ray scattering and wide angle X-ray scattering and by applying the Carreau-Yasuda with a yield stress model to small amplitude oscillatory shear (SAOS) data. Morphological analyses revealed that the clay was intercalated, that its addition resulted in a decrease in the size of the dispersed phase and that it was preferentially located at the interface, except in the case of saturated interfaces, in which case the remaining clay was dispersed in PMMA. By applying the simplified Palierne model to SAOS experiments, the interfacial tension between the polymers forming the blend was inferred and shown to decrease upon addition of clay. The relaxation spectra inferred from the SAOS data, using the Honerkamp and Weese method, revealed four relaxation times: Relaxation of PMMA and PS chains, relaxation of the droplet shape, as well as an additional relaxation phenomenon attributed to the Marangoni stress. Although Marangoni stresses have already been studied in the case of blends compatibilized by block copolymers, this is the first time that it has been evidenced in the case of a clay as compatibilizer. V C 2017 The Society of Rheology. [http://dx

The compatibilization mechanism of poly(methylmethacrylate) (PMMA)/polystyrene (PS) blends induced by PMMA-b-PS block copolymers of different molar masses (30 and 104 kg/mol) was studied. The blend morphologies with and without copolymers were observed by scanning electron microscopy. The rheological behavior was studied performing small amplitude oscillatory shear experiments. The experimental results were compared to Palierne's model predictions. Shear induced coalescence tests were also conducted. Contrary to what was expected, adding block copolymers did not result in a refinement of the droplet size. However, it induced Marangoni stresses, a decrease in interfacial tension and an inhibition of coalescence of the dispersed phase. During coalescence tests, a decrease in the relaxation time due to Marangoni stresses with time was revealed. This interesting behavior contradicts previous works on the subject, and is believed to be due to a migration of block copolymers to the interface during the tests rather than droplets' coalescence. As such, the morphology was explained by the fact that block copolymers are not entirely at the interface initially. Also, the block copolymer with a higher molecular mass was shown more efficient at inhibiting coalescence, indicating that the compatibilization mechanism is a combination of Marangoni stresses and steric hindrance. V

Many plastic waste recycle streams are blends of various types of polypropylene (PP) and polyethylene (PE). When reprocessing these blends into products it is difficult to obtain good mechanical and optical properties due to the immiscibility of the components. Blend morphology is one of the governing factors for these properties. Therefore morphology control is a key challenge when turning plastic waste into valuable materials. In this work, the effect of a novel polymeric compatibilizer on the morphology of PP–PE blends was investigated via rheological and scanning electron microscopy experiments. Homopolymer PP was combined with PE of varying comonomer level. In addition to the effect of including compatibilizer, the effect of blend ratio and viscosity ratio is discussed. It was found that very fine dispersions could be obtained when including the compatibilizing polymer for all studied systems. The blend rheology was compared with predictions from empirical and physics‐inspired mixing rules. The difference between measured and predicted rheology is expected to provide insight into the structure of the various blend systems. POLYM. ENG. SCI., 58:460–465, 2018. © 2017 Society of Plastics Engineers