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Blending polyethylene with thermoplastic polyolefin elastomers (TPOs) is a promising way to manipulate its structures and tailor its properties. Herein, three TPOs, i.e., two ethylene–octene copolymers (EOCs) and an olefin block copolymer (OBC) with different structures, were used to comparatively investigate the miscibility, crystallization, and phase behavior of their blends with a linear low-density polyethylene (LLDPE). It was found that large differences occurred in the crystallization and phase behaviors of the blends due to the different extent of similarity in the molecular structure between the TPO and the LLDPE matrix. In particular, a unique segregated phase morphology comprised a less stable crystalline phase and a rubbery phase was found in an LLDPE/EOC blend. The tensile performance and elasticity of the blends were also studied and correlated with the structures of the blends. This work not only provides novel results on the miscibility and phase behavior of the similar-structured LLDPE/TPO blends, but can also guide the design of LLDPE-based products with tailored performances. [ABSTRACT FROM AUTHOR]

Abstract: Controlling the hierarchical structure of melt-processed polymers is vital to “structuring” processing and tailoring properties of the product. In this work, polypropylene (PP)/octene-ethylene copolymer (POE) blends were injection-molded using so-called dynamic packing injection technique, which imposed oscillatory shear on the gradually cooled melt during the packing solidification stage. In this way, samples with highly oriented PP matrix and elongated POE particles were obtained. Most interestingly, it was found for the first time that the elongated POE particles could not improve any impact toughness of oriented PP, which is completely different from that for the isotropic ones. Polarized optical microscope, scanning electron microscope, micro-Fourier transform infrared spectroscopy and differential scanning calorimetry were used to characterize the microstructures along sample thickness. The crack-initiation term, impact fractured surface and cross-section of the impact surface were inspected to understand the difference in impact behavior between the oriented PP/POE blends and their isotropic counterparts. The results show that massive crazing or plastic flow of the matrix could not be effectively initiated in the oriented blends. Our work provides a good example for better understanding structure–property relationship of polymers via well controlling their internal hierarchical structure. [Copyright &y& Elsevier]

Abstract: In this study, cellulose nanocrystals (CNCs) were incorporated into poly(propylene carbonate) (PPC), which is a biodegradable alternative copolymer of propylene oxide and carbon dioxide, CNCs were prepared by sulfuric treatment of cellulose filter. An effective approach to prepare PPC environment-friendly composites is shown. The obtained PPC/CNCs nanocomposites display orders of magnitude increase in mechanical properties by adding a small amount of CNCs, in particular, with only 0.1wt% of CNCs incorporated, a 10-fold increase in tensile strength and 7-fold increase in Young’s modulus were achieved. The thermal stability of the nanocomposites is significantly improved as measured by dynamic mechanical analysis and differential scanning calorimetry. This is due to a combination of CNCs reinforcement in the soft matrix and increased effective molecular weight of the nanocomposties. The present nanocomposites outperform PPC composites reinforced with other nano-sized stiff and anisotropic fillers. [Copyright &y& Elsevier]