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Blends of two biobased polymers, poly(lactic acid) and poly(trimethylene terephthalate) (PTT), were compatibilized with either maleic anhydride-grafted poly(ethylene-octene) (mPOE) or organically modified clay (Cloisite 30B). Dynamic rheological measurements revealed that the mPOE inclusion resulted in a four-fold increase in viscosity relative to the noncompatibilized blends. By loading 3 wt% Cloisite 30B, the storage moduli of the blends showed a distinct solid-like behavior and high complex viscosity in the low-frequency region, which can be interpreted by the reduced sizes of the PTT phase evidenced from the scanning electron microscopy (SEM) micrography. A temperature sweep of the viscosity of the blends starting from 180°C revealed that the existence of an unmelted PTT dispersed phase might impede the decline in viscosity with increasing temperature near the melting point of PTT. The introduced compatibilizers can restrict the temperature-dependent morphology evolution, and the use of the 3 wt% 30B clay can prohibit the morphology evolution during the temperature sweep.

Improving the dispersion of graphene nanosheets (GN) in a polymer matrix is a critical step in lowering the percolation threshold of nanocomposites. In this paper, an effective method based on an electrostatic assembly process is reported. Polystyrene (PS) latex was first prepared by using hexadecyl trimethyl ammonium bromide (CTAB) as a cationic surfactant, which created positive charges on the surface of the PS micelles. An in situ demulsification process was then conducted by adding negatively charged graphene oxide (GO) particles into the positively charged PS latex. Thus, GO sheets were attached spontaneously to the surfaces of PS particles through electrostatic adsorption. Followed by in situ reduction and hot pressing, the agglomeration of GN was largely prohibited by the PS microspheres and facilitated the formation of GN networks in the PS matrix. The obtained PS/GN nanocomposites exhibited excellent electrical properties with a percolation threshold as low as 0.054 vol.% GN. When the GN content reached 1.53 vol.%, the electrical conductivity was 46.32 S/m and the thermal conductivity 0.47 W/mk. This strategy represents a new environment-friendly pathway, which is also applicable for other polymer matrices, for large-scale production of polymer composites with fully interconnected graphene networks at ultra-low GN content.

The coexistence of two kinds of reactive compatibilizers at the interface in immiscible LDPE/PA6 blends, namely, polyethylene graft maleic anhydride (PE-g-MAH) with a long backbone length and polybutadiene graft maleic anhydride (PB-g-MAH) with a short backbone length, promoted the formation of a flat interface and induced a co-continuous morphology in blends containing 30 wt % PA6. The relationships between the contents and content ratios of the dual reactive compatibilizers as well as the morphologies of the resulting LDPE/PA6 blends are examined quantitatively. The morphologies of the blends are characterized by SEM and TEM combined with a selective solvent extraction process. It is found that in these systems, when the total content of the dual compatibilizers is within 20–30 wt % and the content ratio of PE-g-MAH and PB-g-MAH is within 2:1–3:1, the minor PA6 phase can also form a co-continuous morphology in the LDPE matrix. The balance between the stability (determined by in situ formed PE-g-PA6 graf...

Core-shell particles with a rigid silica core and a poly(butyl acrylate) (PBA) rubber shell are used to toughen epoxy resins without loss of elastic modulus and tensile strength. Both the diameter of silica core (D) and thickness of PBA shell (Ts) of silica-PBA core-shell particles are accurately controlled by sol-gel synthesis and seed emulsion polymerization process, respectively. From the results of notched Izod impact tests, a brittle-ductile transition of these epoxy/silica-PBA composites occurs when the rubber shell thickness (Ts) exceeds a critical value (Tsbd). It is found that Tsbd increases with increasing D which implies a critical rubber content (10 wt%) in the core-shell particles or a critical Ts/D ratio (0.0375), above which all composites transit from brittle to ductile failure. The composite elastic modulus decreases with increasing Ts. However, the critical thickness values of Tsm and Tss, below which composite modulus and tensile strength, respectively, are equal to or higher than the corresponding epoxy matrix values, are both larger than Tsbd. These results prove that brittle polymers can be toughened without loss of elastic modulus and tensile strength. However, the critical surface-to-surface inter-particle distance (Lc) is controlled by both properties of the core-shell particles and polymer matrix. When the rubber shell thickness Ts > Tsbd, Lc is increased when D is decreased. But when Ts