maleated thermoplastic elastomer (TPEg) was prepared from maleicanhydride, grafting a mixture of polyethylene–octene elastomer and semi-crystalline polyolefin plastic (60/40 by weight) in a twin screw extruder. The non-grafted version (TPE) of the mixture was also prepared under the same processing conditions. The TPEg was employed to compatibilize and toughen amorphous copolyester PETG/TPE blends. The addition of the TPEg improves the compatibility between PETG and the TPE and results in fine dispersion of the TPE in the PETG matrix. At a fixed dispersed phase content of 15 wt%, a sharp brittle-ductile transition takes place, when the TPEg content in the dispersed phase increases from 20 to 30 wt%, namely, the TPEg content in the blends increases just from 3 to 4.5 wt%. After the brittle-ductile transition, the blends are maintained at super-tough level with notched impact strength more than twenty-fold higher than that of pure PETG plastic. The influence of the TPEg content on fractography of the PETG/TPE blends was also investigated. When the TPEg content in dispersed phase is below 20 wt%, the impact fracture surface shows a small area of slow crack growth region and numerous feather-like markings in fast crack growth region, indicating a brittle failure mode. While the TPEg content in the dispersed phase is above 30 wt%, the impact fracture surface exhibits drastically enlarged slow crack growth region and some parabolic markings in the fast crack growth region. Massive cavitation and extensive matrix shear yielding are predominant mechanisms of the impact energy dissipation upon impact testing

The major objectives of this work are to understand the effects of organoclay, its extent of exfoliation and orientation, and indenter geometry on the scratch characteristics of polyamide 6/organoclay nanocomposites. Two different organically treated clays are used for this purpose and their structural parameters in a polyamide 6 matrix quantified. It is shown that, while the material properties are important for scratching resistance, they are not the only determinants of the scratch performance of materials. Further, despite proving beneficial to scratch resistance, in terms of residual depth, the presence (and exfoliation) of organoclay promotes the formation of brittle cracks during scratching. But with no organoclay layers, plastic flow controls the scratch damage in neat polyamide 6 with large residual depths. Factors such as orientation of clay layers and variations of indenter tip geometry also exert dominant effects on scratch penetration resistance and damage. Additionally, significant plastic flow and rotation of organoclay layers from the original configuration are observed underneath the sliding indenter.

This paper dealswitha novel concept of inductionofwell-distributedsubmicrometer voids inpolypropylene (PP) and PP/CaCO3 nanocomposites during processing to alleviate their brittleness without sacrificing Young's modulus and yield strength. The role of these voids in initiating/participating in the plastic deformation processes during tensile and double-notch four-point-bend (DN-4-PB) tests is investigated. It is shown that the voids act in a similar way as the cavitated rubber particles in rubber-toughened polymer systems; that is, plastic growth (of the pre-existent voids) in the PPmatrix occurs upon deformation and subsequently triggers large plastic deformation of the surrounding matrix in the form of isolated and domainlike craze structures.

The primary focus of this work is to elucidate the location and extent of exfoliation of clay on fracture (under both static and dynamic loading conditions) of melt-compounded nylon 66/clay/SEBS-g-MAternary nanocomposites fabricated by different blending sequences. Distinct microstructures are obtained depending on the blending protocol employed. The state of exfoliation and dispersion of clay in nylon 66 matrix and SEBS-g-MA phase are quantified and the presence of clay in rubber is shown to have a negative effect on the toughness of the nanocomposites. The level of toughness enhancement of ternary nanocomposites depends on the blending protocol and the capability of different fillers to activate the plastic deformation mechanisms in the matrix. These mechanisms include: cavitation of SEBS-g-MA phase, stretching of voided matrix material, interfacial debonding of SEBS-g-MA particles, debonding of intercalated clay embedded inside the SEBS-g-MA phase,and delamination of intercalated clay platelets. Based on these results, new insights and approaches for the processing of better toughened polymer ternary nanocomposites are discussed.

The fracture toughness of a series of nylon 6/organoclay/maleic anhydride grafted polyethylene-octene elastomer (POE-g-MA) ternary nanocomposites with different compositions of clay and POE-g-MA was evaluated using the J-integral method. The fracture toughness of the ternary nanocomposites increased with POE-g-MA content at a fixed loading of organoclay. In contrast, increasing the loading of organoclay in nylon 6/POE-g-MA (70/30) blends reduced the toughness of the ternary nanocomposites. Transmission electron microscopy (TEM) with single-edge-double-notch four-point-bend (SEDN-4PB) specimens revealed the internal cavitation of POE-g-MA particles leading to effective relief of crack-tip tri-axial stress along with craze-like damage features consisting of line arrays of expanded voids in both un-reinforced and organoclay reinforced nylon 6/POE-g-MA blends, followed by very severe matrix plastic deformation at the crack-tip region. It is this plastic work that mainly contributes to the drastic enhancement of fracture toughness of the ternary nanocomposites, besides the energies absorbed in cavitation and stretching of rubber particles as well as delamination of clay layers.

We report the synthesis and fatigue characterization of fib erglass/epoxy composites with various weight fraction of graphene platelets infiltrated into the epoxy resin as well as directly spray-coated on to the glass micriofibers. Remarkably only-0.2% (with respect to the epoxy resin weight and-0.02% with respect to the entire laminateweight)of graphene additives enhanced the fatigue life of the composite in the flexural bending mode by up to 1200fold. By contrast, under uniaxialtensile fatigue conditions, the graphene fillers resultd in 3-5fold increase in fatige life. The fatigue life increas (in the flexural bending mode)with graphene additives was-1-2 orders of magnitude superior to those obtained using carbon nanotubes. In situ ultrasound analysis of the nanocomposite during the cyclic fatigue test suggests that the graphene net work toughens the fiberglass/epoxy matrix interface and prevents the delamination/buckling of the glass microfibers under compressive stress. Such fatigue resistant hierarchical materials show potential to improve the safety, reliability, and cost effectiveness of fiber reinforced composites that are increasingly the material of choice in the aerospace, automotive, marine, sports, biomedical, and wind energy industries.

Functional polymethylmethacrylate (PMMA)/graphene nanocomposite microcellular foams were prepared by blending of PMMA with graphene sheets followed by foaming with subcritical CO2 as an environmentally benign foaming agent. The addition of graphene sheets endows the insulating PMMA foams with high electrical conductivity and improved electromagnetic interference (EMI) shielding efficiency with microwave absorption as the dominant EMI shielding mechanism. Interestingly, because of the presence of the numerous microcellular cells, the graphene-PMMA foam exhibits greatly improved ductility and tensile toughness compared to its bulk counterpart. This work provides a promising methodology to fabricate tough and lightweight graphene-PMMA nanocomposite microcellular foams with superior electrical and EMI shielding properties by simultaneously combining the functionality and reinforcement of the graphene sheets and the toughening effect of the microcellular cells.

This paper reports the first example of preparation of polypropylene/graphene oxide (PP/GO) nanocomposites via in situ Ziegler-Natta polymerization. A Mg/Ti catalyst species was incorporated into GO via surface functional groups including -OH and -COOH, giving a upported catalyst system primarily structured by nanoscale, redominantly singleGOsheet. Subsequent propylene polymerization led to the in situ formation of PP matrix, which was accompanied by the nanoscale exfoliation of GO, as well as its gradual dispersion.Morphological examination of the ultimate PP/ GO nanocomposites by TEM and SEM techniques revealed effective dispersion in nanoscale of GO in PP matrix. High electrical conductivity was discovered with thus prepared PP/GO nanocomposites; for example, at a GO loading of 4.9 wt %, σc was measured at 0.3 S 3m-1.

This study focuses on achieving high stiffness/strength and high fracture toughness in nylon 6/organoclay nanocomposites prepared via melt compounding by incorporating a maleic anhydride grafted polyethylene-octene elastomer (POE-g-MA) as a toughening agent. Mechanical test results indicated that the ternary nanocomposites exhibited higher stiffness than nylon 6/POE-g-MA binary blends at any given POE-g-MA content. More importantly, the brittle–ductile transition of nylon 6/POE-g-MA blends was not impaired in the presence of organoclay for the compositions prepared in this study. TEM analysis shows that organoclay layers and elastomer particles were dispersed separately in nylon 6 matrix. In the binary nanocomposite, no noticeable plastic deformation was observed around the crack tip. In the ternary nanocomposites, the presence of organoclay in the matrix provided maximum reinforcement to the polymer, while their absence in the elastomer particles allowed the latter to promote high fracture toughness via particle cavitation and subsequent matrix shear yielding. The partially exfoliated clay layers also delaminated and hence, adding to the total toughness of the nanocomposites.