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Micromechanical modeling and mechanical properties of polyurethane (PU) hybrid nanocomposite foams with multi-walled carbon nanotubes (MWCNTs) and graphene nanoplatelets (GNPs) were investigated by mean of tensile strength, hardness, impact strength and modified Halpin-Tsai equation. Three types of graphene, with varied flake sizes and specific surface areas (SSA), were utilized to study the effect of graphene types on the synergistic effect of MWCNT/GNP hybrid nanofillers. The results indicate a remarkable synergetic effect betweenMWCNTs and GNP-1.5 (1:1) with a flake size of 1.5 µm and a higher SSA (750 m 2 /g), which tensile strength of PU was improved by 43% as compared to 19% for PU/MWCNTs and 17% for PU/GNP-1.5 at 0.25 wt% nanofiller loadings. The synergy was successfully predicted using unit cell modeling, in which the calculated data agrees with the experimental results.

In this work, multi‐walled carbon nanotubes (MWCNT) and poly(methyl methacrylate) (PMMA) pellets were compounded via corotating twin‐screw extruder. The produced MWCNT/PMMA nanocomposite pellets were injection molded. The effect of MWCNT concentration, injection melt temperature and holding pressure on mechanical properties of the nanocomposites were investigated. To examine the mechanical properties of the MWCNT/PMMA nanocomposites, tensile test, charpy impact test, and Rockwell hardness are considered as the outputs. Design of experiments (DoE) is done by full factorial method. The morphology of the nanocomposites was performed using scanning electron microscopy (SEM). The results revealed when MWCNT concentration are increased from 0 to 1.5 wt %, tensile strength and elongation at break were reduced about 30 and 40%, respectively, but a slight increase in hardness was observed. In addition, highest impact strength belongs to the nanocomposite with 1 wt % MWCNT. This study also shows that processing condition significantly influence on mechanical behavior of the injection molded nanocomposite. In maximum holding pressure (100 bar), the nanocomposites show highest tensile strength, elongation, impact strength and hardness. According to findings, melt temperature has a trifle effect on elongation, but it has a remarkable influence on tensile strength. In the case of impact strength, higher melt temperature is favorable. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43738.

In this work, the electrical surface conductivity enhancement of injection-molded multiwalled carbon nanotube (MWCNT)/poly(methyl methacrylate) (PMMA) nanocomposite by using CO 2 laser processing was studied. Variable input factors are considered as MWCNT concentration (in three levels 0.5, 1, and 1.5 wt %), the laser feed angle with the flow direction (in five levels 08, 308, 458, 758, and 908), and the cavity machining method that were produced by electrodischarge machining and computer numerical control milling with finishing process. The studies show that the irradiation of laser and utilization of covering gas could enhance the CNT-CNT contacts and the surface electrical conductivity. The morphology of laser-irradiated surface by using scanning electron microscope certified that the conductive network generated from CNT-CNT contacts can transfer the electrical current. The findings clearly show that the laser feed angle with the flow direction influenced the electrical conductivity. The maximum conductivity ($ 5.310 3 10 24 S) was observed at 758.

Combining various carbon nanofillers with different dimensions can lead to a synergistic effect through the formation of an efficient conductive network. Hybrid polyurethane (PU) nanocomposites containing multi-walled carbon nanotubes (MWCNTs) and graphene nanoplatelets (GNPs) were fabricated to study experimental and theoretical aspects of thermal conductivity (TC) enhancement. The optimization of hybrid nanofillers combinations was done to synergically enhance the TC using various types of graphene, nanofillers concentrations and ratios. A synergistic thermal conductivity improvement with MWCNTs and GNPs was confirmed at low nanofillers contents. The TC of hybrid nanocomposite at 0.25 wt% is approximately equivalent to the TC of individual nanofillers at 0.75 wt%. An analytical model for the effective thermal conductivity of single and hybrid nanocomposites was considered with variables of volume fraction, interfacial thermal resistance, straightness of the nanofillers and the percolation effect, in which the predictions of the modified models agreed with the experimental results.