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The effect of perfluoroalkane (PFA) on the morphology, thermal conductivity, mechanical properties and thermal stability of rigid polyurethane (PU) foams was investigated under ambient and cryogenic conditions. The PU foams were blown with hydrofluorolefin. Morphological results showed that the minimum cell size (153 μm) was observed when the PFA content was 1.0 part per hundred polyols by weight (php). This was due to the lower surface tension of the mixed polyol solution when the PFA content was 1.0 php. The thermal conductivity of PU foams measured under ambient (0.0215 W/mK) and cryogenic (0.0179 W/mK at −100°C) conditions reached a minimum when the PFA content was 1.0 php. The low value of thermal conductivity was a result of the small cell size of the foams. The above results suggest that PFA acted as a nucleating agent to enhanced the thermal insulation properties of PU foams. The compressive and shear strengths of the PU foams did not appreciably change with PFA content at either −170°C or 20°C. However, it shows that the mechanical strengths at −170°C and 20°C for the PU foams meet the specification. Coefficient of thermal expansion, and thermal shock tests of the PU foams showed enough thermal stability for the LNG carrier’s operation temperature. Therefore, it is suggested that the PU foams blown by HFO with the PFA addition can be used as a thermal insulation material for a conventional LNG carrier.

The effects of liquid-type additive, methoxynonafluorobutane, on the morphology, thermal conductivity, creep strain, and mechanical strength of polyurethane (PU) foams with an environment-friendly foaming agent, hyrdofluoroolefin, were investigated. The methoxynonafluorobutane under the trade name of NOVEC likely acted as a nucleating agent during the formation of PU foams. When NOVEC was added in the amount of 3 parts per hundred polyol by weight (php), the cell size of the foam was minimal, and the cell size distribution was relatively uniform. At the NOVEC content of 3.0 php, the thermal conductivity of the PU foams was also minimal. This decrease in thermal conductivity was due to the smaller cell size of the foams lowering their thermal conductivity. At 3.0 php NOVEC content, the creep strain of the PU foams was minimal being 0.29% at 1,000 h. At 3.0 php NOVEC, the estimated creep strain of the PU foam exhibited the lowest creep strain of 3.47% at 50 years. As a result, at 3.0 php NOVEC content, the cell wall was relatively less fractured, resulting in a small deformation of the PU foam. These results suggest that the main factors in improving the thermal insulation properties and stability of the PU foams are smaller cell size and narrow cell size distribution.

A functionally effective compatibilizer for PET/PPE blends is highly necessary to fabricate white opaque polyester film having high reflectance through drawing process. In this study, the effects of three different compatibilizers (SAN-g-MAH, SMA-16 and polystyrene-g-oxazoline PS-g-OXA) on the morphological, thermal, mechanical, and rheological properties in the PET/PPE (70/30, wt%) blend system were investigated. For the morphological studies, upon the addition of 7 part(s) per hundreds by weight (phr) of PS-g-OXA, the smallest domain size was observed among the three types used as a compatibilizer. Similarly, for the mechanical and rheological studies, upon the addition of 7 phr of PS-g-OXA, the optimal properties among three different compatibilizers were demonstrated due to the increased tensile strength and complex viscosity. For the thermal study, when the amount of PS-g-OXA added as a compatibilizer exceeded the threshold of the blend system, the Tg of the polyphenylene ether (PPE) was exhausted. In the morphological studies, the compatibilization effect was observed in the surface roughness of the film after stretching. It was concluded that PS-g-OXA was the effective compatibilizer for improving the reflectivity to make white opaque polyester film in PET/PPE blend system. It was concluded that this was due to compatibilization effects. Based on the results, the changes in properties were observed for biaxially oriented polyethylene terephthalate (PET)/PPE (70:30, wt%) blend films.

The electrical conductivity, electromagnetic interference (EMI) shielding efficiency, and the morphological and mechanical properties of the polycarbonate/poly(acrylonitrile-butadiene-styrene) (ABS) (70/30)/carbon fiber (CF) composites were studied. The composites were prepared by two different methods, i.e., the pultrusion process and screw extrusion. The composite prepared by the pultrusion process showed higher electrical conductivity of 1.05×101 S/cm and EMI shielding efficiency of 37.6 dB compared to the composite prepared by screw extrusion of 5.20×10−1 S/cm and 6.8 dB at 10 GHz. The increase in the shielding efficiency of electromagnetic wave by 30.8 dB was due to the increased fiber length when the composite was prepared by the pultrusion process. The tensile and flexural strengths of the polycarbonate/ABS (70/30)/CF composite prepared by the pultrusion process were slightly higher by 8.2 and 7.0% compared to those of the composites prepared by screw extrusion, respectively. The above results suggest that the pultrusion process is a superior method to prepare the polycarbonate/ABS (70/30)/CF composites with favorable electrical and mechanical properties.

Herein, for the first time, FeSiAl (sendust)/metal hybrid materials were synthesized with a magnetic core and a highly electrically conductive metal shell for shielding electromagnetic interference (EMI) pollution. Soft magnetic sendust flakes were electroless-plated with electrically conductive Ag or Ni metal to form Ag-plated and Ni-plated sendust core-shell hybrids. The magnetic and metal hybrid-incorporated paraffin wax composites exhibited a better absorption-dominant EMI shielding performance of 65.6 dB and 58.5 dB, respectively, than that of the sendust wax composite and the composite with a mixture of sendust and electrically conductive Ag/Cu dendrite. The superior shielding performance was attributed to the synergistic combination of the effective magnetic loss, dielectric loss, and conduction loss. These exceptional properties of the new hybrid composite showed that it could be used in absorption-dominant EMI shielding applications.

In this study, the effects of three different types of compatibilizers on the morphological, mechanical, and optical properties of poly(ethylene terephthalate) (PET) and syndiotactic-polystyrene (s-PS) (70/30, wt%) blends and biaxially oriented blend films of the two polymers were investigated. The morphological results of the PET/s-PS (70/30) blends revealed that when the 5 phr polystyrene-g-oxazoline (PS-g-OXA) was used as a compatibilizer, the domain size showed minimum. The mechanical studies of the PET/s-PS (70/30) blends showed that when 5 phr PS-g-OXA was used, increased tensile strength was obtained. The transmittance of the blend film showed the highest value (83.7%) for the biaxially oriented PET/s-PS (70/30) blend films with the PS-g-OXA (5 phr), compared with that of the blends without compatibilizer (70.8%), or with the styrene-co-maleic anhydride as a compatibilizer, at the wavenumber of 600 nm. The tensile strength of the biaxially oriented PET/s-PS (70/30) blend films also showed the highest value when PS-g-OXA (5 phr) was used as a compatibilizer. The morphological, optical, and mechanical results of the PET/s-PS (70/30) blends and biaxially oriented blend films of the two polymers showed that PS-g-OXA was the most effective compatibilizer, and that the optimum compatibilizer content was 5 phr.

The effects of composite preparation methods on the electrical conductivities, the electromagnetic parameters and the electromagnetic interference (EMI) shielding effectiveness of polypropylene (PP)/nickel-coated carbon fiber (CF) composites were investigated. The composites were prepared by injection molding machine, internal mixer, and screw extruder. The electrical properties results showed the PP/CF (70/30, wt%) composites prepared by injection molding demonstrated the highest electrical conductivity and EMI shielding effectiveness, which were 1.75×101 S/cm and 48.4 dB at the frequency of 10 GHz, respectively. These results seem mainly due to the increased CF length when the PP/CF composite was prepared by injection molding, which was advantageous in forming a conductive network of the composite. The results of the electromagnetic parameters of the PP/CF composites showed that the increased electrical conductivity of the composite prepared by injection molding was mainly due to the increased dielectric constants (e' and e") of the PP/ CF composite. This enhancement in dielectric constants seems related to the percolation at a lower concentration of the CF, which was affected by the increased CF length of the composite prepared by injection molding process. The results of dielectric loss and magnetic loss factors of the PP/CF composite showed that the major electromagnetic absorbing mechanism was dielectric loss, namely dipole polarization and interface polarization between filler and matrix, which resulted in improved EMI absorption values. The total EMI shielding effectiveness (SET) of the PP/CF composite comprised 85.1% EMI shielding effectiveness by absorption (SEA), and 14.9% EMI shielding effectiveness by reflection (SER), which suggests that the EMI shielding was predominantly by the absorbing mechanism of the incident electromagnetic wave.

The sound absorption properties and airflow resistivity of polyurethane foams (PUFs) with multiwall carbon nanotube (MWCNT), perfluoroalkane (PFA), dimethylsiloxane (HMDS), and MWCNT/PFA hybrid additives were investigated with varying additive content. The results show the close relationship of the sound absorption coefficient and airflow resistivity, and increasing flow resistivity was found to improve the sound absorption coefficient of the PUF. For the PUF with MWCNT (at 0.50 phr)/PFA (at 1.25 phr) hybrid additives, the sound absorption coefficient and airflow resistivity were 0.80 (in the frequency range of 1,600–2,500 Hz) and 439,900 Ns/m4, respectively, which were the highest values among the investigated additive species and additive content. The sound absorption coefficient of the PUF with MWCNT (at 0.50 phr)/PFA (at 1.25 phr) was increased by 82.0% compared to that of the PUF without additives, probably because the PUF has the smallest cell size among the additive species and compositions investigated in this study. The results of the sound absorption coefficient, airflow resistivity, and cell size of the PUF suggest that to decrease the cell size and to increase the tortuous paths of the foams, MWCNT/PFA hybrid additives appeared to be the most effective additives and showed synergistic effects in the formation of PUF, and its small cell size increased the sound absorption properties of PUF. POLYM. COMPOS., 2017. © 2017 Society of Plastics Engineers

When graphene is shrunk into ~10 nm scale graphene nanoribbons or nanomesh structures, it is expected that not only electrical properties but also thermal conductivity and thermoelectric property are significantly altered due to the quantum confinement effect and extrinsic phonon-edge scattering. Here, we fabricate large-area, sub-10 nm single- and bilayer graphene nanomeshes from block copolymer self-assembly and measure the thermal conductivity, thermoelectric and electrical transport properties to experimentally verify the effect of sub-10 nm quantum confinement, phonon-edge scattering and cross-plane coupling. Among the large variety of the samples, bilayer graphene nanomesh having 8 nm-neck width showed significantly low thermal conductivity down to ~78 W m−1 K−1, which is the lowest thermal conductivity for suspended graphene nanostructures, and a high thermopower value of −520 μV K−1, while it still shows the comparably high carrier mobility. Classical and quantum mechanical calculations successfully supported our nanomesh approach, which can achieve high thermoelectric properties based on the significantly reduced thermal conductivity and higher thermopower due to the confined geometry.

In this study, highly anisotropic Cu oblate ellipsoids incorporated polymer composites were prepared that revealed excellent broadband electromagnetic shielding effectiveness of 80.0 to 62.1 dB at a frequency region between 300.0 KHz and 12.0 GHz, at low Cu contents. Cu-coated hollow polymer beads were fabricated through electroless plating of Cu on the polymer hollow beads. The hollow polymer beads were prepared through thermal expansion of acrylonitrile-based polymer beads containing a blowing agent. These beads were capable of incorporating highly anisotropic 2-dimensional (2D) Cu oblate ellipsoids into polymer composite through simple compression molding process. The resulting broadband electromagnetic shielding performance attributes to a low percolation behavior of the composites due to high anisotropy of the conductive Cu filler and their multilayered structure in the composites.

The sound absorption coefficient, airflow resistivity and cell size of polyurethane (PU) foam with graphene as a solid-type additive and tetramethylsilane (TEMS) as a liquid-type additive were investigated. The results show that the sound absorption coefficient and airflow resistivity are closely related, and that increase of the flow resistivity improves the sound absorption coefficient of the PU foam. For the PU foam/graphene (0.2 phr) composite, the values of the sound absorption coefficient and airflow resistivity were 0.52 (frequency range of 1600 to 2500 Hz) and 292,900 Ns/m4, respectively, which were the highest values among the investigated additive species and additive content. The sound absorption coefficient of the PU foam/graphene (0.2 phr) composite increased by 18.2% compared with that of the PU foam without graphene. The results of the sound absorption coefficient and airflow resistivity of the PU foam suggest that graphene is an effective additive in the formation of the PU foam to decrease the cell size and increase the tortuous paths of the foams, and this small cell size consequently increases the acoustic damping properties of the PU foam.

In this study, the effects of filler characteristics and composite preparation methods on the morphology, mechanical property, electrical conductivity, and electromagnetic interference shielding effectiveness of the polypropylene/polycarbonate (70/30, wt%)/hybrid conductive filler composites were investigated. Nickel-coated carbon fiber (NCCF) was used as main filler and TiO2, multi-walled carbon nanotube, and graphite were used as second fillers in the composites. The pultruded NCCF/polypropylene composite was used in the preparation of the polypropylene/polycarbonate/NCCF/second filler composites. The electrical conductivity and electromagnetic interference shielding effectiveness of the polypropylene/polycarbonate/NCCF/second filler composites were compared with the type of second filler. The superior value of electromagnetic interference shielding effectiveness was observed to be 51.6 dB (decibel) when the hybrid fillers such as NCCF (5.2 vol% or 20 wt%) and TiO2 (1.2 vol% or 5 wt%) were added in the polypropylene/polycarbonate (70/30) composite. The electrical properties of the polypropylene/polycarbonate (70/30)/NCCF/TiO2 composites was compared with the composite preparation methods, which were injection molding and screw extrusion. The results suggested that fiber length of the NCCF affected significantly to the electrical conductivity and electromagnetic interference shielding effectiveness of the polypropylene/polycarbonate (70/30)/NCCF/TiO2 composites.

The effects of lactic acid-grafted multi-walled carbon nanotube (LA-g-MWCNT) on the electrical and rheological properties of the polycarbonate (PC)/poly(lactic acid) (PLA)/LA-g-MWCNT composite were studied. To increase dispersion of the conductive filler in the PC/PLA (70/30) blend, chemically-modified MWCNT, which is LA-g-MWCNT, was used as a compatibilizer between the conductive filler and polymers. For the PC/PLA/LA-g-MWCNT composite, the increased values of the electrical conductivity, electromagnetic interference shielding effectiveness, and complex viscosity were observed compared to those of PC/PLA/MWCNT composite. The results suggested that the increased dispersion of the LA-g-MWCNT in the PC/PLA (70/30) blend is caused by increased connectivity of the MWCNT-MWCNT network structure of the composite. The interfacial tension of the PLA/ MWCNT composite was lower than that of the PC/MWCNT composite. The lower value of interfacial tension of the PLA/MWCNT composite affected the dispersion of the MWCNT in the PLA phase (dispersed phase) more than in the PC phase (continuous phase). After hydrolysis, the PC/PLA/LA-g-MWCNT composite showed higher electrical conductivity than the PC/PLA/MWCNT composites. As a result, it is suggested that the increased dispersion of the LA-g-MWCNT in the PC/PLA blend has affected the increase in the electrical conductivity and lowering of the hydrolytic degradation of the PC/PLA/LA-g-MWCNT composite compared to the PC/PLA/MWCNT composite.

The effects of compatibilizers on the mechanical and rheological properties of PP/PCL and TPO/PCL blends have been studied. The thermoplastic polyolefin (TPO) consists of PP (80 wt%), EPDM (15 wt%) and Talc (5 wt%). Maleic anhydride grafted polypropylene (PP-g-MAH) and maleic anhydride grafted styrene-(ethylene-co-butene)-styrene copolymer (SEBS-g-MAH) were used as compatibilizers. In mechanical properties of PP/PCL and TPO/PCL blends, tensile strength was increased when PP-g-MAH was used as a compatibilizer, and impact strength was increased when SEBS-g-MAH was used as a compatibilizer. From the results of SEM morphology of PP/PCL blend, PCL droplet size was decreased by the addition of PP-g-MAH. From the results of rheological property, complex viscosity of the PP/PCL and TPO/PCL blends did not change appreciably when the compatibilizers were added. From the results of mechanical, morphological and rheological properties of the blends, PP-g-MAH acted as a compatibilizer to increase the tensile strength of the PP/PCL and TPO/PCL blends. While SEBS-g-MAH acted as a impact modifier to increase the impact strength of the PP/PCL and TPO/PCL blends.

Lightweight dual-functional materials with high EMI shielding performance and thermal conductivity are of great importance in modern cutting-edge applications, such as mobile electronics, automotive, aerospace, and military. Unfortunately, a clear material solution has not emerged yet. Herein, we demonstrate a simple and effective way to fabricate lightweight metal-based polymer composites with dual-functional ability of excellent EMI shielding effectiveness and thermal conductivity using expandable polymer bead-templated Cu hollow beads. The low-density Cu hollow beads (ρ ∼ 0.44 g cm−3) were fabricated through electroless plating of Cu on the expanded polymer beads with ultralow density (ρ ∼ 0.02 g cm−3). The resulting composites that formed a continuous 3D Cu network with a very small Cu content (∼9.8 vol%) exhibited excellent EMI shielding (110.7 dB at 7 GHz) and thermal conductivity (7.0 W m−1 K−1) with isotropic features. Moreover, the densities of the composites are tunable from 1.28 to 0.59 g cm−3 in accordance with the purpose of their applications. To the best of our knowledge, the resulting composites are the best lightweight dual-functional materials with exceptionally high EMI SE and thermal conductivity performance among synthetic polymer composites.

In this study, the effects of hybrid fillers such as multi-walled carbon nanotube (MWCNT) and nickelcoated carbon fiber (NCCF) on the electrical conductivity of polypropylene (PP) and polyamide 6 (PA6) blends were investigated. Polypropylene-g-maleic anhydride (PP-g-MAH) was used as a compatibilizer of the PP/PA6 blends. From the results of the transmission electron micrographs of the PP/PA6 (70/30)/MWCNT composites, the MWCNT preferred to locate more in the PA6 phase than in the PP phase. This was possibly due to the lower interfacial tension of the PA6/MWCNT composite compared to that of the PP/MWCNT composite. For the PP/PA6 (70/30)/NCCF/MWCNT (3 phr) hybrid filler composites, values of the electrical conductivities were increased with the increase of the NCCF content. The increase in electrical conductivity was possibly due to the increased electrical pathway with the addition of NCCF content. From the results of the electrical conductivity and morphology of the PP/PA6/NCCF/MWCNT composites, it is suggested that selective localization of the MWCNT in the PA6 phase affected the increased electrical conductivity of the PP/PA6/NCCF/MWCNT composites. The hybrid fillers NCCF and MWCNT could produce a synergistic effect on the electrical conductivity, and the electromagnetic interference shielding efficiency (EMI SE) of the PP/PA6 (70/30)/NCCF/MWCNT composites.

High-density polyethylene (HDPE) composites with modified boron nitride (mBN) fillers, functionalized with an organosilane, were fabricated through conventional melt-extrusion processing techniques. The properties and performances of these composites were compared with those of the composites containing pristine BN and boron carbide (B 4 C) fillers. The silane functionalization of the BN fillers strongly improved the interfacial adhesion between the polymer matrix and the filler. As a result, the HDPE/mBN composites showed a better dispersion state of the filler particles, larger tensile modulus, greater effective thermal conductivity, and better neutron shielding property compared with the HDPE/BN and HDPE/B 4 C composites.

In this study, the effects of multi-walled carbon nanotube (MWCNT) dispersion and poly(styrene-co-acrylonitrile)-g-maleic anhydride (SAN-g-MAH) as a compatibilizer on the electrical conductivity, electromagnetic interference shielding effectiveness (EMI SE), and rheological properties of polycarbonate (PC)/poly(acrylonitrile–butadiene–styrene) (ABS)/MWCNT composites were investigated. The morphological results from the scanning and transmission electron microscope images showed that the droplet size of the ABS decreased when the SAN-g-MAH (5 phr) was added to the PC/ABS (80/20) blend. This result suggests that the SAN-g-MAH acts as an effective compatibilizer in the PC/ABS blend. Also, the MWCNT appeared to be located more in the ABS phase (dispersed phase) than in the PC phase (continuous phase). The interfacial tension of the ABS/MWCNT composite was lower than that of the PC–MWCNT composite, and the lower value of interfacial tension of the ABS/MWCNT composite affected the preferred location of the MWCNT in the ABS phase more than in the PC phase. The electrical conductivities and EMI SE of the PC/ABS/MWCNT composite with the compatibilizer were higher than those of the composite without compatibilizer. The complex viscosity of the PC/ABS/MWCNT composite containing the SAN-g-MAH increased with the frequency compared to that of the composite without SAN-g-MAH. This result is possibly due to the increased degree of MWCNT dispersion. The result of rheological properties is consistent with the results of the morphology, electrical conductivity, and EMI SE of the PC/ABS/MWCNT composite.

The effects of hybrid conductive fillers on the electrical conductivity and electromagnetic interference shielding effectiveness (EMI SE) of polyamide 6 (PA6)/conductive filler composites were investigated. Nickel-coated carbon fiber (NCCF) was used as the main filler and multi-walled carbon nanotube (MWCNT), nickel-coated graphite, carbon black, and titanium dioxide (TiO2) were used as the second fillers in this study. From the results of morphological studies of the PA6/NCCF/second filler composites, NCCF easily formed an electrical pathway since it has a high aspect ratio and random orientation, and the second fillers seemed to disperse evenly in the PA6 matrix. The electrical conductivity and EMI SE of the PA6/NCCF composites were increased with the increase of NCCF content. Among the second fillers used in this study, TiO2 appeared to be the most effective second filler with regard to increasing the EMI SE and electrical conductivity of the PA6/NCCF composite. This was probably because TiO2 has a high dielectric constant with dominant dipolar polarization, consequently leading to greater shielding effectiveness due to the absorption of electromagnetic waves. From the above results of EMI SE and electrical conductivity, it was suggested that the TiO2 produced a synergistic effect when it was hybridized with the NCCF of the PA6/NCCF/TiO2 composites.

Polyurethane (PU) dispersion was prepared with sulfonate groups to make the PU dispersible. Then, polyurethane-polyacrylate (PU-PA) hybrid emulsions were synthesized by seeded emulsifier-free emulsion polymerization with the previously synthesized PU dispersion as a source of seed particles. In the results of the particle-size distribution of the PU-PA hybrid emulsions, the average particle size of the hybrid emulsions increased from 1.2 to 9.1 μm when the polyacrylate content was increased from 0.2 to 1.0 by weight. In addition, the scanning electron microscopy results showed that the size of the polyacrylate latex particles was increased with increases in polyacrylate content. This result suggests that the hydrophobic polyacrylate can easily diffuse into PU particles, where the free radical chain-growth polymerization takes place. In the thermal analysis results, shifts in T g,1 and T g,2 were observed, which are related to the partial compatibility and inter-diffusion of the PU dispersion and PA components. The TGA curves shifted to a higher temperature with increases in polyacrylate content, which indicates a higher thermal stability of the PU-PA hybrid emulsion films. The PU-PA hybrid emulsion films showed improvement in the thermal stability and mechanical properties when compared with the pure polyurethane film, due to the increase in the formation of strong interaction between the PU and PA molecules.

The effects of compatibilizers on the mechanical, morphological, thermal, and rheological properties of poly(propylene carbonate) (PPC)/poly(methyl methacrylate) (PMMA) (70/30) blends were investigated. Three different compatibilizers were used in this study: poly(styrene-g-acrylonitrile)-maleic anhydride (SAN-g-MAH), poly(ethylene-coglycidyl methacrylate) (EGMA) and maleic anhydride (MAH). Tensile strength of the PPC/PMMA (70/30) blend increased with the addition of SAN-g-MAH up to 5 parts per hundred resin by weight (phr). In the morphological studies of the PPC/PMMA (70/30) blend with the SAN-g-MAH 5 phr, the droplet size of the PMMA decreased most significantly (from 3.4 to 0.9 μm) compared to those of the blends with the EGMA and MAH. Glass transition temperature (T g ) of the PPC-rich phase in the PPC/PMMA (70/30) blends shifted to the higher temperature when the SAN-g-MAH was added up to 5 phr. Thermal stability of the blends was improved by the addition of SAN-g-MAH (5 phr). Complex viscosity of the PPC/PMMA (70/30) blends were increased when the SAN-g-MAH was added up to 5 phr. From the above results in mechanical, morphological, thermal and rheological studies of the PPC/PMMA (70/30) blends, it is suggested that the most effective compatibilizer is the SAN-g-MAH and its optimum content in the blend is 5 phr in this study.

In this study, the effects of hybrid fillers on the electrical conductivity and electromagnetic interference shielding efficiency (EMI SE) of the polypropylene (PP)/Ni-coated carbon fiber (NCCF) composites with the second fillers, such as multi-walled carbon nanotube (MWCNT), carbon black and TiO2, were investigated. The morphological behavior showed that the NCCF and the second fillers, such as MWCNT, carbon black and TiO2, seemed to disperse evenly in the PP phase. Among the PP/NCCF composites with MWCNT, carbon black and TiO2, the PP/NCCF/TiO2 composites showed the higher electrical conductivity and EMI SE compared with those of the PP/NCCF/MWCNT and PP/NCCF/carbon black composites. This was the case because TiO2 has high dielectric constant with dominant dipolar polarization. The estimated EMI SE values of the PP/NCCF composites with MWCNT, carbon black and TiO2 are in good agreement with the experimentally obtained values of the composites. Based on the electrical properties of the composites, it was suggested that TiO2 was the most effective second filler when it was hybridized with the NCCF of the PP/NCCF/TiO2 composite. Based on the analysis of the flexural modulus, the PP/NCCF/MWCNT composite had a higher flexural modulus than the PP/NCCF/TiO2 and PP/NCCF/carbon black composites because of the higher aspect ratio of the MWCNT. Open image in new window

The effects of the isocyanate (NCO) index and blowing agent on the morphology, mechanical strength, thermal conductivity and thermal stability of the polyisocyanurate-polyurethane (PIR-PUR) foams were investigated. When the NCO index was increased, the isocyanurate ring content in the PIR-PUR foams was found to be increased regardless the type of blowing agents. As a results, the thermal stability of the PIR-PUR foams was improved. When the isocyanurate ring content in the PIR-PUR foams was increased, the cell size was slightly decreased. The decreased cell size of the foams affected the decrease in the thermal conductivity of the PIR-PUR foams regardless the type of the blowing agents. From the results of thermogravimetric analysis (TGA), the thermal stability of the PIR-PUR foams was found to increase with an increase in the NCO index. When the NCO index was 200, the compressive strength was maximal for the PIR-PUR foams regardless the type of the blowing agents. The compressive strength of the foams blown by cyclopentane was higher than that of the water blown foams. From the above results, it is suggested that the thermal insulation property and thermal stability of the PIR-PUR foams increased with an increase in the NCO index. However, the compressive strength of the PIR-PUR foams showed maximum value at a specific NCO index. Open image in new window

The morphological, electrical, and thermal properties of polyurethane foam (PUF)/single conductive filler composites and PUF/hybrid conductive filler composites were investigated. For the PUF/single conductive filler composites, the PUF/nickel-coated carbon fiber (NCCF) composite showed higher electrical conductivity and electromagnetic interference shielding effectiveness (EMI SE) than did the PUF/multiwall carbon nanotube (MWCNT) and PUF/graphite composites; therefore, NCCF is the most effective filler among those tested in this study. For the PUF/hybrid conductive fillers PUF/NCCF (3.0 php)/MWCNT (3.0 php) composites, the values of electrical conductivity and EMI SE were determined to be 0.171 S/cm and 24.7 dB (decibel), respectively, which were the highest among the fillers investigated in this study. NCCF and MWCNT were the most effective primary and secondary fillers, and they had a synergistic effect on the electrical conductivity and EMI SE of the PUF/NCCF/MWCNT composites. From the results of thermal conductivity and cell size of the PUF/conductive filler composites, it is suggested that a reduction in cell size lowers the thermal conductivity of the PUF/conductive filler composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44373.

2,5-Furandicarboxylic acid (FDCA) is a promising biobased alternative material to terephthalic acid. In this study, three types of poly(butylene adipamide) (PA-4,6) containing 10, 20, and 30 mol % of poly(butylene-2,5-furandicarboxylamide) (PA-4,F) were synthesized through consecutive prepolymerization and solid-state polymerization (SSP). The incorporation of a 10 mol % PA-4,F component into PA-4,6 resulted in slight increases in the intrinsic viscosity (IV) and glass-transition temperature (Tg) after 12 h of SSP at 220 °C. When the SSP temperature and reaction time increased, IV increased proportionally. The highest IV value of 0.75 was obtained by 48 h of SSP at 240 °C, whereas increases in the PA-4,F content to 20 and 30 mol % gave rise to decreases in IV, Tg, and melting temperature; this interrupted the increase in SSP temperature. The thermal decomposition temperature of the PA-4,F-incorporated polyamide was lower than that with PA-4,6 because of the lower thermal stability of the FDCA component. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43391.

In this study, the morphological, electrical, and rheological properties of the poly(propylene carbonate) (PPC)/poly(lactic acid) (PLA)/multi-walled carbon nanotube (MWCNT) composites were investigated. From the results of transmission electron microscopy of the PPC/PLA/MWCNT composites, the MWCNT preferred to locate more in the PPC phase than in the PLA phase. This maybe due to the lower interfacial tension of the PPC/MWCNT composites compared to that of the PLA/MWCNT composites. The electrical conductivities of the PPC/PLA/MWCNT composites were higher than those of the PPC/MWCNT and the PLA/MWCNT composites, which was likely due to the selective localization of the MWCNT in the PPC phase (continuous phase). From the results of the complex viscosity of the composites, the ratio of increasing the complex viscosity of the PPC/MWCNT composites with the MWCNT content was higher than that of the PLA/MWCNT composites. This is maybe due to the fact that the MWCNT dispersion in the PPC phase was higher than in the PLA phase. The results from the morphology, electrical conductivity, and complex viscosity of the PPC/PLA/MWCNT composites suggest that the selective localization of the MWCNT in the PPC phase can improve the conductive path and increase the electrical conductivity of the PPC/PLA/MWCNT composites.

In this study, the effects of repeated extrusion on the mechanical properties, morphology, and interfacial tension of polypropylene (PP)/ethylene propylene diene monomer (EPDM) (80/20) blends were investigated. For the PP/EPDM (80/20) blends, the impact strength of the blends increased with repeated extrusion, which could be attributed to the interaction between the PP and the EPDM. The interfacial tension of the PP/EPDM (80/20) blends, which was determined using the Palierne and Choi–Schowalter models, decreased with an increase in the number of repeated extrusion. Based on the results of the mechanical properties and morphology, the interaction between the PP and the EPDM with repeated extrusion contributed to the reduction of interfacial tension between the PP and the EPDM, which consequently improved the impact strength of the PP/EPDM (80/20) blends. The results for the nuclear magnetic resonance studies supported the increase in impact strength of the PP/EPDM (80/20) blends with repeated extrusion. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

The effects of maleic anhydride-grafted styrene-ethylene-butylene-styrene copolymer (SEBS-g-MAH) on the mechanical and morphological properties of polypropylene (PP) and poly(acrylonitrile-butadiene-styrene) (ABS) blends were investigated. Based on mechanical properties, including impact and tensile strengths, the PP/ABS (70/30) blends containing SEBS-g-MAH showed improved impact strength with minimal loss of tensile strength. As determined from morphological studies of the PP/ABS blends, addition of SEBS-g-MAH decreased PP/ABS blend droplet size more than the addition of SEBS. Additionally, the effects of SEBS-g-MAH and SEBS on the mechanical and morphological properties of the PP/ABS (70/30) blends were investigated during accelerated aging in an oven at 90°C for 72 h (one cycle). The impact strength of the PP/ABS (70/30) blends with SEBS-g-MAH (7 phr) decreased less than 10% after five cycles, but blends with SEBS (7 phr) and blends without compatibilizer decreased as much as 37%. The tensile strengths of the PP/ABS (70/30) blends after accelerated aging indicated a trend similar to that of the impact strength. The morphological studies indicated no significant changes in the PP/ABS (70/30) blends with SEBS-g-MAH; however, many cavities and damages were observed in the blend with SEBS. The above results suggest that SEBS-g-MAH acts as an impact modifier and as a good compatibilizer in the PP/ABS (70/30) blends. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Nonflammability of the thermoplasticized crosslinked polyethylene (PE)/polyolefin elastomer (POE)/metal hydroxide flame retardant/compatibilizer composites were investigated. The thermoplasticized crosslinked PE was decrosslinked from the crosslinked high-density PE under the supercritical methanol condition. Two types of metal hydroxides: aluminum hydroxide (AH) and magnesium hydroxide (MH), and a low-density polyethylene-g-maleic anhydride (LM) were used as flame retardants and a compatibilizer, respectively. Nonflammability of both PE/POE/AH/LM and PE/POE/MH/LM composites was enhanced with metal hydroxide flame retardant concentration. PE/POE/MH/LM composites had better nonflammability than PE/POE/AH/LM composites at the same flame retardant concentration. Interestingly, nonflammability of the composites was also strongly influenced by the compatibilizer concentration. At low compatibilizer concentration, the nonflammability of the PE/POE/MH/LM composites was improved with the compatibilizer concentration. In contrast, at high compatibilizer concentration, the nonflammability of the PE/POE/MH/LM composites was deteriorated with the compatibilizer concentration. This demonstrates that optimum concentration of the compatibilizer can help to enhance the efficiency of the flame retardants in the development of the nonflammable polyolefin for the wire and cable industry. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

This article investigates the effects of liquid-type silane additives and organoclay as a solid-type additive on the morphological, mechanical and thermal insulating properties of polyisocyanurate-polyurethane (PIR-PUR) foams. The organoclay likely acted as nucleating agents during the formation of PIR-PUR foams. When the liquid silane additives and organoclay were added, the cell size and thermal conductivity of the PIR-PUR foams appeared to be decreased. However, organoclay did not contribute to reduce the cell size distribution of the foam. PIR-PUR foams synthesized with tetramethylsilane as a liquid-type additive showed a smaller average cell size and lower thermal conductivity than that of PIR-PUR foams synthesized with the other silane additives or with organoclay as a solid-type additive. For the PIR-PUR foam with organoclay/TEMS (1.5/1.5 php) mixture, cell size and thermal conductivity of the foam showed similar to the foam with TEMS. These results suggest that smaller cell size appears to be one of the major factors in the improvement of thermal insulation properties of the PIR-PUR foams. Silane additives did not seem to have a strong effect on the flammability of the PIR-PUR foams. However, heat resistance was more dominant for the foam with the organoclay at the higher temperature. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Electrical, thermal, and morphological properties of the polyurethane foam (PUF)/multiwall carbon nanotube (MWCNT) composites were investigated with the MWCNT content. Electrical conductivity of the PUF/MWCNT composites increased rapidly from 0 to 0.23 S/cm at 0.1 php MWCNT content, then, the electrical conductivity did not change significantly with the increase of MWCNT content up to 0.5 phr because of the aggregation of the MWCNT when the amount of MWCNT was large (0.5 php). The PUF/MWCNT composite having low MWCNT contents (0.01, 0.05, and 0.1 php) showed lower thermal conductivity than that of the PUF/MWCNT composite having higher content (0.5 php). This is maybe due to that the PUF with the lower MWCNT contents (0.01, 0.05, and 0.1 php) showed smaller cell size than that of the PUF with the higher content of MWCNT (0.5 php). From the results of thermal conductivity and cell size of the PUF/MWCNT composites, it is suggested that reduction in cell size of the composite affects lowering the thermal conductivity of the PUF/MWCNT composites. Also, small amount (0.01, 0.05, and 0.1 php) of MWCNT may contribute to decrease the thermal conductivity of the PUF/MWCNT composites.

In this study, polycarbonate (PC)/multi-walled carbon nanotube (MWCNT) nancomposites have been prepared by pretreating MWCNT solutions with ultrasonication. We demonstrate that the electrical conductivity and rheological properties of PC/MWCNT nanocomposites strongly depend on the mesoscopic shape factor ( l sp / d ), which is represented by the ratio between the static bending persistence length ( l sp ) and outer diameter ( d ) of the MWCNT. The electrical conductivity of PC/MWCNT nanocomposites increases linearly with increasing ( l sp / d ) 2 and the percolation threshold of PC/MWCNT nanocomposites decreases linearly with increasing ( l sp / d ) 2 of MWCNTs. The storage modulus of PC/MWCNT nanocomposites increases linearly with increasing ( l sp / d ) 2 of MWCNTs at all frequency ranges.

Mechanical, morphological and rheological properties of polycarbonate (PC) and poly (lactic acid) (PLA) blends with compatibilizers have been investigated. Three types of compatibilizers were used: poly(styrene-g-acrylonitrile)-maleic anhydride (SAN-g-MAH), poly(ethylene-co-octene) rubber-maleic anhydride (EOR-MAH) and poly(ethylene-co-glycidyl methacrylate) (EGMA). The maximum value of the mechanical properties such as impact and tensile strengths of the PC/PLA (70/30, wt%) blend before or after hydrolysis was observed when the SAN-g-MAH was used as a compatibilizer at the amount of 5 phr. From the interfacial tension between PC and PLA which was determined from the weighted relaxation spectra using Palierne emulsion model, minimum value of interfacial tension (0.08 mN/m) was observed when the SAN-g-MAH (5 phr) was used. From the morphological studies of the PC/PLA (70/30) blends, the PLA droplet size showed minimum (0.19 μm) at the 5.0 phr SAN-g-MAH. From the results of mechanical, morphological and rheological properties of the PC/PLA (70/30) blend, it is suggested that the SAN-g-MAH is the most effective compatibilizer to improve the mechanical strength of the PC/PLA (70/30) blends among the compatibilizers used in this study, especially at the amount of 5 phr.

The effects of compatibilizers and hydrolysis on the mechanical, morphological and rheological properties of polypropylene (PP)/ethylene-propylene-diene monomer rubber (EPDM)/poly(lactic acid) (PLA) blends were studied. The compatibilizers used were polypropylene-g-maleic anhydride (PP-g-MAH) and styrene-ethylene-butylene-styrene-g-maleic anhydride (SEBS-g-MAH) copolymers. Before hydrolysis, mixing the compatibilizers PP-g-MAH (5 phr) and SEBS-g-MAH (5 phr) effectively increased the impact strength of PP/EPDM/PLA (64/16/20) blends without any loss of tensile strength. This result is consistent with the morphological and rheological properties of the PP/EPDM/PLA blends. After hydrolysis, the tensile strength of the PP/EPDM/PLA blends for the PLArich compositions decreased sharply until the hydrolysis time was 3 days. This suggests that the mechanical strength of the PLA already lost its mechanical properties, mostly when the hydrolysis time was 3 days under such hydrolysis conditions. The increase in viscosity and decrease in interfacial tension of the compatibilized PP/EPDM/PLA (64/16/20) blends was interpreted with the qualitative picture of the Palierne emulsion model. The interfacial tension calculated from the emulsion model is consistent with the mechanical and morphological properties of the PP/EPDM/PLA (64/16/20) blends.

Dispersion of the functionalized multiwalled nanotubes (MWNT) in the polyurethane (PU) matrix and DC conductivity of the MWNT/PU composites are investigated with the oxidation conditions, the kind of surfactants and their content. First, the most optimal surfactant type and its critical micelle concentration in the MWNT suspension are determined as a cationic surfactant, benzalkonium chloride (BKC) of 0.6 wt.% to the MWNT content from DEA and FESEM results. All the MWNT oxidized under several conditions are negatively charged and functionalized with carboxylic group, whereas the degree of damage is different from oxidation conditions. In addition, each MWNT/PU composite derived from several oxidation conditions shows different DC conductivity at a characteristic MWNT content. It is found that in order to enhance DC conductivity of the polymeric composites containing the oxidized MWNT the better dispersion of MWNT should be obtained by effective functionalities and surfactant adsorption with preserving the intrinsic geometry of pristine MWNT.

The effects of compatibilizers and hydrolysis on the tensile and impact strength, interfacial tension and morphology of the PP/PLA (80/20) blends were investigated. For the PP/PLA (80/20) blends before hydrolysis, the tensile strength of the blends reached a maximum when the polypropylene-g-maleic anhydride (PP-g-MAH) copolymer was added at 3 phr. For the PP/PLA (80/20) blends after hydrolysis, the tensile strength did not change appreciably with the PP-g-MAH content. For the blends with the styrene-ethylene-butylene-styrene-g-maleic anhydride (SEBS-g-MAH) before or after hydrolysis, the tensile strength of the blends decreased with increasing SEBS-g-MAH content. The interfacial tension of the PP/PLA (80/20) blend was determined from the relaxation time using the Palierne and Choi-Schowalter models, and showed a minimum value at a PP-g-MAH content of 3 phr in each model. For the PP/PLA (80/20) blends with the SEBS-g-MAH before and after hydrolysis, the increase in impact strength was more significant for the blends after hydrolysis. This suggests that PLA becomes less brittle after hydrolysis. The impact strength suggests that the SEBS-g-MAH is an effective impact modifier to improve the impact strength of the PP/PLA (80/20) blends.

The effects of liquid-type nucleating silane additives on the cell structure, mechanical strength, and thermal insulating properties of the polyisocyanurate (PIR) foams have been studied. The PIR foams synthesized with hexamethyldisilazane (HMDS) as a silane additive showed the smaller average cell size and lower thermal conductivity than those of the PIR foams prepared with the hexamethyldisiloxane, dimethoxydimethylsilane, and hexadecyltrimethoxysilane. When HMDS was added, average cell size of the PIR foam was becoming smaller due to lower surface tension of the polyol solution, thereby the nucleation rate and number of bubbles produced were increased and then the cell size becomes smaller. The additives likely act as nucleating agents during the formation of PIR foams. The smaller cell size appears to be one of the major reasons for the improvement of thermal insulation properties and mechanical properties of the PIR foams. From the results of cell size, thermal conductivity, and mechanical strength of the PIR foams, it is suggested that the HMDS may be the efficient liquid-type additive for the reduction of cell size and improvement of the thermal insulation property of the PIR foams.

The electrical, morphological and rheological properties of melt- and dry-mixed composites of polypropylene (PP)/nickel-coated carbon fiber (NCCF) with multi-walled carbon nanotubes (MWCNTs) was investigated. Melt mixed PP/NCCF/MWCNT composites were prepared by mixing the materials with a twin screw extruder. From the results of the electrical conductivity of the PP/NCCF/MWCNT composites, the MWCNTs increased the electric conductivity of the PP/NCCF composites appreciably. A higher aspect ratio of MWCNTs can increase the conductivity of PP/NCCF composites in a polymer matrix compared to the composites without the MWCNTs. The tensile and flexural strengths of the PP/NCCF/MWCNT composites were higher than the composites without MWCNTs. This is might be due to the reinforcing effect of the well dispersed MWCNT in the PP matrix. The results of electrical, morphological and mechanical studies indicate that the MWCNTs increased the electrical conductivity and mechanical strength of the PP/NCCF composites.

The effect of a multiwalled carbon nanotube (MWCNT) dispersion on the electrical, morphological and rheological properties of polycarbonate (PC)/MWCNT composites was investigated, with and without pretreating the MWCNTs with hydrogen peroxide oxidation and lyophilization. The resulting PC/treated MWCNT composites showed higher electrical conductivity than the PC/untreated MWCNT composites. The morphological behavior indicated the treated composites to have greater dispersion of MWCNTs in the PC matrix. In addition, the electromagnetic interference shielding efficiency (EMI SE) of the treated composites was higher than that of the untreated ones. Rheological studies of the composites showed that the complex viscosity of the treated composites was higher than the untreated ones due to increased dispersion of the MWCNTs in the PC matrix, which is consistent with the electrical conductivity, EMI SE and morphological studies of the treated composites. The latter results suggested that the increased electrical conductivity and EMI SE of the treated composites were mainly due to the increased dispersion of MWCNTs in the PC matrix.

Electrical, morphological and rheological properties of polyethylene (PE)/multi-walled carbon nanotube (MWCNT) and poly(phenylene sulfide) (PPS)/MWCNT composites were studied with the MWCNT content using vector network analyzer, scanning electron microscopy and rotational rheometry. From the results of electrical conductivity and electromagnetic interference shielding efficiency (EMI SE) of the PE/MWCNT and PPS/MWCNT composites, the electrical percolation threshold of the composites has found to be 5 and 3 wt% MWCNT, respectively. From the results of the EMI SE of the composites, it was suggested that the increase in homogeneous dispersion of the MWCNT in the PPS matrix has been attributed to the increase in connectivity of the MWCNT–MWCNT network structure of the composite. Therefore, the higher values of the EMI SE with the MWCNT content were observed in the PPS/MWCNT than the PE/MWCNT composites. From the results of the rheological properties of the PE/MWCNT and PPS/MWCNT composites, the increase in the complex viscosity was observed for the PPS/MWCNT than the PE/MWCNT composites. The increase in complex viscosity maybe due to the increase in homogeneous dispersion of the MWCNT in the PPS matrix than that in the PE matrix. From the results of the rheological properties of the PE/MWCNT and PPS/MWCNT composites, it was suggested that the homogeneous dispersion of the MWCNT in the polymer matrix has affected the increase in complex viscosity of the PPS/MWCNT composite. This result of rheological behavior is consistent with the results of the EMI SE of the PE/MWCNT and PPS/MWCNT composites.

This study examined the effects of liquid and solid additives on the morphological, mechanical and thermal insulating properties of rigid polyurethane foams (PUFs). The PUFs synthesized with tetramethylsilane (TEMS) as a liquid-type additive showed a smaller average cell size and lower thermal conductivity than those with the aerosil 200 and clay 30B as solid-type additives. When TEMS was added, the average cell size of the PUF became more uniform and finer due to the reduced surface tension of the polymer solution, which increased the nucleation rate and number of bubbles produced and reduced cell size. The PUFs with TEMS showed the highest closed cell contents among the PUFs prepared using TEMS, aerosil 200 and clay 30B. This suggests that the insulation properties of PUF can be determined by both the size of the cell structure and the amount of closed cell contents in the system. The compression and flexural strengths of the PUF increased slightly when the aerosil 200, clay 30B and TEMS were added compared those of the neat PUF. The reaction profiles of the PUFs showed a similar gel and tack free time with the reaction time among the PUFs synthesized with three different additives and neat PUF. This suggests that the nucleating additives used in this study do not affect the bubble growth of the chemical reaction, and the additives may act as nucleating agents during the formation of PUF. From the above results of the cell size, thermal conductivity, closed cell contents and reaction profile of the PUFs, liquid-type nucleating agent, such as TEMS, is more effective in decreasing the thermal conductivity of the PUF than solid-type nucleating agent, such as aerosil 200 and clay 30B.