Effect of pendant group of polysiloxanes on the thermal and mechanical properties of polybenzoxazine hybrids

Polybenzoxazine (PBa) was successfully hybridized with polysiloxanes by synchronizing two reactions; ring-opening polymerization of benzoxazine (Ba) and sol–gel process of diethoxysilanes. Diethoxydimethylsilane, diethoxymethylphenylsilane, and diethoxydiphenylsilane were used as precursors for the formation of polydimethylsiloxane (PDMS), polymethylphenylsiloxane (PMPS), and polydiphenylsiloxane (PDPS), respectively. The effect of pendant group of polysiloxane on the optical, mechanical, and thermal properties of PBa–polysiloxane hybrids was studied. The progress of sol–gel process was confirmed by IR, ¹H NMR and size exclusion chromatography. Opaque PBa–PDMS hybrid films were obtained up to 15 wt% of PDMS content, corresponding to the phase separation with 1–2 μm domain size of PDMS as observed from the scanning electron microscope. Meanwhile, transparent PBa–polysiloxane hybrid films were obtained up to 29 wt% for PMPS and 36 wt% for PDPS, which revealed no apparent domain of PMPS and PDPS, indicating high compatibility of the polysiloxanes with PBa. Dynamic viscoelastic analysis (DMA) of the PBa–PDMS hybrid revealed two glass transition temperatures corresponding to PDMS and PBa components, while the DMA of the PBa–PMPS and PBa–PDPS hybrids revealed only one glass transition temperature. The tensile strength and elongation at break of the hybrid films increased with increasing polysiloxane content. Thermogravimetric analysis revealed high weight residue at 850 °C for PBa–polysiloxanes with phenyl group.     

The influence of crosslinking and fumed silica nanoparticles on mixed gas transport properties of poly[1-(trimethylsilyl)-1-propyne]

Crosslinking poly[1-(trimethylsilyl)-1-propyne] (PTMSP) films with 3,3′-diazidodiphenylsulfone, a bis(azide) crosslinker, rendered the films insoluble in common solvents for PTMSP such as toluene. At all temperatures, mixed gas CH₄ and n-C₄H₁₀ permeabilities of crosslinked PTMSP were less than those of uncrosslinked PTMSP, which correlates with lower free volume in the crosslinked material. The presence of fumed silica (FS) nanoparticles in both uncrosslinked PTMSP and crosslinked PTMSP increased mixed gas CH₄ and n-C₄H₁₀ permeabilities, consistent with the disruption of polymer chain packing by such nanoparticles. Mixed gas CH₄ permeabilities of all films were significantly less than their corresponding pure gas CH₄ permeabilities. For example, at 35 °C, the mixed gas CH₄ permeabilities were approximately 60–80% less than their pure gas values. The greatest decrease was observed for uncrosslinked PTMSP, while nanocomposite PTMSP films showed the least decrease. The mixed gas n-C₄H₁₀/CH₄ selectivities of crosslinked PTMSP and nanocomposite PTMSP films were less than those of uncrosslinked PTMSP at all temperatures. For example, at 35 °C, the mixed gas n-C₄H₁₀/CH₄ selectivities of uncrosslinked PTMSP, crosslinked PTMSP containing 10 wt% crosslinker, and uncrosslinked PTMSP containing 30 wt% FS were 33, 27, and 17, respectively, when the feed gas contained 2 mol% n-C₄H₁₀ and the total upstream mixture fugacity was 11 atm. For all films, as temperature decreased, mixed gas n-C₄H₁₀ permeabilities increased, and mixed gas CH₄ permeabilities decreased. Consequently, the mixed gas n-C₄H₁₀/CH₄ selectivities increased substantially as temperature decreased and the mixed gas selectivity of uncrosslinked PTMSP increased from 33 to 170 as temperature decreased from 35 °C to ?20 °C when the feed gas contained 2 mol% n-C₄H₁₀ and the total upstream mixture fugacity was 11 atm.     

Supercritical antisolvent micronization of PVP and ibuprofen sodium towards tailored solid dispersions

The supercritical antisolvent technology is used to precipitate polyvinylpyrrolidone (PVP) particles and crystallise ibuprofen sodium (IS) crystals separately and in the form of solid dispersion together. Supercritical carbon dioxide (scCO₂) is used as antisolvent. For PVP particle generation, ethanol, acetone and mixtures of ethanol and acetone are used as solvents. The initial concentration of PVP in the solution was varied between 0.5 wt% and 1.5 wt%, the operation pressure between 10 MPa and 30 MPa and the composition of ethanol/acetone solvent mixtures between 100 wt% and 0 wt% of ethanol at a constant temperature of 313 K. Furthermore, the mean molecular weight of the polymer was varied between 40 kg mol⁻¹, 360 kg mol⁻¹ and 1300 kg mol⁻¹. An increase of the content of the poor solvent acetone in the initial solvent mixture as well as the usage of PVP with a higher molecular weight, leads to a significant decrease in mean particle size. At all the investigated parameters always fully amorphous PVP powder precipitates. For IS, only ethanol was used as the solvent, the initial IS concentration in the solution was varied between 1 wt% and 3 wt% and the operation pressure between 10 MPa and 16 MPa. A variation of these parameters leads to a manipulation of the size and the morphology of the crystallised IS crystals. Irrespective of the parameters used, always the same polymorphic form of ibuprofen sodium is produced. The solid dispersions were generated at different compositions of PVP to IS and with two different molecular weights of PVP at otherwise constant conditions. Fully amorphous solid dispersions consisting of IS and PVP together were generated at different ratios of PVP to IS.The mechanisms that control the final particle properties are discussed taking into account two different models for “ideal” and “non-ideal” solutes. Furthermore, the study of the “unconventional” SAS parameters, molecular weight and solvation power of the solvent shows that these parameters qualify to tailor polymer particle properties via SAS processing. Next to the investigation into the behaviour of both solutes separately, fully amorphous solid dispersions consisting of IS and PVP together were generated. While X-ray diffraction was used to analyze the crystalline structure of the particles, respectively, solid dispersions, their morphology was analysed using scanning electron microscopy (SEM).     

Preparation and mechanical properties of modified epoxy resins with flexible diamines

Diglycidyl ether of bisphenol A (DGEBA) is one of the most widely used epoxy resins for many industrial applications, including cryogenic engineering. In this paper, diethyl toluene diamine (DETD) cured DGEBA epoxy resin has been modified by two flexible diamines (D-230 and D-400). The cryogenic mechanical behaviors of the modified epoxy resins are studied in terms of the tensile properties and Charpy impact strength at cryogenic temperature (77 K) and compared to their corresponding properties at room temperature (RT). The results show that the addition of flexible diamines generally improves the elongation at break and impact strength at both RT and 77 K. The exception is the impact strength at 77 K filled with 21 wt% and 49 wt% D-400. Further, two interesting observations are made: (a) the cryogenic tensile strength increases with increasing the flexible diamine content; and (b) the RT tensile strength can only be improved by adding a proper content of flexible diamines. It is concluded that the addition of a selected amount namely 21–78 wt% of D-230 can simultaneously strengthen and toughen DGEBA epoxy resins at both RT and 77 K. However, only the addition of 21 wt% D-400 can simultaneously enhance the strength and ductility/impact strength of DGEBA epoxy resins at RT. The impact fracture surfaces are examined using scanning electron microscopy (SEM) to explain the impact strength results. Finally, differential scanning calorimetry (DSC) analysis shows that the glass transition temperature (T_g) decreases with increasing the flexible diamine content. The presence of a single T_g reveals that the flexible diamine-modified epoxy resins have a homogeneous phase structure.     

Simultaneous improvements in the cryogenic tensile strength,ductility and impact strength of epoxy resins by a hyperbranched polymer

Improvements in mechanical properties at low temperatures are desirable for epoxy resins such as diglycidyl ether of bisphenol A (DGEBA) that are often used in cryogenic engineering applications. In this study, a hydroxyl functionalized hyperbranched polymer (H30) is employed to improve the mechanical properties of a DGEBA epoxy resin at liquid nitrogen temperature (77 K). The results show that the tensile strength, failure strain (ductility) and impact strength at 77 K are simultaneously improved by adding a proper content of H30. The maximum tensile strength at 77 K is increased by 17.7% from 98.2 MPa of pure epoxy resin to 115.6 MPa of modified epoxy system for the 10 wt% H30 content. The failure strain at 77 K increases consistently with the increase of H30 content. The maximum impact strength at 77 K is attained by introduction of 10 wt% H30 with an improvement of 26.3% over that of pure epoxy resin. For the purpose of comparison, the mechanical properties of modified epoxy resins at room temperature (RT) are also investigated. It is interesting to note that the impact strength is not lower at 77 K than that at RT for the modified systems. Moreover, the glass transition temperature (T_g) is not reduced by the addition of H30 in appropriate amounts.     

Effect of in situ-formed polydimethylsiloxane on the properties of polyimide hybrids

Polyimide-polydimethylsiloxane (PI-PDMS) hybrids were synthesized by combining an in situ sol–gel reaction of diethoxydimethylsilane (DEDMS) and imidization of poly(amide acid) (PAA) prepared from pyromellitic dianhydride (PMDA) and 4,4′-oxydianiline (ODA). Transparent hybrid films were obtained with up to 3 wt.% PDMS content corresponding to the relatively small domain size of PDMS as confirmed by scanning electron microscopy. The hybrid films with up to 3 wt.% of PDMS content showed higher tensile modulus, strength and elongation at break than those of pristine PI, due to the in situ-formed PDMS. The thermal stability of the hybrids also increased with the increase of PDMS content, as evidenced by TGA.     

Jatropha curcas oil based alkyd/epoxy/graphene oxide (GO) bionanocomposites: Effect of GO on curing,mechanical and thermal properties

Jatropha curcas oil based alkyd/epoxy/GO bionanocomposites were prepared by direct solution blending of alkyd/epoxy blend matrix with GO nano filler. Structures and properties of the bionanocomposites were characterized with Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and tensile testing. X-ray diffraction and transmission electron microscopy study demonstrates the formation of highly exfoliated GO layers and its homogeneous dispersion throughout the polymer matrix with 1 and 3 wt% GO. However, the intercalated structure is predominant with 5 wt% GO. The homogeneous dispersion and the strong interaction of the GO layers and the polymer matrix induced the significant improvement in thermal and mechanical properties of the bionanocomposites. The tensile strength and elastic modulus of the bionanocomposite increased by 133% and 68% respectively with 3 wt% GO loading. The thermal stability of the bionanocomposite improved by 39 °C and T_g is shifted toward higher temperature by 20 °C as compared to the pristine polymer. Incorporation of GO significantly decreases the curing time of the alkyd/epoxy resin blend.     

Improved mechanical performance of solution-processed MWCNT/Ag nanoparticle composite films with oxygen-pressure-controlled annealing

A method for the synthesis of solution process-based MWCNT/Ag nanoparticle composite thin films as electrode or interconnect materials for flexible electronic devices is presented. The method produces homogeneously-dispersed CNT networks and increases the density of the Ag matrix, which are major factors in determining the mechanical performance of CNT/Ag films. By introducing nanometer-sized Ag particles as a matrix material, the agglomeration of CNTs is suppressed. In addition, the generation of pores during the synthesis procedure is effectively restrained by oxygen-pressure-controlled annealing. The elastic modulus of the pristine Ag films was observed to increase by 34% by adding 5 wt% CNTs. An improvement in the fatigue resistance of the CNTs under cyclic tensile deformation was confirmed. The normalized resistance change ((R ? R_o)/R_o) of the Ag films containing 5 wt% CNTs after fatigue testing was reduced by about 27% compared to that of the pristine Ag films. For industrial application the process has the advantage of relatively low-temperature processing without any high pressure compaction compared to the conventional powder metallurgy techniques normally used.     

Grafting of epoxy chains onto graphene oxide for epoxy composites with improved mechanical and thermal properties

Epoxy composites filled with both graphene oxide (GO) and diglycidyl ether of bisphenol-A functionalized GO (DGEBA–f–GO) sheets were prepared at different filler loading levels. The correlations between surface modification, morphology, dispersion/exfoliation and interfacial interaction of sheets and the corresponding mechanical and thermal properties of the composites were systematically investigated. The surface functionalization of DGEBA layer was found to effectively improve the compatibility and dispersion of GO sheets in epoxy matrix. The tensile test indicated that the DGEBA–f–GO/epoxy composites showed higher tensile modulus and strength than either the neat epoxy or the GO/epoxy composites. For epoxy composite with 0.25 wt% DGEBA–f–GO, the tensile modulus and strength increased from 3.15 ± 0.11 to 3.56 ± 0.08 GPa (∼13%) and 52.98 ± 5.82 to 92.94 ± 5.03 MPa (∼75%), respectively, compared to the neat epoxy resin. Furthermore, enhanced quasi-static fracture toughness (K_IC) was measured in case of the surface functionalization. The GO and DGEBA–f–GO at 0.25 wt% loading produced ∼26% and ∼41% improvements in K_IC values of epoxy composites, respectively. Fracture surface analysis revealed improved interfacial interaction between DGEBA–f–GO and matrix. Moreover, increased glass transition temperature and thermal stability of the DGEBA–f–GO/epoxy composites were also observed in the dynamic mechanical properties and thermo-gravimetric analysis compared to those of the GO/epoxy composites.     

Hydrolysis behaviour of crosslinked poly(ester anhydride) networks prepared from functionalised poly(ε-caprolactone) precursors

Biodegradable poly(ester anhydride) networks based on functionalised poly(ε-caprolactone) precursors with different hydrophobicities, molecular weights and architectures were synthesised. Networks that were prepared from the star-shaped precursors clearly showed higher gel contents and crosslinking densities than the networks that were prepared from the linear precursors. Functionalising with different alkenylsuccinic anhydrides and/or varying the molecular weight of the precursor, the thermal properties, surface hydrophobicity and erosion of the crosslinked networks were widely tailored. The dissolution behaviour of the networks changed dramatically as the molecular weight of the precursor increased from 2000 to 4000 g/mol or the alkenyl chain of the alkenylsuccinic anhydride increased from 8 to 18 carbons. The networks that were prepared from the lower molecular weight precursors, without an alkenyl chain or with an 8 carbon alkenyl chain, lost their mass in a few days, whereas the networks that were prepared from higher molecular weight precursors or contained a hydrophobic 18 carbon alkenyl chain did not show any mass loss over a period of 8 weeks.     

Ultradrawing above the static melting temperature of ultra-high molecular weight isotactic poly(1-butene) having low ductility in the crystalline state

Ultra-high molecular weight isotactic poly(1-butene) (UHMW-PB1) melt-grown crystal (MGC) films were drawn using the PIN drawing technique. Although the UHMW-PB1 MGC films had poor ductility in the crystalline state, they were ultradrawable in the molten state above the static melting temperature (T_m). The drawability of the MGC films was strongly influenced by the draw temperature, the sample thickness, and the contact time between the metal heater and sample, and it increased with decreasing sample thickness. The maximum draw ratio (DR_max) was nearly constant when the sample thickness was less than 100 μm at a given draw temperature. The contact time between the metal heater and sample needed to draw continuously in the molten state was at least 0.1 s. The ductility increased rapidly above 130 °C, reaching a maximum at 200 °C, and decreased at higher temperatures. A DR_max of 170 was achieved at 200 °C under optimum conditions. The efficiency of the drawing, based on the Herman crystalline orientation function (f_c) and tensile properties versus DR, was lower for films drawn at higher temperatures. The highest f_c of 0.996, tensile modulus of 14 GPa, and strength of 900 MPa were obtained by ultradrawing with DR = 50 at 155 °C. This modulus corresponded to 58% of the X-ray crystal modulus (24 GPa), whereas the modulus of PB1 films drawn in the crystalline state corresponded to only 12–13% (3 GPa) of the theoretical crystal modulus.     

Manipulating the size,the morphology and the polymorphism of acetaminophen using supercritical antisolvent (SAS) precipitation

The supercritical antisolvent technology is used to crystallize paracetamol particles. Supercritical carbon dioxide (scCO₂) is used as antisolvent. Ethanol, acetone and mixtures of ethanol and acetone are used as solvents. The initial concentration of paracetamol in the solution was varied between 1 and 5 wt%, the composition of the ethanol/acetone solvent mixture between 50 and 90 wt% of ethanol and the operation pressure between 10 and 16 MPa at a temperature of 313 K. The most important finding is that the polymorph of paracetamol crystals can be adjusted between monoclinic and orthorhombic by varying the content of ethanol in the solution. The second important finding is that the occurrence of primary and secondary crystal structures can be explained solely by the overall supersaturation during the crystallization process. While X-ray diffraction was used to analyze the polymorph of the particles, their morphology was analyzed using scanning electron microscopy.     

Macauba oil as an alternative feedstock for biodiesel: Characterization and ester conversion by the supercritical method

In this work different samples of Brazilian macauba oil obtained from mechanical pressing were characterized and production of esters of fatty acids using a catalyst-free continuous process under supercritical alcohols was assessed. Analysis of oil samples showed that the major fatty acid on pulp oil was oleic acid (mean value 62.8%), the amount of free fatty acid (FFA) was very high (37.4–65.4%), samples contained glycerides (7.4–16.5% TAG, 14.2–16.8% DAG and 1.0–3.4% MAG) and moisture was around 1.0%. Oil was processed in a continuous reactor using supercritical methanol or ethanol and the effects of temperature (573, 598, 623 and 648 K), pressure (10, 15 and 20 MPa), oil to alcohol molar ratio (1:20, 1:30 and 1:40), water concentration (0, 5 and 10 wt% added) and the flow rate of reaction mixture (1.0, 1.5, 2.0, 2.5 and 3.0 mL/min) on process efficiency were evaluated. The highest ester content achieved in reactions with supercritical methanol was 78.5% (648 K, 15 MPa, 1:30 oil:methanol molar ratio, 5 wt% water and 2.5 mL/min flow rate), while with supercritical ethanol was 69.6% (598 K, 15 MPa, 1:30 oil:ethanol molar ratio, 5 wt% water and 2.0 mL/min flow rate). The extent of the reaction was explored using a novel parameter, convertibility, which corresponds to the maximum ester content attainable from the feedstock. According to the convertibility of macauba pulp oil, the highest ester content corresponded to efficiencies of 98.0% and 86.9%, respectively. Results demonstrate that macauba oil might be a potential alternative for biodiesel production, though purification steps should be taken into account to achieve biodiesel specifications.     

The solid state structure of polycarbonate blends with lead phthalocyanine

The physical properties of polycarbonate blends containing the nonlinear optical dye lead tetracumylphenoxy phthalocyanine were characterized. Blends with up to 20 wt% dye were prepared and characterized in terms of density, refractive index, glass transition temperature, loss modulus, subambient relaxation behavior, and free volume hole size from positron annihilation lifetime spectroscopy. The dye strongly affected the physical properties of the blend. The initial 0.1 wt% dye produced a dramatic increase in the density. A similar trend in the refractive index was accounted for by the change in density using a relationship between density and refractive index derived from the Lorentz–Lorenz equation. Increasing the dye content to 8 wt% led to a large reduction in the glass transition temperature. An increase in E′ and a decrease in the subambient γ-relaxation intensity accompanied the large decrease in T_g. This behavior fit the conventional concept of antiplasticization, which has been described for other low molecular weight diluents in PC. Recognizing that the dye was present as a mixture of monomer, dimer and higher aggregates, it was shown that the monomer form was responsible for the antiplasticization. In the glass, dimer and higher aggregates were viewed as nanoparticle fillers. It was confirmed that the antiplasticization effect was due to a reduction in excess hole free volume of the polymer.     

Hydrogen-storage properties of MgH2–10Ni–2NaAlH4–2Ti prepared by reactive mechanical grinding

A sample of 86 wt% MgH₂–10 wt% Ni–2 wt% NaAlH₄–2 wt% Ti (named MgH₂–10Ni–2NaAlH₄–2Ti) was prepared by reactive mechanical grinding. Activation of the sample was not required at 573 K. At the first hydriding–dehydriding cycle (n = 1), the sample absorbed more than 5 wt% H at 573 K under 12 bar H₂ for 60 min. The hydriding rate increased as the temperature increased from 423 K to 553 K. MgH₂–10Ni–2NaAlH₄–2Ti showed quite high hydridng rates at relatively low temperatures of 423 K and 473 K under 12 bar H₂, absorbing 4.02 wt% H for 60 min at 473 K.     

Application of microwave heating to pervaporation: A case study for separation of ethanol–water mixtures

Membrane pervaporation experiments for dewatering of water–ethanol mixtures were conducted, using a polymeric hydrophilic membrane, under microwave and conventional heating in a multimode microwave oven and a convection oven, respectively. Three feed temperatures (33.5, 45.5 and 51.5 °C) and two feed compositions (5.5 wt% and 20 wt% water in the feed) were considered. At 20 wt% water content, higher water fluxes through the membrane were obtained in the convection oven. At lower water content in the feed (5.5 wt%), the opposite effect was observed; the water fluxes were higher under microwave heating over the considered temperature range. These differences may arise from the different dielectric properties and consequently thermal behaviour of the feed mixtures under microwave heating. Microwave coupling with ethanol is stronger than with water. Moreover, unlike water, the dielectric loss factor of ethanol increases with temperature, which makes microwave dissipation preponderant in hot areas. Hence, high ethanol concentrations in the feed can easily induce thermal gradients.     

Effect of spinel content on hot strength of alumina-spinel castables in the temperature range 1000–1500°C

Hot modulus of rupture of Al₂O₃-spinel castables containing 5–15 wt% alumina-rich magnesia alumina spinel and 1·7 wt% CaO generally increases with increase in spinel content and temperature from 1000 to 1500°C. The magnitudes of hot modulus of rupture of castables containing 15 wt% spinel and 1·7 wt% CaO are 14·3 MPa at 1400°C and 15·6 MPa at 1500°C, while those of castables containing 20 wt% spinel and 1·7 wt% CaO are 12·5 MPa at 1400°C and 14·7 MPa at 1500°C. The former castables contained 15 wt% spinel of −75 μm size, while the latter contained 10 wt% spinel of +75 μm size and another 10 wt% spinel of −75 μm size. The bond linkage between the CA₆ and spinel grains in the matrix is believed to cause both the spinel content and temperature dependence of hot strength of Al₂O₃-spinel castables, as well as fine grain spinel even in amount less than coarser grain spinel to be more effective for enhancing hot strength. The trend of the magnitude of thermal expansion under load (0·2 MPa) above 1500°C of the castables is not necessarily indicative of the magnitude of hot modulus of rupture at 1400 or 1500°C. ©     

Influence of reduction temperature and metal loading on the performance of molybdenum phosphide catalysts for dibenzothiophene hydrodesulfurization

Two series of alumina-supported molybdenum phosphide (MoP) catalysts with low and high metal loadings were prepared by temperature-programmed reduction of the oxidic catalyst precursors in hydrogen to different temperatures (823, 923, 1023 and 1123 K, respectively). Effects of reduction temperature and metal loading on the surface distribution and the type of species formed were studied by TPR, S_BET, XRD, HRTEM, ³¹P NMR, ²⁷Al NMR and in the reaction of dibenzothiophene (DBT) hydrodesulfurization (HDS) performed in a flow reactor at 553 K and total hydrogen pressure of 3.4 MPa. HRTEM and ³¹P NMR confirmed formation of MoP phase on all catalysts. The 9.9 wt% Mo catalyst activated at lowest reduction temperature (823 K) was found to be most active among the catalysts studied. The presence of a low amount of Mo⁰ species on the surface of this catalyst does not appear to be a drawback for the catalytic activity. The increase in both metal loading (from 9.9 to 15 wt% Mo and from 3.2 to 4.8 wt% P) and reduction temperature (from 823 to 1123 K) was found to be detrimental for HDS activity due to sintering of active phase, and also to decrease in specific area and formation of phosphate species.     

Physical properties of carbon nanotube sheets drawn from nanotube arrays

We report mechanical, thermal, and electrical properties of novel sheet materials composed of multiwalled carbon nanotubes, drawn from a CNT array. At low loading there is some slippage of CNTs but at higher loading tensile strength σ₀ = 7.9 MPa and Young’s modulus E = 310 MPa. The room-temperature thermal conductivity of the CNT sheet was 2.5 ± 0.5 W m^?1 K^?1, giving a thermal conductivity to density ratio of κ/ρ = 65 W m^?1 K^?1 g^?1 cm³. The heat capacity shows 1D behavior for T > 40 K, and 2D or 3D behavior at lower temperatures. The room-temperature specific heat was 0.83 J g^?1 K^?1. The iV curves above 10 K have Ohmic behavior while the iV curve at T = 2 K is non-Ohmic, and a model to explain both ranges is presented. Negative magnetoresistance was found, increasing in magnitude with decreasing temperature (?15% at T = 2 K and B = 9 T). The tensile strength, Young’s modulus and electrical conductivity of the CNT sheet are low, in comparison with other CNT materials, likely due to defects. Thermal conductivity is dominantly phononic but interfacial resistance between MWCNTs prevents the thermal conductivity from being higher.     

Tensile shear strength of wood bonded with urea–formaldehyde with different amounts of microfibrillated cellulose

Urea–formaldehyde (UF) adhesive mixtures with a 5% suspension of microfibrillated cellulose (MFC) at 0.5, 1, 3, and 5 wt% loading levels based on the solid weight (62.4%) of the UF adhesive were prepared. Beech lamellas with dimensions of 5 mm×20 mm×150 mm were prepared from beech lumbers using a planer saw. The UF adhesive (E0 class) was mixed with the MFC using a magnetic stirrer to achieve a proper distribution of the MFC in the UF adhesive. The tensile shear strength of single lap-joint specimens bonded with UF adhesive containing MFC was determined in accordance with EN 205 (2003). The specimens bonded with UF adhesive containing the MFC showed better tensile shear strengths as compared to the control. As compared to the control specimens, the tensile shear strength of the specimens increased by 5.7% as 3 wt% of the MFC was incorporated into the UF adhesive. However, a further increment in the MFC content up to 5 wt% decreased the tensile shear strength of the specimens (−14.3% of control specimen). The MFCs were well dispersed in the UF resin and were cross-linked to form a network to reinforce the bond line, improving bonding performance.